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Sensors and Actuators A: Physical
Journal Prestige (SJR): 0.699
Citation Impact (citeScore): 3
Number of Followers: 179  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0924-4247
Published by Elsevier Homepage  [3182 journals]
  • A simple method for detection of low concentrations of fluoride in
           drinking water
    • Abstract: Publication date: Available online 21 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Vahid Moradi, Emmanuelle A. Caws, Peter M. Wild, Heather L. Buckley Naturally occurring elevated levels of fluoride in drinking water pose a health hazard throughout the developing world, with over 200 million people potentially impacted. In some cases, treatment methods or safer alternative sources are available, but robust, simple, affordable technologies for measuring fluoride in drinking water are absent. In this work, a simple method for fluoride detection is presented comprising a 35 nm aluminum coating on the distal tip of a length of single mode optical fiber. Broadband light is launched into the proximal end of the optical fiber and a portion of this light is reflected by the distal tip of the fiber, which is immersed in water containing an unknown concentration of dissolved fluoride. The intensity of the reflected light is detected by a photodiode connected to the proximal end of the fiber. The aluminum coating is removed from the distal tip by reaction with the dissolved fluoride at a rate that depends on the fluoride concentration and the intensity of the light reflected from the distal tip depends upon the thickness of this coating. Therefore, the rate at which the intensity of light detected by the photodiode decreases is correlated with the concentration of fluoride. The fabricated sensor measures fluoride concentration within the range of 0-5 mg L-1
  • Mechanics of Direct Bonding: Splitting Forces
    • Abstract: Publication date: Available online 19 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Y. Zimin, T. Ueda, K. Tatsumi The bonding strength between dissimilar materials depends heavily on internal stresses, which arise due to the differences in the thermal expansion coefficients of the materials. While the existing models describe the splitting forces near the edges of the structure, those in the main part of the structure remote from the edges, where the stresses are uniformly distributed along the interface, have not been calculated yet. This study attempts to fill this knowledge gap in the mechanics of bonded structures. Herein, we propose a model that allows the calculation of the splitting forces in the basic part of the bonded bilayer where the internal stresses along interface are uniformly distributed. The calculations reveal three possible distributions of the splitting forces in the bonded structure, i.e., the splitting forces could be either located at the center or the periphery—which also includes the edges of the structure, or could be completely absent regardless of the total magnitude of the residual stresses. The results obtained could be used in bonding technology as an immediate guide to increasing the bonding strength between dissimilar materials.Graphical abstractGraphical abstract for this article
  • Fabrication of Poly (Vinylidene Fluoride-Trifluoroethylene) – Zinc Oxide
           based Piezoelectric Pressure Sensor
    • Abstract: Publication date: Available online 16 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Subash Cherumannil Karumuthil, Kulwant Singh, Uvais Valiyaneerilakkal, Jamil Akhtar, Soney Varghese We report the fabrication, packaging and characterization of pressure sensing device using piezoelectric polymer nanocomposite as the sensing active layer. We introduce Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))/ 1% Zinc oxide (ZnO) piezoelectric polymer nanocomposite as pressure sensing material. Optimized polymer nanocomposite is employed for real environment pressure sensor fabrication. A recipe for the fabrication of pressure sensor with polymer nanocomposite is suggested and fabricated. Process flow involved in the fabrication and various stages of optimizations are discussed. Packaging and characterization of fabricated pressure sensor devices are also discussed. The ability of the packaged device to sense the air pressure is analyzed through a working prototype having a sensitivity of 0.175 µV/psi. Results obtained from the device shows the capability of material to act as a sensor.Graphical abstractGraphical abstract for this article
  • Enhancing out-of-plane stroke in piezoelectrically driven micro-lens
           actuator with residual stress control
    • Abstract: Publication date: Available online 16 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Ssu-Han Chen, Aron Michael, Chee Yee Kwok This paper presents the fabrication and characterization of a high performance piezoelectrically driven micro-lens actuator. The fabrication method involves controlling the residual stresses in the structure to predefine the initial deflection of the actuator, resulting in a larger actuation stroke. The residual stress control exploits the unique properties of ultra-high vacuum e-beam evaporated film to form thick tensile polysilicon as the actuator structural layer. This is complemented by a compressive RF-sputtered SiO2 layer on top of the structural layer. Such films are subsequently annealed during various fabrication stages to obtain the designated stress values for compensating the residual moments generated from the electrode and piezoelectric layers of the actuator. Two micro-lens actuators of the same design but with different residual stress levels in the structural layers are fabricated and compared, where one device has an initial deflection close to −47 μm and another −98 μm. The device with a larger downward initial deflection shows 57.2% higher actuation sensitivity than the other device. The actuators exhibit a large out-of-plane stroke of 145 μm and 228 μm, respectively, and at 22 V with a resonant frequency close to 2 kHz.Graphical abstractGraphical abstract for this article
  • Development of the extension type pneumatic soft actuator with built-in
           displacement sensor
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators A: Physical, Volume 300Author(s): Osamu Azami, Daisuke Morisaki, Tetsuro Miyazaki, Takahiro Kanno, Kenji Kawashima This paper proposes a method for a soft pneumatic actuator to measure its displacement without external position sensors, which are usually difficult for washing and sterilization. Medical systems and food industry desire disposable, precise, and human-friendly actuators. The method utilizes a metal spring which covers the cylindrical soft actuator, as the inductance of the spring changes according to the length of the metal spring. The spring also restrains the radial expansion of the actuator during pressurization. This actuator is lightweight, weighing about 30 [g] and is washable, sterilizable and disposable. An approximation of the relationship between the frequency and position was obtained, and its validity was evaluated through experiments. The displacement sensing of the proposed actuator has good accuracy for use in medical robots and other robots working with humans.
  • Fluidic oscillator actuated by a cavity at high frequencies
    • Abstract: Publication date: Available online 15 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Taro Handa, Ikuhiro Fujimura In this study, a flat device for generating the small jets flapping at several tens of kHz (i.e., high-frequency fluidic oscillator) is proposed. The device involves a thin flow passage (2.0 mm thickness) with a cavity whose length is adjustable. The jets are discharged through two slots located at both ends of the cavity. The widths of the upstream and downstream slots are 1.0 mm and 4.0 mm, respectively, and the cavity width is 9.0 mm. The flapping frequencies and motions of the jets are experimentally investigated varying the ratio of the upstream stagnation pressure to backpressure from 2.0 to 3.0. In the experiments, the jets are visualized using the schlieren technique and the time-dependent pressure fluctuations in the cavity are measured with a semiconductor-type pressure sensor. The experimental results demonstrate that a flapping jet whose width is ∼1 mm is generated successfully from the device and the flapping frequency is selectable just by adjusting the cavity length between 15 and 29 kHz keeping a supply pressure constant, i.e., the flapping frequency is controllable independently of the mass flow rate in the device. In addition, the flapping frequencies are evaluated by modeling the oscillation mechanism on the basis of the flow visualization results. The flapping frequencies measured in the experiments are successfully reproduced using the model.Graphical abstractGraphical abstract for this article
  • Highly Flexible All-Nonwoven Piezoelectric Generators Based on Electrospun
           Poly(vinylidene fluoride)
    • Abstract: Publication date: Available online 14 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Young Jin Hwang, Sejin Choi, Han Seong Kim Acoustic energy is a sustainable and clean form of energy that is always being generated and wasted in our environment. Acoustic energy harvesting technology is a very promising substitute for fossil fuels and can serve as a suitable power supply for small electronic devices, owing to the high efficiency of piezoelectric devices. Thus, many studies have investigated the conversion of sound energy into electricity for power generation. In this study, we successfully fabricated an all-nonwoven polymer-based piezoelectric generator with a high acoustic energy conversion efficiency and high flexibility. A dispersion of single-walled carbon nanotubes (SWCNTs) was sprayed onto electrospun poly(vinylidene fluoride) (PVDF) webs to produce flexible and durable electrodes. The thickness and flexibility of the PVDF web used as the active piezoelectric layer were controlled by the spinning time. The effect of flexibility on frequency response, sound pressure response, output power, and energy harvesting characteristics was investigated by observing sound wave-induced vibration behavior and evaluating the output characteristics of the generators. The all-nonwoven polymer-based generator with the highest flexibility showed the highest output voltage overall due to its excellent vibration characteristics. Due to its effectiveness and durability suitable for acoustic energy harvesting, this all-nonwoven polymer-based generator can be useful for a wide range of applications, such as wearable electronics and large area flexible devices.Graphical abstractGraphical abstract for this article
  • Temperature-drift characterization of a micromachined resonant
           accelerometer with a low-noise frequency readout
    • Abstract: Publication date: Available online 14 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Zhengxiang Fang, Yonggang Yin, Xiaofei He, Fengtian Han, Yunfeng Liu This paper describes the design and experimental evaluation of a silicon micromachined resonant accelerometer with high scale factor and low temperature drift. The device was fabricated by bulk micromachining and sealed in a hermetic metallic package to ensure the resonator operates with high Q-factor. By optimizing the structure, the scale factor of the resonant accelerometer was increased to 361 Hz/g, which is close to the simulated result of 336 Hz/g taking into account the measurement range of ±14 g. The bias-temperature drift coefficient fell to 4.4 μg/°C. A digital frequency readout was implemented using a continuous time stamping method. The measured relative resolution within the operating frequency range of the resonator was better than 1.8 ppb at 1 Hz data update rate. Thus, we have produced a miniaturized resonator accelerator without the bulky commercial frequency counters used in our previous work. A test chamber at a constant temperature varying by only ±0.01°C was used to characterize the temperature drift of the accelerometer prototypes by isolating the disturbances due to the ambient temperature. After increasing the scale factor and decreasing the temperature sensitivity, the 3-day bias stability was measured to be 2.19 μg and 0.51 μg for room-temperature and constant-temperature operations, respectively. Furthermore, the long-term bias stability was 1.77 μg in 30-day measurements when the temperature variations were controlled to be within ±0.01°C. The experimental results indicate that this resonant accelerometer exhibits excellent long-term temperature stability, which offers the promise for high-performance shipborne inertial navigation applications.Graphical Graphical abstract for this article
  • Design and implementation of a passive micro flow sensor based on
           diamagnetic levitation
    • Abstract: Publication date: Available online 14 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Gizem Aydemir, Ali Koşar, Huseyin Uvet This study presents a prototype of a micro-flow sensor based on magnetic levitation for the use in microfluidic systems. Accurate assessment of flow rates is crucial in the microfluidic system design. Micro-sensors utilizing levitation constitute an important topic in this regard. Diamagnetic levitation is an efficient technique, which is useful in applications with low power consumption and eliminates friction. With the proposed approach, zero mechanical contact in a microfluidic channel can be achieved. A sensor capable of accurately measuring flow rates was designed in this study. The corresponding flow rate range was between 1000 µL/min and 7000 µL/min. Levitation was accomplished with pyrolytic graphite and a ring magnet (NdFeB) acting as a lifter. The displacement of the micro-magnet in the micro channel in longitudinal direction was monitored via a microscope-camera system and was measured via a laser sensor above the lifter-magnet. A commercial analysis software (COMSOL Multiphysics Version 5.3 CPU License No: 17076072) was used for dynamic analysis and validation of experimental results. The flow rates were obtained using the data from the laser sensor via an exclusively coded C# program. The developed sensor prototype, which has the advantages of simple structure, small size and low cost, is a substantial candidate for the use in microfluidic devices requiring high accuracy.Graphical abstractLevitation was accomplished with pyrolytic graphite and a ring magnet (NdFeB) configured as a “lifter-magnet”. The displacement of the micro-magnet in the micro channel in longitudinal direction was monitored via a microscope-camera system and was measured via a laser sensor above the lifter-magnet.Graphical abstract for this article
  • Development of a high-precision gamma-ray source finder based on a single
    • Abstract: Publication date: Available online 13 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Ali Farzanehpoor Alwars, Faezeh Rahmani In this research, the conceptual design of an orphan gamma-ray finder based on a single NaI(Tl) scintillation detector in energy range of ∼50 keV to ∼3 MeV using Monte Carlo (MCNPX2.6) code has been presented. In the conventional finders, usually 2, 3 or more detectors are used. First, the system including three 2-in. NaI(Tl) scintillation detectors has been investigated. Based on the results, a newer approach to find the angular position of γ-ray orphan source for the system including only one 2-in. NaI(Tl) scintillation detector has been proposed. The height difference between an orphan source’s position and central axis of detector will decrease the precision of determining spatial location as well as activity calculation of the source. In this research, 3D localization of an orphan γ-ray source in a limited space using an electromechanical motorized laboratory jack has been enabled. This system can determine location and activity of an orphan source in distances of 2.0 m to 10.0 m from center of this system with activity of 3.77 × 106 Bq with relative errors less than 3% and 6%, respectively.Graphical abstractGraphical abstract for this article
  • Carbon based Polyimide Nanocomposites Thin Film Strain Sensors Fabricated
           by Ink-jet Printing Method
    • Abstract: Publication date: Available online 13 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Qiuyan Li, Shijing Luo, Ying Wang, Qing-Ming Wang Carbon-nanotube (CNT) and graphene-nanoplate (GNP) are two popular fillers to fabricate carbon-based nanocomposite devices. In this study, CNT-polyimide (PI) and GNP-PI nanocomposite thin film piezoresistive strain sensors were fabricated on flexible polyimide substrates and their electromechanical properties were characterized. The percolation thresholds were first determined for the two nanocomposites by investigating the volumetric conductivity as a function of filler concentration. Inkjet printing technique was employed to produce the nanocomposite devices with filler concentrations around the percolation threshold. The interdigital electrodes pre-deposited on the substrate were used for the electrical measurement of the devices. The piezoresistive sensitivity of the nanocomposite strain sensors was characterized by uniaxial tensile tests. The optimal compositions of 1.8 wt% CNT-PI and 1.4wt% GNP-PI nanocomposites were suggested for maximum gauge factors of 3.5 and 26, respectively. The temperature coefficients of resistance (TCR) for the fabricated nanocomposite thin film strain sensors were also characterized. The results demonstrate that GNP-PI nanocomposite strain sensors exhibit higher strain sensitivity than the CNT-PI counterpart. Temperature compensation is therefore necessary in practical applications of these nanocomposite strain sensors.Graphical abstractGraphical abstract for this article
  • Binary coded cantilevers for enhancing multi-harmonic atomic force
    • Abstract: Publication date: Available online 13 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yaoping Hou, Chengfu Ma, Wenting Wang, Yuhang Chen Harmonic atomic force microscopy (AFM) has been widely applied to characterize local mechanical properties of the specimens under imaging. However, the harmonic amplitude is commonly quite weak owing to the fast decay at an off-resonance state for a conventional cantilever and the internal resonance between eigenfrequencies and higher harmonics can amplify the harmonic response. Therefore, specific dynamic characteristics of AFM cantilevers are frequently required. Here, we proposed a coding scheme of a cantilever where the structure is described by a two-dimensional binary matrix to tailor its dynamic characteristics. Genetic algorithms combined with finite element analysis were used to optimize the code configuration. Cantilever properties including eigenfrequencies, stiffness and quality factor can be conveniently tuned to satisfy multiple requirements. AFM cantilevers were then re-designed with the second and the third resonance frequencies being moved to integer multiples of the fundamental one for higher harmonic enhancement, yet with minor stiffness alteration. Harmonic AFM imaging on a polymer mixture demonstrated that the amplitude difference between two material phases was increased up to at least 2.7 times for the 6th harmonic and 1.6 folds for the 18th harmonic using the optimized cantilevers. The enhancement of harmonic contrast can benefit the discrimination of different materials. The proposed binary coding method has advantages such as flexible tailoring of dynamic characteristics, multiple outputs of optimal structures, and automatic optimization. Consequently, it could be a promising way to design cantilevers for enhanced performances in various dynamic AFM imaging applications and also cantilever-based sensing.Graphical abstractGraphical abstract for this article
  • A Review on MEMS based Micro Displacement Amplification Mechanisms
    • Abstract: Publication date: Available online 13 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Sohail Iqbal, Afzaal Malik This paper provides a comprehensive review on the design and development of micro displacement amplification mechanisms. Micro displacement amplification mechanisms are gaining importance in MEMS applications where motion precision, reliability, accuracy, and compactness are needed. These displacement amplification mechanisms improve the sensitivity of micro-sensors and voltage stroke ratio of micro actuators. There advantages have opened doors for new and improved micro devices with unprecedented performance. In this paper, we have reviewed compliant displacement amplification mechanisms including bridge type mechanism, positioning stage amplification mechanism, Scott–Russell mechanism, mechanisms with micro-lever micromechanical levers concept, multi-stage force displacement amplification mechanism, hydraulic displacement amplification mechanism and thermally actuated displacement amplification mechanism. Different displacement amplification mechanisms incorporated with micro grippers, micro actuators especially piezoelectric are reviewed in detail.Graphical abstractGraphical abstract for this article
  • MEMS AlN pyroelectric infrared detector with medium to long wave IR
    • Abstract: Publication date: Available online 11 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Surender P. Gaur, Kamaljit Rangra, Dinesh Kumar Polycrystalline Aluminum Nitride (AlN) thin films are of significant interest due to their pyroelectric properties for last few years. In this paper, study on development of a polycrystalline AlN thin film based bulk micromachned pyroelectric IR detector is presented. Structural optimization of IR detector has been carried out using 3D finite element modeling (FEM) and simulations. A 1.0 µm thick thermally grown SiO2 layer used for thermal isolation, also serves as a diaphragm to hold the fabricated IR detector. Rate of temperature change (dT/dt) of the detector under dynamic heating is 0.12 to 0.15 ºK/s, and agrees well with the simulated value of 0.1 ºK/s. High pressure, N2 ambient sputtered Au film of thickness 160 nm has been used to enhance the IR absorptivity. IR absorptivity of detector on medium to long wave (2.5-25 µm) radiations is nearly 67%, and creates thermal gradient of 0.23 ºK between detector and substrate. Developed pyroelectric IR detector exhibits response time 8.0 ms, pyroelectric coefficient (ρ) 0.32 × 10-4 C/m2K, ρ/ε figure of merit (FOM) 0.3 C/m2K, and pyroelectric current responsivity (Ri) of 2.5 × 10-6 A/W.Graphical Graphical abstract for this article
  • Performance comparison of acoustic emission sensor arrays in different
           topologies for the localization of gas leakage on a flat-surface structure
    • Abstract: Publication date: Available online 11 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Xiwang Cui, Yong Yan, Yonghui Hu, Miao Guo The topology of the acoustic emission sensor array has an important effect on the performance of the leak localization technique. This paper compares the performances of different topologies of acoustic emission sensor arrays in the localization of gas leakage on a flat-surface structure. The principle of the leak localization is based on the near-field beamforming according to the spherical wave model and the narrowband filtering which can effectively avoid the influence of acoustic dispersion. The effect of different arrangements of the sensing elements in a sensor array on the localization accuracy is investigated and discussed. Eight typical topologies, including line, L-shaped, cross, triangle, star, circular, semi-circular and square shapes, are appraised through computer simulation. Simulation results suggest that all the arrays can perform leak localization but with different accuracies and that the L-shaped array outperforms all other topologies under the similar conditions. Furthermore, the optimal number of sensors in the L-shaped array which can maintain a reasonable accuracy of localization is analyzed. Experimental work was carried out on a laboratory scale test rig to verify and assess the effectiveness of the L-shaped array. The simulation and experimental results demonstrate that the L-shaped array is capable of identifying the location of a leak hole in a plate structure with a reasonably good accuracy.Graphical abstractGraphical abstract for this article
  • Highly integrable and normally open microvalve for industrial
           thermoplastic-based lab on PCB
    • Abstract: Publication date: Available online 9 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Francisco Perdigones, Jose Manuel Quero In this paper, a prototype of a highly integrable and normally-open in-line microvalve for industrial Lab on Printed Circuit Board, Lab on PCB (LoP) is described. This work is justified due to the lack of this kind of microvalves in LoPs. In addition, the proposed principle of working to close the microvalve has not been previously published. The microvalve is composed of industrial fabrication materials, that is, polymethylmethacrylate (PMMA) and Printed Circuit Board (PCB). The LoP and the microvalve share the same fabrication process, providing the characteristic of highly integrable. The procedure of fabrication of the device is based on milling for the plastic part, wet etching for the PCB, and a thermo-mechanical adhesion to perform the assembly. The actuation method is based on the increase of temperature due to the Joule effect of a copper line inside the working microchannel. The generated heat melts the PMMA microchannel and blocks it when the temperature reaches a value higher than the melting point of the plastic. The microvalve needs 3.1 A to be closed, being the time of closing 15 s with a power consumption of 440 mW.Graphical abstractGraphical abstract for this article
  • Thin-Film Bidirectional Transducers for Haptic Wearables
    • Abstract: Publication date: Available online 9 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Ian Trase, Zhe Xu, Zi Chen, Hong Tan, John X.J. Zhang We have designed, fabricated, and characterized a flexible electrostatic transducer (FET) for potential use as a wearable haptic actuator. This transducer both generates motion through the vibration of a curved electrode and measures the displacement of the same curved electrode to act as a displacement sensor. The transducer was analyzed through theory, simulation, and experiment to determine its displacement and sensing performance. It was found that a transducer with a footprint of 25 mm X 12.5 mm was able to generate displacements between 0.1 mm and 3.2 mm of displacement when operated at voltages between 25 V and 150 V. It was also capable of audible actuation at frequencies anywhere between 0.01 Hz and 10 kHz, including at target frequencies relevant to haptic communication. The transducer was able to sense changes to its shape through a change of capacitance, with a signal change of around 10% during maximum displacement. This sensing allows for both bidirectional communication and automatic displacement control through self-sensing. Simulation and theoretical results provide insight into the mechanism of actuation for the actuation and sensing systems, including predictions of displacement for a given voltage. User studies were also conducted, where it was found that the transducer generated perceivable and comfortable vibrations at both 26 Hz and 260 Hz, with 260 Hz being perceivable at lower amplitudes. The present work describes and characterizes a promising transducer for haptic communication.Graphical abstractGraphical abstract for this article
  • A giant magnetoimpedance-based separable-type method for supersensitive
           detection of 10 magnetic beads at high frequency
    • Abstract: Publication date: Available online 7 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Tao Wang, Yuyi Chen, Bicong Wang, Yi He, Hengyu Li, Mei Liu, Jinjun Rao, Zhizheng Wu, Shaorong Xie, Jun Luo A sensitive separable-type detection method based on giant magnetoimpedance effect in NiFe/Cu/NiFe/Cu/Cr films for detecting traces of magnetic beads (4.5 μm) at high frequency (> 5 MHz) was presented in this paper. A microcavity with a basement thickness of 0.3 mm was fabricated by Micro-nano carving technology, and was immobilized on the meander-shaped sensing elements for loading Dynabeads. Large resistance variations were observed in the frequency range of 30 MHz∼120 MHz by the presence of Dynabeads. This method is able to detect Dynabeads as low as 10 particles using one single giant magnetoimpedance sensor without using external magnetic fields and redundant washing steps, demonstrating high sensitivity, low complexity and nondestructive characteristic.Graphical abstractGraphical abstract for this article
  • Laser machined ultrathin microscale platinum thermometers on transparent
           oxide substrates
    • Abstract: Publication date: Available online 7 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Letian Wang, Zeqing Jin, Dongwoo Paeng, Yoonsoo Rho, Jiangyou Long, Matthew Eliceiri, YS. Kim, Costas P. Grigoropoulos Ultrathin microscale platinum resistive thermometers are of key value to transient temperature measurements. Neither transparent oxide substrates nor femtosecond laser patterning have been investigated for the fabrication of Pt thin film thermometers. Here, we have fabricated a laser machined, 50 μm wide and 50 nm thick, serpentine, Pt thin film sensor capable of sensing temperatures up to 650 °C over multiple heating and cooling cycles. Various materials and associated processing conditions were studied, including both sapphire and silica as transparent substrates, alumina and TiO2 as adhesion layers, and lastly alumina and silicon oxide as capping layer. In-situ resistance monitoring helps verify the multi-cycle stability of the sensor and guide the optimization. 10 μm sized sensors are laser machinable, but did not survive multiple heating and cooling cycles. We demonstrate that sensors with amorphous Ge thin layers can also repeatably measure temperatures up to 650 °C. It is anticipated that this sensor can be used for fast, high spatial resolution temperature probing for laser processing applications.Graphical abstractGraphical abstract for this article
  • A wave-inspired ultrastretchable strain sensor with predictable cracks
    • Abstract: Publication date: Available online 7 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Qiang Zou, Jia Zheng, Qi Su, Wanli Wang, Wei Gao, Zhuomin Ma The phenomenon in nature can always inspire human beings in technology. Waves in nature are the transmission of force and energy and the microstructure of wave can concentrate stress at the troughs. The concept of wave is applied to our crack-based strain sensor to benefit the improvement of stretchability of the crack sensor with a formation of predictable cracks. The wave-inspired crack-based strain sensor has wide strain range under the condition of ensuring the extremely high sensitivity. The specific tensile properties of the wave-like crack-based strain sensor are gauge factor (GF)∼80 (0% < ε < 30%), GF∼380 (30% < ε < 60%), GF∼2585(ε> 60%). In addition, it is easy to fabricate such sensors on a large scale with simple manufacturing processes. To demonstrate its excellent sensitivity, the sensor is employed in the monitoring of human expressions and motions. Meanwhile, robot behavior control and weight measurement are used to embody the wide strain range of the sensor. The crack-based strain sensor inspired by wave shows tremendous superiority in flexible wearable devices.Graphical abstractGraphical abstract for this article
  • Review of piezoelectric energy harvesting system and application of
           optimization techniques to enhance the performance of the harvesting
    • Abstract: Publication date: Available online 7 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Mahidur R. Sarker, Sabariah Julai, Mohd Faizul Mohd Sabri, Suhana Mohd Said, Md. Mainul Islam, Muhammad Tahir The energy harvesting (EH) from unused natural waste energy sources is common nowadays because of rising power demand. The sources have the potential of producing micro to milliwatts power depending on the ambient conditions. Many researchers have been concentrating on micro-level energy harvesting to provide power to the micro-devices in a remote area. The concept leads to a drastic reduction in cost. Once the structure is established, it can generate electricity with minimal cost or effort like renewable sources. This paper reviews the two key areas of the piezoelectric energy harvesting system (PEHS), namely, mechanical and electronic approaches, developed by several researchers. From the thorough review, it is realized that the existing technologies more or less can capable to EH by using the piezoelectric elements; however, the consistency and stability of the systems are not up to the mark yet. In this study, vibration-based PEHS has been considered for the application of the optimization technique to enhance its performance. This review has been focused on numerous challenges and recommendations for next-generation EH by utilizing vibration-based piezoelectric elements.Graphical Graphical abstract for this article
  • Highly Sensitive and Wide-Range Resonant Pressure Sensor Based on the
           Veering Phenomenon
    • Abstract: Publication date: Available online 5 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): N. Alcheikh, A.Z. Hajjaj, M.I. Younis We report a highly sensitive wide-range resonant pressure sensor. The concept is based on tracking multiple modes of vibration of an electrothermally heated initially curved micro-beam experiencing the veering phenomenon between its first and third vibration modes. For low values of pressure, the third resonance frequency is very sensitive, and thus its variation with pressure is monitored and recorded. As increasing pressure, the resonance frequency of the third mode decreases until reaching the veering phenomenon. At that point, the first mode exchanges role with the third mode, becoming very sensitive, and hence its frequency is tracked afterward as varying pressure. We show that using this concept, the sensitivity of the resonant pressure micro-sensor is significantly enhanced. Finite element method (FEM) simulations and experimental data show that the proposed micro-sensor becomes highly sensitive for wide-range of pressure from 38 mTorr to 200 Torr. The effect of various parameters on the performance of the proposed pressure sensor is investigated including the thickness of the micro-beam, the vacuum chamber size, and the thermal actuation load.Graphical abstractGraphical abstract for this article
  • Characteristic Analysis and Robust Control Design of Double-stage
           Precision Stabilized Platform
    • Abstract: Publication date: Available online 2 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yao Mao, Wei Ren, Wei Yu, Ge Ren Aiming at insufficiency in the passive and active disturbance suppression of the precision stabilized platform (PSP) system, in this study, a novel cascading double-stage PSP is designed and analyzed. Compared with the traditional structure, a new secondary PSP is provided to improve the disturbance suppression capability of the system over the full frequency range. The stabilizing mechanism of the secondary PSP is discussed in detail through dynamic modeling analysis of the double-stage PSP. This method can be used to solve the difficult compromise between the mechanical resonance and the control bandwidth in the design of the PSP with flexible support structure. Meanwhile, due to the reaction force of the primary PSP on the secondary PSP, the controlled object of the secondary PSP will be subjected to uncertain perturbation. Therefore, a robust control design method with a model is proposed to solve control problem of the secondary PSP. Theoretical and experimental results show that the secondary PSP brings better active and passive disturbance suppression ability for the stability control of the primary PSP.Graphical abstractGraphical abstract for this articleFig. 5 Model of double-stage PSP
  • A Metamaterial/Liquid-Core Waveguide Microfluidic Optical Sensor
    • Abstract: Publication date: Available online 1 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yixuan Wu, Yuan Meng, Baha Yakupoglu, Mark Adams This paper introduces the design of a novel microfluidic refractometric optical sensor. The sensor is able to detect a liquid analyte by converting the change in the refractive index (RI) of the analyte to a shift of resonance peak in the output spectrum. A liquid-core waveguide and gold/dielectric metamaterial are integrated in the sensor design, producing resonance in the waveguide when the light interacts with the metamaterial structure in the core. Finite element analysis is used to simulate the properties of the sensor to optimize the design. Sample sensors are fabricated and tested with liquid analytes which have known refractive indices. Experimental results are well matched to the simulation proving high sensitivity and good repeatability of the sensors. A sensitivity greater than 1280 nm/RIU is achieved by this novel sensor.
  • A Sub-Sampling Pulse-Resonance OOK Modulated Digital Ultrasound
           Communication System for Biomedical IoT
    • Abstract: Publication date: Available online 1 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Mohamed O. Abouzeid, Ahmet Tekin, Ahmed Nader Mohieldin A pulse-resonance On-Off keying ultrasound communication microsystem is presented. It is a viable alternative to today’s widely used RF technologies in order to avoid the associated health risks for a specific group of interest, namely babies. Special signal processing and circuit techniques are proposed to overcome drawbacks of classical ultrasound communications; such as echoes and excess ringing, achieving a measured communication range of 28m with a 50bits/s data rate and bit error rate (BER) of 0.01. Targeting a biomedical sensory pacifier, the proposed design needs to be insulated, small size, and low power. Utilizing a 40 kHz ultrasound transducer and a 5-pin low-power controller, a wirelessly-charged high-accuracy remote temperature sensor system with nominal average current consumption of 0.416µA is designed and tested. Multiple subsystems were merged in total volume of 12mm diameter and 15mm height, excluding the charging coil, which is designed as the pacifier’s handler. Thanks to echo avoidance, ringing suppression, dynamic detection threshold adjustment techniques along with 3-bit preamble synchronization; the proposed low-power sub-sampling IQ demodulation of OOK bits results in high-sensitivity robust ultrasound communication system without any alignment requirement for the transducers. The lifetime of the sensor prototype with 8mAh LiR battery is about 27 months.Graphical abstractGraphical abstract for this article
  • Microparticle concentration and separation inside a droplet using
           phononic-crystal scattered standing surface acoustic waves
    • Abstract: Publication date: Available online 30 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Jin-Chen Hsu, Yu-Ding Lin Rapid particle and biocell concentration and separation are important for the development of miniaturized physical, biological, and chemical systems. In this study, the scattering of standing surface acoustic waves (SSAWs) in an acoustofluidic phononic crystal (PnC) device is used to actuate spatial concentration and separation of suspended microparticles with two different sizes in a sessile droplet. The simulation design of the device and manipulation mechanisms of the two distinct particles are presented and discussed. A surface acoustic wave (SAW) acoustofluidic device with a nickel pillar-type PnC electroplated on a piezoelectric substrate, 128°YX LiNbO3, is designed and fabricated. A 30-MHz SSAW field is scattered within the directional phononic bandgap of the PnC to generate simultaneously acoustic radiation force and acoustic streaming flow to concentrate and separate 2- and 20-μm polystyrene microparticles. Experiments are conducted to verify the device functions on concentrating and separating microparticles. The results also suggest the possibilities of regarding phononic crystals as an effective element to tailor the SAW field for building other innovative acoustofluidic devices to achieve novel concentration, separation, and acoustic manipulation of biocells and biomolecules in discrete microfluidic systems.Graphical abstractGraphical abstract for this article
  • Intuitive Ultrasonic INS Augmentation for Pedestrian Path Tracking and
    • Abstract: Publication date: Available online 29 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Matthew Straeten, Mohammed Jalal Ahamed In this paper, the benefits of augmenting an inertial navigation system (INS) with an ultrasonic sensor, and an intuitive method of algorithmic correction are presented. An ultrasonic sensor was combined with a shoe-mounted INS allowing for the collection of information regarding wall location relative to the walked path. This information can be utilized to improve long term stability of the INS through the use of wall parallelism and perpendicularity corrections. Through the implementation of the correction methods herein, INS final location error was reduced from 5.9% to 0.35% of the total 160 m walked distance. During an experiment with 8-shaped path walking, peak error was reduced from 12.75 m to 1.22 m, a reduction in error of 90.4%. With long term INS stability being dependent on the ability of the gyroscopes to estimate heading rotation accurately, the correction method presented allows for the improvement of rotation estimation when the system is used in an indoor environment where walls can be detected by the system.Graphical abstractGraphical abstract for this article
  • Challenges for detection of small defects of submillimeter size in steel
           using magnetic flux leakage method with higher sensitive magnetic field
    • Abstract: Publication date: Available online 28 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Hiroaki Kikuchi, Ralf Tschuncky, Klaus Szielasko Recently, several types of miniaturized magnetic field sensors with high sensitivity have been developed, thereby allowing us to detect small defects in steel using the magnetic nondestructive testing technique. Trials to detect a small-sized defect in the submillimeter scale in steel using the magnetic flux leakage method are described herein. Magnetic field sensors with high sensitivity such as giant magneto-resistance (GMR) and giant magneto-impedance (GMI) were used in this study to scan leakage field on the surface of a specimen. When we used a GMI sensor, a defect of size 100 µm was detected by applying a low field; its limitation was restricted by the size of the sensor and the dynamic range. Meanwhile, we detected a small defect of diameter 30 μm using a GMR sensor acting as a gradiometer.Graphical abstractGraphical abstract for this article2D maps for specimens with differing hole diameters. (a) 150 µm, (b) 90 µm, (c) 70 µm, (d) 50 µm, and (e) 30 µm. Hole depth is 0.2 mm. The white dotted circles indicate the signal due to the hole. Graph in right side and below is relation between the peak value and hole diameter.
  • Functionalization of Polypropylene Nonwoven Fabrics Using Cold Plasma (O2)
           for developing Graphene-Based Wearable Sensors
    • Abstract: Publication date: Available online 28 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Md Mehedi Hasan, Feichao Zhu, Arsalan Ahmed, Nazakat Ali Khoso, Hridam Deb, Lai Yuchao, Md Zahidul Islam, Hui Sun, Bin Yu Melt blown-Nonwoven Polypropylenes based materials have numerous applications, such as nonwoven fabrics, filtration membranes used in clothing and potential industrial use due to its higher breathability, durability, absorbency, or filtration properties. Nonwoven PP-fabrics are very often used to develop wearable articles such as garments. In this research melt blown-nonwoven polypropylene (NW-PP) membranes were functionalized using (O2) cold plasma for the conversion of highly hydrophobic into hydrophilic nature to enhance the absorption and adhesion of graphene films on the fiber surface. The graphene oxide, (GO) the NW membrane was successfully introduced on the fibrous mat and reduced into reduced Graphene oxide (rGO) with green chemical and thermal reduction. L-Ascorbic Acid was used as a reducing agent at a low-temperature microwave-assisted reduction at 90 °C. The as developed NW membrane was connected two copper electrodes and used as wearable pressure (WP) sensors. The physical sensor responds with different stretching and bending cycles under dynamic pressure of loading. The sensitivity of the developed pressure sensor was 0.050 kPa-1 in a wide pressure range (0-60 kPa). The resultant rGO coated NW-PP wearable pressure sensor (RNPWP) is capable of responding to human body movement and motion. The study demonstrates that mass production on an industrial scale graphene-based conductive nonwoven PP fabric potentially replaces the metal-based conductive wearable textiles for physical sensors.Graphical Graphical abstract for this article
  • An integrated three-dimensional micro-solenoid giant magnetoimpedance
           sensing system based on MEMS technology
    • Abstract: Publication date: Available online 28 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Zhu Feng, Shaotao Zhi, Mingchen Wei, Yong Zhou, Cui Liu, Chong Lei In this paper, we proposed an integrated three-dimensional (3D) micro-solenoid giant magnetoimpedance (GMI) sensing system. The sensing system is composed by a 3D micro-solenoid inside which patterned Cobalt-based ribbon is kept as magnetic core and this system was fabricated by Micro-electromechanical Systems (MEMS) technology. The system was measured by non-contact method, which has the advantages of high sensitivity, low power consumption and widespread application prospect. The influence of external magnetic field direction and excitation frequency on micro-solenoid GMI sensing system has been discussed respectively. The fabricated system exhibits an optimum magnetoimpedance (MI) ratio of 4360±40 % at the excitation frequency of 13 MHz under longitudinal external magnetic field. In consequence, 3D micro-solenoid GMI sensing system offers great magnetic performance and this integrated sensing system has potential applications in the field of weak magnetic field detection.Graphical abstractGraphical abstract for this article
  • A 3-bit fully inkjet-printed flexible chipless RFID for wireless
           concentration measurements of liquid solutions
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Zonghao Li, Sharmistha Bhadra A fully inkjet-printed flexible chipless RFID tag is presented in this paper. It is based on a coplanar waveguide (CPW) coupled to a multiresonator circuit to encode the information in the frequency domain. Two cross-polarized ultra-wideband (UWB) antennas connected to the CPW receive and transmit the signals. As a proof-of-concept, three spiral resonators are used to encode a 3-bit signature, which can be easily expanded to more bits by adding more resonators. The RFID tag is applied for wireless concentration measurements of liquid solutions by characterizing the insertion loss response. Water/sodium chloride (NaCl) solution and water/isopropanol solution are measured wirelessly by the sensor. A capillary tube is placed on one of the resonators to allow the interaction between the sensor and the solutions. By the observations of measurements, different parameters are used to quantify the sensitivity. The change of the insertion loss at the resonant frequency ΔS21 and the half-power 3-dB bandwidth, ΔBW are used to analyze the water/NaCl solution. ΔS21 and the shift of resonant frequency, Δfres are used to analyze the water/isopropanol sample. The proposed RFID shows the potential for measuring liquid solutions wirelessly.Graphical abstractGraphical abstract for this article
  • High-sensitivity Refractive Index and Temperature Sensor Based on
           Cascading FBGs and Droplet-like Fiber Interferometer
    • Abstract: Publication date: Available online 28 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yong Du, Qun Han, Haofeng Hu, Mei Sang, Xueru Zhao, Xiaowei Song, Hongyuan Wang, Tiegen Liu In this paper, a highly sensitive refractive index (RI) and temperature sensor based on two fiber Bragg gratings (FBGs) cascaded with a droplet-like fiber interferometer (DLFI) is proposed and experimentally demonstrated. The DLFI was fabricated by mechanically bending a section of coating-stripped single-mode fiber. As the surrounding RI changes, the transmission spectrum of the DLFI shifts, which causes the intensity difference of the two FBGs change. Whereas, the temperature change induces a Bragg wavelength shift of the FBGs. Thus, RI and temperature can be simultaneously measured by the senor through monitoring the intensity-difference change and the wavelength change. In our experiment, the proposed sensor exhibits a RI sensitivity of 385.2 dB/RIU (refractive index unit) in the range of 1.3388-1.3998, which is the highest in RI sensors based on intensity demodulation so far. Meanwhile, the temperature sensitivity is 11 pm/℃ in the range of 25–70℃.Graphical abstractGraphical abstract for this articleDifferential intensity demodulation increasing the sensitivity and avoiding the effects of source power fluctuations, Yong Du, SNA 111631.
  • High Specific Detectivity Infrared Detector using Crystal Ion Slicing
           Transferred LiTaO3 Single-crystal Thin Films
    • Abstract: Publication date: Available online 27 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Jiarui Luo, Wenbo Luo, Kaisheng Zhang, Xiaowei Sun, Yao Shuai, Tao Wang, Chuangui Wu, Wanli Zhang LiTaO3 (LT) single crystalline films have been used to fabricate pyroelectric infrared detectors. Sub-micrometer thick LT films have been transferred on LT holder substrate by Crystal Ion Slicing (CIS) technology using hydrogen ions implantation and SiO2 bonding process. The surface roughness result from the Gauss distribution of hydrogen ions was decreased from 18.7 nm to 1.5 nm after Ar+ ion bombardment. The pyroelectric coefficient of CIS fabricated LT film (2 × 10-8 C/cm2·K) is comparable to that of LT bulk crystal. Detectors fabricated using the CIS fabricated LT films show larger detectivity at higher modulation frequency than the commercially available pyroelectric devices using LT bulk crystal or PZT polycrystalline thin films. The highest value of specific detectivity is 2.49 × 108 cm·Hz1/2W-1 at 300 Hz. The results demonstrate that the LT single crystal film fabricated by CIS technology is a promising material to fabricate quick response pyroelectric devices.Graphical abstractGraphical abstract for this article
  • Indium sulfide based metal-semiconductor-metal ultraviolet-visible
    • Abstract: Publication date: Available online 26 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): B. Hemanth Kumar, M.C. Santhosh Kumar In recent years, the photodetectors gained much attention due to their wide range of applications in industry, military, space and biological fields. In this work, the metal-semiconductor-metal (MSM) photodetector was fabricated using In2S3 thin films with Al interdigitated electrodes. The In2S3 thin films were prepared by co-evaporation technique with various thicknesses in the range 130-700 nm at a constant substrate temperature of 350 °C. The structural, morphological, compositional, optical and electrical properties of In2S3 thin films were studied as a function of thickness. The energy band gap of films is found to be in the range 2.53-2.71 eV. I-V characteristics and photo response of photodetectors were recorded under UV and visible light illumination. The parameters of a photodetector such as photo sensitivity, responsivity and detectivity were calculated. The observed photo responsivity increases with increase of film thickness. The photo response of all photodetectors confirmed the stable and reproducible characteristics such as photo sensitivity, responsivity and detectivity.Graphical abstractGraphical abstract for this article
  • A fibre optic based approach and device for sensing alpha particles in
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Carly A. Whittaker, Christopher A.G. Kalnins, Heike Ebendorff-Heidepreim, David Ottaway, Nigel A. Spooner In-situ measurement of alpha particle emitting radionuclides within mineral processing liquids requires a highly sensitive detector which is capable of operating in harsh chemical environments at elevated temperatures. In this study, a sensing device suitable for directly measuring trace quantities of alpha particles under environmental conditions analogous to those encountered in mineral processing is presented. The sensor is constructed using plastic scintillating optical fibres which have been characterized in terms of their alpha particle scintillation response, transmission loss and, in a previous study, their performance under the proposed environmental conditions Alpha particles in Po210 test solutions were detected at levels as low as 0.42 Bq/ml, with the sensor demonstrating the ability to operate in a semi-continuous manner.Graphical abstractGraphical abstract for this article
  • Measurement of high-bandwidth nanonewton forces in a low-compliance
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Wei Chen, Emrullah Korkmaz, B. Arda Gozen, O. Burak Ozdoganlar This paper presents a technique for precise and reproducible measurements of high bandwidth nanonewton forces in a low-compliance configuration. Precisely measuring high-bandwidth nanonewton forces is a critical enabler for many areas of nanotechnology. However, the prevailing nanonewton force measurement approaches can only measure low-frequency forces (
  • A S-Shaped Long-Period Fiber Grating with Ultra-High Strain Sensitivity
    • Abstract: Publication date: Available online 23 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Weiliang Liu, Hang Du, Xingyu Bai, Xudong Chen, Tao Geng, Chengguo Tong, Cuiting Sun, Xiren Jin, Yue Li, Yuxiang Li, Chunlian Lu, Libo Yuan A S-shaped long-period fiber grating (SLPFG) is presented in this paper as a new type of strain sensor with ultra-high strain sensitivity. The sensor is fabricated by using the CO2-laser-polished method. It is illustrated by experiments that the WLFPG has structural stability and repeatability. The strain sensitivity of the proposed sensor reaches 29.3 pm/με in the range of 0∼1000 με, and the temperature sensitivity is 76.3 pm/°C in the range of 30∼170 °C. Compared to other CO2-laser-induced long-period fiber gratings (CO2-LPFGs), the strain sensitivity of the SLPFG is nearly ten times higher.Graphical abstractGraphical abstract for this article
  • Quartz tuning fork enhanced photothermal spectroscopy gas detection system
           with a novel QTF-self-difference technique
    • Abstract: Publication date: Available online 23 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Qinduan Zhang, Jun Chang, Zhenhua Cong, Zongliang Wang A novel self-difference technique based on quartz tuning fork (QTF) is proposed in this manuscript. C2H2 is selected as the target analyte to verify the effectiveness of this technique. The measurement technique consists of two laser beams, one laser beam passes through the gas cell as the probe laser beam and the other beam is used as the reference laser beam. The vibration direction of the QTF caused by the two laser beams is opposite by adjusting the position where the two laser beams illuminate QTF. The two quartz tuning fork enhanced photothermal spectroscopy (QEPTS) signals are subtracted by utilizing the mechanical vibration characteristics of the QTF. As a result, the SNR increases 5.1 times in QTF-self-difference based system compared to a traditional differential gas detection system. Finally, the system achieved a minimum detection limit (MDL) of 723 ppbv, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 7.85×10-10 cm-1 W/Hz 1/2.Graphical sGraphical abstract for this article
  • Range-Extended Wireless Food Spoilage Monitoring with a High Energy
           Efficient Battery-Free Sensor Tag
    • Abstract: Publication date: Available online 22 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Xuan-Tu Cao, Wan-Young Chung In this study, we developed a smart sensor tag without a battery for monitoring spoilage in packaged foods. To give our smart sensor tag a compact structure for inserting into food packaging, we designed a double PCB structure with two 6-turn rectangular antennas. The first PCB includes several low power sensors for monitoring food spoilage, a transceiver IC for communication with a reader, a microcontroller for the smart sensor tag operations, and a 6-turn rectangular antenna at the edge of the PCB. The second relay PCB contains another 6-turn rectangular antenna (that is the same size as the first antenna) and is parallel to the first board. This second PCB is designed as a relay resonator to improve the RF energy harvesting efficiency from the reader side. The antenna on the first board transmits data to the reader and simultaneously operates as a receiver resonator for RF energy harvesting. To evaluate the food spoilage, the proposed smart sensor tag was designed to have several low power sensors that monitor factors including humidity, temperature, total volatile organic compounds, and equivalent carbon dioxide. Validation results showed that the proposed smart sensor tag with the sensor module is able to collect the sensing data on food spoilage without a battery, at a maximum distance of 50 cm from a reader. The collected sensing data were analyzed with a personal computer to evaluate spoilage level in food packages.Graphical Graphical abstract for this articleExperimental setup for the spoilage testing of the fish (a, c) and boiled rice (b, d) packages at a room temperature and in a refrigerator.
  • A flexible piezoelectric nanogenerator using conducting polymer and silver
           nanowire hybrid electrodes for its application in real-time muscular
           monitoring system
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Shubhangi Khadtare, Eui Jin Ko, Young Hoon Kim, Hyoung Seok Lee, Doo Kyung Moon In the present work, a flexible piezoelectric nanogenerators (PNGs) using poly(vinylidene fluoride) (PVDF) as an active layer with hybrid electrode is demonstrated. Here, a poly(3,4-ethylenedioxythiophene) (PEDOT) derivative, poly(2-hexyl-2,3-dihydrothieno[3,4-b][1,4]dioxine:dodecyl sulfate (PEDOT-C6:DS) was introduced. The polymer material has a good solubility and dispersion with organic solvents. Also, the polymer has a good electrical conductivity with hydrophobic surface and uniform conducting network on PVDF. The device performance of hybrid layer with a type of uniformly covered silver nanowire (AgNWs) network and synthesized PEDOT-C6:DS with different concentration as an electrode has been tested. This PNG exhibit superior energy harvesting performance with maximum piezoelectric output voltage and current 7.02 V and 1.11 μA, at 8 Hz operating frequency, respectively. The fabricated hybrid electrode PNG (1.5 cm × 2.5 cm) generates a maximum output power of 1.18 μW. The fabricated PNG device is capable to lit up white LEDs and charged a commercial capacitor of 1 μF with charged voltage 2.68 V in 80 s. Further, with the results obtained it is confirmed that the 1 wt% PEDOT-C6:DS is a promising material for hybrid electrodes in electronic applications.Graphical abstractGraphical abstract for this article
  • From magnetoresistor element to in-plane sensitive Hall device
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Siya Lozanova, Avgust Ivanov, Chavdar Roumenin This paper contributes to the development of in-plane sensitive Hall-effect configurations based on a new sensor concept. An original coupling of pairs of identical two-contact (2C) magnetoresistors transduce an in-plane magnetic field, i.e., parallel to the silicon chip surface into a Hall voltages by means of four-contact (4C) and eight-contact (8C) devices. Two different arrangements are accomplished – hybrid realization with a discrete resistor bridge and fully integrated implementation. The pair’s ohmic contacts of the magnetoresistors are cross-coupled and parallel connected. These configurations has linear and odd output signal as a function of the magnetic field and supply current. The quadratic and even magnetoresistance of innovative solutions is completely suppressed, which ensures high measurement accuracy alongside with identification of the magnetic field polarity. The experimental prototypes feature simplified technological fabrication, sensitivity about 100 V/AT, low output temperature drift and high linearity. The lowest detected magnetic induction at current of 3 mA over frequency range 5 Hz ÷ 500 Hz at a signal-to-noise ratio equal to unity is around 10–12 μT. A benchmarking of the characteristics was performed with both new configurations as well as with an in-plane sensitive four-contact Hall element with closed design. It is established that the new arrangements have advantage and confirms the innovativeness of the proposed concept. The complete electrical, temperature and technological matching of proposed Hall devices is very promising for many practical applications.
  • Vertically-stacked MEMS PM2.5 sensor for wearable applications
    • Abstract: Publication date: 1 November 2019Source: Sensors and Actuators A: Physical, Volume 299Author(s): Dorsa Fahimi, Omid Mahdavipour, John Sabino, Richard M. White, Igor Paprotny Exposure to fine airborne particulate matter (PM), i.e., PM with an aerodynamic diameter (AD) less than 2.5 μm, is associated with many adverse health effects, including impaired pulmonary function, asthma, cardiovascular diseases, and Alzheimer. Consequently, there is a strong need for the development of small, low-cost wearable PM2.5 sensors that can be used by regular citizens to monitor their PM exposure. This work presents the design, fabrication, and experimental evaluation of a stacked-channel wearable direct-read micro-electro-mechanical system (MEMS) PM2.5 sensor that directly measures the mass concentration of the ambient PM by deposition on a mass-sensing resonator. The sensor employs a vertically stacked air-microfluidic channel geometry and an out-of-plane vertical virtual impactor (VVI), fabricated using a novel delayed deep reactive ion etch (DDRIE) process. As a result, this new device not only allows for a greater level of miniaturization than the previously reported air-microfluidic PM sensors, but also significantly reduces internal fouling due to PM accumulation in its channels. The small footprint of the sensor (27 mm × 14 mm × 2 mm) allows for the integration of the sensor into a wearable or cellular platform. An opto-gravimetric method was used to evaluate the collection efficiency of the VVI, which confirmed its 50% cutpoint at 2.5 μm. The experimental evaluation of the functionality of the sensor confirmed the sensitivity of the new design at 7 Hz/min per μg/m3, which is the highest sensitivity of direct-read mass-based PM2.5 sensor presented to this date. Such sensitivity allows for the limit of detection (LOD) of one μg/m3 within 7 min of integration time at a noise level of 50 Hz.Graphical abstractGraphical abstract for this article
  • GdVO4:Er3+/Yb3+ nanocrystalline powder as fluorescence temperature sensor.
           Application to monitor the temperature of an electrical component
    • Abstract: Publication date: Available online 21 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Franzette Paz Buclatin, Fernando Rivera-López, Oswaldo B. González Hernández, Inocencio R. Martín, Leopoldo L. Martin, Dragana J. Jovanović The temperature sensing properties of an Er3+/Yb3+ co-doped GdVO4 nanocrystalline powder were studied. The down-conversion emission spectrum of the sample was observed under excitation at 457 nm. Two methods were used to calibrate the temperature of the sample: one based on the Fluorescence Intensity Ratio (FIR) technique and the other using the fluorescence lifetime of the thermally-coupled energy levels of Er3+. The relative sensitivities for each method were calculated and it was found out that the FIR-based temperature sensor has higher sensitivity (1.17% K-1) than the lifetime-based sensor (0.24% K-1). Furthermore, a temperature uncertainty of 0.37 K was obtained for the FIR-based sensor. The GdVO4 nanoparticles were also used to study the change in temperature of an electrical component when it is operating and not.Graphical abstractGraphical abstract for this article
  • Fabrication and Performance of Ionic Polymer-Metal Composites for
           Biomimetic Applications
    • Abstract: Publication date: Available online 21 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Wuxian Peng, Yajing Zhang, Jinhai Gao, Yiming Wang, Yang Chen, Yiran Zhou Ionic Polymer-Metal Composites (IPMCs) consisting of ionic polymer membrane sandwiched between platinum and copper (Cu-Pt) electrodes have been synthesized via electroless plating and electroplating. The tip displacement of Cu-Pt coated IPMC reached about 10.7 mm when a sinusoidal potential of 3V, 0.6Hz was applied through the membrane. The surface roughness of Pt coated IPMC, Cu-Pt coated IPMC and Cu-Pt coated IPMC after bending deformation tests were 1.21, 0.77 and 0.71 μm respectively, indicating that Cu electrode could reduce surface roughness. It was also found that a new generated Cu layer healed the cracks of Pt electrode, was formed through using voltage polarity. Butyl rubber and polydimethysiloxane (PDMS) were employed to encapsulate Cu-Pt coated IPMC to prevent Cu electrode from oxidation. The output deformation of packaged Cu-Pt coated IPMCs were stable under various amplitude of potential. The deflection of Cu-Pt coated IPMCs kept in air for 3, 7, 15 and 22 days respectively had no significant changes and were all about 10.1 mm by applying the potential of 3V, 0.6Hz, revealing that Cu electrode is durable and Cu-Pt coated IPMCs exhibit remarkable promise as biomimetic actuators.Graphical Graphical abstract for this articleThe deflection of packaged Cu-Pt coated IPMCs kept in air for 3,7,15 and 22 days respectively, had no apparent changes and were all about 10.1 mm by applying a potential of 3 V, 0.6 Hz (Fig.11), which further validates that the encapsulation process used in this study significantly improved the durability of the Cu electrode. Cu-Pt coated IPMCs exhibited steady actuation performance after 22 days.Figure11. Bending deformation of Cu-Pt coated IPMC kept in air for various days under sinusoidal potential of 3V, π/5Hz, (a) 3days; (b) 7days; (c)15days;(d)22days
  • Tape’n Roll Inertial Microfluidics
    • Abstract: Publication date: Available online 20 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Mohammad Asghari, Murat Serhatlioglu, Resul Saritas, Mustafa Tahsin Guler, Caglar Elbuken Particle focusing and separation in microfluidic devices are critical for biological and medical applications. Inertial microfluidics is used for high throughput bio-particle focusing and separation. Most of the inertial microfluidic systems use planar structures for squeezing the particles in streams. Particle manipulation in 3D structures is often overlooked due to the complexity of the fabrication. In this study, we introduce some novel microchannel designs for inertial microfluidics by using a simple fabrication method that allows construction of both 2D and 3D structures. First, inertial migration of particles in 2D layouts including straight, spiral, and square spiral channels is investigated. Afterward, by applying a “tape’n roll” method, helical and double oriented spiral channels are configured and unexplored inertial migration behaviours are observed. Thanks to the simplicity of the fabrication and the unique characteristics of the new designs, high performance microfluidic inertial migration results can be obtained without any need for complicated microfabrication steps. The design optimization cycle can also be shortened using a computational approach we introduce in this study.Graphical abstractGraphical abstract for this article
  • Enhancement of the magnetoelectric response of Polyurethane polymer /
           Piezoceramic bi-layer materials
    • Abstract: Publication date: Available online 20 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Rabah Belouadah, Laurence Seveyrat, Benoit Guiffard, Daniel Guyomar This paper deals with the eddy current-induced magnetoelectric (ME) effect in a bi-layered structure consisting of a piezoelectric ceramic and a thermoplastic polyurethane (PU) film with three different values of Young’s modulus. It is observed a great effect of the elastic properties of the polymer on the magnetoelectric characteristics of the laminate samples.To study the influence of the elastic modulus (c) and damping coefficient (η) of the bilayers on the DC direct current magnetic induction (Bdc) induced piezomagnetic coefficient (λ) and magnetoelectric current magnitude (I), a model based on a forced damped elastic system has been developed to calculate c, η, the first and second complex magnetoelectric coefficient αp and βp for different samples. The effect of the polymer elastic modulus on the magnetoelectric response is presented and discussed. The calculated values of the I(Bdc) and S(Bdc) obtained with this model are in good agreement with experimental data. The optimal value of the effective ME voltage coefficient (αE t) was obtained for the stiffest polyurethane grade.Graphical abstractGraphical abstract for this article
  • Eddy current displacement sensor with ultrahigh resolution obtained
           through the noise suppression of excitation voltage
    • Abstract: Publication date: Available online 20 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Guo Feng Zhao, Yin Jin, Wu Lei, Zhi Hua Feng This paper presents a method for heightening the resolution of an eddy current sensor (ECS). A typical ECS based on AC bridge and orthogonal phase sensitive detector is used to explain the principle and is verified with experiments. For this type of ECS, the noise in the excitation voltage applied on the bridge is considered to have an important influence on the sensor’s resolution. A high-Q passive LC bandpass filter used for depressing the noise in the excitation voltage is designed and analyzed. Experimental results show that the sensor’s resolution is greatly improved with the help of the filter. With a working range of 20 µm and a bandwidth of 7.2 Hz, the sensor’s resolution is heightened from 0.35 nmrms to 0.05 nmrms.Graphical abstractIn the full-scale range, the sensor’s resolution was tested in both filtered and unfiltered cases. It can be seen that the sensor’s resolution reaches 0.05 nmrms by using filter, and the sensor’s resolution is nearly six times higher than the original at the full-scale position.Graphical abstract for this article
  • A flexible capacitive sensor based on the electrospun PVDF nanofiber
           membrane with carbon nanotubes
    • Abstract: Publication date: Available online 20 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Xiaofeng Yang, Yishou Wang, Xinlin Qing Flexible pressure sensors have been increasingly recognized over the past several decades, but there is still a challenge to fabricate them with a superb sensitivity and large sensing range. In this paper, a flexible capacitive pressure sensor based on the electrospun polyvinylidene fluoride (PVDF) nanofiber membrane with carbon nanotubes (CNTs) was developed to measure the pressure. The electrospinning CNT-PVDF nanofiber membrane can overcomes the limitations of the traditional solution-dip-coating for adhering conductive materials to the porous surface. The microstructure and characterization of the CNT-PVDF nanofiber membrane were analyzed by SEM, AFM and FTIR. By increasing the permittivity and decreasing the Young's modulus of the CNT-PVDF dielectric layer, the capacitive sensor exhibits high sensitivity (∼0.99/kPa), fast response (∼29 ms) and excellent cyclic loading/unloading stability (>1000 cycles). Moreover, experiments were also conducted to investigate influence of the thickness and bending radius of the sensor as well as temperature and humidity of the environment. In addition, a 3 × 3 sensor network attached on the hand was used to measure the spatial distribution and magnitude of tactile pressure. The proposed sensor has great potential for application in soft robotics and electronic skin.Graphical abstractGraphical abstract for this article
  • Self-support phenomenon and formation characteristics of dual synthetic
    • Abstract: Publication date: Available online 6 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Zhiyong Liu, Zhenbing Luo, Qiang Liu, Xiong Deng, Wenqiang Peng A formation criterion of dual synthetic jet (DSJ) is proposed. A DSJ actuator, featured by two cavities, one oscillatory diaphragm, and two exits is a real zero-net mass-flux actuator and has the superiority of higher energy utilization efficiency. However, self-support phenomenon which is unique to DSJ may result in weak jets or even no jets. Two-dimensional numerical simulations have been conducted to investigate the formation characteristics of DSJ. Based on analysis of transverse motion, a dimensionless parameter Stk is drawn out as well as the jet formation criterion of π4a/s
  • Computational and experimental analysis of droplet transportation/jetting
           behaviours driven by thin film surface acoustic waves
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Mehdi H. Biroun, M.T. Rahmati, M. Jangi, Ran Tao, B.X. Chen, Y.Q. Fu A Coupled Level Set Volume of Fluid (CLSVOF) approach has been applied to investigate severe deformation/transportation/jetting behaviours of sessile droplet driven by thin-film surface acoustic waves (SAW) devices. For validation of this computational method, a series of experimental studies of droplet transportation/jetting were performed using ZnO/Si thin film based SAW devices with resonant frequencies ranging from 64.49 MHz to 271.36 MHz. Good agreements between the computational and experimental results showed the capability of the developed CLSVOF method in modelling complex acoustofluidics phenomena such as significant internal streaming, pumping and jetting of the droplet driven by the propagating SAW.Results obtained from the computational model are used to clarify the fluidic mechanisms of droplet oscillation and wobbling behaviours during transportation. Numerical results reveal the liquid streaming patterns and airflow velocity field around the droplet at different stages of transportation/jetting process. Effects of droplet volume, the resonant frequency of SAW devices and applied SAW power on droplet transportation/jetting were investigated both theoretically and experimentally. In particular, comparisons between experimental and computational results showed that the model predicted well the minimum RF power to start droplet pumping and jetting at various resonant frequencies.
  • Development of low voltage gas ionization tunneling sensor based on p-type
           ZnO nanostructures
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Armin Agharazy Dormeny, Parsoua Abedini Sohi, Dmytry Grudin, Mojtaba Kahrizi In this article, we report design, fabrication, and characterization of a gas field ionization-tunneling sensor (GFITS) based on zinc oxide (ZnO) nanowires. The device that operates at very low voltages is made up of two parallel plates separated by a narrow gap. ZnO nanowires are grown on one of the plates and used as the anode of this capacitive device. The nanowires that were synthesized using electrochemical technique on silicon or gold substrates, amplify the electric field between the two plates and reduce the ionization voltage of the gas molecules. Electrons from the gas atoms tunnel through the potential barrier of the gas atoms into the tips of nanowires. The generated tunneling current can be used to identify unknown gases. Nanowires with different aspect ratios and various morphologies were used to assemble the device, which was then tested for several gases. Distinct I-V characteristics for gases like Ar, He, and N2 at low pressures were achieved. Our observations show that nanowires grown on gold substrates do not have vertically parallel structures, rather they grow in the form of flower shapes and the devices made of those samples operate at much lower voltages compared to those made of parallel nanowires grown on semiconductor substrates. To investigate the effect of geometrical field enhancement on the operating voltage of the sensor, the electric field enhancement of nanowires has been simulated using COMSOL Multiphysics. The results show that the enhancement factor of flower-like nanostructures of ZnO is much higher than those of freestanding nanowires.Graphical abstractGraphical abstract for this article
  • Extrusion Printing of Carbon Nanotube-Coated Elastomer Fiber with
           Microstructures for Flexible Pressure Sensors
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yang Gao, Mengdi Xu, Guohui Yu, Jianping Tan, Fuzhen Xuan Microstructured wearable pressure sensors with high sensing performance have promising applications in soft robots, wearable electronics, and biomedical devices. However, current methods for the fabrication of the devices are complex, cost-ineffective, or time-consuming. Inspired by the crystalline ice plant having tiny crystalline beads on its stem, an extrusion printing method is developed to prepare carbon nanotube (CNT)-coated microstructured elastomer fibers for resistive and capacitive wearable pressure sensors. Due to the microstructures on the CNT-coated elastomer fiber, the resistive device has a sensitivity eight times higher than the smooth one, with a fast response time (20 ms), and a detectable limit of ∼5.0 Pa. The capacitive device constructed using CNT-coated microstructured elastomer fiber provides a highest sensitivity of 0.17 kPa−1, a response time around 25 ms, and a detectable limit of 0.02 kPa. The microstructured elastomer fiber based devices demonstrate the ability in measuring various external stimuli, exhibiting the potential for the aforementioned applications.Graphical abstractGraphical abstract for this articleAn extrusion printing method is developed to prepare carbon nanotube (CNT)-coated microstructured elastomer fibers for resistive and capacitive wearable pressure sensors. The resistive and capacitive sensors exhibit high sensitivity, low detectable limit, fast response time and good mechanical durability. The device can be employed to measure various external stimuli.
  • Mechanically Actuated Frequency Reconfigurable Metamaterial Absorber
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Jongyeong Kim, Heijun Jeong, Sungjoon Lim In this paper, a mechanically actuated frequency reconfigurable metamaterial electromagnetic absorber is proposed. The absorber’s metamaterial unit cell is designed to exploit LC resonance from inductive and capacitive coupling. Because this inductance and capacitance determine the absorber’s resonant frequency, we propose a mechanical tuning method that changes the resonant frequency by changing the overall thickness of the metamaterial unit cell. The proposed unit cell consists of an FR4 dielectric substrate with fixed thickness and an air substrate with tunable thickness. When the air substrate thickness is varied over the range of 17 mm to 26 mm, the absorber’s resonant frequency changes from 6.96 GHz to 5.79 GHz in EM simulation. In order to verify the proposed idea, a metamaterial absorber was fabricated as a 17 × 17 array of unit cells and a linear actuator was used to control the thickness of the air substrate. We experimentally demonstrated that the absorption frequency changes from 6.96 GHz to 5.78 GHz with 0.12 (GHz/mm) sensitivity when the air substrate thickness is mechanically changed from 17 mm to 26 mm.Graphical abstractGraphical abstract for this article
  • Development of negative-group-delay circuit for high-frequency ultrasonic
           transducer applications
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Hojong Choi Compared with low-frequency (≤15 MHz) ultrasonic transducers, high-frequency ultrasonic transducers provide higher spatial resolutions while reducing the echo-signal amplitudes and bandwidths owing to the size reduction of the piezoelectric materials. Therefore, performance improvement of high-frequency ultrasonic transducers can enhance the performance of the whole ultrasound instrument. To improve the echo-signal quality, such as the amplitudes, signal distortions, and bandwidths, negative-group-delay circuits for high-frequency ultrasonic transducers have been applied. The components of the negative-group-delay circuit can be constructed using the measured magnitude and phase characteristics of the electrical impedances of the ultrasonic transducers. Therefore, the relationship between the negative group-delay circuit and ultrasonic transducers must be analyzed to identify the adequate components of the negative-group-delay circuit. To confirm the proposed idea, the performances of negative-group-delay circuits were measured and compared. The differences in the measured phase angles of the electrical impedances between the ultrasonic transducer and the combined resistor limiter, negative-group-delay circuit, and preamplifier (including a coaxial cable) were 0.66°, 1.31°, and 9.45° at the resonant, center, and anti-resonant frequencies, respectively (
  • On the modelling of the switching mechanisms of a Coanda fluidic
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Shiqi Wang, Ahmad Batikh, Lucien Baldas, Azeddine Kourta, Nicolas Mazellier, Stéphane Colin, Stéphane. Orieux A Coanda fluidic oscillator has been studied numerically and experimentally to understand the internal switching mechanism and to estimate the frequency of resulting pulsed jets. 2D numerical simulations were performed and the oscillator switching mechanism was unveiled. The results of the simulation confirmed that the pressure difference between the two control ports and the pressure difference between the two branches control the oscillation dynamics of the oscillator. A detailed function defining the pulsation frequency has been proposed, taking into account the forth and back velocities of the pressure wave in the feedback loops which are difficult to measure experimentally. A simplified form of the frequency function has thus been proposed. An experimental study was performed to validate the numerical results, using two oscillator prototypes having the same central part but different feedback loop configurations. The experimental results confirmed the frequency function proposed from the computational study. The effects of the inlet pressure and the length of feedback loops have been experimentally studied. It has been found that with a given feedback loop, the oscillation period initially decreases as the input pressure increases.Graphical abstractGraphical abstract for this article
  • High-resolution and fast-response optical waveguide temperature sensor
           using asymmetric Mach-Zehnder interferometer structure
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Donghai Niu, Daming Zhang, Lilei Wang, Tianhang Lian, Minghui Jiang, Xiaoqiang Sun, Zhiyong Li, Xibin Wang We propose and demonstrate a high-resolution and fast-response optical waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer (MZI) structure. The sensing region is composed of an asymmetric MZI structure, which consists of two different kinds of cores formed with commercial polymer materials EpoClad and Norland optical adhesive 73 (NOA 73), respectively, in the two arms. Due to the higher thermo-optic coefficient of NOA 73, the phase changes of the two MZI arms are different with the temperature which in turn induces output optical power variations, enabling simple and real-time temperature detection. The sensor exhibits a large sensitivity of -1.685 ℃-1, high resolution of 1.48 × 10-3 ℃ and fast response time of about 510 μs. The advantages of high sensitivity and resolution, low-cost, competent integration and compatible with most biological assays make the designed sensor potential application in temperature detections of molecular analysis, biotechnology and chemical synthesis.Graphical abstractGraphical abstract for this articleThe proposed high-resolution and fast-response optical waveguide temperature sensor is based on the asymmetric Mach-Zehnder interferometer (MZI) structure, which consists of two different kinds of cores with different thermo-optic coefficients in the sensing region. The phase changes of the two MZI arms are different with the temperature which in turn induces output optical power variations, enabling simple and real-time temperature detection. The advantages of high sensitivity and resolution, low-cost, competent integration and compatible with most biological assays make the designed sensor potential application in temperature detections of molecular analysis, biotechnology and chemical synthesis.
  • Construction of Cu doped ZnO nanorods by chemical method for Low
           temperature detection of NO2 gas
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): V.L. Patil, S.A. Vanalakar, N.L. Tarwal, A.P. Patil, T.D. Dongale, J.H. Kim, P.S. Patil In this report, we have prepared Cu-doped ZnO nanorods by a simplistic wet chemical method with subsequent annealing. The phase formation, optical, surface morphological studies along with the electrical properties of the Cu doped ZnO thin films were characterized by X-ray diffraction (XRD), photoluminescence (PL), field emission scanning electron microscopy (FESEM) and Hall measurements, respectively. The addition of copper (Cu) in to the matrix of ZnO influenced the surface morphology of the product dramatically. The regular hexagonal nanorods-like surface morphology of ZnO becomes a broken rod-like morphology, after addition of copper. Owing to the complexes surface morphology of Cu doped ZnO, the system was used to detect the toxic gases like NO2. The effect of doping on the gas-sensing properties of ZnO was slightly counterintuitive in that they initially increased up to Cu concentrations of 1% before beginning to decline. Meanwhile, the Cu doped ZnO exhibited the gas response of ˜ 71 for 1 ppm of NO2 gas at low operating temperatures. This higher gas sensing response is due to the defect states observed in Cu doped ZnO films. In addition to above mentioned findings, the transformation of n-type ZnO to p-type Cu doped ZnO was also observed. The p-type conductivity is attributed to the holes created in the merging of Cu on Zn sites.Graphical abstractGraphical abstract for this article
  • Piezoelectric print-head drive-waveform optimization method based on
    • Abstract: Publication date: Available online 14 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Wang Jianjun, Huang Jin, Peng Ju, Zhang Jie The piezoelectric print-head, which controls the droplet formation process by regulating the pressure wave in the tube with a voltage drive waveform, is an important device for droplet deposition. However, the structural deformation caused by the voltage-drive waveform is generally accompanied by structural vibration owing to the dynamic characteristics of the piezoelectric print-head. To precisely control the deformation of the print-head structure, this paper proposes a structural deformation control method for the piezoelectric print-head, based on self-sensing. This self-sensing principle is analyzed, and its measuring circuit is presented. A lumped-parameter model for the structural deformation of the piezoelectric print-head is established and its parameters are identified, based on self-sensing. An iterative learning control method for the structural deformation is presented, based on the identified system model. To verify the control effect of the proposed method, the radial displacement of a coaxial extruded piezoelectric print-head is controlled along a standard trapezoidal trajectory. The experimental results demonstrate that the structural deformation control precision of the piezoelectric print-head with the optimized drive waveform is considerably higher than that without the optimized drive waveform.Graphical Graphical abstract for this article
  • An integrated opto-mechatronic system for self-calibration of
           accelerometer in large dynamic range
    • Abstract: Publication date: Available online 14 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yu Chen, Xiangyu Sun, Long Zhang, Yicheng Wang, Xiaoshi Li, Dongdong Gong, Tianyu Yang, Feng Qin Long-term instability and scale factor drift are inherent problems in micro inertial measurement units (MIMU) such as accelerometers. This research achieves a novel integrated opto-mechatronic system of less than 1.6 cm3, containing an advanced six degree-of-freedom (DOF) piezoelectric microvibrator, a commercial micro-accelerometer and an optical displacement sensing system. In the integrated opto-mechatronic system, the piezoelectric microvibrator is the source of standard acceleration for self-calibration. It is capable of providing an acceleration of up to 30 g and an angular velocity of 1100°/s. The optical sensing system is applied to detect the real-time acceleration of the microvibrator to provide detection data for self-calibration. Moreover, the optical sensing system also self-detects and self-adjusts the output acceleration of the microvibrator. The external control and processing unit calculates the error coefficient of the accelerometer to obtain the compensation model to achieve self-calibration, according to the acceleration detected from the optical sensing system and the acceleration output from the accelerometer. The experimental results show that the output accuracy of the micro accelerometer is significantly improved after a complete self-calibration process from 0 to 24 g acceleration range.Graphical abstractGraphical abstract for this articleA chip-scale opto-electromechanical sensor and actuator integrated MEMS system including an on-chip microvibrator, accelerometer and optical displacement sensing system to self-calibrate the accelerometer.
  • Pressure-conductive rubber sensor based on liquid-metal-PDMS composite
    • Abstract: Publication date: Available online 13 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Jun Ho Oh, Ju Yeon Woo, Sunghwan Jo, Chang-Soo HanABSTRACTWe present a pressure-conductive rubber sensor using a liquid-metal-polydimethylsiloxane (PDMS) composite suitable for incorporation onto surfaces with a complex curvature such as the human body. The composite is synthesized by physical mixing of Galinstan and PDMS based on magnetic stirring. This composite is conductive only when a mechanical pressure exceeding the threshold value or strain is applied; the pristine state of the composite is not conductive. The threshold value can be controlled by adjusting the mixing ratio of liquid metal and PDMS. This material is mechanically robust, allowing it to operate reliably under various elastic deformations such as pressing, stretching, and bending without structural failure and performance degradation. Moreover, a fabricated sensor array can detect the distribution of the applied pressure in plane. As a feasibility study, we demonstrate a pressure-conductive rubber sensor for detecting finger movements and bio-signals such as blood pressure and respiration rate. Our results reveal that our rubber sensor is practical as a wearable sensor because of its mechanical robustness and electrical reliability.Graphical abstractGraphical abstract for this articleThe deformable pressure-conductive rubber using a liquid-metal-polydimethylsiloxane (PDMS) composite are successfully fabricated in simple and cost-effective manufacturing methods. The fabricated sensor array are mechanically robust and electrically reliable enough to be applicable to bio-signal sensing electronics.
  • Fabrication of P-N Heterojunction Based MoS2 Modified CuPc Nanoflowers for
           Humidity Sensing
    • Abstract: Publication date: Available online 12 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Abir Jana, Komal Kumari, Anup Dey, P.S.Sreenivas Reddy, Bikram Biswas, Bhaskar Gupta, Subir Kumar Sarkar In recent times, there has been an increased demand for cost-effective, robust and highly reliable humidity sensors. 2D material MoS2 (n-type) have demonstrated their potential application in chemical and humidity sensing. In this work, an organic-inorganic p-n heterojunction based sensor has been fabricated using the inorganic MoS2 and the organic CuPc, and its viability towards humidity sensing has been experimentally demonstrated. The thin film sensor was characterized by SEM and the results revealed the formation of CuPc nanoflowers on MoS2 surface. The XRD results also indicate excellent crystallization. The sensor shows reduced resistance with increasing RH% and the variation has been observed to be almost linear. The sensing range is from 20% RH to 98% RH. The measured sensitivity is 0.615 MΩ/%RH. The demonstrated results are of great interest in terms of sensitivity, linear response, range of humidity monitoring and stability.Graphical abstractGraphical abstract for this article
  • Actively controlling the contact force of a stick-slip piezoelectric
           linear actuator by a composite flexible hinge
    • Abstract: Publication date: Available online 11 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Feng Qin, Liya Tian, Hu Huang, Jiru Wang, Tianwei Liang, Xinyu Zu, Hongwei Zhao Stick-slip piezoelectric actuators have been widely employed in those fields where both large working stroke and high positioning accuracy are required. However, the problems of backward motion and relatively low load capability limit their applications, and these two problems are usually contradictory. Attempted to solve these two problems at the same time, in this study, a composite flexible hinge was designed to actively control the contact force between the driving foot and the slider of a stick-slip piezo-driven linear actuator. To confirm the validity, a prototype actuator was designed and fabricated. The dimensions of the actuator in X, Y and Z directions are about 80 mm, 60 mm and 20 mm, respectively. The output characteristics of the actuator were evaluated by experiments. The results showed that without the active control of the contact force, the maximum speed being free of external load were 1.39 and 2.18 mm/s when the driving frequencies were 100 and 200 Hz, respectively. Correspondingly, the maximum horizontal loads of the actuator were 25 g and 50 g, respectively. However, with the active control of the contact force, the maximum speed were 1.74 and 4.1 mm/s under the driving frequency of 100 and 370 Hz, respectively. Moreover, the maximum horizontal loads under 100 Hz and 200 Hz were improved to be 40 g and 70 g, respectively.Graphical abstractGraphical abstract for this article
  • Compact, digital and self-powered piezoelectric vibration energy harvester
           with generation control using voltage measurement circuit
    • Abstract: Publication date: Available online 10 September 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Yushin Hara, Kensuke Saito, Kanjuro Makihara As piezoelectric vibration energy harvesting (PVEH) extracts electrical energy from vibration, it is a promising portable power device. Although harvesting efficiency can be increased by using switch controls based on vibration displacement, such controls require external controllers and sensors, which consume energy and occupy space in a device. To separate external energy sources and sensors from a switch controller, we propose a measurement circuit and a digital controller for PVEH to increase autonomy, flexibility, and compactness. In the present study, switch controls are realized on a self-powered digital controller using the piezoelectric voltage as an observation value, where achieves a switch-controlled PVEH independent from additional external sensors. We discuss the characteristics of the proposed circuit and evaluate the harvesting performance. The experimental results demonstrated that the proposed sensor-less harvester has a harvesting performance comparable to that of a conventional sensor-equipped harvester.Graphical abstractGraphical abstract for this article
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