Subjects -> MANUFACTURING AND TECHNOLOGY (Total: 363 journals)
    - CERAMICS, GLASS AND POTTERY (31 journals)
    - MACHINERY (34 journals)
    - MANUFACTURING AND TECHNOLOGY (223 journals)
    - METROLOGY AND STANDARDIZATION (6 journals)
    - PACKAGING (19 journals)
    - PAINTS AND PROTECTIVE COATINGS (4 journals)
    - PLASTICS (42 journals)
    - RUBBER (4 journals)

MACHINERY (34 journals)

Showing 1 - 27 of 27 Journals sorted alphabetically
Acta Mechanica Solida Sinica     Hybrid Journal   (Followers: 8)
Advanced Energy Materials     Hybrid Journal   (Followers: 31)
Applied Mechanics Reviews     Full-text available via subscription   (Followers: 27)
CORROSION     Full-text available via subscription   (Followers: 20)
Electric Power Components and Systems     Hybrid Journal   (Followers: 7)
Foundations and TrendsĀ® in Electronic Design Automation     Full-text available via subscription   (Followers: 1)
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 8)
International Journal of Machining and Machinability of Materials     Hybrid Journal   (Followers: 4)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 8)
International Journal of Precision Technology     Hybrid Journal   (Followers: 1)
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 3)
International Journal of Rotating Machinery     Open Access   (Followers: 2)
Journal of Machinery Manufacture and Reliability     Hybrid Journal   (Followers: 2)
Journal of Manufacturing and Materials Processing     Open Access  
Journal of Mechanics     Hybrid Journal   (Followers: 9)
Journal of Strain Analysis for Engineering Design     Hybrid Journal   (Followers: 5)
Journal of Terramechanics     Hybrid Journal   (Followers: 4)
Machine Design     Partially Free   (Followers: 183)
Machine Learning and Knowledge Extraction     Open Access   (Followers: 12)
Machines     Open Access   (Followers: 4)
Materials     Open Access   (Followers: 4)
Mechanics Based Design of Structures and Machines: An International Journal     Hybrid Journal   (Followers: 8)
Micromachines     Open Access   (Followers: 2)
Pump Industry Analyst     Full-text available via subscription   (Followers: 1)
Russian Engineering Research     Hybrid Journal  
Sensor Review     Hybrid Journal   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 6)
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Micromachines
Journal Prestige (SJR): 0.493
Citation Impact (citeScore): 2
Number of Followers: 2  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2072-666X
Published by MDPI Homepage  [84 journals]
  • Micromachines, Vol. 13, Pages 680: A Review on Gel Polymer Electrolytes
           for Dye-Sensitized Solar Cells

    • Authors: Prasad Raut, Vinay Kishnani, Kunal Mondal, Ankur Gupta, Sadhan C. Jana
      First page: 680
      Abstract: Significant growth has been observed in the research domain of dye-sensitized solar cells (DSSCs) due to the simplicity in its manufacturing, low cost, and high-energy conversion efficiency. The electrolytes in DSSCs play an important role in determining the photovoltaic performance of the DSSCs, e.g., volatile liquid electrolytes suffer from poor thermal stability. Although low volatility liquid electrolytes and solid polymer electrolytes circumvent the stability issues, gel polymer electrolytes with high ionic conductivity and enduring stability are stimulating substitutes for liquid electrolytes in DSSC. In this review paper, the advantages of gel polymer electrolytes (GPEs) are discussed along with other types of electrolytes, e.g., solid polymer electrolytes and p-type semiconductor-based electrolytes. The benefits of incorporating ionic liquids into GPEs are highlighted in conjunction with the factors that affect the ionic conductivity of GPEs. The strategies on the improvement of the properties of DSSCs based on GPE are also presented.
      Citation: Micromachines
      PubDate: 2022-04-27
      DOI: 10.3390/mi13050680
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 681: Preparation of a Vertical
           Graphene-Based Pressure Sensor Using PECVD at a Low Temperature

    • Authors: Xin Cao, Kunpeng Zhang, Guang Feng, Quan Wang, Peihong Fu, Fengping Li
      First page: 681
      Abstract: Flexible pressure sensors have received much attention due to their widespread potential applications in electronic skins, health monitoring, and human–machine interfaces. Graphene and its derivatives hold great promise for two-dimensional sensing materials, owing to their superior properties, such as atomically thin, transparent, and flexible structure. The high performance of most graphene-based pressure piezoresistive sensors relies excessively on the preparation of complex, post-growth transfer processes. However, the majority of dielectric substrates cannot hold in high temperatures, which can induce contamination and structural defects. Herein, a credibility strategy is reported for directly growing high-quality vertical graphene (VG) on a flexible and stretchable mica paper dielectric substrate with individual interdigital electrodes in plasma-enhanced chemical vapor deposition (PECVD), which assists in inducing electric field, resulting in a flexible, touchable pressure sensor with low power consumption and portability. Benefitting from its vertically directed graphene microstructure, the graphene-based sensor shows superior properties of high sensitivity (4.84 KPa−1) and a maximum pressure range of 120 KPa, as well as strong stability (5000 cycles), which makes it possible to detect small pulse pressure and provide options for preparation of pressure sensors in the future.
      Citation: Micromachines
      PubDate: 2022-04-27
      DOI: 10.3390/mi13050681
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 682: Early Notice Pointer, an IoT-like
           Platform for Point-of-Care Feet and Body Balance Screening

    • Authors: Florina Silvia Iliescu, Ling Tim Hong, Jin Ming Jaden Toh, Mirela Petruta Suchea, Octavian Narcis Ionescu, Ciprian Iliescu
      First page: 682
      Abstract: Improper foot biomechanics associated with uneven bodyweight distribution contribute to impaired balance and fall risks. There is a need to complete the panel of commercially available devices for the self-measurement of BMI, fat, muscle, bone, weight, and hydration with one that measures weight-shifting at home as a pre-specialist assessment system. This paper reports the development of the Early Notice Pointer (ENP), a user-friendly screening device based on weighing scale technology. The ENP is designed to be used at home to provide a graphic indication and customised and evidence-based foot and posture triage. The device electronically detects and maps the bodyweight and distinct load distributions on the main areas of the feet: forefoot and rearfoot. The developed platform also presents features that assess the user’s balance, and the results are displayed as a simple numerical report and map. The technology supports data display on mobile phones and accommodates multiple measurements for monitoring. Therefore, the evaluation could be done at non-specialist and professional levels. The system has been tested to validate its accuracy, precision, and consistency. A parallel study to describe the frequency of arch types and metatarsal pressure in young adults (1034 healthy subjects) was conducted to explain the importance of self-monitoring at home for better prevention of foot arch- and posture-related conditions. The results showed the potential of the newly created platform as a screening device ready to be wirelessly connected with mobile phones and the internet for remote and personalised identification and monitoring of foot- and body balance-related conditions. The real-time interpretation of the reported physiological parameters opens new avenues toward IoT-like on-body monitoring of human physiological signals through easy-to-use devices on flexible substrates for specific versatility.
      Citation: Micromachines
      PubDate: 2022-04-27
      DOI: 10.3390/mi13050682
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 683: Deformation Analysis of Continuous
           Milling of Inconel718 Nickel-Based Superalloy

    • Authors: Xueguang Li, Yahui Wang, Liqin Miao, Wang Zhang
      First page: 683
      Abstract: As a difficult-to-process material, Inconel718 nickel-based superalloy is more and more widely used in aerospace, ocean navigation, and large-scale machinery manufacturing. Based on ABAQUS simulation software, this paper takes the milling force and temperature in the milling process of the nickel-based superalloy as the research object, and establishes the empirical formula for the prediction model of cutting force and cutting temperature based on the method of multiple linear regression. The significance of the prediction model was verified by the residual analysis method. Through data analysis, it is obtained: within a certain experimental range, the influence degrees of each milling parameter on the cutting force and cutting temperature are fz>ap>n and fz>ap≈n, respectively. The actual orthogonal cutting test was carried out on the machine tool, and the reliability and accuracy of the prediction model of cutting force, cutting temperature and tool wear amount were verified. The model formulas of the shear velocity field, shear strain field and shear strain rate field of the main shear deformation zone are constructed by using mathematical analysis methods. The influence law of cutting speed and tool rake angle on the variables of main shear zone is calculated and analyzed. Through the combination of theory and experiment, the relationship between cutting force, chip shape and machined surface quality in milling process was analyzed. Finally, with the increase in the cutting force, the serration of the chip becomes more and more serious, and the roughness of the machined surface becomes greater and greater.
      Citation: Micromachines
      PubDate: 2022-04-27
      DOI: 10.3390/mi13050683
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 684: Measuring Liquid Droplet Size in
           Two-Phase Nozzle Flow Employing Numerical and Experimental Analyses

    • Authors: Lin Jiang, Wei Rao, Lei Deng, Atilla Incecik, Grzegorz Królczyk, Zhixiong Li
      First page: 684
      Abstract: The flavoring process ensures the quality of cigarettes by endowing them with special tastes. In this process, the flavoring liquid is atomized into particles by a nozzle and mixed with the tobacco in a rotating drum. The particle size of the flavoring liquid has great influence on the atomization effect; however, limited research has addressed the quantitation of the liquid particle size in two-phase nozzle flow. To bridge this research gap, the authors of this study employed numerical and experimental techniques to explore the quantitative analysis of particle size. First, a simulation model for the flavoring nozzle was established to investigate the atomization effect under different ejection pressures. Then, an experimental test is carried out to compare the test results with the simulation results. Lastly, the influencing factors of liquid particle size in two-phase nozzle flow were analyzed to quantify particle size. The analysis results demonstrated that there was a cubic correction relationship between the simulation and experiment particle size. The findings of this study may provide a reliable reference when evaluating the atomization effect of flavoring nozzles.
      Citation: Micromachines
      PubDate: 2022-04-27
      DOI: 10.3390/mi13050684
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 685: Acoustic Wave-Driven Liquid Metal
           Expansion

    • Authors: Youngbin Hyun, Jeong-Bong Lee, Sangkug Chung, Daeyoung Kim
      First page: 685
      Abstract: In this paper, we report a volume expansion phenomenon of a liquid metal droplet naturally oxidized in an ambient environment by applying an acoustic wave. An oxidized gallium-based liquid metal droplet was placed on a paper towel, and a piezo-actuator was attached underneath it. When a liquid metal droplet was excited by acoustic wave, the volume of liquid metal was expanded due to the inflow of air throughout the oxide crack. The liquid metal without the oxide layer cannot be expanded with an applied acoustic wave. To confirm the effect of the expansion of the oxidized liquid metal droplet, we measured an expansion ratio, which was calculated by comparing the expanded size in the x (horizontal), y (vertical) axis to the initial size of the liquid metal droplet, using a high-speed camera. For various volumes of the droplet, when we applied various voltages in the range of 5~8 Vrms with 18.5~24.5 kHz using the piezo-actuator, we obtained a maximum expansion ratio of 2.4 in the x axis and 3.8 in the y axis, respectively. In addition, we investigated that the time to reach the maximum expansion in proportion to the volume size of liquid metal differed by five times from 4 s to 20 s, and that the time to maintain the maximum expansion differed from 23 s to 2.5 s, which was inversely proportional to the volume size. We also investigated the expansion ratios depending on the exposure time to the atmosphere. Finally, a circuit containing LED, which can be turned on by expanded liquid metal droplet, was demonstrated.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050685
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 686: Ultra-Thin Terahertz Deflection Device
           Based on Laser Direct Writing Graphene Oxide Paper

    • Authors: Yixin Suo, Luming Zhang, Yihang Li, Yu Wu, Jian Zhang, Qiye Wen
      First page: 686
      Abstract: In the world of terahertz bands, terahertz beam deflection has gradually attracted substantial attention, due to its great significance in wireless communications, high-resolution imaging and radar applications. In this paper, a low-reflection and fast-fabricated terahertz beam deflection device has been realized by utilizing graphene oxide paper. Using laser direct writing technology, graphene oxide has been patterned as a specific sample. The thickness of the graphene oxide-based terahertz devices is around 15–20 μm, and the processing takes only a few seconds. The experimental results show that the beam from this device can achieve 5.7° and 10.2° deflection at 340 GHz, while the reflection is 10%, which is only 1/5 of that of existing conventional devices. The proposed device with excellent performance can be quickly manufactured and applied in the fields of terahertz imaging, communication, and perception, enabling the application of terahertz technology.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050686
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 687: Flow Regulation Performance Analysis of
           Microfluidic Passive Valve for High Throughput Liquid Delivery

    • Authors: Qi Su, Weiran Chen, Weiping Chen, Zhijiang Jin, Zhenhao Lin
      First page: 687
      Abstract: A microfluidic passive valve (MPV) is important for precise flow control, and it determines the reliability of the microfluidic system. In this paper, a novel MPV capable of delivering a constant flow rate independently of inlet pressure changes is proposed. The flow rate of the MPV is adjusted by the difference between the fluid force on the upper surface of the valve core and the spring force. The constant flow rate of the MPV is maintained by automatically changing the size of the gap channel formed by the groove on the valve core and the baffle on the valve body. The nearly constant flow rate of the MPV is 6.26 mL/min, with a variation of 6.5% under the inlet pressure varied from 1.25 kPa to 3.5 kPa. In addition, the flow characteristics of the MPV are analyzed by numerical simulation. With the increase in the inlet pressure, the maximum velocity gradually increases, while the increment of the maximum velocity decreases. In the movement process of the valve core, the region of pressure drop becomes larger. This work has a certain reference value for the design and research of the MPVs with high throughput liquid delivery.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050687
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 688: Three-Dimensional Kidney-on-a-Chip
           Assessment of Contrast-Induced Kidney Injury: Osmolality and Viscosity

    • Authors: Kipyo Kim, Beomgyun Jeong, Yun-Mi Lee, Hyung-Eun Son, Ji-Young Ryu, Seokwoo Park, Jong Cheol Jeong, Ho Jun Chin, Sejoong Kim
      First page: 688
      Abstract: Increased viscosity of concentrated contrast media (CM) in the renal tubules can perturb renal hemodynamics and have a detrimental effect on tubular epithelial cells. However, the effects of viscosity on contrast-induced nephropathy (CIN) remain poorly understood. Conventional in vitro culture studies do not reflect the rheological properties of CM. Therefore, we investigated the effects of CM viscosity on renal tubules using a kidney-on-a-chip and two different types of CM. Renal proximal tubule epithelial cells (RPTEC) were cultured in a three-dimensional microfluidic culture platform under bidirectional fluid shear stress. We treated the RPTEC with two types of CM: low- (LOCM, iopromide) and iso-osmolar contrast media (IOCM, iodixanol). Renal tubular cell injury induced by LOCM and IOCM was examined under different iodine concentrations (50–250 mgI/mL) and shear-stress conditions. LOCM showed a significant dose-dependent cytotoxic effect, which was significantly higher than that of IOCM under static and low-to-moderate shear stress conditions. However, high shear-stress resulted in reduced cell viability in IOCM; no difference between IOCM and LOCM was found under high shear-stress conditions. The cytotoxic effects were pronounced at a mean shear stress of 1 dyn/cm2 or higher. The high viscosity of IOCM slowed the fluid flow rate and augmented fluid shear-stress. We suggest an alternative in vitro model of CIN using the three-dimensional kidney-on-a-chip. Our results indicate a vital role of viscosity-induced nephrotoxicity under high shear-stress conditions, contrary to the findings of conventional in vitro studies.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050688
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 689: High Sensitivity Optical Fiber
           Mach–Zehnder Refractive Index Sensor Based on Waist-Enlarged Bitaper
           

    • Authors: Na Zhao, Zelin Wang, Zhongkai Zhang, Qijing Lin, Kun Yao, Fuzheng Zhang, Yunjing Jiao, Libo Zhao, Bian Tian, Ping Yang, Zhuangde Jiang
      First page: 689
      Abstract: A Mach–Zehnder fiber optic sensor with high refractive index response sensitivity was developed. By fabricating a waist-enlarged bitaper structure on the interference arm of a single mode–multimode–single mode (SMS) Mach–Zehnder interferometer (MZI), the spectral contrast and response sensitivity were improved. Subsequently, the response sensitivity was further improved by etching the interference arm. When a beam of light was introduced into the sensor, due to the structural mismatch between the multimode fiber and the normal transmission light, the difference between the low-order mode and the high-order mode was generated in the fiber core and the fiber cladding. In the process of transmission in the sensing arm, due to the different refractive indices of the core and cladding, the optical path difference of the high-order mode and the low-order mode was different, which eventually generated interference fringes. The experimentally measured response sensitivity of SMS MZI in the range of 1.351 RIU to 1.402 RIU is 57.623 nm/RIU; the response sensitivity of a single mode–multimode–bitaper–multimode–single mode (SMBMS) MZI is 61.607 nm/RIU; and the response sensitivity of the etched SMBMS (ESMBMS) MZI is 287.65 nm/RIU. The response sensitivity of the new ESMBMS MZI is three times higher than that of the original SMS MZI. The sensor has the characteristics of compact structure, high sensitivity, easy manufacture, and a wide range of refractive index measurements, and can be used in food processing, pharmaceutical manufacturing and other fields.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050689
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 690: Reversible Thermo-Responsive Valve for
           Microfluidic Paper-Based Analytical Devices

    • Authors: Hiroki Toda, Wataru Iwasaki, Nobutomo Morita, Taisei Motomura, Kenshin Takemura, Masaya Nagano, Yoshitaka Nakanishi, Yuta Nakashima
      First page: 690
      Abstract: Fluid control on a paper channel is necessary for analysis with multiple reagents, such as enzyme-linked immunosorbent assay (ELISA) in microfluidic paper-based analytical devices (µPADs). In this study, a thermo-responsive valve was fabricated by polymerizing N-isopropylacrylamide on a PVDF porous membrane by plasma-induced graft polymerization. The polymerized membrane was observed by scanning electron microscopy (SEM), and it was confirmed that more pores were closed at temperatures below 32 °C and more pores were opened at temperatures above 32 °C. Valve permeability tests confirmed that the proposed polymerized membrane was impermeable to water and proteins at temperatures below 32 °C and permeable to water at temperatures above 32 °C. The valve could also be reversibly and repeatedly opened and closed by changing the temperature near 32 °C. These results suggest that plasma-induced graft polymerization may be used to produce thermo-responsive valves that can be opened and closed without subsequent loss of performance. These results indicate that the thermo-responsive valve fabricated by plasma-induced graft polymerization could potentially be applied to ELISA with µPADs.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050690
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 691: Cost-Efficient Approaches for
           

    • Authors: Alexandru Dinu, Gabriel Mihail Danciu, Petre Lucian Ogrutan
      First page: 691
      Abstract: Digital integrated circuits play an important role in the development of new information technologies and support Industry 4.0 from a hardware point of view. There is great pressure on electronics companies to reduce the time-to-market for product development as much as possible. The most time-consuming stage in hardware development is functional verification. As a result, many industry and academic stakeholders are investing in automating this crucial step in electronics production. The present work aims to automate the functional verification process by means of genetic algorithms that are used for generating the relevant input stimuli for full simulation of digital design behavior. Two important aspects are pursued throughout the current work: the implementation of genetic algorithms must be time-worthy compared to the application of the classical constrained-driven generation and the verification process must be implemented using tools accessible to a wide range of practitioners. It is demonstrated that for complex designs, functional verification powered by the use of genetic algorithms can go beyond the classical method of performing verification, which is based on constrained-random stimulus generation. The currently proposed methods were able to generate several sets of highly performing stimuli compared to the constraint-random stimulus generation method, in a ratio ranging from 57:1 to 205:1. The performance of the proposed approaches is comparable to that of the well-known NSGA-II and SPEA2 algorithms.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050691
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 692: Polysaccharide Layer-by-Layer Coating
           for Polyimide-Based Neural Interfaces

    • Authors: Eugenio Redolfi Redolfi Riva, Angela D’Alessio, Silvestro Micera
      First page: 692
      Abstract: Implantable flexible neural interfaces (IfNIs) are capable of directly modulating signals of the central and peripheral nervous system by stimulating or recording the action potential. Despite outstanding results in acute experiments on animals and humans, their long-term biocompatibility is hampered by the effects of foreign body reactions that worsen electrical performance and cause tissue damage. We report on the fabrication of a polysaccharide nanostructured thin film as a coating of polyimide (PI)-based IfNIs. The layer-by-layer technique was used to coat the PI surface due to its versatility and ease of manufacturing. Two different LbL deposition techniques were tested and compared: dip coating and spin coating. Morphological and physiochemical characterization showed the presence of a very smooth and nanostructured thin film coating on the PI surface that remarkably enhanced surface hydrophilicity with respect to the bare PI surface for both the deposition techniques. However, spin coating offered more control over the fabrication properties, with the possibility to tune the coating’s physiochemical and morphological properties. Overall, the proposed coating strategies allowed the deposition of a biocompatible nanostructured film onto the PI surface and could represent a valid tool to enhance long-term IfNI biocompatibility by improving tissue/electrode integration.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050692
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 693: Modeling of Key Specifications for RF
           Amplifiers Using the Extreme Learning Machine

    • Authors: Shaohua Zhou, Cheng Yang, Jian Wang
      First page: 693
      Abstract: The amplifier is a key component of the radio frequency (RF) front-end, and its specifications directly determine the performance of the system in which it is located. Unfortunately, amplifiers’ specifications degrade with temperature and even lead to system failure. To study how the system failure is affected by the amplifier specification degradation, it is necessary to couple the amplifier specification degradation into the system optimization design. Furthermore, to couple the amplifier specification degradation into the optimal design of the system, it is necessary to model the characteristics of the amplifier specification change with temperature. In this paper, the temperature characteristics of two amplifiers are modeled using an extreme learning machine (ELM), and the results show that the model agrees well with the measurement results and can effectively reduce measurement time and cost.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050693
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 694: Flexible Wearable Pressure Sensor Based
           on Collagen Fiber Material

    • Authors: Zhiqing Peng, Shijie Zheng, Xia Zhang, Junlong Yang, Shizhou Wu, Chen Ding, Lei Lei, Lei Chen, Guoying Feng
      First page: 694
      Abstract: Flexible wearable pressure sensors play a pivotal role in healthcare monitoring, disease prevention, and humanmachine interactions. However, their narrow sensing ranges, low detection sensitivities, slow responses, and complex preparation processes restrict their application in smart wearable devices. Herein, a capacitive pressure sensor with high sensitivity and flexibility that uses an ionic collagen fiber material as the dielectric layer is proposed. The sensor exhibits a high sensitivity (5.24 kPa−1), fast response time (40 ms), long-term stability, and excellent repeatability over 3000 cycles. Because the sensor is resizable, flexible, and has a simple preparation process, it can be flexibly attached to clothes and the human body for wearable monitoring. Furthermore, the practicality of the sensor is proven by attaching it to different measurement positions on the human body to monitor the activity signal.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050694
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 695: Enhanced Light Output Power on
           Near-Infrared Light-Emitting Diodes with TITO/Ag Multilayer Reflector

    • Authors: Hyung-Joo Lee, In-Kyu Jang, Dae-Kwang Kim, Yu-Jung Cha, Sung Woon Cho
      First page: 695
      Abstract: A titanium–indium tin oxide (TITO) multilayer reflector was investigated to improve the light efficiency of high-power, near-infrared, light-emitting diodes (NIR-LEDs). The TITO/Ag was fabricated by combining a patterned TITO and an omnidirectional reflector (ODR). For fabricating a high-power NIR-LED, the wafer bond process required the TITO reflective structure, which has patterns filled by AlAu contact metal, bonded directly to the Ag reflector deposited on the silicon wafer. Among Ag-based single- and multilayer reflectors, the TITO/Ag showed the highest reflectance (R = 96%), which was favorable for wafer-bonded high-power NIR-LEDs. Therefore, the TITO/Ag reflector enabled the production of wafer-bonded NIR-LED chips that exhibit superior output performance (190 mW) compared with conventional cases using a single Ag reflector.
      Citation: Micromachines
      PubDate: 2022-04-28
      DOI: 10.3390/mi13050695
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 696: Self-Tuning Control Using an
           Online-Trained Neural Network to Position a Linear Actuator

    • Authors: Rodrigo Hernandez-Alvarado, Omar Rodriguez-Abreo, Juan Manuel Garcia-Guendulain, Teresa Hernandez-Diaz
      First page: 696
      Abstract: Linear actuators are widely used in all kinds of industrial applications due to being devices that convert the rotation motion of motors into linear or straight traction/thrust motion. These actuators are ideal for all types of applications where inclination, lifting, traction, or thrust is required under heavy loads, such as wheelchairs, medical beds, and lifting tables. Due to the remarkable ability to exert forces and good precision, they are used classic control systems and controls of high-order. Still, they present difficulties in changing their dynamics and are designed for a range of disturbances. Therefore, in this paper, we present the study of an electric linear actuator. We analyze the positioning in real-time and attack the sudden changes of loads and limitation range by the control. It uses a general-purpose control with self-tuning gains, which can deal with the essential uncertainties of the actuator and suppress disturbances, as they can change their weights to interact with changing systems. The neural network combined with PID control compensates the simplicity of this type of control with artificial intelligence, making it robust to drastic changes in its parameters. Unlike other similar works, this research proposes an online training network with an advantage over typical neural self-adjustment systems. All of this can also be dispensed with the engine model for its operation. The results obtained show a decrease of 42% in the root mean square error (RMSE) during trajectory tracking and saving in energy consumption by 25%. The results were obtained both in simulation and in real tests.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050696
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 697: The Cause of Ribbon Fluctuation in
           Magnetorheological Finishing and Its Influence on Surface Mid-Spatial
           Frequency Error

    • Authors: Bo Wang, Feng Shi, Guipeng Tie, Wanli Zhang, Ci Song, Ye Tian, Yongxiang Shen
      First page: 697
      Abstract: In the high-power laser system, the mid-spatial frequency error of the surface of the high-power laser component will affect the normal operation of the high-power laser system. In order to improve the mid-spatial frequency error of the high-power laser component after magnetorheological finishing, the causes and influencing factors of the ribbon fluctuation in magnetorheological finishing are studied, and the influence of different ribbon fluctuation on the mid-spatial frequency error of the surface is studied. Firstly, the influence of different ribbon fluctuations on the mid-spatial frequency error of the machined surface is simulated by a computer. Secondly, the magnetic field in the circumferential direction of the polishing wheel, the fluctuation amount and frequency of the magnetorheological polishing ribbon are measured, and then the causes of the fluctuation of the magnetorheological polishing ribbon are analyzed. Moreover, through the principle of a single variable, the influence of process parameters on the fluctuation of magnetorheological polishing ribbon is explored. Finally, the fused silica component is scanned uniformly under the process parameters of magnetorheological polishing ribbon fluctuation of 40 μm, 80 μm, 150 μm, and 200 μm. The experimental results show that the greater the ribbon fluctuation, the greater the surface mid-spatial frequency error of the component, and the ribbon fluctuation is approximately linear with the RMS of the PSD2 in the mid-spatial frequency band on the surface of the component. Therefore, the fluctuation of the ribbon can be controlled by controlling the magnetorheological processing parameters, and the mid-spatial frequency band error on the surface of the high-power laser component can be significantly reduced by optimizing process parameters after magnetorheological finishing.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050697
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 698: Identification of Preisach Model
           Parameters Based on an Improved Particle Swarm Optimization Method for
           Piezoelectric Actuators in Micro-Manufacturing Stages

    • Authors: Lei Yang, Bingxiao Ding, Wenhu Liao, Yangmin Li
      First page: 698
      Abstract: The Preisach model is a typical scalar mathematical model used to describe the hysteresis phenomena, and it attracts considerable attention. However, parameter identification for the Preisach model remains a challenging issue. In this paper, an improved particle swarm optimization (IPSO) method is proposed to identify Preisach model parameters. Firstly, the Preisach model is established by introducing a Gaussian−Gaussian distribution function to replace density function. Secondly, the IPSO algorithm is adopted to Fimplement the parameter identification. Finally, the model parameter identification results are compared with the hysteresis loop of the piezoelectric actuator. Compared with the traditional Particle Swarm Optimization (PSO) algorithm, the IPSO algorithm demonstrates faster convergence, less calculation time and higher calculation accuracy. This proposed method provides an efficient approach to model and identify the Preisach hysteresis of piezoelectric actuators.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050698
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 699: Microstructure and Wear of
           W-Particle-Reinforced Al Alloys Prepared by Laser Melt Injection

    • Authors: Zhidong Xu, Dengzhi Wang, Wenji Song, Congwen Tang, Pengfei Sun, Jiaxing Yang, Qianwu Hu, Xiaoyan Zeng
      First page: 699
      Abstract: W-particle-reinforced Al alloys were prepared on a 7075 aluminum alloy surface via laser melt injection to improve their wear resistance, and the microstructure, microhardness, and wear resistance of the W/Al layers were studied. Scanning electron microscopy (SEM) results confirmed that a W/Al laser melting layer of about 1.5 mm thickness contained W particles, and Al4W was formed on the surface of the Al alloys. Due to the reinforcement of the W particles and good bonding of the W and Al matrix, the melting layer showed excellent wear resistance compared to that of Al alloys.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050699
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 700: Design of Quad-Band Bandpass Filter
           Using Dual-Mode SLRs and Coupled-Line for DCS/WLAN/WiMAX and 5G
           Applications

    • Authors: Sugchai Tantiviwat, Siti Zuraidah Ibrahim, Mohammad Shahrazel Razalli, Ping Jack Soh
      First page: 700
      Abstract: A design of a microstrip quad-band BPF with flexibly controlled bandwidth is presented in this paper. Two dual-mode short-circuited SLRs with a common via-hole are proposed, which are utilized to obtain the first and second passband, while the third passband is generated by implementing the second-order half-wavelength coupled-line resonator. Another dual-mode open-circuited SLR can be operated at the fourth passband. The proposed quad-band BPF is centered at 1.80/2.45/3.50/4.90 GHz for DCS/WLAN/WiMAX and 5G applications. By appropriately choosing the lengths of the four sets of resonators, all passbands can be fully varied independently with minimal effect on other passbands. Moreover, the bandwidth of each passband can be flexibly controlled by tuning the coupling parameters. The dimension of the fabricated proposed filter is about 0.12 × 0.20 λg, indicating the compactness of the design, whereas the measurements are in good agreement with the simulated results. The measured S11 are at least 12 dB in the four passbands. The passbands S21 are approximately 0.65, 1.42, 0.78, and 1.20 dB, which exhibit low insertion loss at the passband frequency of the first, second, third, and fourth passband, respectively.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050700
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 701: Flux Pinning Properties of Single-Grain
           Bulk GdBCO Superconductors Processed by Different Thicknesses of Y123
           Liquid Source

    • Authors: Yufeng Zhang, Ziwei Lou, Penghe Zhang, Chunyan Li, Jiaying Zhang, Xiaojuan Zhang
      First page: 701
      Abstract: The performance of critical current density of GdBa2Cu3O7−δ (GdBCO or Gd123) superconductor bulk has an important influence on its practical applications. In this work, four single-domain GdBCO superconductor bulks were successfully processed by the modified top-seeded melt-texture growth method. The addition of a YBa2Cu3O7−δ (Y123) liquid source with different thicknesses, 0 mm (S0), 3 mm(S3), 5 mm (S5), 7 mm (S7), was introduced to study the influence on the superconducting properties. GdBCO bulk with the addition of the Y123 liquid source with a 3-mm thickness shows the best superconducting properties. The addition of the Y123 liquid source results in a decrease in the Gd3+ ion concentration required for Gd123 growth; thus, Gd2BaCuO5 (Gd211) particles in the liquid source need a larger self-decomposition to diffuse Gd3+ ions to Gd123 growth front, which refines the size and leads to a homogenous distribution of the Gd211 particles in the bulks. Thus, the more pinning centers of fined Gd211 particles improve the superconducting properties of GdBCO bulk. With increases in the thickness of Y123 liquid source to 5 mm and 7 mm, high RE3+ (Gd3+ and Y3+) concentration can coarsen Gd211 particles and fuse with Gd211 liquid source. The superconducting properties apparently drop. Therefore, the addition of a Y123 liquid source with a suitable thickness is a positive modification to obtain high-performance GdBCO bulk.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050701
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 702: Optimization AlGaN/GaN HEMT with Field
           Plate Structures

    • Authors: Ningping Shi, Kejia Wang, Bing Zhou, Jiafu Weng, Zhiyuan Cheng
      First page: 702
      Abstract: AlGaN/GaN HEMTs with several different designs of field plate structure are studied for device optimization purposes. To increase device breakdown voltage, optimal dimensions of field plates were first investigated using Silvaco TCAD software, and the electrical characteristics of the devices are analyzed. Several devices were designed and fabricated based on the simulation results. It has been confirmed that the gate-source composite field plate (SG-FP) has a higher breakdown voltage than other types of field plate structures, with FOM reaches 504 MW/cm−2, showing that the device with SG-FP structure outperforms the other three structures. The experiment and simulation verify that the gate-source composite field plate optimizes FOM by increasing the breakdown voltage and reducing the intrinsic on-resistance so that the device has better electrical performance and a wider application range.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050702
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 703: Toward an Accurate IR Remote Sensing of
           Body Temperature Radiometer Based on a Novel IR Sensing System Dubbed
           Digital TMOS

    • Authors: Moshe Avraham, Jonathan Nemirovsky, Tanya Blank, Gady Golan, Yael Nemirovsky
      First page: 703
      Abstract: A novel uncooled thermal sensor based on a suspended transistor, fabricated in standard CMOS-SOI process, and released by dry etching, dubbed Digital TMOS, has been developed. Using the transistor as the sensing element has advantages in terms of internal gain, low power, low-cost technology, and high temperature sensitivity. A two channel radiometer, based on the new nano-metric CMOS-SOI-NEMS Technology, enables remote temperature sensing as well as emissivity sensing of the forehead and body temperatures of people, with high accuracy and high resolution. Body temperature is an indicator of human physiological activity and health, especially in pediatrics, surgery, and general emergency departments. This was already recognized in past pandemics such as SARS, EBOLA, and Chicken Flu. Nowadays, with the spread of COVID-19, forehead temperature measurements are used widely to screen people for the illness. Measuring the temperature of the forehead using remote sensing is safe and convenient and there are a large number of available commercial instruments, but studies show that the measurements are not accurate. The surface emissivity of an object has the most significant effect on the measured temperature by IR remote sensing. This work describes the achievements towards high–performance, low-cost, low power, mobile radiometry, to rapidly screen for fever to identify victims of the coronavirus (COVID-19). The main two aspects of the innovation of this study are the use of the new thermal sensor for measurements and the extensive modeling of this sensor.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050703
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 704: Electrochemical Deposition of
           Pure-Nickel Microstructures with Controllable Size

    • Authors: Xiaolei Bi, Lingchao Meng
      First page: 704
      Abstract: Pure nickel microstructures have been widely used in MEMS and have great application potential as a sacrificial mandrel for fabricating terahertz micro-cavity components. The performance of MEMS and terahertz micro-cavity components can be significantly improved through the use of high-quality pure nickel microstructures. Up to now, microfabrication techniques, such as laser micromachining, wire electrical-discharge machining, and cold-spray additive manufacturing, have been used to machine various types of such microstructures. However, huge challenges are involved in using these micromachining techniques to fabricate pure-nickel microstructures with controllable size and good dimensional accuracy, surface roughness, and edge radius. In this paper, taking the example of a pure-nickel rectangular mandrel that corresponds to the size of the end face of a 1.7-THz rectangular waveguide cavity, the machining processes for the electrochemical deposition of pure-nickel microstructures with controllable size, high dimensional accuracy, and good surface roughness and edge radius are discussed systematically. This proposed method can be used to manufacture various types of high-quality pure-nickel microstructures.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050704
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 705: Simulation Design of Surface Acoustic
           Wave Sensor Based on Langasite Coplanar Integration with Multiple
           Parameters

    • Authors: Xiaorui Liang, Yongwei Zhang, Fangmeng Xu, Qiulin Tan, Juan Zhang
      First page: 705
      Abstract: In the harsh environment of high temperature and high rotation, a single parameter is difficult to satisfy the multi-parameter test requirements of aerospace metallurgy. Therefore, a multi-parameter coplanar integrated surface acoustic wave (SAW) sensor based on Langasite (LGS) is proposed. In this paper, the optimal cut for different measurement parameters is analyzed, and the optimal cut to temperature, pressure and vibration are obtained. The simulation results show that (0°, 138.5°, 25°) LGS has superior second-order temperature sensitivity, the edge of the rectangular sealed cavity is more suitable for pressure sensors, and the optimal cut is (0°, 138.5°, 30°). The stress of the vibration sensor cantilever beam is mainly concentrated on the edge of the fixed end, and the optimal cut is (0°, 138.5°, 35°). Based on the optimal sensitive tangential direction of each sensitive element and the symmetry of the Langasite wafer, the reasonable layout of the coplanar integrated structure with the three parameters of temperature, pressure and vibration is determined. Moreover, according to the optimal orientation selection and reasonable structure layout of each parameter, combined with frequency separation rules, the parameters of interdigital electrode were determined, and the idea of multi-parameter integrated design was simulated and verified.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050705
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 706: Microfluidic Paper-Based Blood Plasma
           Separation Device as a Potential Tool for Timely Detection of Protein
           Biomarkers

    • Authors: Francisco Burgos-Flórez, Alexander Rodríguez, Eliana Cervera, Marcio De Ávila, Marco Sanjuán, Pedro J. Villalba
      First page: 706
      Abstract: A current challenge regarding microfluidic paper-based analytical devices (µPAD) for blood plasma separation (BPS) and electrochemical immunodetection of protein biomarkers is how to achieve a µPAD that yields enough plasma to retain the biomarker for affinity biosensing in a functionalized electrode system. This paper describes the development of a BPS µPAD to detect and quantify the S100B biomarker from peripheral whole blood. The device uses NaCl functionalized VF2 filter paper as a sample collection pad, an MF1 filter paper for plasma retention, and an optimized microfluidic channel geometry. An inverted light microscope, scanning electron microscope (SEM), and image processing software were used for visualizing BPS efficiency. A design of experiments (DOE) assessed the device’s efficacy using an S100B ELISA Kit to measure clinically relevant S100B concentrations in plasma. The BPS device obtained 50 μL of plasma from 300 μL of whole blood after 3.5 min. The statistical correlation of S100B concentrations obtained using plasma from standard centrifugation and the BPS device was 0.98. The BPS device provides a simple manufacturing protocol, short fabrication time, and is capable of S100B detection using ELISA, making one step towards the integration of technologies aimed at low-cost POC testing of clinically relevant biomarkers.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050706
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 707: Variable Range Hopping Model Based on
           Gaussian Disordered Organic Semiconductor for Seebeck Effect in
           Thermoelectric Device

    • Authors: Ying Zhao, Jiawei Wang
      First page: 707
      Abstract: We investigate the carrier concentration dependent Seebeck coefficient in Gaussian disordered organic semiconductors (GD-OSs) for thermoelectric device applications. Based on the variable-range hopping (VRH) theory, a general model predicting the Seebeck effect is developed to reveal the thermoelectric properties in GD-OSs. The proposed model could interpret the experimental data on carrier concentration- and temperature-dependence of the Seebeck coefficient, including various kinds of conducting polymer film and small molecule based field-effect transistors (FETs). Compared with the conventional Mott’s VRH and mobility edge model, our model has a much better description of the relationship between the Seebeck coefficient and conductivity. The model could deepen our insight into charge transport in organic semiconductors and provide instructions for the optimization of thermoelectric device performance in a disordered system.
      Citation: Micromachines
      PubDate: 2022-04-29
      DOI: 10.3390/mi13050707
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 708: Numerical Modelling of Mixing in a
           

    • Authors: Mesuli B. Mbanjwa, Kevin Harding, Irvy M. A. Gledhill
      First page: 708
      Abstract: Droplets generated in microfluidic channels are effective self-contained micromixers and micro-reactors for use in a multiplicity of chemical synthesis and bioanalytical applications. Droplet microfluidic systems have the ability to generate multitudes of droplets with well-defined reagent volumes and narrow size distributions, providing a means for the replication of mixing within each droplet and thus the scaling of processes. Numerical modelling using computational fluid dynamics (CFD) is a useful technique for analysing and understanding the internal mixing in microfluidic droplets. We present and demonstrate a CFD method for modelling and simulating mixing between two species within a droplet travelling in straight microchannel, using a two-phase moving frame of reference approach. Finite element and level set methods were utilised to solve the equations governing the coupled physics between two-phase flow and mass transport of the chemical species. This approach had not been previously demonstrated for the problem of mixing in droplet microfluidics and requires less computational resources compared to the conventional fixed frame of reference approach. The key conclusions of this work are: (1) a limitation of this method exists for flow conditions where the droplet mobility approaches unity, due to the moving wall boundary condition, which results in an untenable solution under those conditions; (2) the efficiency of the mixing declines as the length of the droplet or plug increases; (3) the initial orientation of the droplet influences the mixing and the transverse orientation provides better mixing performance than the axial orientation and; (4) the recirculation inside the droplet depends on the superficial velocity and the viscosity ratio.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050708
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 709: Advances and Challenges in
           Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes

    • Authors: Xiaojie Jiang, Zhen Fan, Li Luo, Lishuang Wang
      First page: 709
      Abstract: Light-emitting diodes based on colloidal quantum dots (QLEDs) show a good prospect in commercial application due to their narrow spectral linewidths, wide color range, excellent luminance efficiency, and long operating lifetime. However, the toxicity of heavy-metal elements, such as Cd-based QLEDs or Pb-based perovskite QLEDs, with excellent performance, will inevitably pose a serious threat to people’s health and the environment. Among heavy-metal-free materials, InP quantum dots (QDs) have been paid special attention, because of their wide emission, which can, in principle, be tuned throughout the whole visible and near-infrared range by changing their size, and InP QDs are generally regarded as one of the most promising materials for heavy-metal-free QLEDs for the next generation displays and solid-state lighting. In this review, the great progress of QLEDs, based on the fundamental structure and photophysical properties of InP QDs, is illustrated systematically. In addition, the remarkable achievements of QLEDs, based on their modification of materials, such as ligands exchange of InP QDs, and the optimization of the charge transport layer, are summarized. Finally, an outlook is shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance. This review provides an overview of the recent developments of InP QLED applications and outlines the challenges for achieving the high-performance devices.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050709
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 710: Experimental Investigation of Grinding
           Force and Material Removal Mechanism of Laser-Structured Zirconia Ceramics
           

    • Authors: Jingzhu Pang, Xia Ji, Yan Niu, Shaojun Chen
      First page: 710
      Abstract: Zirconia is a high demanded structural ceramic with desirable mechanical, thermal, and chemical properties. Poor surface integrity and limited material removal rate caused by high cutting force and wheel wear are the main problems in ceramic grinding. In order to reduce the grinding force and enhance the removal rate in grinding, zirconia ceramics are firstly ablated by laser and then be grinded. A nanosecond laser is used to ablate the surface of zirconia ceramic, the laser-ablated structures with micro pits and thermal microcracks are generated. With the input of subsequent grinding, the machinability of zirconia ceramic workpiece with laser-ablated structures changes. Grinding experiments are conducted to study the grinding force and the material remove of laser-structured zirconia ceramic. Results show that the grinding forces in tangential and normal direction are significantly reduced. Compared to the grinding surface without laser-structured, a damage-free grinding surface is obtained by laser assistance.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050710
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 711: Omnidirectional Manipulation of
           Microparticles on a Platform Subjected to Circular Motion Applying Dynamic
           Dry Friction Control

    • Authors: Sigitas Kilikevičius, Kristina Liutkauskienė, Ernestas Uldinskas, Ribal El Banna, Algimantas Fedaravičius
      First page: 711
      Abstract: Currently used planar manipulation methods that utilize oscillating surfaces are usually based on asymmetries of time, kinematic, wave, or power types. This paper proposes a method for omnidirectional manipulation of microparticles on a platform subjected to circular motion, where the motion of the particle is achieved and controlled through the asymmetry created by dynamic friction control. The range of angles at which microparticles can be directed, and the average velocity were considered figures of merit. To determine the intrinsic parameters of the system that define the direction and velocity of the particles, a nondimensional mathematical model of the proposed method was developed, and modeling of the manipulation process was carried out. The modeling has shown that it is possible to direct the particle omnidirectionally at any angle over the full 2π range by changing the phase shift between the function governing the circular motion and the dry friction control function. The shape of the trajectory and the average velocity of the particle depend mainly on the width of the dry friction control function. An experimental investigation of omnidirectional manipulation was carried out by implementing the method of dynamic dry friction control. The experiments verified that the asymmetry created by dynamic dry friction control is technically feasible and can be applied for the omnidirectional manipulation of microparticles. The experimental results were consistent with the modeling results and qualitatively confirmed the influence of the control parameters on the motion characteristics predicted by the modeling. The study enriches the classical theories of particle motion on oscillating rigid plates, and it is relevant for the industries that implement various tasks related to assembling, handling, feeding, transporting, or manipulating microparticles.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050711
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 712: Microstructure and Corrosion Behavior
           of Iron Based Biocomposites Prepared by Laser Additive Manufacturing

    • Authors: Yan Zhou, Lifeng Xu, Youwen Yang, Jingwen Wang, Dongsheng Wang, Lida Shen
      First page: 712
      Abstract: Iron (Fe) has attracted great attention as bone repair material owing to its favorable biocompatibility and mechanical properties. However, it degrades too slowly since the corrosion product layer prohibits the contact between the Fe matrix and body fluid. In this work, zinc sulfide (ZnS) was introduced into Fe bone implant manufactured using laser additive manufacturing technique. The incorporated ZnS underwent a disproportionation reaction and formed S-containing species, which was able to change the film properties including the semiconductivity, doping concentration, and film dissolution. As a result, it promoted the collapse of the passive film and accelerated the degradation rate of Fe matrix. Immersion tests proved that the Fe matrix experienced severe pitting corrosion with heavy corrosion product. Besides, the in vitro cell testing showed that Fe/ZnS possessed acceptable cell viabilities. This work indicated that Fe/ZnS biocomposite acted as a promising candidate for bone repair material.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050712
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 713: Partitioning of Small Hydrophobic
           Molecules into Polydimethylsiloxane in Microfluidic Analytical Devices

    • Authors: Patrícia M. Rodrigues, Miguel Xavier, Victor Calero, Lorenzo Pastrana, Catarina Gonçalves
      First page: 713
      Abstract: Polydimethylsiloxane (PDMS) is ubiquitously used in microfluidics. However, PDMS is porous and hydrophobic, potentially leading to small molecule partitioning. Although many studies addressed this issue and suggested surface/bulk modifications to overcome it, most were not quantitative, did not address which variables besides hydrophobicity governed molecule absorption, and no modification has been shown to completely obviate it. We evaluated qualitatively (confocal microscopy) and quantitatively (fluorescence spectroscopy) the effects of solute/solvent pairings, concentration, and residence time on molecule partitioning into PDMS. Additionally, we tested previously reported surface/bulk modifications, aiming to determine whether reduced PDMS hydrophobicity was stable and hindered molecule partitioning. Partitioning was more significant at lower concentrations, with the relative concentration of rhodamine-B at 20 µM remaining around 90% vs. 10% at 1 µM. Solute/solvent pairings were demonstrated to be determinant by the dramatically higher partitioning of Nile-red in a PBS-based solvent as opposed to ethanol. A paraffin coating slightly decreased the partitioning of Nile-red, and a sol–gel modification hindered the rhodamine-B diffusion into the PDMS bulk. However, there was no direct correlation between reduced surface hydrophobicity and molecule partitioning. This work highlighted the need for pre-assessing the absorption of test molecules into the microfluidic substrates and considering alternative materials for fabrication.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050713
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 714: Antenna Current Calculation Based on
           Equivalent Transmission Line Model

    • Authors: Shusheng Wei, Wusong Wen
      First page: 714
      Abstract: This paper provides a new way for spatial current/field profiles for frequency-selective surface analytical approximation. It confirms that the per unit length radiation resistance of an equivalent transmission line model for line antenna has little influence on the normalized current distribution. The two-wire equivalent transmission line model (typically used for transmitting line antenna) is applied to the receiving line antenna. In this case, the corresponding incident field is decomposed into odd and even mode for asymmetric distribution. A one-wire equivalent transmission line model is then introduced for any antenna composed of relative narrow strips. The incident field does not need to be decomposed. According to the simulation, the transmission line loss has little influence on the current distribution.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050714
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 715: Vanadium Dioxide-Based Terahertz
           Metamaterial Devices Switchable between Transmission and Absorption

    • Authors: Haoqing Jiang, Yue Wang, Zijian Cui, Xiaoju Zhang, Yongqiang Zhu, Kuang Zhang
      First page: 715
      Abstract: Terahertz metamaterial plays a significant role in the development of imaging, sensing, and communications. The function of conventional terahertz metamaterials was fixed after fabrication. They can only achieve a single function and do not have adjustable characteristics, which greatly limits the scalability and practical application of metamaterial. Here, we propose a vanadium dioxide-based terahertz metamaterial device, which is switchable between being a transmitter and an absorber. The transmission and absorption characteristics and temperature tunable properties of phase change metamaterials in the terahertz band were investigated. As the temperature of vanadium dioxide is varied between 20 °C and 80 °C, the device can switch between transmission and quad-band resonance absorption at the terahertz frequency range, with a high transmission rate of over 80% and a peak absorbance of 98.3%, respectively. In addition, when the device acts as an absorber, the proposed metamaterial device is tunable, and the modulation amplitude can reach 94.3%; while the device is used as a transmissive device, the modulation amplitude of the transmission peak at 81%. The results indicate that the proposed metamaterial device can promote the applications of terahertz devices, such as switching, modulation, and sensing.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050715
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 716: Lane-GAN: A Robust Lane Detection
           Network for Driver Assistance System in High Speed and Complex Road
           Conditions

    • Authors: Yan Liu, Jingwen Wang, Yujie Li, Canlin Li, Weizheng Zhang
      First page: 716
      Abstract: Lane detection is an important and challenging part of autonomous driver assistance systems and other advanced assistance systems. The presence of road potholes and obstacles, complex road environments (illumination, occlusion, etc.) are ubiquitous, will cause the blur of images, which is captured by the vision perception system in the lane detection task. To improve the lane detection accuracy of blurred images, a network (Lane-GAN) for lane line detection is proposed in the paper, which is robust to blurred images. First, real and complex blur kernels are simulated to construct a blurred image dataset, and the improved GAN network is used to reinforce the lane features of the blurred image, and finally the feature information is further enriched with a recurrent feature transfer aggregator. Extensive experimental results demonstrate that the proposed network can get robust detection results in complex environments, especially for blurred lane lines. Compared with the SOTA detector, the proposed detector achieves a larger gain. The proposed method can enhance the lane detail features of the blurred image, improving the detection accuracy of the blurred lane effectively, in the driver assistance system in high speed and complex road conditions.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050716
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 717: Latest Performance Improvement
           Strategies and Techniques Used in 5G Antenna Designing Technology, a
           Comprehensive Study

    • Authors: Iftikhar Ahmad, Wenhao Tan, Qasim Ali, Houjun Sun
      First page: 717
      Abstract: In the recent era, fifth-generation technology (5G) has not been fully implemented in the realm of wireless communication. To Have excellent accessible bandwidth feasibility, and in order to achieve the aims of 5G standards, such as higher data rates and ultrahigh-definition video streaming, the millimeter wave (mmWave) band must be employed. Services with minimal latency and many other features are feasible only in the mmWave spectrum. To avoid numerous communication complexities such as high connection losses, short wavelength, and restricted bandwidth, as well as path-loss challenges in the mmWave range, an antenna with wide bandwidth, high gain, narrow steerable beam, high isolation, low side-lobe levels, and multiband features is required to alleviate these difficulties and meet 5G communication standards. To overcome these challenges, specific strategies and techniques should be employed in the traditional antenna designing procedure to excellently improve the performance of the antenna in terms of bandwidth, gain, and efficiency and to reduce the mutual coupling effect between the closely colocated antenna elements in MIMOs and arrays. The researchers reported on a variety of bandwidth and gain improvement approaches. To gain broader coverage, traditional antenna design techniques must be modified. In this study, the latest state-of-the-art work is reviewed, such as the role of the metamaterials (MMTs), parasitic patches, hybrid feeding, EBG structure, impact of the slots with different geometrical shapes in the radiator to achieve the goal of wide bandwidth, boosted gain, reduced side-lobes level, as well as stable radiation properties. Mutual coupling reduction techniques are also briefly reported. The role of reconfigurability is focused on in this study, and at the end, the future challenges in the field of antenna design and possible remedies to such issues are reviewed.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050717
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 718: Determination of Transdermal Rate of
           Metallic Microneedle Array through an Impedance Measurements-Based
           Numerical Check Screening Algorithm

    • Authors: Jingshan Mo, Junqing Liu, Shuang Huang, Baoming Liang, Xinshuo Huang, Cheng Yang, Meiwan Chen, Jing Liu, Tong Zhang, Xi Xie, Jun Guo, Fanmao Liu, Hui-Jiuan Chen
      First page: 718
      Abstract: Microneedle systems have been widely used in health monitoring, painless drug delivery, and medical cosmetology. Although many studies on microneedle materials, structures, and applications have been conducted, the applications of microneedles often suffered from issues of inconsistent penetration rates due to the complication of skin-microneedle interface. In this study, we demonstrated a methodology of determination of transdermal rate of metallic microneedle array through impedance measurements-based numerical check screening algorithm. Metallic sheet microneedle array sensors with different sizes were fabricated to evaluate different transdermal rates. In vitro sensing of hydrogen peroxide confirmed the effect of transdermal rate on the sensing outcomes. An FEM simulation model of a microneedle array revealed the monotonous relation between the transdermal state and test current. Accordingly, two methods were primely derived to calculate the transdermal rate from the test current. First, an exact logic method provided the number of unpenetrated tips per sheet, but it required more rigorous testing results. Second, a fuzzy logic method provided an approximate transdermal rate on adjacent areas, being more applicable and robust to errors. Real-time transdermal rate estimation may be essential for improving the performance of microneedle systems, and this study provides various fundaments toward that goal.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050718
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 719: Research on the High Sensitivity
           Detection Method of Carbon Nanotube/Polydimethylsiloxane Composites
           Structure

    • Authors: Lishuang Liu, Ruirong Wang, Hao Guo, Jinping Liu, Xin Li, Yue Qin, Jun Tang
      First page: 719
      Abstract: In this paper, a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composite force-sensitive structure with good flexibility is proposed and fabricated, and the measurement of scanning electron microscopy (SEM) and Raman are carried out. The equivalent circuit of force-sensitive test of structure is performed and analyzed under direct current (DC) and alternating current (AC) conditions. Under AC conditions, experimental results further show that the sensitivity and sensitivity factors of force-sensitive structures are 0.15 KPa−1 and 2.17 in the pressure range of 600–1000 KPa compressive stress and 20–50% tensile stress, respectively. These results are increased by 36.4% and 38.2% compared to the results of compressive stress (0.11 KPa−1) and tensile stress (1.57) under DC conditions, respectively. It shows that the carbon nanotube/PDMS composite has higher test accuracy under AC conditions.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050719
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 720: Effect of Wind-Induced Vibration on
           Measurement Range of Microcantilever Anemometer

    • Authors: Ye, Wan, He
      First page: 720
      Abstract: In this paper, the effect of wind-induced vibration on measurement range of microcantilever anemometer is investigated for the first time. The microcantilever anemometer is composed of a flexible substrate and a piezoresistor. The wind speed can be detected through the airflow-induced deformation in the flexible substrate. Previous work indicated that the flexible substrate vibrates violently once the wind speed exceeds a critical value, resulting in severe output jitter. This wind-induced vibration limits the measurement range of the anemometer, and the relationship between the anemometer measurement range and its structural parameters has not been explored systematically. Therefore, this paper aims to reveal this relationship theoretically and experimentally, demonstrating that a shorter and thicker cantilever with larger stiffness can effectively suppress the wind-induced vibration, leading to the critical speed rising. By eliminating the wind-induced vibration, the measurement range of the microcantilever anemometer can be increased by up to 697%. These results presented in this paper can pave the way for the design and fabrication of wide-range mechanical anemometers.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050720
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 721: Optofluidic Particle Manipulation
           Platform with Nanomembrane

    • Authors: Zachary J. Walker, Tanner Wells, Ethan Belliston, Sage Romney, Seth B. Walker, Mohammad Julker Neyen Sampad, S M Saiduzzaman, Ravipa Losakul, Holger Schmidt, Aaron R. Hawkins
      First page: 721
      Abstract: We demonstrate a method for fabricating and utilizing an optofluidic particle manipulator on a silicon chip that features a 300 nm thick silicon dioxide membrane as part of a microfluidic channel. The fabrication method is based on etching silicon channels and converting the walls to silicon dioxide through thermal oxidation. Channels are encapsulated by a sacrificial polymer which fills the length of the fluid channel by way of spontaneous capillary action. The sacrificial material is then used as a mold for the formation of a nanoscale, solid-state, silicon dioxide membrane. The hollow channel is primarily used for fluid and particle transport but is capable of transmitting light over short distances and utilizes radiation pressure for particle trapping applications. The optofluidic platform features solid-core ridge waveguides which can direct light on and off of the silicon chip and intersect liquid channels. Optical loss values are characterized for liquid and solid-core structures and at interfaces. Estimates are provided for the optical power needed to trap particles of various sizes.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050721
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 722: Experimental Study on Texture Coupling
           Mechanism and Antifriction Performance of Piston Rod Seal Pair

    • Authors: Jie Tang, Jie Zeng, Xin Lu
      First page: 722
      Abstract: The effect of the coupling texture on the friction and wear of a piston rod-rubber seal pair under lubricating conditions is studied in this paper. Crescentiform textures with different area densities were fabricated on high carbon chromium bearing steel (GCr15) and ethylene propylene diene monomer (EPDM) materials by using a laser marking machine. We compare and analyze the effects of untextured, single-textured, and coupling-textured surfaces on the friction characteristics of the piston rod-rubber seal pair by conducting tests on the reciprocating module of the UMT-2 friction and wear testing machine. The results showed that the coupling-textured surface had the lowest coefficient of friction and wear compared to the untextured and single-textured surfaces. When the normal load was 10 N under the optimal coupling texture area density (6.4%), the friction and wear of the sealing pair decreased the most. Compared with the untextured surface, the friction coefficient was reduced by 27.9% and the wear amount was reduced by 30.0%; compared with the single-textured surface, the friction coefficient was reduced by 18.9%, and the wear amount was reduced by 23.8%. The coupling effect generated by the coupling texture effectively enhanced the formation and stabilization of the oil lubricant film and effectively captured wear debris, preventing it from continuously scratching the surface and reducing wear and roughness.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050722
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 723: A Magnetorheological Duckbill Valve
           Micropump for Drug Delivery Applications

    • Authors: Rubayet Hassan, Sevki Cesmeci, Mahmoud Baniasadi, Anthony Palacio, Austin Robbins
      First page: 723
      Abstract: In this study, we propose a duckbill valve microfluidic pump that relies on an electromagnetic actuation mechanism. An FEA/CFD-based approach was adopted for the design of the device due to the coupled electromagnetic–solid–fluid interactions in the device. The simulation methodology was confirmed with the previously published data in the literature to ensure the accuracy of the simulations. The proposed optimum duckbill valve micropump can pump 2.45 µL of fluid during the first 1 s, including both contraction and expansion phases, almost 16.67% more than the basic model. In addition, the model can pump a maximum volume of 0.26 µL of fluid at the end of the contraction phase (at 0.5 s) when the magnetic flux density is at maximum (0.027 T). The use of a duckbill valve in the model also reduces the backflow by almost 7.5 times more than the model without any valve. The proposed device could potentially be used in a broad range of applications, such as an insulin dosing system for Type 1 diabetic patients, artificial organs to transport blood, organ-on-chip applications, and so on.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050723
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 724: Fabrication of Titanium and
           Copper-Coated Diamond/Copper Composites via Selective Laser Melting

    • Authors: Lu Zhang, Yan Li, Simeng Li, Ping Gong, Qiaoyu Chen, Haoze Geng, Minxi Sun, Qinglei Sun, Liang Hao
      First page: 724
      Abstract: The poor wettability and weak interfacial bonding of diamond/copper composites are due to the incompatibility between diamond and copper which are inorganic nonmetallic and metallic material, respectively, which limit their further application in next-generation heat management materials. Coating copper and titanium on the diamond particle surface could effectively modify and improve the wettability of the diamond/copper interface via electroless plating and evaporation methods, respectively. Here, these dense and complex composites were successfully three-dimensionally printed via selective laser melting. A high thermal conductivity (TC, 336 W/mK) was produced by 3D printing 1 vol.% copper-coated diamond/copper mixed powders at an energy density of 300 J/mm3 (laser power = 180 W and scanning rate = 200 mm/s). 1 and 3 vol.% copper-coated diamond/copper composites had lower coefficients of thermal expansions and higher TCs. They also had stronger bending strengths than the corresponding titanium-coated diamond/copper composites. The interface between copper matrix and diamond reinforcement was well bonded, and there was no cracking in the 1 vol.% copper-coated diamond/copper composite sample. The optimization of the printing parameters and strategy herein is beneficial to develop new approaches for the further construction of a wider range of micro-sized diamond particles reinforced metal matrix composites.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050724
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 725: Conductive Bridge Random Access Memory
           (CBRAM): Challenges and Opportunities for Memory and Neuromorphic
           Computing Applications

    • Authors: Haider Abbas, Jiayi Li, Diing Shenp Ang
      First page: 725
      Abstract: Due to a rapid increase in the amount of data, there is a huge demand for the development of new memory technologies as well as emerging computing systems for high-density memory storage and efficient computing. As the conventional transistor-based storage devices and computing systems are approaching their scaling and technical limits, extensive research on emerging technologies is becoming more and more important. Among other emerging technologies, CBRAM offers excellent opportunities for future memory and neuromorphic computing applications. The principles of the CBRAM are explored in depth in this review, including the materials and issues associated with various materials, as well as the basic switching mechanisms. Furthermore, the opportunities that CBRAMs provide for memory and brain-inspired neuromorphic computing applications, as well as the challenges that CBRAMs confront in those applications, are thoroughly discussed. The emulation of biological synapses and neurons using CBRAM devices fabricated with various switching materials and device engineering and material innovation approaches are examined in depth.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050725
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 726: Asymptotic Synchronization of
           Memristive Cohen-Grossberg Neural Networks with Time-Varying Delays via
           Event-Triggered Control Scheme

    • Authors: Wei Yao, Fei Yu, Jin Zhang, Ling Zhou
      First page: 726
      Abstract: This paper investigates the asymptotic synchronization of memristive Cohen–Grossberg neural networks (MCGNNs) with time-varying delays under event-triggered control (ETC). First, based on the designed feedback controller, some ETC conditions are provided. It is demonstrated that ETC can significantly reduce the update times of the controller and decrease the computing cost. Next, some sufficient conditions are derived to ensure the asymptotic synchronization of MCGNNs with time-varying delays under the ETC method. Finally, a numerical example is provided to verify the correctness and effectiveness of the obtained results.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050726
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 727: Wireless Photometry Prototype for
           Tri-Color Excitation and Multi-Region Recording

    • Authors: Aatreya Chakravarti, Amin Hazrati Marangalou, Ian Matthew Costanzo, Devdip Sen, Mirco Sciulli, Yusuke Tsuno, Ulkuhan Guler
      First page: 727
      Abstract: Visualizing neuronal activation and neurotransmitter release by using fluorescent sensors is increasingly popular. The main drawback of contemporary multi-color or multi-region fiber photometry systems is the tethered structure that prevents the free movement of the animals. Although wireless photometry devices exist, a review of literature has shown that these devices can only optically stimulate or excite with a single wavelength simultaneously, and the lifetime of the battery is short. To tackle this limitation, we present a prototype for implementing a fully wireless photometry system with multi-color and multi-region functions. This paper introduces an integrated circuit (IC) prototype fabricated in TSMC 180 nm CMOS process technology. The prototype includes 3-channel optical excitation, 2-channel optical recording, wireless power transfer, and wireless data telemetry blocks. The recording front end has an average gain of 107 dB and consumes 620 μW of power. The light-emitting diode (LED) driver block provides a peak current of 20 mA for optical excitation. The rectifier, the core of the wireless power transmission, operates with 63% power conversion efficiency at 13.56 MHz and a maximum of 87% at 2 MHz. The system is validated in a laboratory bench test environment and compared with state-of-the-art technologies. The optical excitation and recording front end and the wireless power transfer circuit evaluated in this paper will form the basis for a future miniaturized final device with a shank that can be used in in vivo experiments.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050727
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 728: Design, Fabrication, and
           Characterization of a Laser-Controlled Explosion-Initiating Device with
           Integrated Safe-and-Arm, EMP-Resistant, and Fast-Acting Technology Based
           on Photovoltaic Power Converter

    • Authors: Yin, Bao, Zhao, Ren, Ji, Cheng, Ren
      First page: 728
      Abstract: To augment the intelligence and safety of a rocket or ammunition engine start, an intelligent initiation system needs to be included in the data link. A laser-controlled intelligent initiation system with inherent safety and a laser-controlled explosion-initiating device (LCEID) incorporating electromagnetic pulse (EMP) resistant, safe-and-arms fast-acting modular device based on photovoltaic power converter technology is designed and fabricated in this work. LCEID is an integrated multi-function module consisting of the optical beam expander, GaAs photovoltaic (PV) array, safe-and-arms integrated circuit, and low-energy initiator. These components contribute to EMP resistance, fast-acting, safe-and-arm, and reliable firing, respectively. To achieve intelligent initiation, each LCEID has a unique “identification information” and a “broadcast address” embedded in integrated-circuit read-only memory (ROM), which is controlled by encoded laser addressing. The GaAs PV array was investigated to meet the low-energy initiator firing voltage requirements. Experimental results show that the open-circuit voltage, short-circuit current, and maximum power output of the four-junction GaAs PV array illuminated by a 5.5 W/cm2 laser beam were 220 mA, 21.5 V, and 3.70 W, respectively. When the voltage of the 22 μF energy storage capacitor exceeds 20 V, the laser charging time is found to be shorter than 2.5 s. Other aspects of LCEID, such as laser energy coupling efficiency, the firing process, and the energy-boosting mechanism, were explored. Measurements show that the coupling efficiency of the micro lens with a radius of curvature D = 20 μm and size of r = 50 μm reaches a maximum of 93.5%. Furthermore, for more than 18 V charge voltage, the LCEID is found to perform reliably. The fabricated LCEID demonstrated a high level of integration and intrinsic safety, as well as a finely tailored initiation performance that could be useful in military applications.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050728
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 729: The Effects of Viscoelasticity on
           Droplet Migration on Surfaces with Wettability Gradients

    • Authors: Ying Jun Ren, Sang Woo Joo
      First page: 729
      Abstract: A finite-volume method based on the OpenFOAM is used to numerically study the factors affecting the migration of viscoelastic droplets on rigid surfaces with wettability gradients. Parameters investigated include droplet size, relaxation time, solvent viscosity, and polymer viscosity of the liquid comprising droplets. The wettability gradient is imposed numerically by assuming a linear change in the contact angle along the substrate. As reported previously for Newtonian droplets, the wettability gradient induces spontaneous migration from hydrophobic to hydrophilic region on the substrate. The migration of viscoelastic droplets reveals the increase in the migration speed and distance with the increase in the Weissenberg number. The increase in droplet size also shows the increase in both the migration speed and distance. The increase in polymer viscosity exhibits the increase in migration speed but the decrease in migration distance.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050729
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 730: Microfluidic Platforms for the
           Isolation and Detection of Exosomes: A Brief Review

    • Authors: Duraichelvan Raju, Srinivas Bathini, Simona Badilescu, Anirban Ghosh, Muthukumaran Packirisamy
      First page: 730
      Abstract: Extracellular vesicles (EVs) are a group of communication organelles enclosed by a phospholipid bilayer, secreted by all types of cells. The size of these vesicles ranges from 30 to 1000 nm, and they contain a myriad of compounds such as RNA, DNA, proteins, and lipids from their origin cells, offering a good source of biomarkers. Exosomes (30 to 100 nm) are a subset of EVs, and their importance in future medicine is beyond any doubt. However, the lack of efficient isolation and detection techniques hinders their practical applications as biomarkers. Versatile and cutting-edge platforms are required to detect and isolate exosomes selectively for further clinical analysis. This review paper focuses on lab-on-chip devices for capturing, detecting, and isolating extracellular vesicles. The first part of the paper discusses the main characteristics of different cell-derived vesicles, EV functions, and their clinical applications. In the second part, various microfluidic platforms suitable for the isolation and detection of exosomes are described, and their performance in terms of yield, sensitivity, and time of analysis is discussed.
      Citation: Micromachines
      PubDate: 2022-04-30
      DOI: 10.3390/mi13050730
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 731: Compute-in-Memory for Numerical
           Computations

    • Authors: Dongyan Zhao, Yubo Wang, Jin Shao, Yanning Chen, Zhiwang Guo, Cheng Pan, Guangzhi Dong, Min Zhou, Fengxia Wu, Wenhe Wang, Keji Zhou, Xiaoyong Xue
      First page: 731
      Abstract: In recent years, compute-in-memory (CIM) has been extensively studied to improve the energy efficiency of computing by reducing data movement. At present, CIM is frequently used in data-intensive computing. Data-intensive computing applications, such as all kinds of neural networks (NNs) in machine learning (ML), are regarded as ‘soft’ computing tasks. The ‘soft’ computing tasks are computations that can tolerate low computing precision with little accuracy degradation. However, ‘hard’ tasks aimed at numerical computations require high-precision computing and are also accompanied by energy efficiency problems. Numerical computations exist in lots of applications, including partial differential equations (PDEs) and large-scale matrix multiplication. Therefore, it is necessary to study CIM for numerical computations. This article reviews the recent developments of CIM for numerical computations. The different kinds of numerical methods solving partial differential equations and the transformation of matrixes are deduced in detail. This paper also discusses the iterative computation of a large-scale matrix, which tremendously affects the efficiency of numerical computations. The working procedure of the ReRAM-based partial differential equation solver is emphatically introduced. Moreover, other PDEs solvers, and other research about CIM for numerical computations, are also summarized. Finally, prospects and the future of CIM for numerical computations with high accuracy are discussed.
      Citation: Micromachines
      PubDate: 2022-05-02
      DOI: 10.3390/mi13050731
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 732: Mechanical Behaviors of the
           Origami-Inspired Horseshoe-Shaped Solar Arrays

    • Authors: Zhi Li, Chengguo Yu, Luqiao Qi, Shichao Xing, Yan Shi, Cunfa Gao
      First page: 732
      Abstract: The importance of flexibility has been widely noticed and concerned in the design and application of space solar arrays. Inspired by origami structures, we introduce an approach to realizing stretchable and bendable solar arrays via horseshoe-shaped substrate design. The structure has the ability to combine rigid solar cells and soft substrates skillfully, which can prevent damage during deformations. The finite deformation theory is adapted to find the analytic model of the horseshoe-shaped structure via simplified beam theory. In order to solve the mechanical model, the shooting method, a numerical method to solve ordinary differential equation (ODE) is employed. Finite element analyses (FEA) are also performed to verify the developed theoretical model. The influences of the geometric parameters on deformations and forces are analyzed to achieve the optimal design of the structures. The stretching tests of horseshoe-shaped samples manufactured by three-dimensional (3D) printing are implemented, whose results shows a good agreement with those from theoretical predictions. The developed models can serve as the guidelines for the design of flexible solar arrays in spacecraft.
      Citation: Micromachines
      PubDate: 2022-05-02
      DOI: 10.3390/mi13050732
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 733: Feasibility of Optical Bearing
           Fabrication Using Radiation Pressure

    • Authors: Yasuhiko Arai, Eri Yane, Ryosuke Koyama
      First page: 733
      Abstract: A three-dimensional (3D) printer was used to create a model device to discuss the reduction in friction generated by rotation and investigate the possibility of friction reduction in microelectromechanical systems (MEMSs) using light as a future technology. Experiments on this model showed that friction could be reduced using the light radiation pressure. In addition, the possibility of reducing the effect of the friction generated during rotation was demonstrated by adding a mechanism to the rotating rotor mechanism that reduces friction based on the radiation pressure. The effectiveness and associated problems of 3D printers as a fabrication technology for MEMSs were explored.
      Citation: Micromachines
      PubDate: 2022-05-02
      DOI: 10.3390/mi13050733
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 734: A Snapback-Free and Low Turn-Off Loss
           15 kV 4H–SiC IGBT with Multifunctional P-Floating Layer

    • Authors: Xiaodong Zhang, Pei Shen, Zhijie Zou, Mingxin Song, Linlin Zhang
      First page: 734
      Abstract: In this paper, a 4H–SiC IGBT with a multifunctional P-floating layer (MP-IGBT) is proposed and investigated by Silvaco TCAD simulations. Compared with the conventional 4H–SiC field stop IGBT (FS-IGBT), the MP-IGBT structure features a P-floating layer structure under the N-buffer layer. The P-floating layer increases the distributed path resistance below the buffer layer to eliminate the snapback phenomenon. In addition, the P-floating layer acts as an amplifying stage for the hole currents’ injection. The snapback-free structure features a half-cell pitch of 10 μm. For the same forward voltage drop, the turn-off loss of the MP-IGBT structure is reduced by 42%.
      Citation: Micromachines
      PubDate: 2022-05-03
      DOI: 10.3390/mi13050734
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 735: Microfluidic Applications of Artificial
           Cilia: Recent Progress, Demonstration, and Future Perspectives

    • Authors: Vignesh Sahadevan, Bivas Panigrahi, Chia-Yuan Chen
      First page: 735
      Abstract: Artificial cilia-based microfluidics is a promising alternative in lab-on-a-chip applications which provides an efficient way to manipulate fluid flow in a microfluidic environment with high precision. Additionally, it can induce favorable local flows toward practical biomedical applications. The endowment of artificial cilia with their anatomy and capabilities such as mixing, pumping, transporting, and sensing lead to advance next-generation applications including precision medicine, digital nanofluidics, and lab-on-chip systems. This review summarizes the importance and significance of the artificial cilia, delineates the recent progress in artificial cilia-based microfluidics toward microfluidic application, and provides future perspectives. The presented knowledge and insights are envisaged to pave the way for innovative advances for the research communities in miniaturization.
      Citation: Micromachines
      PubDate: 2022-05-03
      DOI: 10.3390/mi13050735
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 736: Design and Comparative Study of a
           Small-Stroke Energy Harvesting Floor Based on a Multi-Layer Piezoelectric
           Beam Structure

    • Authors: Xiang Zhong, Hengyang Wang, Lin Chen, Mingjie Guan
      First page: 736
      Abstract: Recently, research on the energy harvesting floor is attracting more and more attention due to its possible application in the smart house, invasion monitoring, internet of things, etc. This paper introduced a design and comparative study of a small-stroke piezoelectric energy harvesting floor based on a multi-layer piezoelectric beam structure. The multi-layer piezoelectric beams are designed based on simply supported beams in an interdigitated manner. Theoretical analysis is explored to find out the beam number and layer number of the structure. Through this design, the input power from the human footsteps was effectively utilized and transformed into electrical power. The designed piezoelectric energy harvesting floor structure was tested by our designed stepping machine, which can simulate the stepping effect of a walking human on the floor with different parameters such as stepping frequency. Comparative studies of the energy harvester are carried out regarding different stepping frequencies, external circuits, and initial beam shapes. The experimental results showed that the maximum output power of a group of four-layer prototypes was 960.9 µW at a stroke of 4 mm and a step frequency of 0.83 Hz, with the beams connected in parallel.
      Citation: Micromachines
      PubDate: 2022-05-03
      DOI: 10.3390/mi13050736
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 737: Off-State Performance Characterization
           of an AlGaN/GaN Device via Artificial Neural Networks

    • Authors: Jing Chen, Yufeng Guo, Jun Zhang, Jianhua Liu, Qing Yao, Jiafei Yao, Maolin Zhang, Man Li
      First page: 737
      Abstract: Due to the complexity of the 2D coupling effects in AlGaN/GaN HEMTs, the characterization of a device’s off-state performance remains the main obstacle to exploring the device’s breakdown characteristics. To predict the off-state performance of AlGaN/GaN HEMTs with efficiency and veracity, an artificial neural network-based methodology is proposed in this paper. Given the structure parameters, the off-state current–voltage (I–V) curve can therefore be obtained along with the essential performance index, such as breakdown voltage (BV) and saturation leakage current, without any physics domain requirement. The trained neural network is verified by the good agreement between predictions and simulated data. The proposed tool can achieve a low average error of the off-state I–V curve prediction (Ave. Error < 5%) and consumes less than 0.001‰ of average computing time than in TCAD simulation. Meanwhile, the convergence issue of TCAD simulation is avoided using the proposed method.
      Citation: Micromachines
      PubDate: 2022-05-05
      DOI: 10.3390/mi13050737
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 738: Wafer-Level Self-Packaging Design and
           Fabrication of MEMS Capacitive Pressure Sensors

    • Authors: Yuanjie Wan, Zhiwei Li, Zile Huang, Baofa Hu, Wenlong Lv, Chunquan Zhang, Haisheng San, Shaoda Zhang
      First page: 738
      Abstract: This paper reports a MEMS capacitive pressure sensor (CPS) based on the operating principle of touch mode. The CPS was designed and fabricated using wafer-level self-packaged MEMS processes. The variable capacitance sensing structure was vacuum-sealed in a cavity using the Si–glass anodic bonding technique, and the embedded Al feedthrough lines at the Si–glass interface were used to realize the electrical connections between the parallel plate electrodes and the electrode pads through Al vias. The optimal design of the CPS structure was performed to trade-off the performance and reliability using finite element simulation. The CPS based on a circular-shaped diaphragm with a radius of 2000 µm and a thickness of 40 µm exhibits good comprehensive performance with a sensitivity of 52.3 pF/MPa and a nonlinearity of 2.7%FS in the pressure range of 100–500 kPa when the ambient temperature is less than 50 °C.
      Citation: Micromachines
      PubDate: 2022-05-06
      DOI: 10.3390/mi13050738
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 739: The Effect of Dynamic, In Vivo-like
           Oxaliplatin on HCT116 Spheroids in a Cancer-on-Chip Model Is
           Representative of the Response in Xenografts

    • Authors: Job Komen, Sanne M. van Neerven, Elsbeth G. B. M. Bossink, Nina E. de Groot, Lisanne E. Nijman, Albert van den Berg, Louis Vermeulen, Andries D. van der Meer
      First page: 739
      Abstract: The cancer xenograft model in which human cancer cells are implanted in a mouse is one of the most used preclinical models to test the efficacy of novel cancer drugs. However, the model is imperfect; animal models are ethically burdened, and the imperfect efficacy predictions contribute to high clinical attrition of novel drugs. If microfluidic cancer-on-chip models could recapitulate key elements of the xenograft model, then these models could substitute the xenograft model and subsequently surpass the xenograft model by reducing variation, increasing sensitivity and scale, and adding human factors. Here, we exposed HCT116 colorectal cancer spheroids to dynamic, in vivo-like, concentrations of oxaliplatin, including a 5 day drug-free period, on-chip. Growth inhibition on-chip was comparable to existing xenograft studies. Furthermore, immunohistochemistry showed a similar response in proliferation and apoptosis markers. While small volume changes in xenografts are hard to detect, in the chip-system, we could observe a temporary growth delay. Lastly, histopathology and a pharmacodynamic model showed that the cancer spheroid-on-chip was representative of the proliferating outer part of a HCT116 xenograft, thereby capturing the major driver of the drug response of the xenograft. Hence, the cancer-on-chip model recapitulated the response of HCT116 xenografts to oxaliplatin and provided additional drug efficacy information.
      Citation: Micromachines
      PubDate: 2022-05-06
      DOI: 10.3390/mi13050739
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 740: Growth of Laser-Induced Microbubbles
           inside Capillary Tubes Affected by Gathered Light-Absorbing Particles

    • Authors: Jia-Wen He, Hao-Dong Wang, Bo-Wei Li, Wen Bai, Dong Chen, Min-Cheng Zhong
      First page: 740
      Abstract: Microbubbles have important applications in optofluidics. The generation and growth of microbubbles is a complicated process in microfluidic channels. In this paper, we use a laser to irradiate light-absorbing particles to generate microbubbles in capillary tubes and investigate the factors affecting microbubble size. The results show that the key factor is the total area of the light-absorbing particles gathered at the microbubble bottom. The larger the area of the particles at bottom, the larger the size of the microbubbles. Furthermore, the area is related to capillary tube diameter. The larger the diameter of the capillary tube, the more particles gathered at the bottom of the microbubbles. Numerical simulations show that the Marangoni convection is stronger in a capillary tube with a larger diameter, which can gather more particles than that in a capillary tube with a smaller diameter. The calculations show that the particles in contact with the microbubbles will be in a stable position due to the surface tension force.
      Citation: Micromachines
      PubDate: 2022-05-06
      DOI: 10.3390/mi13050740
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 741: Study on Dynamic and Static Performance
           of a Micro Digital Hydraulic Valve

    • Authors: Meisheng Yang
      First page: 741
      Abstract: Previous researchers mostly carried out simulation research and scattered experimental research on the static and dynamic characteristics of the digital valve, but did not form a systematic and in-depth study on the characteristics of the valve. Based on expounding the basic principles and functions of the valve and the test system, this paper carries out the test research under various variables for three kinds of static characteristics, including pressure differential-flow characteristics, signal-pressure characteristics, and signal-flow characteristics. The optimal control frequency of the valve is obtained from the comprehensive consideration of linear interval, linearity, and hysteresis. Three methods are systematically used to deeply study the dynamic characteristics, and the influencing factors of test results under various test conditions are analyzed. Through the research of this paper, it can provide relevant performance parameters for taking the digital valve as the system control element in the next step, and lay the foundation for the accurate control of the system.
      Citation: Micromachines
      PubDate: 2022-05-07
      DOI: 10.3390/mi13050741
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 742: Investigation of Wafer-Level Fabricated
           Permanent Micromagnets for MEMS

    • Authors: Mani Teja Bodduluri, Björn Gojdka, Niklas Wolff, Lorenz Kienle, Thomas Lisec, Fabian Lofink
      First page: 742
      Abstract: Monolithic integration of permanent micromagnets into MEMS structures offers many advantages in magnetic MEMS applications. A novel technique called PowderMEMS, based on the agglomeration of micron-sized powders by atomic layer deposition (ALD), has been used to fabricate permanent micromagnets on 8-inch wafers. In this paper, we report the fabrication and magnetic characterization of PowderMEMS micromagnets prepared from two different NdFeB powder particle sizes. A remanence of 423 mT and intrinsic coercivity of 924 mT is achieved at the low ALD process temperature of 75 °C, making this process compatible with MEMS technology. The magnetic reversible mechanism in the micromagnets is discussed with the help of the Wohlfarth equation. To ensure the operability of such integrated micromagnets in different application environments, we conducted a set of experiments to systematically investigate the thermal and corrosive stability. NdFeB micromagnets with larger powder particle size (d50 = 25 µm) exhibit high thermal stability in air. Furthermore, the corrosion stability of the micromagnets is significantly improved by an additional silicon oxide passivation layer deposited by plasma-enhanced chemical vapor deposition (PECVD). The presented results demonstrate the durability of PowderMEMS micromagnets, enabling their application in various fields, e.g., microfluidics, sensors, actuators, and microelectronics.
      Citation: Micromachines
      PubDate: 2022-05-07
      DOI: 10.3390/mi13050742
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 743: Electron Radiation Effects of
           Grain-Boundary Evolution on Polycrystalline Silicon in MEMS

    • Authors: Lei Wang, Haiyun Liu, Xing Liu
      First page: 743
      Abstract: A specimen observed with a transmission electron microscope (TEM) was processed by focused ion beam (FIB) from a surface-micromachined polycrystalline silicon MEMS structure. Electron irradiation and in situ observation were performed on a selected grain boundary in the specimen. The grain boundary was observed and located by using lattice-oriented selective TEM photography. An evolution progress of amorphization of small silicon grain within the grain boundary and recrystallization of amorphous silicon were observed. A silicon grain turned into several smaller bar grains within the grain boundary. The mechanism of grain-boundary evolution inducing a change of conductivity of polycrystalline silicon has been revealed. The conductivity of polycrystalline silicon influenced by electron irradiation could be attributed to the change of grain boundary.
      Citation: Micromachines
      PubDate: 2022-05-08
      DOI: 10.3390/mi13050743
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 744: Darcy-Forchheimer Flow of Water
           Conveying Multi-Walled Carbon Nanoparticles through a Vertical Cleveland
           Z-Staggered Cavity Subject to Entropy Generation

    • Authors: Ghulam Rasool, Abdulkafi Mohammed Saeed, Animasaun Isaac Lare, Aissa Abderrahmane, Kamel Guedri, Hanumesh Vaidya, Riadh Marzouki
      First page: 744
      Abstract: To date, when considering the dynamics of water conveying multi-walled carbon nanoparticles (MWCNT) through a vertical Cleveland Z-staggered cavity where entropy generation plays a significant role, nothing is known about the increasing Reynold number, Hartmann number, and Darcy number when constant conduction occurs at both sides, but at different temperatures. The system-governing equations were solved using suitable models and the Galerkin Finite Element Method (GFEM). Based on the outcome of the simulation, it is worth noting that increasing the Reynold number causes the inertial force to be enhanced. The velocity of incompressible Darcy-Forchheimer flow at the middle vertical Cleveland Z-staggered cavity declines with a higher Reynold number. Enhancement in the Hartman number causes the velocity at the center of the vertical Cleveland Z-staggered cavity to be reduced due to the associated Lorentz force, which is absent when Ha = 0 and highly significant when Ha = 30. As the Reynold number grows, the Bejan number declines at various levels of the Hartmann number, but increases at multiple levels of the Darcy number.
      Citation: Micromachines
      PubDate: 2022-05-08
      DOI: 10.3390/mi13050744
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 745: THz MEMS Switch Design

    • Authors: Yukang Feng, Han-yu Tsao, N. Scott Barker
      First page: 745
      Abstract: In this work, an mm-wave/THz MEMS switch design process is presented. The challenges and solutions associated with the switch electrical design, modeling, fabrication, and test are explored and discussed. To investigate the feasibility of this design process, the switches are designed on both silicon and fused quartz substrate and then tested in the 140–750 GHz frequency range. The measurement fits design expectations and simulation well. At 750 GHz the measurement results from switches on both substrates have an ON state insertion loss of less than 3 dB and an OFF state isolation larger than 12 dB.
      Citation: Micromachines
      PubDate: 2022-05-08
      DOI: 10.3390/mi13050745
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 746: Activity-Induced Enhancement of
           Superdiffusive Transport in Bacterial Turbulence

    • Authors: Chenliang Xie, Yanan Liu, Hao Luo, Guangyin Jing
      First page: 746
      Abstract: Superdiffusion processes significantly promote the transport of tiny passive particles within biological fluids. Activity, one of the essential measures for living matter, however, is less examined in terms of how and to what extent it can improve the diffusivity of the moving particles. Here, bacterial suspensions are confined within the microfluidic channel at the state of bacterial turbulence, and are tuned to different activity levels by oxygen consumption in control. Systematic measurements are conducted to determine the superdiffusion exponent, which characterizes the diffusivity strength of tracer particles, depending on the continuously injecting energy converted to motile activity from swimming individuals. Higher activity is quantified to drastically enhance the superdiffusion process of passive tracers in the short-time regime. Moreover, the number density of the swimming bacteria is controlled to contribute to the field activity, and then to strengthen the super-diffusivity of tracers, distinguished by regimes with and without collective motion of interacting bacteria. Finally, the non-slip surfaces of the microfluidic channel lower the superdiffusion of immersed tracers due to the resistance, with the small diffusivity differing from the counterpart in the bulk. The findings here suggest ways of controlled diffusion and transport of substances within the living system with different levels of nutrition and resources and boundary walls, leading to efficient mixing, drug delivery and intracellular communications.
      Citation: Micromachines
      PubDate: 2022-05-08
      DOI: 10.3390/mi13050746
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 747: Modeling and Control of a Wheeled Biped
           Robot

    • Authors: Zemin Cui, Yaxian Xin, Shuyun Liu, Xuewen Rong, Yibin Li
      First page: 747
      Abstract: It is difficult to realize the stable control of a wheeled biped robot (WBR), as it is an underactuated nonlinear system. To improve the balance and dynamic locomotion capabilities of a WBR, a decoupled control framework is proposed. First, the WBR is decoupled into a variable-length wheeled inverted pendulum and a five-link multi-rigid body system. Then, for the above two simplified models, a time-varying linear quadratic regulator and a model predictive controller are designed, respectively. In addition, in order to improve the accuracy of the feedback information of the robot, the Kalman filter is used to optimally estimate the system state. The control framework can enable the WBR to realize changing height, resisting external disturbances, velocity tracking and jumping. The results obtained by simulations and physical experiments verify the effectiveness of the framework.
      Citation: Micromachines
      PubDate: 2022-05-08
      DOI: 10.3390/mi13050747
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 748: Investigation on Capacitance Collapse
           Induced by Secondary Capture of Acceptor Traps in AlGaN/GaN Lateral
           Schottky Barrier Diode

    • Authors: Haitao Zhang, Xuanwu Kang, Yingkui Zheng, Ke Wei, Hao Wu, Xinyu Liu, Tianchun Ye, Zhi Jin
      First page: 748
      Abstract: In this study, a dedicated dynamic measurement system was used to investigate the transient capacitance and recovery process of AlGaN/GaN lateral Schottky barrier diodes (SBDs). With the consideration of acceptor traps in the C-doped buffer, the C-V characteristics and transient capacitance were measured and analyzed, and the results were simulated and explained by Silvaco TCAD (technology computer aided design). The ionization of acceptor traps and the change of electric potential were monitored in transient simulation to investigate the origin of the capacitance collapse in the SBD. The results suggest the significant impact of traps in the GaN buffer layer on the capacitance collapse of the device, and the secondary capture effect on the variation of acceptor ionization. Based on the study of transient capacitance of SBD, this work could be extended to the Miller capacitance in high electron mobility transistor (HEMT) devices. Moreover, the report on the stability of capacitance is essential for GaN devices, and could be further extended to other aspects of device research.
      Citation: Micromachines
      PubDate: 2022-05-09
      DOI: 10.3390/mi13050748
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 749: Editorial for the Special Issue
           “MEMS Packaging Technologies and 3D Integration”

    • Authors: Seonho Seok
      First page: 749
      Abstract: As fabrication technologies advance, the packaging of MEMS device is being developed in two main directions: MEMS device packaging and MEMS or sensor system integration [...]
      Citation: Micromachines
      PubDate: 2022-05-09
      DOI: 10.3390/mi13050749
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 750: Refractive Index Sensor Based on a
           Metal–Insulator–Metal Bus Waveguide Coupled with a U-Shaped
           Ring Resonator

    • Authors: Xiaoyu Zhang, Shubin Yan, Jilai Liu, Yifeng Ren, Yi Zhang, Lifang Shen
      First page: 750
      Abstract: In this study, a novel refractive index sensor structure was designed consisting of a metal–insulator–metal (MIM) waveguide with two rectangular baffles and a U-Shaped Ring Resonator (USRR). The finite element method was used to theoretically investigate the sensor’s transmission characteristics. The simulation results show that Fano resonance is a sharp asymmetric resonance generated by the interaction between the discrete narrow-band mode and the successive wide-band mode. Next, the formation of broadband and narrowband is further studied, and finally the key factors affecting the performance of the sensor are obtained. The best sensitivity of this refractive-index sensor is 2020 nm/RIU and the figure of merit (FOM) is 53.16. The presented sensor has the potential to be useful in nanophotonic sensing applications.
      Citation: Micromachines
      PubDate: 2022-05-09
      DOI: 10.3390/mi13050750
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 751: Micromanipulation and Automatic Data
           Analysis to Determine the Mechanical Strength of Microparticles

    • Authors: Zhihua Zhang, Yanping He, Zhibing Zhang
      First page: 751
      Abstract: Microparticles are widely used in many industrial sectors. A micromanipulation technique has been widely used to quantify the mechanical properties of individual microparticles, which is crucial to the optimization of their functionality and performance in end-use applications. The principle of this technique is to compress single particles between two parallel surfaces, and the force versus displacement data are obtained simultaneously. Previously, analysis of the experimental data had to be done manually to calculate the rupture strength parameters of each individual particle, which is time-consuming. The aim of this study is to develop a software package that enables automatic analysis of the rupture strength parameters from the experimental data to enhance the capability of the micromanipulation technique. Three algorithms based on the combination of the “three-sigma rule”, a moving window, and the Hertz model were developed to locate the starting point where onset of compression occurs, and one algorithm based on the maximum deceleration was developed to identify the rupture point where a single particle is ruptured. Fifty microcapsules each with a liquid core and fifty porous polystyrene (PS) microspheres were tested in order to produce statistically representative results of each sample, and the experimental data were analysed using the developed software package. It is found that the results obtained from the combination of the “3σ + window” algorithm or the “3σ + window + Hertz” algorithm with the “maximum-deceleration” algorithm do not show any significant difference from the manual results. The data analysis time for each sample has been shortened from 2 to 3 h manually to within 20 min automatically.
      Citation: Micromachines
      PubDate: 2022-05-10
      DOI: 10.3390/mi13050751
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 752: Design and Development of a 2 × 2
           Array Piezoelectric–Electromagnetic Hybrid Energy Harvester

    • Authors: Bing Han, Shubin Zhang, Jianbin Liu, Yanfeng Jiang
      First page: 752
      Abstract: Energy harvesting technology is regarded as a feasible solution for the continuous power supply of microelectronic devices. Efforts have been made to improve the output power of all kinds of energy harvesting devices. This paper reports a 2 × 2 array piezoelectric–electromagnetic hybrid energy harvester that achieves high power output through the combination of piezoelectric and electromagnetic conversion. The harvester included four piezoelectric–electromagnetic hybrid modules, each of which consisted of a piezoelectric sheet, a permanent magnet and a wound coil. The permanent magnet, also serving as the mass block of the cantilever beam when subjected to external stimulus, contributed to a large displacement of the vibration and generated high output power. At an acceleration of 1 g and a resonance frequency of 70.4 Hz, the measured maximum output power of the hybrid energy harvester was 66.08 mW, of which the piezoelectric and electromagnetic portions were 56.96 and 9.12 mW, respectively. Furthermore, in a charging experiment, a capacitor of 23.5 mF was charged to 11.5 V within 20 s, which demonstrates a practical application of the hybrid energy harvester for microelectronic devices.
      Citation: Micromachines
      PubDate: 2022-05-10
      DOI: 10.3390/mi13050752
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 753: A Dynamic Thermal-Mechanical Coupling
           Numerical Model to Solve the Deformation and Thermal Diffusion of Plates

    • Authors: Wenxing Chen, Shuyang Dai, Baojuan Zheng
      First page: 753
      Abstract: Elastic materials include metal plates, rubber, foam, airbags and so on, which have a good buffer effect, toughness and strong recovery ability. In this paper, the deformation and thermal diffusion of 2D and 3D thin plates are studied. Two models are established for the deformation of 2D thin plates. The bending deformation equation of rectangular and circular plates is derived, and the semi-analytical solution of the deflection function w(x,y) is found through the Fourier series approximation in the polar coordinate. The consistencies of the numerical solution and the theoretical solution are verified by numerical method. Then, we find that the factors affecting the deformation are related to the Young’s modulus, load, plate length and deformation factor α of the material. In a separate temperature physics field, we establish a heat conduction model of 2D graphene film. Three numerical schemes of the transient heat conduction equation of FDM-FEM are given. In contrast, this paper uses the implicit Euler method to discrete the time term. Furthermore, we compared the difference between the adiabatic condition and the convection condition by the graphical method and the curve trend. The results show that the temperature near the adiabatic boundary is higher. Finally, we proposed a 3D dynamic thermal–mechanical coupling model (3D-DTMCM) that has been established. A laser heating monocrystalline silicon sheet with periodic motion formula is given. The temperature radiation of the laser heat source has Gaussian distribution characteristics. Our proposed model can dynamically determine Young’s modulus with a variable temperature. The numerical results show that the higher the temperature is, the higher the strain energy density of the plate is. In addition, the deformation amplitude of the plates in the coupling field is larger than that in the single mechanical field. Finally, we also discussed the stress field distribution of mixed cracks under high temperature and high load. Our research provides theoretical support for the deformation of different plates, and also reflects the value of the coupled model in practical applications.
      Citation: Micromachines
      PubDate: 2022-05-10
      DOI: 10.3390/mi13050753
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 754: Laser Scanning Guided Localization
           Imaging with a Laser-Machined Two-Dimensional Flexible Ultrasonic Array

    • Authors: Jianzhong Chen, Wei Liu, Dianbao Gu, Dawei Wu
      First page: 754
      Abstract: Advances in flexible integrated circuit technology and piezoelectric materials allow high-quality stretchable piezoelectric transducers to be built in a form that is easy to integrate with the body’s soft, curved, and time-dynamic surfaces. The resulting capabilities create new opportunities for studying disease states, monitoring health/wellness, building human–machine interfaces, and performing other operations. However, more widespread application scenarios are placing new demands on the high flexibility and small size of the array. This paper provides a 8 × 8 two-dimensional flexible ultrasonic array (2D-FUA) based on laser micromachining; a novel single-layer “island bridge” structure was used to design flexible array and piezoelectric array elements to improve the imaging capability on complex surfaces. The mechanical and acoustoelectric properties of the array are characterized, and a novel laser scanning and positioning method is introduced to solve the problem of array element displacement after deformation of the 2D-FUA. Finally, a multi-modal localization imaging experiment was carried out on the multi-target steel pin on the plane and curved surface based on the Verasonics system. The results show that the laser scanning method has the ability to assist the rapid imaging of flexible arrays on surfaces with complex shapes, and that 2D-FUA has wide application potential in medical-assisted localization imaging.
      Citation: Micromachines
      PubDate: 2022-05-10
      DOI: 10.3390/mi13050754
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 755: Microfluidics for High Pressure:
           Integration on GaAs Acoustic Biosensors with a Leakage-Free PDMS Based on
           Bonding Technology

    • Authors: Saber Hammami, Aleksandr Oseev, Sylwester Bargiel, Rabah Zeggari, Céline Elie-Caille, Thérèse Leblois
      First page: 755
      Abstract: Microfluidics integration of acoustic biosensors is an actively developing field. Despite significant progress in “passive” microfluidic technology, integration with microacoustic devices is still in its research state. The major challenge is bonding polymers with monocrystalline piezoelectrics to seal microfluidic biosensors. In this contribution, we specifically address the challenge of microfluidics integration on gallium arsenide (GaAs) acoustic biosensors. We have developed a robust plasma-assisted bonding technology, allowing strong connections between PDMS microfluidic chip and GaAs/SiO2 at low temperatures (70 °C). Mechanical and fluidic performances of fabricated device were studied. The bonding surfaces were characterized by water contact angle measurement and ATR-FTIR, AFM, and SEM analysis. The bonding strength was characterized using a tensile machine and pressure/leakage tests. The study showed that the sealed chips were able to achieve a limit of high bonding strength of 2.01 MPa. The adhesion of PDMS to GaAs was significantly improved by use of SiO2 intermediate layer, permitting the bonded chip to withstand at least 8.5 bar of burst pressure. The developed bonding approach can be a valuable solution for microfluidics integration in several types of MEMS devices.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050755
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 756: Enhanced Spectral Broadening of
           Femtosecond Optical Pulses in Silicon Nanowires Integrated with 2D
           Graphene Oxide Films

    • Authors: Yuning Zhang, Jiayang Wu, Yunyi Yang, Yang Qu, Linnan Jia, Baohua Jia, David J. Moss
      First page: 756
      Abstract: We experimentally demonstrate enhanced spectral broadening of femtosecond optical pulses after propagation through silicon-on-insulator (SOI) nanowire waveguides integrated with two-dimensional (2D) graphene oxide (GO) films. Owing to the strong mode overlap between the SOI nanowires and the GO films with a high Kerr nonlinearity, the self-phase modulation (SPM) process in the hybrid waveguides is significantly enhanced, resulting in greatly improved spectral broadening of the femtosecond optical pulses. A solution-based, transfer-free coating method is used to integrate GO films onto the SOI nanowires with precise control of the film thickness. Detailed SPM measurements using femtosecond optical pulses are carried out, achieving a broadening factor of up to ~4.3 for a device with 0.4-mm-long, 2 layers of GO. By fitting the experimental results with the theory, we obtain an improvement in the waveguide nonlinear parameter by a factor of ~3.5 and in the effective nonlinear figure of merit (FOM) by a factor of ~3.8, relative to the uncoated waveguide. Finally, we discuss the influence of GO film length on the spectral broadening and compare the nonlinear optical performance of different integrated waveguides coated with GO films. These results confirm the improved nonlinear optical performance of silicon devices integrated with 2D GO films.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050756
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 757: Mold Size Effect in Microscale Laser
           Dynamic Flexible Bulging Assisted by Laser Pre-Shocking

    • Authors: Yijun Fang, Pin Li, Xijin Zhen, Jindian Zhang, Zongbao Shen
      First page: 757
      Abstract: The size effect seriously affects the forming quality of micro-formed parts in the field of micro-forming. This paper focuses on the influence of the mold size effect in microscale laser dynamic flexible bulging (μLDFB). The experimental results indicate that, for the copper foil with a given thickness, there are suitable mold characteristic sizes to obtain better forming quality. The surface quality of bulging parts is poor when the mold characteristic size is small. However, the forming symmetry and forming uniformity of bulging samples are reduced when the mold characteristic size is large. As the laser pulse energy increases, the plastic strain increases, and the bulging samples experience five stages: uniform plastic deformation, local necking, cracks in the bulging zone, complete fracture in the bulging zone and complete rupture at the mold entrance zone. The increase of the surface roughening rate caused by the increase of grain size and mold characteristic size makes local necking easier, which further leads to fracture. On this basis, in this paper laser pre-shocking (LPS) is introduced to improve the forming quality. Comparative experiments show that LPS has a positive effect on improving the surface quality and the forming performance of bulging samples. The forming limit of bulging samples is increased and the occurrence of local necking is delayed.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050757
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 758: Polyimide-Based High-Performance Film
           Bulk Acoustic Resonator Humidity Sensor and Its Application in Real-Time
           Human Respiration Monitoring

    • Authors: Yusi Zhu, Pan Xia, Jihang Liu, Zhen Fang, Lidong Du, Zhan Zhao
      First page: 758
      Abstract: Respiration monitoring is vital for human health assessment. Humidity sensing is a promising way to establish a relationship between human respiration and electrical signal. This paper presents a polyimide-based film bulk acoustic resonator (PI-FBAR) humidity sensor operating in resonant frequency and reflection coefficient S11 dual-parameter with high sensitivity and stability, and it is applied in real-time human respiration monitoring for the first time. Both these two parameters can be used to sense different breathing conditions, such as normal breathing and deep breathing, and breathing with different rates such as normal breathing, slow breathing, apnea, and fast breathing. Experimental results also indicate that the proposed humidity sensor has potential applications in predicting the fitness of individual and in the medical field for detecting body fluids loss and daily water intake warning. The respiratory rates measured by our proposed PI-FBAR humidity sensor operating in frequency mode and S11 mode have Pearson correlation of up to 0.975 and 0.982 with that measured by the clinical monitor, respectively. Bland–Altman method analysis results further revealed that both S11 and frequency response are in good agreement with clinical monitor. The proposed sensor combines the advantages of non-invasiveness, high sensitivity and high stability, and it has great potential in human health monitoring.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050758
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 759: Integrated Piezoresistive Normal Force
           Sensors Fabricated Using Transfer Processes with Stiction Effect Temporary
           Handling

    • Authors: Ni Liu, Peng Zhong, Chaoyue Zheng, Ke Sun, Yifei Zhong, Heng Yang
      First page: 759
      Abstract: Tactile sensation is a highly desired function in robotics. Furthermore, tactile sensor arrays are crucial sensing elements in pulse diagnosis instruments. This paper presents the fabrication of an integrated piezoresistive normal force sensor through surface micromachining. The force sensor is transferred to a readout circuit chip via a temporary stiction effect handling process. The readout circuit chip comprises two complementary metal-oxide semiconductor operational amplifiers, which are redistributed to form an instrumentation amplifier. The sensor is released and temporarily bonded to the substrate before the transfer process due to the stiction effect to avoid the damage and movement of the diaphragm during subsequent flip-chip bonding. The released sensor is pulled off from the substrate and transferred to the readout circuit chip after being bonded to the readout circuit chip. The size of the transferred normal force sensor is 180 μm × 180 μm × 1.2 μm. The maximum misalignment of the flip-chip bonding process is approximately 1.5 μm, and sensitivity is 93.5 μV/μN/V. The routing of the piezoresistive Wheatstone bridge can be modified to develop shear force sensors; consequently, this technique can be used to develop tactile sensors that can sense both normal and shear forces.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050759
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 760: Influences of Microscopic Imaging
           Conditions on Accuracy of Cell Morphology Discrimination Using
           Convolutional Neural Network of Deep Learning

    • Authors: Masashi Yamamoto, Shogo Miyata
      First page: 760
      Abstract: Recently, automated cell culture devices have become necessary for cell therapy applications. The maintenance of cell functions is critical for cell expansion. However, there are risks of losing these functions, owing to disturbances in the surrounding environment and culturing procedures. Therefore, there is a need for a non-invasive and highly accurate evaluation method for cell phenotypes. In this study, we focused on an automated discrimination technique using image processing with a deep learning algorithm. This study aimed to clarify the effects of the optical magnification of the microscope and cell size in each image on the discrimination accuracy for cell phenotypes and morphologies. Myoblast cells (C2C12 cell line) were cultured and differentiated into myotubes. Microscopic images of the cultured cells were acquired at magnifications of 40× and 100×. A deep learning architecture was constructed to discriminate between undifferentiated and differentiated cells. The discrimination accuracy exceeded 90% even at a magnification of 40× for well-developed myogenic differentiation. For the cells under immature myogenic differentiation, a high optical magnification of 100× was required to maintain a discrimination accuracy over 90%. The microscopic optical magnification should be adjusted according to the cell differentiation to improve the efficiency of image-based cell discrimination.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050760
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 761: A Magnetically Coupled
           Piezoelectric–Electromagnetic Low-Frequency Multidirection Hybrid
           Energy Harvester

    • Authors: Yongqiang Zhu, Zhaoyang Zhang, Pingxia Zhang, Yurong Tan
      First page: 761
      Abstract: The traditional single electromechanical conversion energy harvester can collect energy only in a single vibration direction. Moreover, it requires high environmental vibration frequency, and its output power is low. To solve these problems, a cross-shaped magnetically coupled piezoelectric–electromagnetic hybrid harvester is proposed. The harvester comprised a ring-shaped support frame, a piezoelectric generation structure, and an electromagnetic generation structure. The harvester could simultaneously generate energy piezoelectrically and electrically, in addition, it could generate electricity efficiently at a lower environmental vibration, and it can collect the energy in two vibration directions simultaneously. To verify the effectiveness of the device, we set up a vibration experiment system and conducted comparative experiments about non-magnetically coupled piezoelectric, magnetically coupled piezoelectric, and magnetically coupled piezoelectric–electromagnetic hybrid energy harvesters. The experimental results showed that the output power of the magnetically coupled piezoelectric–electromagnetic hybrid energy harvester was 2.13 mW for the piezoelectric structure and 1.76 mW for the electromagnetic structure under the vibration of single-direction resonant frequency. The total hybrid output power was 3.89 mW. The hybrid harvester could collect vibration energy parallel to the ring in any direction. Furthermore, compared with the non-magnetically coupled piezoelectric energy harvester and the magnetically coupled piezoelectric energy harvester, the output power was increased by 141.6% and 55.6%, respectively.
      Citation: Micromachines
      PubDate: 2022-05-11
      DOI: 10.3390/mi13050761
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 762: Effects of pH Values and H2O2
           Concentrations on the Chemical Enhanced Shear Dilatancy Polishing of
           Tungsten

    • Authors: Liang Xu, Lin Wang, Hongyu Chen, Xu Wang, Fangyuan Chen, Binghai Lyu, Wei Hang, Wenhong Zhao, Julong Yuan
      First page: 762
      Abstract: In order to obtain tungsten with great surface qualities and high polishing efficiency, a novel method of chemical enhanced shear dilatancy polishing (C-SDP) was proposed. The effects of pH values and H2O2 concentrations on the polishing performance of tungsten C-SDP were studied. In addition, the corrosion behaviors of tungsten in solutions with different pH values and H2O2 concentrations were analyzed by electrochemical experiments, and the valence states of elements on the tungsten surface were analyzed by XPS. The results showed that both pH values and H2O2 concentrations had significant effects on tungsten C-SDP. With the pH values increasing from 7 to 12, the MRR increased from 6.69 µm/h to 13.67 µm/h. The optimal surface quality was obtained at pH = 9, the surface roughness (Ra) reached 2.35 nm, and the corresponding MRR was 9.71 µm/h. The MRR increased from 9.71 µm/h to 34.95 µm/h with the H2O2 concentrations increasing from 0 to 2 vol.%. When the concentration of H2O2 was 1 vol.%, the Ra of tungsten reached the lowest value, which was 1.87 nm, and the MRR was 26.46 µm/h. This reveals that C-SDP technology is a novel ultra-precision machining method that can achieve great surface qualities and polishing efficiency of tungsten.
      Citation: Micromachines
      PubDate: 2022-05-12
      DOI: 10.3390/mi13050762
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 763: A MEMS-Based High-Fineness Fiber-Optic
           Fabry–Perot Pressure Sensor for High-Temperature Application

    • Authors: Suwei Wang, Jun Wang, Wenhao Li, Yangyang Liu, Jiashun Li, Pinggang Jia
      First page: 763
      Abstract: In this paper, a high-fineness fiber-optic Fabry–Perot high-temperature pressure sensor, based on MEMS technology, is proposed and experimentally verified. The Faber–Perot cavity of the pressure sensor is formed by the anodic bonding of a sensitive silicon diaphragm and a Pyrex glass; a high-fineness interference signal is obtained by coating the interface surface with a high-reflection film, so as to simplify the signal demodulation system. The experimental results show that the pressure sensitivity of this sensor is 55.468 nm/MPa, and the temperature coefficient is 0.01859 nm/°C at 25~300 °C. The fiber-optic pressure sensor has the following advantages: high fineness, high temperature tolerance, high consistency and simple demodulation, resulting in a wide application prospect in the field of high-temperature pressure testing.
      Citation: Micromachines
      PubDate: 2022-05-12
      DOI: 10.3390/mi13050763
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 764: A Comparative Evaluation of
           Magnetorheological Micropump Designs

    • Authors: Sevki Cesmeci, Rubayet Hassan, Mahmoud Baniasadi
      First page: 764
      Abstract: In this study, we assessed the performance characteristics of five different magnetorheological micropump designs, two of which were our proposed designs, while others were from the existing designs in the literature. Comparisons have been performed based on physics-based simulations, and the fully coupled magneto-solid-fluid interaction simulations were carried out in COMSOL Multiphysics software. For a fair and meaningful comparison, both the material and geometric properties were kept the same, and the simulations were run for one complete pumping cycle. The results showed that the proposed flap and duckbill valve models could pump 1.09 µL and 1.16 µL respectively in 1 s, which was more than the rest of the existing micropump models. Moreover, at 0.5 s, when the magnetic flux density was maximum, the flap and duckbill valve models could pump almost twice as fluid as some of the existing valve models did. The results also demonstrated that the flap and duckbill valve models were nearly five times faster than some of existing models. In conclusion, the proposed two micropump models could propel more net fluid volume than the existing micropump designs, experienced low leakage during the contraction and expansion phase, and had faster response times. We believe that the present study provides valuable insights for future micropump designs, which have an extensive range of application areas, ranging from insulin dosing systems for T1D patients to artificial organs to transport blood and from organ-on-chip applications to micro-cooling systems.
      Citation: Micromachines
      PubDate: 2022-05-12
      DOI: 10.3390/mi13050764
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 765: Manufacturing of Porous Glass by
           Femtosecond Laser Welding

    • Authors: Hua Tan, Jiahui Pan, Xiaojia Zheng, Xiaoquan Fu, Yuxun Zhang, Yanxing Liu, Qiheng Huang
      First page: 765
      Abstract: Based on femtosecond laser glass welding, four different porous structures of welding spots were formed by the manufacturing processes of spatiotemporal beam shaping and alternating high repetition rate transformation. Compared with an ordinary Gaussian beam, the welding spot fabricated by the flattened Gaussian beam had smoother welding edges with little debris, and the bottom of the welding spot pore was flat. Instead of a fixed high repetition rate, periodically alternating high repetition rates were adopted, which induced multiple refractive indices in the welding spot pore. The welding spot pores manufactured by spatiotemporal beam shaping and alternating high repetition rate transformation have a special structure and excellent properties, which correspond to superior functions of porous glass.
      Citation: Micromachines
      PubDate: 2022-05-12
      DOI: 10.3390/mi13050765
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 766: Analysis of Tool Wear and Roughness of
           Graphite Surfaces Machined Using MCD and NCD-Coated Ball Endmills

    • Authors: Hyeonhwa Lee, Jinsoo Kim, Jeongyeon Park, Jongsu Kim
      First page: 766
      Abstract: The high-purity G5 graphite material is widely used for glass moulding and provides high hardness and brittleness because it is sintered to fine particles unlike other graphite materials. Hence, tool cutting of a G5 workpiece is performed by local fracture instead of plastic deformation of the machined surface. Although a diamond-coated tool with outstanding hardness is used to machine very hard graphite, the tool shows variability regarding the service life and machining performance depending on the grain size, even in the same machining environment. We investigated the wear and change trend of machined surface roughness considering microcrystalline diamond (MCD) and nanocrystalline diamond (NCD)-coated tools, which are generally used to machine graphite materials, and analysed their relation with coating. For rough machining, the MCD-coated tool, for which the delamination of coating occurred later, showed less wear and improved machined surface roughness. For precision machining, the NCD tool showed less tool wear rate relative to the cutting length, leading to a small difference in the machined surface roughness between the two tools. We conclude that if rough and precision machining processes are performed using the same cutting tool, the MCD-coated tool is advantageous in terms of service life, while the difference in roughness of the final machined surface between the tools is negligible.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050766
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 767: Particularities of R134a Refrigerant
           Temperature Variations in a Transient Convective Regime during
           Vaporization in Rectangular Microchannels

    • Authors: Ioan Mihai, Cornel Suciu, Claudiu Marian Picus
      First page: 767
      Abstract: An analysis of the R134a (tetrafluoroetane) coolant’s non-stationary behavior in rectangular microchannels was conducted with the help of a newly proposed miniature refrigerating machine of our own design and construction. The experimental device incorporated, on the same plate, a condenser, a lamination tube and a vaporizer, all of which integrated rectangular microchannels. The size of the rectangular microchannels was determined by laser profilometry. R-134a coolant vapors were pressurized using a small ASPEN rotary compressor. Using the variable soft spheres (VSS) model, the mean free path, Knudsen and Reynolds numbers, as well as the dimensionless velocity profile can be assessed analytically. In order to determine the average dimensionless temperature drop in the vaporizer’s rectangular microchannels, in non-stationary regime, an analytical solution for incompressible flow with slip at the walls, fully developed flow and laminar regime was used, by aid of an integral transform approach. In the experimental study, the transitional distribution of temperature was tracked while modifying the R134a flow through the rectangular microchannels. Coolant flow was then maintained at a constant, while the amount of heat absorbed by the vaporizer was varied using multiple electric resistors. A comparative analysis of the analytical and experimental values was conducted.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050767
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 768: Oscillation Characteristics of an
           Artificial Cochlear Sensory Epithelium Optimized for a Micrometer-Scale
           Curved Structure

    • Authors: Hiroki Yamazaki, Yutaro Kohno, Satoyuki Kawano
      First page: 768
      Abstract: Based on the modern microelectromechanical systems technology, we present a revolutionary miniaturized artificial cochlear sensory epithelium for future implantation tests on guinea pigs. The device was curved to fit the spiral structure of the cochlea and miniaturized to a maximum dimension of <1 mm to be implanted in the cochlea. First, the effect of the curved configuration on the oscillation characteristics of a trapezoidal membrane was evaluated using the relatively larger devices, which had a trapezoidal and a comparable curved shape designed for high-precision in vitro measurements. Both experimental and numerical analyses were used to determine the resonance frequencies and positions, and multiple oscillation modes were clearly observed. Because the maximum oscillation amplitude positions, i.e., the resonance positions, differed depending on the resonance frequencies in both trapezoidal and curved membrane devices, the sound frequency was determined based on the resonance position, thus reproducing the frequency selectivity of the basilar membrane in the organ of Corti. Furthermore, the resonance frequencies and positions of these two devices with different configurations were determined to be quantitatively consistent and similar in terms of mechanical dynamics. This result shows that despite a curved angle of 50–60°, the effect of the curved shape on oscillation characteristics was negligible. Second, the nanometer-scale oscillation of the miniaturized device was successfully measured, and the local resonance frequency in air was varied from 157 to 277 kHz using an experimental system that could measure the amplitude distribution in a two-dimensional (2D) plane with a high accuracy and reproducibility at a high speed. The miniaturized device developed in this study was shown to have frequency selectivity, and when the device was implanted in the cochlea, it was expected to discriminate frequencies in the same manner as the basilar membrane in the biological system. This study established methods for fabricating and evaluating the miniaturized device, and the proposed miniaturized device in a curved shape demonstrated the feasibility of next-generation cochlear implants.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050768
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 769: Beating of a Spherical Liquid Crystal
           Elastomer Balloon under Periodic Illumination

    • Authors: Wenyan Cheng, Quanbao Cheng, Changshen Du, Yuntong Dai, Kai Li
      First page: 769
      Abstract: Periodic excitation is a relatively simple and common active control mode. Owing to the advantages of direct access to environmental energy and controllability under periodic illumination, it enjoys broad prospects for application in soft robotics and opto-mechanical energy conversion systems. More new oscillating systems need to be excavated to meet the various application requirements. A spherical liquid crystal elastomer (LCE) balloon model driven by periodic illumination is proposed and its periodic beating is studied theoretically. Based on the existing dynamic LCE model and the ideal gas model, the governing equation of motion for the LCE balloon is established. The numerical calculations show that periodic illumination can cause periodic beating of the LCE balloon, and the beating period of the LCE balloon depends on the illumination period. For the maximum steady-state amplitude of the beating, there exists an optimum illumination period and illumination time rate. The optimal illumination period is proved to be equivalent to the natural period of balloon oscillation. The effect of system parameters on beating amplitude are also studied. The amplitude is mainly affected by light intensity, contraction coefficient, amount of gaseous substance, volume of LCE balloon, mass density, external pressure, and damping coefficient, but not the initial velocity. It is expected that the beating LCE balloon will be suitable for the design of light-powered machines including engines, prosthetic blood pumps, aircraft, and swimmers.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050769
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 770: Kinetics Analysis and ADRC-Based
           Controller for a String-Driven Vascular Intervention Surgical Robotic
           System

    • Authors: Wei Zhou, Shuxiang Guo, Jin Guo, Zhengyang Chen, Fanxu Meng
      First page: 770
      Abstract: Vascular interventional surgery is a typical method for diagnosing and treating cardio-cerebrovascular diseases. However, a surgeon is exposed to significant X-radiation exposure when the operation is conducted for a long period of time. A vascular intervention surgical robotic system for assisting the surgeon is a promising approach to address the aforementioned issue. When developing the robotic system, a high displacement accuracy is crucial, and this can aid in enhancing operating efficiency and safety. In this study, a novel kinetics analysis and active disturbance rejection control (ADRC)-based controller is proposed to provide high accuracy for a string-driven robotic system. In this controller, kinetics analysis is initially used to improve the accuracy affected by the inner factors of the slave manipulator. Then, the ADRC controller is used to further improve the operating accuracy of the robotic system. Finally, the proposed controller is evaluated by conducting experiments on a vascular model. The results indicate maximum steady errors of 0.45 mm and 6.67°. The experimental results demonstrate that the proposed controller can satisfy the safety requirements of the string-driven robotic system.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050770
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 771: Atomization Characteristics of Hydrogen
           Peroxide Solutions in Electrostatic Field

    • Authors: Xuefeng Huang, Ling Sheng, Yibin Lu, Shengji Li
      First page: 771
      Abstract: Hydrogen peroxide (H2O2) can be considered as a sterilant or a green propellant. For a common use in industrial application, spray is an effective method to form fine H2O2 droplets. In this paper, electrostatic atomization based on the configuration of needle ring electrodes is proposed to produce H2O2 spray by minimizing its effective surface tension. The breakup performances of H2O2 ligaments can be improved by increasing the electric field intensity, reducing the nozzle size, and adjusting suitable volume flow rate. The smallest average diameter of breakup droplets for 35 wt. % concentration H2O2 solution reached 92.8 μm under optimum operation conditions. The H2O2 concentration significantly influenced the breakup performance owing to the concentration effect on comprehensive physical properties such as density, surface tension, viscosity, and permittivity. The average diameters of breakup droplets decreased with decreasing H2O2 concentration. At 8 wt. % concentration, the average breakup droplet diameter was reduced to 67.4 μm. Finally, electrostatic atomization mechanism of H2O2 solution was analyzed by calculating dimensionless parameters of Re, We, and Oh numbers with the combination of the operation conditions and physical properties for in-depth understanding the breakup behaviors. The calculation showed that the minimum average diameter of breakup droplets was obtained at 8 wt. % concentration at the investigated range of H2O2 concentration, which kept in agreement with the experimental results.
      Citation: Micromachines
      PubDate: 2022-05-13
      DOI: 10.3390/mi13050771
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 772: Low Cost Three-Dimensional Programmed
           Mini-Pump Used in PCR

    • Authors: Chengxiong Lin, Yaocheng Wang, Zhengyu Huang, Yu Guo, Wenming Wu
      First page: 772
      Abstract: Programmed mini-pumps play a significant role in various fields, such as chemistry, biology, and medicine, to transport a measured volume of liquid, especially in the current detection of (COVID-19) with PCR. In view of the cost of the current automatic pipetting pump being higher, which is difficult to use in a regular lab, this paper designed and assembled a three-dimensional programmed mini-pump with the common parts and components, such as PLC controller, motor, microinjector, etc. With the weighting calibration before and after pipetting operation, the error of the pipette in 10 μL (0.2%), 2 μL (1.8%), and 1 μL (5.6%) can be obtained. Besides, the contrast test between three-dimensional programmed mini-pump and manual pipette was conducted with the ORF1ab and pGEM-3Zf (+) genes in qPCR. The results proved that the custom-made three-dimensional programmed mini-pump has a stronger reproducibility compared with manual pipette (ORF1ab: 24.06 ± 0.33 vs. 23.50 ± 0.58, p = 0.1014; pGEM-3Zf (+): 11.83.06 ± 0.24 vs. 11.50 ± 0.34, p = 0.8779). These results can lay the foundation for the functional, fast, and low-cost programmed mini-pump in PCR or other applications for trace measurements.
      Citation: Micromachines
      PubDate: 2022-05-14
      DOI: 10.3390/mi13050772
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 773: Interlacing Infills for Multi-Material
           Fused Filament Fabrication Using Layered Depth Material Images

    • Authors: Irfan Mustafa, Tsz Ho Kwok
      First page: 773
      Abstract: One major concern regarding multi-material additive manufacturing (MMAM) is the strength at the interface between materials. Based on the observation of how nature puts materials together, this paper hypothesizes that overlapping and interlacing materials with each other enhance the interface bonding strength. To test this hypothesis, this research develops a new slicing framework that can efficiently identify the multi-material regions and develop interlaced infills. Based on a ray-tracing technology, we develop layered depth material images (LDMI) to process the material information of digital models for toolpath planning. Each sample point in the LDMI has an associated material and geometric properties that are used to recover the material distribution in each slice. With this material distribution, this work generates an interlocking joint and an interlacing infill in the regions with multiple materials. The experiments include comparisons between similar materials and different materials. Tensile tests have shown that our proposed infill outperforms the interlocking joint in all cases. Fractures occur even outside the interlacing area, meaning that the joint is at least as strong as the materials. The experimental results verify the enhancement of interface strength by overlapping and interlacing materials. In addition, existing computational tools have limitations in full use of material information. To the best of our knowledge, this is the first time a slicer can process overlapped material regions and create interlacing infills. The interlacing infills improve the bonding strength, making the interface no longer the weakest area. This enables MMAM to fabricate truly functional parts. In addition, the new LDMI framework has rich information on geometry and material, and it allows future research in multi-material modeling.
      Citation: Micromachines
      PubDate: 2022-05-14
      DOI: 10.3390/mi13050773
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 774: Module-Fluidics: Building Blocks for
           Spatio-Temporal Microenvironment Control

    • Authors: Bowen Ling, Ilenia Battiato
      First page: 774
      Abstract: Generating the desired solute concentration signal in micro-environments is vital to many applications ranging from micromixing to analyzing cellular response to a dynamic microenvironment. We propose a new modular design to generate targeted temporally varying concentration signals in microfluidic systems while minimizing perturbations to the flow field. The modularized design, here referred to as module-fluidics, similar in principle to interlocking toy bricks, is constructed from a combination of two building blocks and allows one to achieve versatility and flexibility in dynamically controlling input concentration. The building blocks are an oscillator and an integrator, and their combination enables the creation of controlled and complex concentration signals, with different user-defined time-scales. We show two basic connection patterns, in-series and in-parallel, to test the generation, integration, sampling and superposition of temporally-varying signals. All such signals can be fully characterized by analytic functions, in analogy with electric circuits, and allow one to perform design and optimization before fabrication. Such modularization offers a versatile and promising platform that allows one to create highly customizable time-dependent concentration inputs which can be targeted to the specific application of interest.
      Citation: Micromachines
      PubDate: 2022-05-14
      DOI: 10.3390/mi13050774
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 775: Design Aspects of Additive
           Manufacturing at Microscale: A Review

    • Authors: Nikolaos Rogkas, Christos Vakouftsis, Vasilios Spitas, Nikos D. Lagaros, Stelios K. Georgantzinos
      First page: 775
      Abstract: Additive manufacturing (AM) technology has been researched and developed for almost three decades. Microscale AM is one of the fastest-growing fields of research within the AM area. Considerable progress has been made in the development and commercialization of new and innovative microscale AM processes, as well as several practical applications in a variety of fields. However, there are still significant challenges that exist in terms of design, available materials, processes, and the ability to fabricate true three-dimensional structures and systems at a microscale. For instance, microscale AM fabrication technologies are associated with certain limitations and constraints due to the scale aspect, which may require the establishment and use of specialized design methodologies in order to overcome them. The aim of this paper is to review the main processes, materials, and applications of the current microscale AM technology, to present future research needs for this technology, and to discuss the need for the introduction of a design methodology. Thus, one of the primary concerns of the current paper is to present the design aspects describing the comparative advantages and AM limitations at the microscale, as well as the selection of processes and materials.
      Citation: Micromachines
      PubDate: 2022-05-15
      DOI: 10.3390/mi13050775
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 776: Simulation of Temperature Field in
           Micro-EDM Assisted Machining of Micro-Holes in Printed Circuit Boards

    • Authors: Manqun Lian, Xinke Feng, Bin Xu, Lianyu Fu, Kai Jiang
      First page: 776
      Abstract: High-speed mechanical drilling based on the micro-bit is the mainstream process technology for machining micro-holes in the printed circuit board (PCB). However, the above process to obtain PCB micro-holes is prone to defects, such as hole burrs and nail heads in the hole. In this paper, the micro electrical discharge machining (micro-EDM) was used as an auxiliary means for machining PCB micro-holes to effectively eliminate the defects such as hole burrs and nail heads. However, during the process of micro-EDM, the micro-bit will be gradually worn, thus negatively affecting the machining quality of PCB micro-holes. To solve the above problems, in this paper, the temperature field model of micro-EDM-assisted machining of PCB micro-holes was established to predict the micro-bit wear by analyzing the temperature field with COMSOL Multiphysics software. This paper made an extensive study of the influences of spindle speed, machining voltage, and pulse width on temperature field and micro-bit wear. The simulation results show that with the increase in machining voltage and pulse width, the temperature of PCB micro-hole machining increases, resulting in an increase in micro-bit wear. The spindle rotation is beneficial to the updating of the machining medium and the discharge of heat generated from EDM. Therefore, with the increase in spindle speed, the temperature of PCB micro-hole machining and the micro-bit wear is reduced.
      Citation: Micromachines
      PubDate: 2022-05-15
      DOI: 10.3390/mi13050776
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 777: Influence of Polyvinylpyrrolidone
           Concentration on Properties and Anti-Bacterial Activity of Green
           Synthesized Silver Nanoparticles

    • Authors: Raghad Zein, Ibrahim Alghoraibi, Chadi Soukkarieh, Mohammad Taher Ismail, Abdalrahim Alahmad
      First page: 777
      Abstract: Environmentally green synthesis of stable polyvinyl pyrrolidone (PVP)-capped silver nanoparticles (PVP-AgNPs) was successfully carried out. The present study focused on investigating the influence of adding PVP during the synthesis process on the size, optical properties and antibacterial effect of silver nanoparticles produced. An aqueous extract of Eucalyptus camaldulensis leaves was used as a reducing agent. The effects of different PVP concentrations and reducing time on the synthesis of nanoparticles (NPs) were characterized by UV–Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and nano tracker analysis (NTA). The addition of PVP was studied. The prepared PVP-AgNPs were spherical with an average size of 13 nm. FTIR analysis confirmed that PVP protects AgNPs by a coordination bond between silver nanoparticles and both N and O of PVP. DLS results indicated the good dispersion of silver nanoparticles. PVP-AgNPs were found to be stable for nearly 5 months. Antibacterial studies through the agar well diffusion method confirmed that silver nanoparticles synthesized using PVP had no inhibitor activity toward Gram-positive and Gram-negative bacteria as opposed to silver nanoparticles prepared without adding PVP, which showed a significant antibacterial activity towards some of the tested pathogens.
      Citation: Micromachines
      PubDate: 2022-05-15
      DOI: 10.3390/mi13050777
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 778: Micro Aspheric Convex Lenses Fabricated
           by Precise Scraping

    • Authors: Meng-Ju Lin
      First page: 778
      Abstract: An easy, fast, inexpensive, and simple method utilizing a microshaper with a very small knife nose is used to fabricate microconvex aspherical lenses. The microshaper is mounted on a computer numerical control (CNC) machine. To achieve an accurately designed profile of the lens surface, a cutter-path planning algorithm with compensation for knife interference is developed. Exerting this algorithm in CNC machining, the microconvex aspheric surface is precisely scraped. To verify the precise machining of the cutter path planning algorithm, three aspheric surfaces of conic sections (ellipsoid, paraboloid, and hyperboloid) are successfully fabricated. The profiles scraped by the microshaper agree well and precisely with the designed theoretical conic section curve. Using a simple polishing method to make the machined surface smoother, the roughness is reduced from 143 and 346 nm to 52 and 44 nm for the path line direction and its transverse direction, respectively. The micro-aspherical lenses have moderate machining properties using a simple polishing method. The results show that the designed profiles of micro-aspheric convex lenses can be machined precisely and efficiently by the microshaper with the cutter-path planning algorithm developed in this work. From the image comparison formed by the aspherical and spherical microlenses, the aspherical lenses provide a better image. It is feasible that the designed profile of the micro-aspherical lenses with specific functions could be machined using the cutter-path planning algorithm developed in this work.
      Citation: Micromachines
      PubDate: 2022-05-15
      DOI: 10.3390/mi13050778
      Issue No: Vol. 13, No. 5 (2022)
       
  • Micromachines, Vol. 13, Pages 779: High Quality-Factor and Spectrum-Clean
           AlN Lamb-Wave Resonators with Optimized Lateral Reflection Boundary
           Conditions and Transducer Design

    • Authors: Haiyan Sun, Shitao Lv, Aoyu Zhang, Chenguang Song, Xinyi Sun, Fazeng Tan, Liuhong Liang, Yinfang Zhu, Jicong Zhao
      First page: 779
      Abstract: This paper presents a high quality-factor (Q) and spectrum-clean AlN Lamb-wave resonator (LWR). The width of its lateral reflection boundary was optimized to weaken the transverse modes’ coupling and wave guiding, and then to improve the LWR’s Q value and spectral purity, which was verified by finite element analysis and experimental characterization. In addition, the series resonance quality factor (Qs) value of the interdigitated (IDT)-Ground LWR is similar to that of the IDT-Floating LWR, but its parallel resonance quality factor (Qp) is nearly doubled, due to the reduction of the electrical loss induced by its static capacitance (C0). The measured results show that the designed LWR with optimized boundary reflection conditions and IDT-Ground structure exhibit Qs and Qp values as high as 4019.8 and 839.5 at 401.2 MHz and 402.9 MHz, respectively, meanwhile, it has good spectral purity. Moreover, the influence of the metal ratio and material of the LWR’s IDT electrodes on the device’s performance was also studied by theoretical analysis and experimental verification.
      Citation: Micromachines
      PubDate: 2022-05-15
      DOI: 10.3390/mi13050779
      Issue No: Vol. 13, No. 5 (2022)
       
 
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