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Sensors and Actuators A: Physical
Journal Prestige (SJR): 0.699
Citation Impact (citeScore): 3
Number of Followers: 144  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0924-4247
Published by Elsevier Homepage  [3162 journals]
  • Design, Fabrication and Calibration of a High-G MEMS Accelerometer
    • Abstract: Publication date: Available online 4 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Yunbo Shi, Yongqi Zhao, Hengzhen Feng, Huiliang Cao, Jun Tang, Jie Li, Rui Zhao, Jun Liu This paper presents a high-G MEMS accelerometer (HGMA). HGMA employs our-beams and central-island mass silicon structure, which features a robust stability in shock environment. Theoretical analysis is conducted to investigate the influence of structure parameters on the Von Mises stress distribution, mechanical sensitivity and natural frequency. With consideration of smaller stress, higher mechanical sensitivity and natural frequency, the structure parameters are optimized and the theoretical sensitivity of HGMA is calculated as 0.488μV/g. Then, the optimized structure is analyzed with finite element analysis software, which shows a maximum stress of 23.19 MPa and a frequency response of 408.19 kHz when a 100 000 g shock is loaded. Finally, a processing flow is designed and the structure is fabricated. Hopkinson bar is utilized to calibrate HGMA sample, and shows an experimental sensitivity of 0.5611μV/g. Long-term static bias and temperature experiments are arranged to evaluate HGMA. Test results verify the presented theoretical analysis, processing flow, and experiment method, which are of great value for guiding the design, fabrication and calibration of other HGMAs.
       
  • An underwater parametric array source transducer composed of
           PZT/thin-polymer composite
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Yonghwan Hwang, Hongmin Ahn, Duc-Nam Nguyen, Wonho Kim, Wonkyu Moon The source transducers for parametric array (PA) sound are required to radiate the primary wave with high intensity and directivity so as to generate nonlinear interactions between strong acoustic waves at different frequencies effectively, resulting in so-called PA sound. Thickness-mode piezoelectric transducers using 1–3 lead zirconate titanate (PZT) polymer composites were used to produce wide-bandwidth PA sound due to their ability to generate high-intensity, high-frequency sound beams over a relatively wide frequency band. The small mechanical quality factor of 1–3 PZT polymer composites results in high damping of the polymer matrix leading to a transducer with relatively flat frequency response but yet decreased-power efficiency. A PZT polymer composite that can enhance the power efficiency of a PA source transducer over a wide frequency bandwidth was proposed. This is achieved by adopting thinner polymer matrix layers and PZT rods with dual resonance frequencies. A transducer demonstrated ultrasonic sound up to 197 and 203 dB (re = 1 μP) at 98 and 135 kHz, respectively. The power efficiencies were 50% at 98 kHz and 33% at 135 kHz. PA sound was successfully generated up to 150 dB (re = 1 μP) at 30 kHz with a half-power beam width of 3.4°.
       
  • YSZ/Al2O3 multilayered film as insulating layer for high temperature thin
           film strain gauge prepared on Ni-based superalloy
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Hao Liu, Shuwen Jiang, Xiaohui Zhao, Hongchuan Jiang, Wanli Zhang The insulating layer plays a vital role to provide adequate electrical insulation for developing sputtered thin film sensors on Ni-based turbine blades of aircraft engine running at high temperature environment. Here, the multilayered YSZ/Al2O3 thin film as insulating layer was deposited by reactive sputtering. The prepared multilayered film exhibited improved insulation property as compared to the single Al2O3 thin film, the insulation resistance of the four-layered YSZ/Al2O3/YSZ/Al2O3 film increased roughly two orders of magnitude. During thermal cycle tests, the four-layered film insulating layer showed stable electrical insulation and no shorts to substrate occurred up to 800 ℃. Subsequently, the PdCr thin film strain gauge using the four-layered film as insulating layer was fabricated on Ni-based substrate and performed very well with highly sensitive resistance-strain response, stable apparent strain output and no drift error at elevated temperatures, indicating the feasibility and validity of the four-layered YSZ/Al2O3/YSZ/Al2O3 film as insulating layer for high temperature thin film sensors.
       
  • Design and fabrication of thin-walled reservoir based on microcasting
           assisted by vacuum for neutral argon plasma system in minimally invasive
           medical devices
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): J.A. Rodrigues, M.F. Silva, H. Puga, J.H. Correia This paper presents a solution to implement neutral argon plasma (NAP) in minimally invasive medical devices for therapeutic endoscopy. The NAP system is composed of compressed inert gas (argon), two electrodes, and a high-voltage source to ionise the argon. The miniaturisation of an argon reservoir is required. Finite-element method simulations of small reservoirs of an aluminium alloy with thicknesses of 0.2, 0.4, and 0.6 mm at a pressure of 7 atm were performed. The numerical results show total deformation of 108 μm, stress of 160 MPa, and a safety factor of 1.8 for the thinnest argon reservoir, resulting in a component with no permanent deformation. A small reservoir was formed via vacuum-assisted microcasting. The prototype exhibited a small and thin-walled argon reservoir.
       
  • A bioinspired structure modification of piezoelectric wind energy
           harvester based on the prototype of leaf veins
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Weiyuan Wang, Xiuming He, Xiaobo Wang, Mingming Wang, Kai Xue This paper describes a novel leaf-like piezoelectric wind energy harvester based on the venation growth algorithm, which are derived from the prototype of dicotyledonous plant leaves that have the netted distributions of veins. Some triangle polyvinylidene fluoride (PVDF) leaves are designed and fabricated to be the energy harvesting element that is driven by the vortex induced vibration in the wind flow behind a bluff body. Wind tunnel experiments were carried out to investigate and compare the performances of energy harvesting capacity of different elements. Experimental results show that the output powers of the veined structures are 4–6 times higher than that of the structure without veins. The largest root mean square of open circuit output voltage reaches 1.094 V under the wind velocity of 11 m/s for the 110 μm thickness PVDF leaf with veins. The dynamic analysis indicates that the veins can greatly influence the mechanical coupling properties between the harvesters and the wind flow although the system has not reached a typical state of instability. It is confirmed that the presence of veins has an important effect on the efficiency of the energy harvesting system.
       
  • Roughness discrimination with bio-inspired tactile sensor manually sliding
           on polished surfaces
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Longhui Qin, Yilei Zhang As an important application of tactile sensing, the capability of texture discrimination is desired in many researches, such as artificial limbs, dexterous manipulation, and humanoid haptic mechanism, etc. In this research, a bio-inspired tactile sensor containing two perpendicular sensing films was developed and manually controlled to slide across 15 polished surfaces with different roughness. Algorithms of discrete wavelet transform (DWT), sequential feature selection (SFS) and extreme learning machine (ELM) were combined together to form a signal processing system for signal decomposition, feature selection and roughness discrimination respectively. Factors affecting roughness discrimination accuracy were evaluated and compared with human tactile sensing capability. Particularly, influences of starting point and sliding duration on discrimination accuracy were analyzed to identify the optimal signal period for the following analysis. Effects of sampling rate on the discrimination accuracy were then investigated using the ELM classifier. Another two typical classification models, k-nearest-neighbor (kNN) and support vector machine (SVM), of different parameter configurations were compared with ELM in surface roughness discrimination. Results showed that the developed method based on manual sliding of the developed tactile sensor is capable of providing a surface roughness discrimination accuracy of 72.93 ± 10.48% with the real polished surfaces.
       
  • A sensor-dependent vibration data driven fault identification method via
           autonomous variational mode decomposition for transmission system of
           shipborne antenna
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Zipeng Li, Jinglong Chen, Yanyang Zi, Shuilong He With the increasing distance and time of voyage, condition monitoring and fault diagnosis of shipborne antenna play a crucial role in ship communication for navigation safety. However, it is still a challenging task to identify the hidden shipborne antenna fault from practical sensor-dependent vibration signals since the vibration features are always multi-modulated and submersed by heavy noise. Therefore, autonomous variational mode decomposition (AVMD) based on Independence-oriented Variational Mode Decomposition (IOVMD) and the Largest Lyapunov Exponent (LLE) criterion is proposed in this paper. First, the signal is decomposed into Intrinsic Mode Functions (IMFs) by IOVMD. Second, LLE of modes is calculated to measure fault information degree and then modes without fault features are eliminated. The combination rule is also defined and modes are combined orderly to enhance the fault feature expression. Then, an index structured by Kurtosis and LLE of combined signals is calculated and the combined signal is selected for demodulation. Finally, the combined signal is analyzed for fault identification by Hilbert Demodulation. A simulation and two cases show the effectiveness and superiority of the proposed method.
       
  • Fabrication and evaluation of energy harvesting floor using piezoelectric
           frequency up-converting mechanism
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Phosy Panthongsy, Don Isarakorn, Pattanaphong Janphuang, Kazuhiko Hamamoto This paper reports on the fabrication and evaluation of an energy harvesting floor tile using unimorph PZT piezoelectric cantilevers to convert kinetic energy from human footsteps into usable electricity. The operation of the tile is based on frequency up-converting mechanism in which low frequency input vibrations are converted into high frequency vibrations of an electromechanical transduction. The operational frequency of the PZT unimorph cantilever was converted up by an interaction between a permanent magnet and an iron bar. Vertical displacement of the oscillating cantilever was localized with a stopper preventing damage to the piezoelectric layer from shock or over-displacement excitation. The magnetic field density between the magnet and the iron bar was investigated through finite element analysis simulation in order to define an optimal air gap. Experimentally, a unimorph PZT cantilever was initially prototyped to validate the design. The results showed a successful frequency up-conversion with a resonant frequency of 10.54 Hz. Then, it was scaled up by accommodating 24 unimorph PZT cantilevers followed by experimental validation to evaluate its energy harvesting performance. Each cantilever was connected to a full wave bridge rectifier then connected in parallel with the other cantilevers. The generated electrical power and energy were investigated through various resistive loads. The average power and total output energy produced by one foot step on the tile were found to be 1.24 mW and 3.49 mJ, respectively at an optimal load resistance of 74.44 kΩ. The energy conversion efficiency reached 17.12% demonstrating the potential of harvesting energy from human motion.
       
  • Biocompatible fabrication of cell-laden calcium alginate microbeads using
           microfluidic double flow-focusing device
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Qing-Quan Liao, Shu-Kun Zhao, Bo Cai, Rong-Xiang He, Lang Rao, Yue Wu, Shi-Shang Guo, Quan-Yan Liu, Wei Liu, Xing-Zhong Zhao Cell encapsulation based on droplet microfluidics has been widely adopted in single cell researches, and corresponding highly-uniform cell-laden microgels play significant roles in tissue engineering and cell therapy. However, the encapsulation always faces challenges to maintain favorable cell viability. Herein, based on a double flow-focusing regime, cells were encapsulated in biocompatible sodium alginate droplets, and enveloped in oil droplets to form double emulsions. Ca2+ ions in the outer aqueous phase diffused through the oil and introduced the gelation of sodium alginate to form cell encapsulation. This indirect gelation process and the spontaneous detachment of oil helped to keep cell viability well, which was validated by FDA/PI staining tests.Graphical abstractWe employed a microfluidic double emulsion gelation method to generate highly-viable cell encapsulation. Cells encapsulated in sodium alginate droplets were entrapped again in oil droplets to form double emulsions. Through indirect gelation process realized by this double emulsion method, cell-laden alginate microgels were generated to keep cell viability well. Oil droplets could detach spontaneously to further increase the biocompatiblity for encapsulation.Graphical abstract for this article
       
  • Selective bonding method for self-assembly of heterogeneous components
           using patterned surfaces
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Kazuki Kimura, Taiki Okuyama, Taiji Okano, Hiroaki Suzuki This study demonstrates the selective bonding of millimeter-scale components using the complementary patterning of hydrophilic and hydrophobic surfaces. The hydrophobic surface of the millimeter-scale components fabricated from hydrophobic polydimethylsiloxane (PDMS) was partially made hydrophilic with a designed pattern by exposure to an excimer light of 172 nm through a stencil mask. We used liquid paraffin as the adhesive and deposited it only on the hydrophobic surface. We prepared twenty components with two different complementary patterns, which were agitated in water by the computer-controlled propeller stirrer. As a result, we succeeded in obtaining a significantly higher yield of correct bonds, in comparison to that of erroneous bonds under an appropriate stirring condition. The result can be explained by the contrast in bonding strength between the correct and erroneous bonds. This principle could be used as a versatile strategy to realize programmed self-assembly with selective bonding patterns.
       
  • Nonlinear-optical switching in gold nanoparticles driven by
           magneto-optical effects exhibited by carbon nanotubes
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): J.A. García-Merino, C.L. Martínez-González, M. Trejo-Valdez, H. Martínez-Gutiérrez, C. Torres-Torres Herein is addresses the application of attractive and large magnetization of carbon nanotubes for modulating optical signals. A cascade system based on multiwall carbon nanotubes in thin film form and Au nanoparticles embedded in a TiO2 thin solid film were combined to achieve a nonlinear magneto-optical switching action. An all-optical switching device rising from an optical Kerr effect in the second stage is proposed to transmit a magneto-optical signal from the first stage. Multiwall carbon nanotubes with large magnetic sensitivity were incorporated in the arm of a Michelson interferometer to promote a change in the refractive index due to the Aharonov-Bohm effect. The Michelson interferometer was monitoring magneto-optical processes by a 532 nm wavelength. The second stage was recorded with a 532 nm nanosecond two-wave mixing configuration testing Au nanoparticles embedded in a TiO2 thin film. The development of simultaneous all-optical and magneto-optical systems is attractive since multifunctional quantum operations can be contemplated to be performed in low-dimensional platforms. In this paper is proposed a switching device that exploits interferometry for detecting magnetic signals and optical Kerr gating with the advantages of distinct nanostructures.
       
  • A multiple energy-harvester combination for pattern-recognizable
           power-free wireless sensing to vibration event
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Qisheng He, Chuan Dong, Keli Li, Jiachou Wang, Dacheng Xu, Xinxin Li By using combination of multiple energy-harvesters, a novel self-powered wireless-sensing-node is proposed and developed for event-driven autonomous alarming, where the vibration pattern can be recognized. The energy-harvester based wireless-sensing-node has three unique advantages of (1) vibration pattern distinguishable sensing, (2) event-driven autonomous wireless monitoring and alarming, and (3) no electric-power supply needed. In the sensing microsystem, two threshold-triggered harvesters are designed and fabricated to monitor vibration in a vibration pattern distinguishable way. Each of the two threshold-triggered harvesters can independently switch into electric-generating state only when the monitored acceleration exceeds the preset-threshold. In the dual-harvester array, one threshold-triggered harvester is more sensitive to low-frequency shake and the other is triggered more easily by high-frequency knock, thereby, both vibration amplitude and frequency can be distinguished that allows vibration pattern identification. For quick wireless-transmission, another electromagnetic energy-harvester is involved to rapidly generate electric-power. The wireless-sensing-node is installed onto a protection-fence for engineering protection. In this experiment, the device can clearly distinguish the vibration patterns between hand-shake and hammer-knock. The vibration-event induced alarm messages together with the vibration pattern information is wirelessly sent to a phone. The developed technique is really promising for smart wireless-monitoring where no on-site power can be supplied.
       
  • A wirelessly-controlled piezoelectric microvalve for regulated drug
           delivery
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Marwan Nafea, Amirjan Nawabjan, Mohamed Sultan Mohamed Ali This paper reports a novel wireless control of a normally-closed piezoelectric microvalve activated by a wireless inductor-capacitor (LC) resonant circuit, and enabled by an external magnetic field. The LC circuit is formed by connecting a multilayer coil to a piezoelectric actuator (PEA) that behaves as a capacitor and a resistor in parallel. The LC circuit is activated by modulating the field frequency to its resonant frequency (fr) of 10 kHz, which matches the optimal operating frequency of the device, while considering the resonant frequency of the PEA. The working fluid is stored in an 88.9 μL polydimethylsiloxane balloon reservoir that pumps the liquid due to the difference in pressure, which eliminates the need for a pump. The design of the device was optimized using several analytical and experimental approaches. This device was fabricated using a time and cost-effective out-of-clean-room fabrication process. The valving performance was initially characterized in air, then in phosphate buffered saline (PBS) solution to mimic the drug release kinetics into human interstitial body fluids. Maximum flow rate values of 8.91 and 7.42 μL/min are achieved in air and PBS solution respectively, at a maximum input pressure value of ∼13 kPa. A programmed short-term delivery of desired liquid volumes in separate batches shows that the volumes are delivered into air and PBS solution with maximum percentage errors of 7.49% and 7.91%, respectively. Additionally, a programmed 3-day long-term reliability test shows that the device was able to achieve desired flow rate values between 160 and 320 μL/day in air and PBS solution with a maximum percentage error of 3.11% and 4.39%, respectively. The results show that the developed device has high potential to be used in drug delivery applications.
       
  • AFM imaging and plasmonic detection of organic thin-films deposited on
           nanoantenna arrays
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jharna Paul, Scott G. McMeekin, Richard M. De La Rue, Nigel P. Johnson In this study, atomic force microscopy (AFM) imaging has been used to reveal the preferential deposition of organic thin-films on patterned nanoantenna array surfaces - identifying the localised formation of both monolayer and multilayer films of octadecanethiol (ODT) molecules, depending on the concentration of the solutions used. Reliable identification of this selective deposition process has been demonstrated for the first time, to our knowledge. Organic thin-films, in particular films of ODT molecules, were deposited on plasmonic resonator surfaces through a chemi-sorption process - using different solution concentrations and immersion times. The nanoantennas based on gold asymmetric-split ring resonator (A-SRR) geometries were fabricated on zinc selenide (ZnSe) substrates using electron-beam lithography and the lift-off technique. Use of the plasmonic resonant-coupling technique has enabled the detection of ODT molecules deposited from a dilute, micromolar (1 μM) solution concentration - with attomole sensitivity of deposited material per A-SRR – a value that is three orders of magnitude lower in concentration than previously reported. Additionally, on resonance, the amplitude of the molecular vibrational resonance peaks is typically an order of magnitude larger than that for the non-resonant coupling. Fourier-transform infrared (FTIR) spectroscopy shows molecule specific spectral responses – with magnitudes corresponding to the different film thicknesses deposited on the resonator surfaces. The experimental results are supported by numerical simulation.
       
  • Model-free data driven control for trajectory tracking of an amplified
           piezoelectric actuator
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Muhammad Shafiq, Ashraf Saleem, Mostefa Mesbah Micro/nanopositioning systems commonly use piezoelectric actuators due to their high stiffness, fast response and ultra-high precision. However, three main factors affect their tracking performance, namely hysteresis, creep, and structural vibrations. To overcome these limitations, this paper proposes a new combined feedback and feedforward control strategy. Unlike most existing control algorithms for micro/nanopositioning systems, the new controller is a model-free learning-based capable of smoothly tracking continuous reference signals. It is further endowed with an ability to prevent fallacious learning associated with sensor noise and reference signal discontinuities. The paper also provides complete proofs for the convergence of the tracking error and boundedness of the control signals. Experimental trajectory tracking results obtained using the proposed controller applied on a commercially available amplified piezoelectric actuator verify the theoretical findings.
       
  • MEMS piezoresistive flow sensors for sleep apnea therapy
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Behrokh Abbasnejad, William Thorby, Amir Razmjou, Dayong Jin, Mohsen Asadnia, Majid Ebrahimi Warkiani A MEMS liquid crystal polymer (LCP), used in the membrane-based pressure sensor, has been found highly useful as a flow sensor. Here we conducted a set of elaborate experiments using an air flow generator to investigate the potential of our LCP flow sensor for sleep apnea therapy. Critical properties of the LCP flow sensor, including flow range, resolution (sensitivity), accuracy, and response time, have been systematically characterized. As a result, LCP flow sensor achieves a limit of detection of 8 LPM to measure flow rate, better than the commercial flow sensor (>10 LPM). Our LCP flow sensor shows a favourable response in a large flow range (8–160 LPM) with a sensitivity of detecting a linear voltage response of 0.004 V per 1 LPM flow rate. With minimum detectable flow, high sensitivity and resolution, we further demonstrated our LCP flow sensor for detecting human respiration. Moreover, using a two- dimensional simulation in COMSOL Multiphysics, we demonstrated the deformation of LCP membrane in response to different flow velocities which leads to resistance change in sensor’s strain gauge.
       
  • Exploiting broader dynamic range in Si-bridge modified QTF’s for
           sensitive thermometric applications
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): J.E. Hawk, M.S. Ghoraishi, Arindam Phani, Thomas Thundat The response of modified Quartz Tuning Forks (QTFs) on affixing an opto- or chemo-responsive bridging element between the terminal ends of the fork have been demonstrated to be both selective and highly sensitive. However, the Hookean model, widely employed in analysis currently, substantiates numerical accuracy when the stiffness of the bridging element is much smaller than that of the QTF motional arm. This paper presents a distributed beam model applicable for a broader range of stiffness ratios of the respective parts and is tested using a silicon bridging element to detect optically mediated thermal responses. Using this approach we demonstrate a sensor responsivity (ℜ) of 23 kN/m W, and a Noise Equivalent Power (NEP) of 8.5×10−7 W. The minimum detectable change in temperature of the bridge sensing element is calculated to be 2 mK. Thus, employing silicon bridging elements as demonstrated here, offers greater control over the reproducibility of the modified QTF over that of individually affixed polymer strands, as well as affords the opportunity to expand device reproducibility for larger scale implementation.
       
  • A portable, optical scanning microsystem for large field of view, high
           resolution imaging of biological specimens
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Georgia Korompili, Georgios Kanakaris, Christos Ampatis, Nikos Chronis Adapting medical technology for use at the point of care, demands the development of portable, robust and accurate systems for the early diagnosis and monitoring of a wide range of diseases. Microscopy at the point of care, fueled by recent advances in micro-optics, micro-electronics and micro-electromechanical systems, is an emerging and promising field. However, imaging devices already developed remain rather sophisticated and bulky, mainly because of failure to address the most challenging technical limitation: to combine large field-of-view (FOV) with high resolution imaging of biological specimens. To address this need, we developed a portable, optical scanning microsystem that can image - with approximately 1 μm resolution- large areas (6 mm × 40 mm) from various biological samples. This is achieved through the use of a microfabricated - 2D lens array that scans a sample in 1 direction in few minutes. We demonstrated that our system can image blood smear and identify single white blood cells immobilized in a microfluidic chip.
       
  • Polyvinylidene fluoride grafted poly(styrene sulfonic acid) as ionic
           polymer-metal composite actuator
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Shayan Mehraeen, Sahl Sadeghi, Fevzi Çakmak Cebeci, Melih Papila, Selmiye Alkan Gürsel A high performance ionic polymer-metal composite actuator (IPMC) based on proton conductivity of poly(styrene sulfonic acid) was fabricated using a simple and novel method. Poly(styrene sulfonic acid) (PSSA) as a well-known hydrophilic proton conductive functional group was radiation grafted on polyvinylidene fluoride (PVDF) at different graft levels. The material system is well known for the proton exchange membranes of fuel cells, however, its IPMC application is novel. Flexible, soft and porous membranes were prepared by simple solution casting technique. Physical, mechanical, thermal and actuation properties of prepared membranes were characterized and compared with Nafion®. The membrane with highest graft level showed comparable ion exchange capacity and proton conductivity with that of Nafion whereas its water uptake is near three-fold greater than Nafion. To make PVDF-g-PSSA based IPMC actuators, Pt particles were deposited on both sides of the membranes using electroless plating method. Actuation performance of the IPMC actuators under various AC potentials and different frequencies were investigated in air. The results revealed that the PVDF-g-PSSA membrane with highest graft level showed highest average bending strain at 0.1 Hz and 4 V. The enhanced bending actuation behavior was attributed to porous morphology and large water uptake of graft polymerized actuators. Compared with traditional Nafion-based IPMC, our bending actuator is cheaper, and its preparation is fast and simple. So, it can be a viable replacement candidate for the traditional Nafion in soft actuator systems.Graphical abstractGraphical abstract for this article
       
  • Fabrication of high fill-factor microlens array using spatially
           constrained thermal reflow
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jinfeng Qiu, Mujun Li, Huichun Ye, Junjie Zhu, Chao Ji In this paper, we introduce a simple method for fabricating high fill-factor microlens array using a novel spatially constrained thermal reflow process. The major difference with the conventional methods is that the proposed thermal reflow is conducted in polydimethylsiloxane (PDMS) solution instead of in the air. During the reflow process, PDMS would serve as a barrier to prevent the merging of adjacent microlenses which is usually a big obstacle of achieving high fill-factor in conventional thermal reflow methods. Moreover, for the microlenses are spatially constrained by the PDMS, the reflow process is very stable and much easier to control. To give a good understanding of the process, theoretical models are also established. Experimental results showed that almost 100% fill-factor and relative PDMS soft mold could be obtained efficiently and easily, and the microlens was good in both shape and surface quality. The proposed method may provide a low-cost and accurate method for fabricating high fill-factor microlens array in a very simple way.
       
  • RF-MEMS technology as an enabler of 5G: Low-loss ohmic switch tested up to
           110 GHz
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jacopo Iannacci Microsystems for Radio Frequency (RF) passive elements, known as RF-MEMS, have been attracting the attention of academic and industrial research since their first discussion, thanks to the remarkable performance they can trigger. Despite the flattering premises, RF-MEMS technology did not score consistent spread into mass-market applications, yet, as technical issues still needed to be managed, but also because consumer products did not use to really need such pronounced characteristics. Nowadays, the application scenarios of 5G (i.e. 5th generation of mobile communications and networks) and of the Internet of Things (IoT), highlight a growing need for cutting edge performance that RF-MEMS are capable of addressing. Given such a context, this short communication discusses an RF-MEMS series ohmic micro-switch, electrostatically driven and fabricated in a surface micromachining process, exhibiting good characteristics up to 110 GHz. In brief details, the micro-relay shows isolation (when OPEN) better than −15 dB and loss (when CLOSE) better than −1 dB up to 40 GHz. The actuation voltage is around 50 V, although it can be lowered acting on the release step temperature. Despite the design concept admits margins for improvement, the characteristics of the micro-switch reported in the following are already quite interesting in the discussion of next generation of RF passive components for 5G and IoT.
       
  • Preparation and electromechanical properties of the chitosan gel polymer
           actuator based on heat treating
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Gang Zhao, Junjie Yang, Yujian Wang, Honghao Zhao, Zhijie Wang As a new kind of smart materials for fabricating ionic electric actuator, Chitosan Gel Polymer (CGP) known as bionic artificial muscle, has broad application prospects and high academic value with advantages of simple structure, good biocompatibility and large deflection under low driving voltage (≤5 V). In this paper, effects and enhancement mechanism of the heat treating optimization technology on response speed performance of the CGP actuator were mainly investigated. Furthermore, its preparation process including material selection, membrane fabrication and the assembly along with fabrication principle were deeply researched. The CGP actuator consisted of two parts; electric actuating membrane which is sandwiched between non-metallic electrode membranes. On one hand, high viscosity chitosan inside the actuating membrane served as framework which gives access to anions and cations within the electrode membranes. On the other hand, Multi-walled Carbon Nanotube (MCNT) was adopted to modify chitosan in the electrode membrane for obtaining good conductivity and stable chemical character. Moreover, response speed of the CGP actuator that underwent repeated heat treating for a short time, would be continuously improved with the increase of heat treating times. But as the heat treating time prolonged, electromechanical properties of the CGP actuator began to degrade. In addition, since conduction velocity of microscopic ions inside the CGP actuator was presented as macroscopic current magnitude, the experimental results revealed that the changing trend of response speed was almost in accord with the current trend of the CGP actuator. Both of these are fitted in a quadratic function relationship.
       
  • Convective losses of thermal infrared emitters with cantilevered heating
           elements
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): T. Ott, M. Schossig, G. Gerlach Non-dispersive infrared- (NDIR-) gas sensors usually consist of a thermal infrared emitter, a tube and a pyroelectric detector with a filter that is transparent to the characteristic wavelength of the gas to be detected. Since pyroelectric sensors are only sensitive to alternating radiation, the radiation must be modulated. This is easiest to achieve by electrical modulation of the emitter. Under this cyclic excitation the thermodynamic properties of the IR source affect the emitted infrared radiation and, in consequence, the sensor signal. Optimal gas sensor operations (e.g. with regard to gas measurement resolution) require to know which factors influence the thermodynamic properties of thermal emitters. In the course of miniaturization and with regard to portable use, gas measuring devices must also become more compact and energy-efficient. Consequently, the radiation source must have low power consumption and high (radiation) efficiency. The heating and cooling curves measured during electrical (square-wave) modulation contain all information about the thermal losses of real emitters and, therefore, about their energy efficiency as well. In this paper, a thermodynamic model of an infrared emitter will be introduced, which also includes all thermal losses (radiation, heat conduction and convection in the filling gas). The comparison of the measured and calculated heating and cooling curves allows to quantify the thermal losses of the emitter and to draw conclusions about its energy efficiency. As a result, this paper reveals that the majority of the electrical energy supplied is dissipated into the filling gas by convection and heat conduction, which significantly reduces the energy efficiency of the radiation source. Vacuum measurements confirm this assumption and support the model.
       
  • Efficient electrode configuration for electro-conjugate fluid flow
           generation with dibutyl decanedioate: Experimental and theoretical
           investigation
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Y. Kuroboshi, K. Takemura, K. Edamura Electro-conjugate fluid (ECF) is a functional fluid that can generate a high-power flow induced by a high direct-current voltage. While ECF has been used in various fields, including mechanical, chemical, and biomedical systems, its underlying principles have not been sufficiently understood to be applicable to ECF system design, and the lack of theoretical models hampers further applications of ECF. This study aims to investigate underlying principles of ECF flow generation with a rectangular-slit electrode pair. By analyzing the effect of electrode configuration on the flow generation, this paper proposes a theoretical model for electrode design for efficient flow generation. The proposed model has been validated by comparing the simulation results with the visualized characteristics from flow experiments. The results show that the flow rate can be controlled by changing the electrode configuration with the maximum flow rate with the rectangular-slit electrode gap of 1.0 mm and the slit electrode gap of 5.0 mm.
       
  • The influence of electrodeposited conducting polymer electrode structure
           on the actuation performance of muscle-like ionic actuators
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Haleh Rasouli, Leila Naji, Mir Ghasem Hosseini This study demonstrates the influences of physical and electrochemical characteristics of conducting polymer (CP) film as electrode material on the actuation performances of ionic actuators which is of considerable interest for increasing the application of metal-free ionic actuators in different fields. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and polypyrrole (PPy) were applied as electrode materials in fabrication of metal-free Nafion-based electromechanical actuators. These polymers were electrochemically deposited on both surfaces of polymeric membrane and variations in physical, electrochemical and electromechanical characteristics of actuators were followed as a function of the applied polymer type. Pt-electrode Nafion based actuators were prepared as standard. Electrochemical studies revealed that the mechanism of actuation is mainly related to double-layer capacitance (Cdl) and that faradic capacitance (CF) plays less significant role. PPy-electrode actuators showed higher ion and water permeability due to formation of thinner electrode layers with finer morphology. The largest tip displacement (25 mm) was obtained in PPy-electrode actuators, in response to 6 V dc potential. These actuators exhibited the highest specific capacitance of 146.26 m F.cm−2 and capacitance retention of 87.41% after 100 cycles. The electro-mechanical energy efficiency and the maximum tip displacement of PPy-electrode actuators were 46.42% and 31.57% higher than that considered for PEDOT:PSS-electrode actuators, respectively.
       
  • Dynamic modeling of liquid impulse pressure generator for calibration of
           pressure sensors
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jun Yang, Shangchun Fan, Bo Li, Riheng Huang, Yusong Shi, Bo Shi Impulse pressure generator with dropped mass is commonly used for dynamic pressure calibration, but there is always high frequency oscillation in the rising edge of the pressure waveform especially for the low amplitude impulse pressure. Through the dynamic analysis and modeling of the whole process of the impulse pressure generator based nonlinear mass spring system, the corresponding numerical simulations of the process in various cases are carried out. Numerical analysis and experiments show that the repeated collision between the hammer and the piston is the direct cause of high frequency oscillation. Based on the model and experiment, the influence of air, hammer mass, piston size and mass, damping and so on the high frequency oscillation characteristics of impulse pressure is further analyzed. The dynamics model is established to further improve the design basis of the liquid impulse pressure generator, optimize the impulse pressure waveform and extend the lower limit of the range.
       
  • Sol-gel deposition and characterization of vanadium pentoxide thin films
           with high TCR
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Siamack V. Grayli, Gary W. Leach, Behraad Bahreyni Vanadium pentoxide thin films have been deposited on quartz substrates via sol-gel synthesis and dip coating. The process was developed to establish a reliable and inexpensive method to produce thin films with a high temperature coefficient of resistance (TCR) for sensing applications. Sol-gel precursor concentration and post-deposition annealing conditions were varied to address their effects on film composition, morphology, structure, resistivity, and TCR response. The resulting thin films were structurally characterized by thin film profilometry, x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. Resistivity and TCR measurements were carried out to determine their efficacy as sensor materials. Both low and high concentration alkoxide sol-gel precursors led to films of pure α-V2O5 composition but with characteristically different structural and electrical properties. Low concentration films showed a modest decrease in resistivity and TCR with increasing annealing temperature, consistent with the formation of increasing grain size and the coalescence of largely planar grains with common crystalline orientation. In contrast, films fabricated from higher alkoxide precursor concentration are characterized by a higher density of grains with a larger dispersion in orientation and better-developed grain boundaries, leading to a general increase in resistivity and TCR with annealing temperature. The TCR of the films lied in the range of -3%°C−1 to -4%°C−1, comparing favorably with films produced through conventional techniques such as DC magnetron sputtering, chemical vapor deposition, or pulsed laser deposition. Further, their TCR and resistivity characteristics can be controlled through sol-gel precursor concentration and post-deposition annealing temperature, indicating that sol-gel deposited vanadium pentoxide films are promising candidates for infrared sensor applications.
       
  • A high stability and uniformity W micro hot plate
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Maria Eloisa Castagna, Roberto Modica, Salvatore Cascino, Maurizio Moschetti, Viviana Cerantonio, Alberto Messina, Antonello Santangelo In this paper, we report on the simulation, design, fabrication and characterization of a tungsten (W) hot plate with a high electro-thermal stability and thermal uniform distribution. The device is constituted by a tungsten multi-rings resistor embedded in a dielectric membrane. Different layouts have been simulated, drawn and tested in order to evaluate and optimize the uniformity of the hot region and the power consumption. For the optimized device the diameter of the hot plate region is 1.25 mm, instead the membrane diameter is 1.83 mm. An innovative layout has been drawn to monitor the temperature uniformity of the hot region: distributed contacts have been integrated on it to be used as sense terminals and to extrapolate the single ring temperature. The same W resistor branches are used as thermal sensors by evaluating in advance the TCR (Temperature Coefficient of Resistance) and extrapolating the temperature by the resistance change. Thermal mapping shows that the temperature uniformity over the heated area is lower than 6% at 400 °C with a power consumption of only 135 mW.Thermal treatments have been performed in order to enhance the device thermal and electrical performances repeatability on wafer.
       
  • Impedimetric detection of miRNA-34a using graphene oxide modified
           chemically activated graphite electrodes
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Gulsah Congur, Ece Eksin, Arzum Erdem Graphene oxide (GO) modified graphite electrodes were developed for sensitive and selective impedimetric detection of miRNA-34a which is the biomarker of Alzheimer’s disease and various types of cancer. For this purpose, pencil graphite electrodes (PGEs) were used as recognition platform. First, chemical activation of the surfaces of PGEs was done using covalent agents (CA), then GO modification was performed at the surface of chemically activated disposable PGEs. The results of microscopic and electrochemical characterization of GO-CA-PGEs were represented. The step-by-step hybridization process was implemented for impedimetric detection of miRNA-34a and the experimental conditions were optimized for each modification/ immobilization step. Under the optimum conditions, the detection limits for miRNA-34a target were estimated as 1.84 μg/mL (261.7 nM) in PBS (pH 7.4) and 0.5 μg/mL (72.5 nM) in diluted FBS:PBS (1:1). The selectivity of GO based impedimetric biosensor was tested against to other miRNAs; miRNA-15a, miRNA-155 and miRNA-660.Graphical abstractGraphical abstract for this article
       
  • High surface roughness gold nanoparticle/centimeter level silver nanowire
           heterostructure detectors for SERS application
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Dapeng Xu, Wei Yang, Song Zhang, Jian Chen Gold nanoparticle/centimeter level silver nanowire heterostructures were prepared by vacuum thermal evaporation method and solid-state ionics method under 10 μA direct current electric field (DCEF) using fast ionic conductor RbAg4I5 films. The surface morphology and chemical composition of the heterostructures were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. The surface enhanced Raman scattering (SERS) performance was detected by Rhodamine 6 G (R6 G) aqueous solutions as probe molecules. The results indicate that the gold nanoparticle/silver nanowire heterostructures were long-range order and short-range order with the longest length of 2 cm were prepared by vacuum thermal evaporation method and solid-state ionics method. The diameters of the heterostructures ranged from 40 to 90 nm and many regularly arranged gold nanoparticles with the diameter from 5 to 20 nm lie in the prepared heterostructures, which lead to the heterostructures have high surface roughness. The molar ratio of Au:Ag in the heterostructures is 1:19. The limiting concentrations of R6 G for the prepared high surface roughness gold nanoparticle/silver nanowire heterostructures SERS substrates is 10−17 mol/L.Graphical abstractGraphical abstract for this article
       
  • Comparative evaluation of performances of TiAlN, AlCrN, TiAlN/AlCrN coated
           carbide cutting tools and uncoated carbide cutting tools on turning
           Inconel 825 alloy using Grey Relational Analysis
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Sampath Kumar T., R. Ramanujam, M. Vignesh, N. Tamiloli, Nishant Sharma, Shivam Srivastava, Akash Patel This study evaluates the machining performance of nanostructured Titanium Aluminium Nitride (TiAlN), Aluminium Chromium Nitride (AlCrN) and TiAlN/AlCrN bilayer coated and uncoated carbide tools used for machining Inconel 825 alloy. Taguchi’s L9 orthogonal experimental design was used in the turning operation by fixing machining parameters namely, cutting speed (v), feed rate (f) and depth of cut (d) at different levels. Taguchi’s Response Graph (TRG), Analysis of Variance (ANOVA) and Grey Relational Analysis (GRA) were used for examining the effects of machining parameters and their contributions to the cutting force, tool wear and surface roughness. The optimal cutting parameters were evaluated for “Smaller-the-Better” (STB) quality characteristic of all the three output responses. The GRA results, show AlCrN and TiAlN/AlCrN coated tool having obtained high Grey Relational Grade (GRG) at L1 trial when v = 50 m/min, f = 0.14 mm/rev and d = 0.15 mm. The TiAlN coated tool and uncoated tool obtained high GRG at v = 100 m/min, f = 0.25 mm/rev and d = 0.15 mm for L8 trial. The feed rate showed a high percentage contribution, followed by the depth of cut and cutting speed for TiAlN and AlCrN coated cutting tools based on the ANOVA obtained for GRG values. But, the TiAlN/AlCrN coated and uncoated tool have shown the depth of cut obtaining a high percentage contribution followed by feed rate and cutting speed based on ANOVA obtained for GRG results. Machining studies show a better performance of the TiAlN/AlCrN bi-layer coated tool when compared to TiAlN, AlCrN coated and uncoated carbide tool for machining Inconel 825 alloy.Graphical abstractGraphical abstract for this article
       
  • A fully spray processed embedded composite thermocouple for the use at
           high temperatures and harsh environments
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Marcel Knoll, Christina Offenzeller, Bernhard Jakoby, Wolfgang Hilber We present a fully spray processed polymer based temperature sensor which can be embedded in the organic coating of metallic machine components. The main aim of the sensor is to measure the temperature in such coatings. This could be used, e.g., in friction bearings for condition monitoring. For the present demonstrator, the sensor element is embedded on a steel substrate. Here, the sensing element is a thermocouple, which is made out of two conductive paints with carbon black and silver as organic or metallic filler particles, respectively. The used carbon black paint is custom-made and uses polyamide-imide as polymer binder which serves also as the polymer backbone of the insulation and the encapsulation layer. The commercially available silver paint is based on polyimide which yields the desired bond strength with respect to the insulation and encapsulation layer. The investigated thermocouples are characterized on a temperature test rig with and without top coating up to a junction temperature of 200 °C. Subsequently, the influence of prolonged heat treatment (in total 16.5 days at 200 °C) on the thermocouple sensitivity is investigated. Finally, the thermocouple cross-sensitivity study of the pressure influence on the temperature sensitivity is performed. First a test was made with pure pressure load of 40 MPa without a temperature gradient between junction and terminal. The final cross-sensitivity measurement was performed in a climatic chamber including a pressure test rig which is able to apply a load of 200 MPa at a maximum temperature of 141.5 °C.
       
  • Particle size dependence of the magnetic, dielectric and gas sensing
           properties of Co substituted NiFe2O4 nanoparticles
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): E. Ranjith Kumar, Ch. Srinivas, M.S. Seehra, M. Deepty, I. Pradeep, A.S. Kamzin, M.V.K. Mehar, N. Krisha Mohan Changes in the magnetic, dielectric and gas sensing properties of Ni0.8Co0.2Fe2O4 nanoparticles are reported. These polycrystalline nanoparticles (NPs) were prepared by evaporation method in the presence of egg-white as a bio-template. X-ray diffraction (XRD)studies of the samples showed single phase ferrite cubic structure without any secondary phases, with the crystallite size D = 10.5 nm, 16.4 nm and 21.9 nm for the samples heat-treated at 600 °C, 750 °C and 900 °C respectively. TEM micrograph shows nearly spherical shaped particles with particle size consistent with the XRD results. The magnetic hysteresis loops measured at ambient show that with increase in D, saturation magnetization MS increases but coercivity HC decreases. This size dependence of MS and HC is interpreted in terms of the core-shell model with spins in the shell of thickness d = 0.4 nm not contributing to MS becauseof disorder resulting from the lower symmetry at the surface.The frequency dependence of the dielectric properties of the samples although typical of that reported in other ferrites show significant particle size dependence. The sample with the smallest D = 10.5 nm shows the best performance as a sensor for detecting different gases (LPG, H2, NH3, and CO) at the operating temperature of 250 °C using changes in the electrical resistivity on controlled exposure to gases as the criterion.
       
  • Contact resonance spectroscopy for on-the-machine manufactory monitoring
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Maik Bertke, Michael Fahrbach, Gerry Hamdana, Jiushuai Xu, Hutomo Suryo Wasisto, Erwin Peiner A piezo resistive, phase locked loop (PLL) controlled micro tactile measurement system for on-the-machine contact resonance spectroscopy (CRS) mapping of square centimetre-sized areas is developed and characterized. The CRS uses the influence of material parameters like the Young’s modulus on the contact stiffness between probing tip and sample surface and thus, the resonance frequency of the in-contact cantilever. Recently, we showed a robust, large-dimension, piezo resistive silicon cantilever (5 mm × 200 μm × 50 μm) with a silicon tip at its free end for tactile probing of high-aspect-ratio geometries and high-speed topography scans (i.e., up to 15 mm/s). For CRS-based layer and material analysis, this cantilever can be excited into resonance by a piezo chip actuator as described in this work. A compact, LabVIEW-controlled, fully automated scanning system using a homemade, μ-controller-implemented software PLL for resonance frequency tracking and out-reading was realized. To verify the measurement principle, analytical modelling was done. Different layer thicknesses of photo resist (PR) on silicon (11 ± 2 nm to 1653 ± 76 nm), point-by-point line scans of material transitions with various Young’s moduli (Si-PR-Si), bulk materials and nano-/micro-structures were investigated to validate the system. For optimization of the sensor sensitivity and efficiency, amplitude and phase were analysed under different conditions (contact force, excitation amplitudes). On-the-machine CRS with tools and work pieces can be a valuable method for quality assurance and reproducibility of future industrial manufacturing and just-in-time production.
       
  • An ASIC chip with pipeline ADCs for CCD sensor imaging system
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Zhenya Sun, Da Zhang, Wei Fang This paper introduces the design of an application specific integrated circuit (ASIC). It will conduct the image processing for photoelectric image sensor charge coupled device (CCD). The ASIC can convert the analog signal of CCD into a suitable digital signal, which is used as the input for the next stage. To realize the ASIC, a two-channel analog to digital converter (ADC) with the speed of 40 MS/s-100 MS/s and a low voltage differential signaling (LVDS) has been proposed. In the ASIC, the correlated double sampling (CDS) has been integrated into the programmable gain amplifier (PGA). A novel CDS circuit is employed to reduce the amplifier gain error. The unique design reduces the size of ASIC by sharing the same operational amplifier (OPA) block. In the low sampling rate of 40 MHz, the spurious-free dynamic range (SFDR) is larger than 91 dB, and the signal-to-noise-ratio (SNR) is more than 79 dB. In the high sampling rate of 100 MHz, the ADC achieved a high SFDR of 92.2 dB and SNR of 81.47 dB. With a 0.13-μm 1P-6M CMOS process, the ASIC only occupies on the die with a size of 21.16 mm2. With the power supply of 3.3 V and 1.8 V, the power consumption is as low as 405 mW. By using the ASIC with the specially designed ADC, the saturated output image reaches a high SNR of 52.2 dB.
       
  • A heat-resistance and high-sensitivity acoustic pressure sensor based on
           aluminum-polyimide diaphragm
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Xinxin Li, Shenglai Zhen, Kai Qian, Xiudong Liang, Xiaoguang Wang, Jinhui Shi, Xuqiang Wu, Benli Yu A fiber-optic acoustic pressure sensor based on aluminum-polyimide diaphragm is proposed in this paper. The sensing diaphragm exhibits excellent properties including heat resistance and long-term stability (4 months). Together with hybrid configuration of Mach-Zehnder and Sagnac interferometer with triple detection passive demodulation algorithm, the sensor can measure the absolute amplitude of acoustic pressure. The sensor has a high sensitivity of 110 nm/Pa with the acoustic pressure amplitude of 2.05 mPa–7.15 Pa and gives a minimum detectable pressure of 37.7 μPa/Hz1/2 at 4 kHz. The sensor also demonstrates a flat frequency response in the range of 600 Hz–6 kHz and is expected to be used for weak acoustic pressure sensing and photo-acoustic spectroscopy.
       
  • Effect of spatial variations and desiccation cracks on the DPHP and MPHP
           sensors
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Vinay S. Palaparthy, Somenath Mondal, Devendra N. Singh, Maryam Shojaei Baghini, G.K. Ananthasuresh In sensing soil-moisture, there are inherent field related issues such as uncertainty and unpredictable distribution of minute amounts of trapped water and morphological changes of soil such as lumps and cracks due to desiccation. This poses problems for measurements done using a dual-probe heat-pulse (DPHP) technique that uses a narrow cylindrical sampling zone between heater and temperature probes. Thus, DPHP sensors are susceptible to errors. Hence, we studied and compared single-point and multi-point soil-moisture measurements using the heat-pulse technique. For this, we designed and developed a multi-point heat-pulse (MPHP) sensor with three temperature probes that enhanced the sampling zone to a volume of 840 mm3, which is three times that of the DPHP sensor. Sequentially deployed DPHP and MPHP sensors with spatial variations revealed that the maximum difference between the measured percentage of moisture from the DPHP sensor and standard oven-dried instrument was more than 10%, whereas for the MPHP sensor the discrepancy was only around 3%. Furthermore, when cracks appeared in the soil mass, it was observed that the discrepancy of DPHP sensor is around 16% while that for the MPHP sensor was still only 3%.
       
  • Technical method of improving overload of pressure sensitive chip based on
           sacrificial layer technology
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Rongyan Chuai, Yuxin Yang, Xin Li, Jian Wang, Bing Zhang For pressure sensitive chips made by sacrificial layer technology, their overload capacity can be significantly improved through accurate control over the thickness of the sacrificial layer and the pressure sensitive diaphragm. Based on the analysis for the simulation of the stress distribution of the pressure sensitive structure, the relationship between sizes of the sensitive structure and the overload capacity is elaborated in virtue of the influence of sensitive structure sizes on fracture strength of the polysilicon sensitive diaphragm; and then a design method in improving overload capacity is proposed. Our simulation and analysis indicate that the overload can exceed thirty one-fold of the full scale pressure when properly reducing the thickness of the sacrificial layer and the diaphragm. A sample pressure sensor chip is fabricated with a full scale range of 2 MPa. The test results show that the overpressure of the sample is 18MPa, and its full scale output voltage is 288 mV under 5 V power supply.
       
  • Enhanced thermo-electro-mechanical characteristics of purified P(VDF-TrFE)
           films for ultrasonic transducers
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Cheon-Ho Park, Quang Van Duong, Yong-Ju Moon, Kanglyeol Ha, Seung Tae Choi In this study, the fabrication process of a piezoelectric poly[(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)] film was optimized to maximize its crystallinity and piezoelectric properties and to improve its thermal stability. The effect of purification of P(VDF-TrFE) solution dissolved in methyl ethyl ketone [MEK] and uniaxial stretching on the properties and performance of P(VDF-TrFE) film was studied. In the purification process, the solution was filtered with a syringe filter with 2.7 μm pores. X-ray diffraction measurements showed that the stretching and purification processes increased the crystallinity of the P(VDF-TrFE) films by approximately 16.2% and 2.2%, respectively. A high-temperature storage test showed that the unstretched P(VDF-TrFE) films lose most of their polarization after 1-h storage at 70 °C. The stretching process greatly increased the thermal stability of the films so that the purified and stretched P(VDF-TrFE) films exhibited a small variation within 6% in the piezoelectric strain constant (d33) for 96 h at 70 °C. Ultrasonic transducers (UTs) were also fabricated with the purified and stretched P(VDF-TrFE) films. The pulse-echo measurement showed that the sensitivity and bandwidth of the UTs increased by 4.5 dB and decreased by 24.3%, respectively, compared to UTs fabricated with the purified P(VDF-TrFE) film without stretching.
       
  • Bio-inspired fluidic thermal angular accelerometer with inherent linear
           acceleration rejection
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Hommood Alrowais, Patrick Getz, Min-gu Kim, Jin-Jyh Su, Reginald Tran, Wilbur A. Lam, Oliver Brand This paper reports on the design, simulation, fabrication and characterization of a bio-inspired angular accelerometer. The sensor mimics the semicircular canals in mammalian vestibular systems. The device pairs a fluid-filled microtorus with a thermal detection principle based on thermal convection. The microtorus is intersected by a set of heaters surrounded with temperature detectors on either side, which sense a temperature profile asymmetry upon applied angular acceleration. The device fabrication is based on a two-mask process. Proper arrangement of four resistive temperature sensors in a Wheatstone bridge reduces the impact of heater-induced buoyancy effects. The toroidal microchannel results in inherent geometric linear acceleration insensitivity. The sensor demonstrates a sensitivity of 124 μV/deg/s2 for in-plane angular acceleration, two orders of magnitude suppression of cross-axis angular accelerations, three orders of magnitude suppression of linear accelerations, and a test setup limited dynamic range of ±2000 deg/s2 at 1 Hz.
       
  • Analysis of impedance data from bubble flow in a glass/SU8 microfluidic
           device with on-channel sensors
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Mohammadmahdi Talebi, Peter Woias, Keith Cobry This paper presents the design and original fabrication of a fully transparent microfluidic reactor with integrated electrical sensors over the microchannel. The transparent chip design allows for microscale photochemistry, and permits direct, real-time visual and electrical observation. The microchip uses optically transparent indium tin oxide (ITO) electrodes as sensing elements for in-channel phase tracking. High-speed videography was used to validate the electrical measurement data. The device permits visual observation of microchannel bubble flow while simultaneously acquiring electrical data. The aim of this work is to develop and optically verify electrical data acquisition and signal analysis methodologies, which in future applications may be used for inexpensive non-destructive monitoring of two-phase microchannel flows, in systems where detailed visual observation may be infeasible.
       
  • Impedance calculation of arbitrary-shaped thin-walled coils for
           eddy-current testing of planar media
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Dehui Wu, Fan Yang, Xiaohong Wang, Tianfu He Eddy-current testing is used in a variety of fields, so it is important to analyze the coil impedance. Previous studies on impedance calculation have mainly focused on circular and rectangular coils. This paper presents a general method to evaluate the impedance of an arbitrary-shaped thin-walled coil facing with a planar media. The impedance formulas are deduced by using second order vector potential (SOVP) method. In the formulas, the coil function, which is in double-integral form, is defined. The impedance calculation for arbitrary-shaped coils can be represented by the corresponding coil function. The coil functions for common coils such as circular, triangular, rectangular and trapezoidal coils are also derived in this paper. Finally, the impedance and impedance change of various shaped coils above an aluminum plate are measured, and compared with calculated values. The results indicated that they have a good agreement.
       
  • Design, fabrication and characterization of an annularly grooved membrane
           combined with rood beam piezoresistive pressure sensor for low pressure
           measurements
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Chuang Li, Jianbing Xie, Francisco Cordovilla, Jinqiu Zhou, R. Jagdheesh, José L. Ocaña A novel structure piezoresistive pressure sensor with annularly grooved membrane combined with rood beam has been designed for low pressure measurements. By introducing high concentrated stress profile (HCSP) and partially stiffened membrane (PSM) into the sensitive regions, the strain energy was concentrated at the rib structure and an oversize deflection was avoided at the center of the membrane, which effectively improved the sensitivity and linearity of the sensor. The structure design and geometry optimization of the sensitive membrane were also studied by finite element method (FEM), which helped the sensor chip achieve a high sensitivity and small pressure nonlinearity (PNL). Finally, the fabrication of a sensor with annularly grooved membrane and rood beam was reported. Experimental results showed that the sensor obtained a sensitivity of 30.9 mV/V/psi and a pressure nonlinearity of 0.25% FSS in the operating range of 0–1 psi at room temperature. Such results indicate that this novel structure sensor is suitable to be applied in measuring absolute micro pressure lower than 1 psi.
       
  • Miniature mechanical safety and arming device with runaway escapement
           arming delay mechanism for artillery fuze
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Ji-hun Jeong, Junseong Eom, Seung S. Lee, Dong Wan Lim, Yong Ik Jang, Kyoung Woong Seo, Seong Soo Choi, Chun Jae Lee, Jong Soo Oh In this research, a miniature mechanical SAD (Safety and Arming Device) with arming delay was developed for actual munitions application. Reliable arming delay performance was achieved by applying a runaway escapement system that operates by a rack-and-pinion motion. The miniature mechanical SAD was fabricated using a stainless steel wet etching process that provided not only miniaturization but also a high processing yield. The miniature mechanical SAD performed successfully under the desired safety and arming conditions in lab tests and showed fine agreement with the finite element method simulation results. Field tests were performed with a grenade launcher to validate its performance under the actual firing conditions. One hundred samples that were shot 23.6 m (safety distance) and 200 m (arming distance), and every specific test criterion was met successfully. The new SAD was also found to be appropriate for safe use in artillery fuzes by conducting environmental tests under a variety of temperature, vibration, and impact conditions.
       
  • All-dielectric metasurface-based roll-angle sensor
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Xiuguo Chen, Ze Tao, Chao Chen, Cai Wang, Li Wang, Hao Jiang, Daniel Fan, Yasin Ekinci, Shiyuan Liu We propose and demonstrate an all-dielectric metasurface-based roll-angle sensor, in which the roll angle is translated into the change of polarization state of the probe light. A circular polarization beam splitter is designed and fabricated to split the probe light into right-circularly polarized and left-circularly polarized light beams, whose intensities are then collected to estimate the roll angle. The experimental results show that the developed roll-angle sensor has a measurement resolution of 0.1° and a measurement range of 30°. The all-dielectric metasurface-based design promises to substantially reduce the size of the roll-angle sensor and is expected to gain wide applications especially on space-limited occasions.
       
  • High-sensitive ultrasonic sensor using fiber-tip PVC diaphragm Fabry-Perot
           interferometer and its imaging application
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Tingting Gang, Chi Zuo, Xiaobo Liu, Xiaohong Bai, Manli Hu A polyvinyl chloride (PVC) diaphragm based on fiber-tip Fabry-Perot interferometer (FPI) is proposed and demonstrated experimentally for ultrasonic wave (UW) three-dimensional imaging. The sensor probe is created by coating the PVC diaphragm to the end facet of a well-cut single mode fiber (SMF) using a plastic welder. The probe performs with an ultra-high UW sensitivity due to high pressure sensitivity of the PVC, and thus is capable of detecting gradient seismic physical models with different angles. By scanning the model using the proposed sensor in water and three-dimensional signals reconstruction, the imaging of the spherical model is achieved.
       
  • A low cost n-SiCN/p-PS/p-Si heterojunction for high temperature
           ultraviolet detecting applications
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Tse-Heng Chou, Ta-Wei Kuo, Chun-Yu Lin, Fu-Shun Lai In this paper, we investigated the n-SiCN/p-PS/p-Si heterojunction for low cost and high temperature ultraviolet (UV) detecting applications. The crystalline SiCN film was deposited on p-(100) porous silicon (PS)/silicon substrate with rapid thermal chemical vapor deposition (RTCVD) system. The p-PS serves as a buffer layer with features of high resistivity and flexibility to suppress dark current of an optical sensing device at high temperature. As a result a high photocurrent to dark current ratio (PDCR) can be achieved. At room temperature, the measured PDCR of the n-SiCN/p-PS/p-Si heterojunction with and without irradiation of 254 nm UV light, under −5 V bias and 0.5 mW/cm2 light power is ∼98.3. Even up to 200 °C, the ratio is still high to ∼8.5. These results are better than that of the reported SiCN film or ZnO nanowires on Si substrate UV detectors without the p-PS buffer layer.
       
  • A flexible sensing system capable of sensations imitation and motion
           monitoring with reliable encapsulation
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Menglu Li, Lei Zheng, Tianbai Xu, Hualei Wo, Umar Farooq, Weiqiang Tan, Changqian Bao, Xiaozhi Wang, Shurong Dong, Wei Guo, Jikui Luo, Jong Min Kim In this work, a flexible multiple sensor system is demonstrated for robotic and prosthetic applications. The system consists of two strain sensors, a microheater, a temperature sensor and a pressure sensor for imitating different sensations of human skin. The strain sensors are designed for monitoring the movement and bending angle of the fingers; while the temperature and pressure sensors are used to collect the information of temperature, grabbing force and stiffness of the objects being grabbed, respectively. Combination of the temperature sensor and microheater mimics the temperature sensation of human skin, allowing measuring temperature and apparent temperature of the objects grasped. Liquid metal with reliable polymer encapsulation is innovatively used to interface the sensor system with peripheral circuits. This allows reliable signal transmission and processing for the flexible sensor system for strains up to 40%. This multiple sensor system is capable of precisely monitoring movement of fingers, providing different sensations and judging some characteristics of objects for a robot hand.
       
  • Three dimensional force estimation for steerable catheters through
           bi-point tracking
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Junghwan Back, Lukas Lindenroth, Kawal Rhode, Hongbin Liu Contact forces play a significant role in the success of cardiac ablation. However, it is still challenging to estimate the applied contact force during the intervention when a catheter is under large bending or experiences multiple contact points along its body. A multi-element kinetostatic model of a tendon-driven catheter is proposed for real-time intrinsic force sensing. The model is able to accurately predict the steerable section shape of the catheter for given tendon tensions as well as the contact force at any known location on the steerable section. An algorithm is proposed which estimates the contact force on the steerable section using the model-based shape prediction in combination with end-position tracking of the steerable section. In this paper, undefined parameters and contact states of the force and shape estimation are defined and investigated. The shape prediction is validated in 3D space. The contact force estimation is validated with different catheter shpae, contraint catheter and buckling. It can be seen that end-position of the steerable section can be predicted with an accuracy of about 2.3 mm. In the validations, the 3-dimensional contact forces can be estimated accurately with an error of about 0.018 N and 1.6 ms computation time. Furthermore, the contact force estimation algorithm are able to incorporate external physical constraints along the catheter, which is validated in an experimental setup.
       
  • Temperature characteristics of langasite surface acoustic wave resonators
           coated with SiO2 films
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Ling Li, Bin Peng, Heng Yu, Wanli Zhang In this paper, the SiO2 temperature compensation layers were deposited on LGS SAW resonators. The temperature characteristics of SAW resonators with different thicknesses of SiO2 coating layers were investigated from room temperature to 450 °C. The results show that the SAW velocity, the turnover temperature, the first and second order temperature coefficients of frequency (TCF1 and TCF2 ) increase as the SiO2 films thickness increasing. The Q factor of the SAW resonator decreases greatly due to the poor quality of the SiO2 film. Zero TCF1 is achieved when the SiO2 coating layer is about 0.25 μm. The results show that the LGS SAW resonators can be temperature compensated by SiO2 coating layer.
       
  • A novel sprayable fast-responding pressure-sensitive paint based on
           mesoporous silicone dioxide particles
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Di Peng, Feng Gu, Yongzeng Li, Yingzheng Liu A novel formulation of sprayable fast-responding pressure-sensitive paint (PSP) has been developed which uses mesoporous, hollow silicone dioxide particles as hosts for luminescent molecules (PtTFPP). The mesoporous particles are formed by nano-scale particles through Van del Waals force and chemical bonds, providing favorable environment for luminophore deposition. The resulting highly porous structures facilitate oxygen diffusion within the PSP binder which leads to a response time as low as 50 μs. More importantly, the current formulation can resolve the conflict between dynamic response and paint durability (in high-speed flows). The mesoporous-particle-based PSP (MP-PSP) prepared by mix-and-spray method features both fast response (about 100 μs) and high paint durability due to its highly porous structure and uniform luminophore distribution throughout the binder. Meanwhile, other negative effects of bonding polymer on PSP’s sensing properties are reduced, which results in increased pressure sensitivity and greatly improved photostability. The influence of particle size, paint thickness and fabrication method on sensing performance is also discussed in detail. This novel MP-PSP has shown great potential for applications in high-speed, unsteady aerodynamic testing.
       
  • Investigation of VTP:PC71BM organic composite as highly
           responsive organic photodetector
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Nur Adilah Roslan, Shahino Mah Abdullah, Wan Haliza Abd Majid, Azzuliani Supangat In this work, we report the use of vanadyl 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis(dimethylamino)-29H,31H-phthalocyanine (VTP) in the fabrication of organic photodetector that aimed to be more responsive in the lower region of visible light. The thin active layer of the photodetector has been developed from the vanadyl 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis(dimethylamino)-29H,31H-phthalocyanine (VTP) [6,6]:-phenyl C71 butyric acid methyl ester (PC71BM) blend solution. The combination of VTP and PC71BM has significantly enhanced the absorption of visible light especially below 650 nm for the ITO/PEDOT:PSS/VTP:PC71BM/Al photodetector. The detector showed good photocurrent-illumination linearity, fast response-recovery time and high consistency towards the rapid change of light intensities. It is found that the detector exhibits a good photoresponsivity of 2.30 × 10-1 A/W.
       
  • n-ZnO/p-Si heterojunction nanodiodes based sensor for
           monitoring UV radiation
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): P.D. Sahare, Sudhisht Kumar, Surender Kumar, Fouran Singh ZnO nanowire array on p-type Si (100) substrate based PN-heterojunction photodiode type UV radiation detector was fabricated using rf-magnetron sputtering. The detector exhibited visible blindness below the band gap of the material (3.2 eV) and ultra-fast response for ultraviolet radiation with a peak responsivity at around 380 nm. The temporal photocurrent response of the detector was measured to be 0.1 s which is much better than a commercially available UV-detector. The design, construction and working of the detector are discussed here in detail. The origin of selective and fast response has also been discussed with support of existing theoretical models. Accordingly, electron hole pairs created by the UV radiation at the p-type Si and n-type ZnO nanowire junctions and separated by junction barrier get immediately recombined to enhance the photoconductivity due to applied electric field. The barrier potential and the junction capacitor could be tuned and depend on the size of the nanowires and the band bending on surfaces of nanowires due to heterojunction. The steady state response of the detector studied by keeping it in a reverse biased condition and exposing to UV radiation shows very high stability of the device (around 4% decrease in the photocurrent in over five weeks for −3 V biasing and ∼50 μW/cm2 UV power). Other potential applications for this UV detector are in the field of medicine and in spectroscopy where UV sources are being used. It could also be used to take protective measures for eye damages and skin cancer by monitoring UV radiation levels.Graphical abstractGraphical abstract for this article
       
  • Ion beam assisted fortification of photoconduction and photosensitivity
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Pragati Kumar, Nupur Saxena, F. Singh, Vinay Gupta A new approach to substantially improve UV/Visible photo sensitivity of nanocrystalline CdS (nc-CdS) thin films is investigated. nc-CdS thin films grown on Si wafer by pulsed laser deposition followed by irradiation treatment were used to fabricate photo-sensors. Swift heavy ion irradiation (SHII) of the nc-CdS thin films was carried out using 70 MeV 58Ni6+ ions. The influence of irradiation fluence on the transport behaviour of nc-CdS is investigated by device performance under the illuminating light of wavelengths 355 nm, 405 nm and 470 nm. Indeed, the sensors presented here are easy to fabricate without requirement of rigorous synthesis procedure. Moreover, they illustrate characteristics similar to those of photo-sensors designed with complex structures and tedious procedures. The improvement in conductivity under the exposure of SHII is a consequence of enrichment in carrier concentration as reveals from current–voltage (I–V) measurements. The sensor exhibits improvements in the response time, responsivity, photosensitivity, quantum efficiency, and specific detectivity as a function of both the ion fluence and illuminating light wavelength. These sensors show superior value of all device parameters under the illumination wavelength 470 nm of visible light. The utmost values achieved for responsivity, sensitivity, external quantum efficiency, and specific detectivity are ∼ 82 A/W, 1.02 × 103 %, 19.5 × 103 %, and 5.05 × 1011 cm Hz1/2W−1 respectively under same illumination at 5 V for 1 × 1013 ions/cm2 irradiated photosensor. Under the same illumination, bias voltage and irradiation fluence the minimum value achieved for rise time and fall time is 183 ms and 61 ms respectively. A possible mechanism involved in both the SHII and illumination wavelength induced moderation of conductivity and consequently photosensitivity is explained on the basis of variation in the defect densities.
       
  • Highly sensitive 3C-SiC on glass based thermal flow sensor realized using
           MEMS technology
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Vivekananthan Balakrishnan, Toan Dinh, Hoang-Phuong Phan, Dzung Viet Dao, Nam-Trung Nguyen This paper presents a silicon carbide (SiC) based thermal flow sensor on a transparent and electrically insulating glass substrate via anodic bonding process. The paper elaborates on the fabrication steps of the thermal flow sensor. Three resistive heater size configurations of dimensions 100 μm × 100 μm, 300 μm × 300 μm, and 1000 μm × 1000 μm were fabricated. The thermoresistive properties of 3C-SiC on glass were investigated from ambient temperature to 443 K. The characterization of the SiC heater and temperature sensors revealed a high thermoresistive effect with a temperature coefficient of resistance (TCR) of approximately −20,716 ppm/K at ambient temperature(298 K) and −9367 ppm/K at 443 K respectively. The performance of the sensors was evaluated based on the sensitivity of the flow sensor. For a turbulent flow velocity of 7.4 m/s, the sensitivity of the sensor operating in the constant -voltage mode is 0.091 s/m with a power consumption of 133.50 mW for the 1000 μm × 1000 μm heater. Finally, a study on the flow direction was conducted to confirm the operation of 2-D direction independent hot-film flow sensor. Results indicated that the performance of the sensor remained the same when the flow direction was perpendicular to SiC heater and sensor respectively. However, the best sensitivity was achieved by passing air flow perpendicular to the sensing elements. The high TCR of the single crystalline 3C-SiC material, the relatively low power consumption on the order of milliwatts and the high sensitivity of our sensor demonstrates its potential use for high temperature flow sensing applications.
       
  • Towards a low current Hall effect sensor
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Yossi Sharon, Bagrat Khachatryan, Dima Cheskis Many modern electronic devices utilize linear Hall sensors to measure current and the magnetic field, as well as to perform switching and latching operations. Smartphones, laptops, and e-readers all work with very low (sub-milliampere) currents. To perform a switching function in low-power devices, however, Hall sensors must work in the microampere regime. This paper demonstrates, for the first time, the ability of a standard Hall detector to work linearly in the microampere regime between 0 and 0.7 Tesla. To do so, we developed a current source with RMS noise on the order of 10–100 pA/Hz. An optimized electronic circuit with minimal connections feeds current to the Hall sensor, and the Hall voltage is measured with an industrial nanovoltmeter. After cooling this system down to temperatures as low as 77 K, we found mostly 1/f noise. In this regime the thermal noise was negligible. We demonstrate the capabilities of this system by precisely measuring the slope of the Hall effect with a four-point probe at current intensities of 100, 10, and 1 μA. We expect that our system can work as a microampere Hall sensor using external voltage detectors.
       
  • MEMS gyros temperature calibration through artificial neural networks
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Rita Fontanella, Domenico Accardo, Rosario Schiano Lo Moriello, Leopoldo Angrisani, Domenico De Simone In this paper, the application of Artificial Neural Networks to perform the thermal calibration of bias for Micro Electro-Mechanical gyros that are installed in Inertial Measurement Units is discussed. In recent years, the interest in using these systems to perform integrated inertial navigation has increased. Several new applications, related to the use of autonomous systems and personal navigation systems in GPS-challenging environments, have been developed. Thermal calibration of bias is a key issue to be assessed to achieve the best performance of a Micro Electro-Mechanical gyro. It can reduce sensor bias to one order of magnitude lower than non-calibrated conditions. Usually, thermal calibration is performed by exploiting polynomial fitting, i.e. finding the least-square polynomial that fits experimental data collected during laboratory tests in a climatic chamber. Polynomials have some drawbacks when they are applied to Micro Electro-Mechanical gyro calibration. They are not adequate to model abrupt change of bias trend in small temperature intervals and sensor hysteresis. For this reason, in the present paper, the use of Back Propagation Artificial Neural Networks is suggested as an improvement of polynomial fitting. Indeed, Neural Networks have intrinsic adaptive configurations and standard training and testing techniques, so that they can be adequately adopted for mapping thermal bias variations. In this paper, the polynomial fitting and Neural Network compensation algorithms are compared on selected testing points where the two techniques have the largest difference. Results highlight that the proposed method has better performance on these points. Therefore, the time in which the flight attitude accuracy meets the requirements imposed by the current regulations is improved by 20%.
       
  • Photoelectrochemical ultraviolet photodetector by anodic titanium dioxide
           nanotube layers
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Siowwoon Ng, Fong Kwong Yam, Siti Nurfarhana Sohimee, Khi Poay Beh, Sau Siong Tneh, Yuit Ling Cheong, Zainuriah Hassan A prototype ultraviolet (UV) photodetector based on photoelectrochemical (PEC) cell from material synthesis up to assembly was demonstrated in this work. Self-organized titanium dioxide (TiO2) nanotube layers (1 and 5 μm thicknesses) prepared by electrochemical anodization were applied as the sensing layer in the photodetector. A printed circuit board (PCB) platform with physical size of 2 cm × 2 cm was designed to mount the sensing layer. The photodetector system comprised of a sandwich structure can be described as glass/ITO/electrolyte/TiO2 nanotube layer/Ti/PCB platform. For this system, a low applied voltage of 0.5–1 V was required to drive the photodetector. TiO2 nanotube layers have shown positive photoresponse in the entire UV spectral region (λ = 250–400 nm, classified as UV-A, B and C). In particular, the highest response with>850 sensitivity, and responsivity of ≈740 mA/W had been achieved by the 5 μm TiO2 nanotube layer for detection in the UV-A region, and the respective rise and decay time were 0.88 and 1.28 s. This work shows that the sandwich structure PEC cell UV photodetector with TiO2 nanotube layer as sensing layer is stable, highly sensitive and provides rapid response. Such platform can be potentially applied for other sensing materials as an efficient photodetector.
       
  • A mass sensor based on 3-DOF mode localized coupled resonator under
           atmospheric pressure
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Yuan Wang, Chun Zhao, Chen Wang, Delphine Cerica, Mathieu Baijot, Qijun Xiao, Serguei Stoukatch, Michael Kraft In this paper, for the first time, the mass sensitivity of a 3-DoF mode localized electrostatically coupled resonator is investigated and characterized under atmospheric pressure. A reversible method is used in which nanoparticles are added on and removed from one resonator of the 3-DOF coupled resonator system. Furthermore, a comparison of three mass sensitivity characterization methods was carried out: resonance frequency shift, resonance vibration amplitude change and resonance vibration amplitude ratio. MATLAB/SIMULINK and COMSOL Multiphysics models for the 3-DoF coupled resonator system are presented. The simulation results and theoretical calculations are in good agreement with the experimental data. The results show that a 3-DOF mode localized coupled resonator has potential to be employed for biosensing applications.
       
  • Static characteristics calibration of Pt/Au thin-film thermocouple by
           means of laser heating and temperature extrapolation method
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jiong Ding, Rouru Chen, Jiayin Wang, Suijun Yang, Shuliang Ye Thin-film thermocouples (TFTCs), owing to their fast response, show promise for use in temperature measurements with high spatial and temporal resolution. Because of the huge difference in the temperature profiles in the calibration and application, in the strictest sense, the standardised thermocouple calibration method is no longer suitable for TFTCs. However, this issue is always ignored in some TFTC research literature. To realise accurate calibration of a TFTC, a novel method is proposed in this article. The highlight of this method is the use of a laser to heat the hot junction of the TFTC. Then, according to the surrounding calibrated platinum resistance thermometers and the temperature distribution model, the temperature of the hot junction is calculated with an extrapolation method. Finally, the static characteristics of the TFTC are calibrated through establishing the function between the calculated temperatures and the electromotive forces (EMFs). In order to verify the applicability of this method, a Pt/Au TFTC sensor is designed on a thin cylindrical substrate. Through numerical simulation, a logarithmic model is obtained to describe the temperature distribution regularity of the sensor under laser heating. With screen-printed sensor fabrication and experimental setup realisation, the EMFs and resistances of the platinum resistors are recorded simultaneously. The results leads to the following three conclusions. First, this method can calibrate the Seebeck coefficient of the legs of the TFTC, where the temperature gradient is concentrated in applications. Second, the method shows good repeatability and stability in three repeated experiments. Third, the value of the calibrated temperature and the EMF curve of the TFTC are similar to those of bulk Pt/Au thermocouple. This signifies that the proposed calibration method is reliable and effective.
       
  • A novel triaxial optoelectronic based dynamometer for machining processes
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Omer Subasi, Sertac Guneri Yazgi, Ismail Lazoglu A compact triaxial dynamometer for detecting the cutting forces in machining is developed. Force measurements are performed using photo-interrupters. Structural parameters of a monolithic flexural component are chosen through parametric analysis for coupling the exerted forces with the optical sensors. A prototype of the dynamometer is manufactured, and the calibration tests are conducted in three orthogonal directions to determine the linearity, hysteresis, repeatability and resolution. Force measurements are also compared with a reference dynamometer (Kistler 9256C1). Modal analysis and milling tests are performed to observe the dynamic properties and operability of the force sensor for machining applications. Results of the experimental studies validate that the proposed sensor is a feasible low-cost solution for force measurement in machining without compromising reliability and accuracy.
       
  • Preparation and optical characterization of β-MnO2 nano thin films for
           application in heterojunction photodiodes
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): M.M. Makhlouf The present work shows that manganese dioxide (β-MnO2) nano films can be applied as a potential candidate for solar energy conversion. β-MnO2 nano thin films were successfully grown on glass and quartz substrates using thermal evaporation technique. The structural properties of as-deposited and annealed thin films were analyzed using both X-ray diffraction and field emission scanning electron microscopy techniques. The spectroscopic characterizations of β-MnO2 nano thin films with different film thickness were studied using spectrophotometric technique in the wavelength of 200–2400 nm. The optical constants of these films were calculated and showed variation with film thickness and annealing temperature. Wemple -DiDomenico oscillator model was applied in the non-absorbing region of refractive index spectrum in order to evaluate the dispersion parameters. The nonlinear optical parameters were calculated using the linear optical parameters. The annealing temperature considered to be a good tool for enhancement of the nonlinear optical parameters of β-MnO2 nano films. Unraveling the correlated optical properties with the photoresponse characterizations of β-MnO2 nano films opens the avenue to design and fabricate heterojunction photodiodes based on β-MnO2 nano-films. The photoresponsivity, photoconductivity and specific detectivity of fabricated Au/β-MnO2/p-Si/Al photodiodes were studied.Graphical abstractGraphical abstract for this article
       
  • Optical fiber liquid refractive index sensor based on Fresnel reflection
           of anti-Stokes light
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Dong Wang, Jingkuo Tong, Baoquan Jin, Yu Wang, Mingjiang Zhang An optical fiber liquid refractive index (RI) sensing method based on Fresnel reflection of Raman anti-Stokes light is firstly proposed and demonstrated. A specially fabricated sensor head formed by a fiber end and a fiber coil is designed, and they are used to sense RI and temperature respectively. Experimental results show that the sensor has a RI resolution up to 0.0002 RIU (Refractive Index Unit) and a temperature accuracy of ±1 °C within a measurement range of 10 km. The performance confirms that the sensor has potential to act as a remote refractometer and thermometer. Its case of simple fabrication of using only one multimode fiber offers attractive remote RI and temperature sensing applications involving chemical and biological fields.
       
  • Microwave sensing technique based label-free and real-time planar glucose
           analyzer fabricated on FR4
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Zainul Abedeen, Poonam Agarwal In this paper, we have demonstrated a real-time label-free microwave analyzer fabricated on FR4 board for quantitative analysis of the glucose concentration. In this, sensing area configured of interdigital (IDT) structures is embedded in the centre of coplanar waveguide (CPW) transmission line. Here, centre of the IDT structures is acting as sensing area, where analyte under test (AUT) is confined by integrating a Poly-DiMethyl-Siloxane (PDMS) cavity on to the IDT structures. Analyte’s inherent electrical property that is dielectric constant is used as source of quantitative analysis when electromagnetic (EM) waves interact with AUT. The glucose concentration dependent dielectric constant causes shift in RF parameters which are investigated in the form of S-parameters, peak frequency, impedance, resistance and reactance. These parametric measurements are carried out using Vector Network Analyzer (VNA) and the variation in each parameter w.r.t the glucose concentration ranging from 0 g/mL to 1 g/mL, are closely observed. A rigorous study has been carried out for multidimensional characterization where measured sensitivity in terms of S11 magnitude is 15.30 dB/g/mL, S11 peak frequency is 235.32 MHz/g/mL, S12 magnitude is 5 dB/g/mL, S12 peak frequency is 168 MHz/g/mL, resistance is 10.91 Ω/g/mL, reactance is 23.82 Ω/g/mL, and impedance is 63.11 Ω/g/mL with linear regression coefficient always better that 0.87. Experimental results show that proposed planar analyzer has a great potential to determine glucose multidimensional quantitative analysis for high accuracy and with improved sensitivity.
       
  • Fiber-optic Fabry-Perot interferometer based high sensitive cantilever
           microphone
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Ke Chen, Zhenfeng Gong, Min Guo, Shaochen Yu, Chao Qu, Xinlei Zhou, Qingxu Yu We demonstrate a high sensitive cantilever microphone based on fiber-optic Fabry-Perot interferometer. A stainless steel cantilever is manufactured by laser micro-machining technique. The size of the cantilever is 2 mm × 1 mm, and the thickness is 10 μm. The air gap between the fiber endface and the cantilever forms the Fabry-Perot cavity. Acoustic sensing test demonstrates high sensitivities in the frequency range from 100 Hz to 3 kHz. The pressure sensitivity and the noise-limited minimum detectable acoustic pressure level are measured to be 364 nm/Pa and 8.5 μPa/Hz1/2 at the frequency of 1 kHz, respectively. The Fabry-Perot interferometer based cantilever microphone shows advantages of high sensitivity, small size, easy to install and immune to electromagnetic interference.
       
  • A practical FBG pressure sensor based on diaphragm-cantilever
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Yong Zhao, Hong-kun Zheng, Ri-qing Lv, Yang Yang A practical FBG pressure sensor on the basis of diaphragm-cantilever was proposed and experimentally demonstrated. The measurement principle and the simulation verification were introduced. The proposed sensor is composed of a diaphragm, a cantilever, a rod and a cover. The rod transfer the deformation of the diaphragm to the cantilever. A pair of FBGs were stuck on the two sides of the cantilever respectively. Theoretical relationship between the wavelength shift and pressure had been established by theoretical analysis. The experiment showed the sensitivity was 258.28 pm/MPa in the range of 0–2 MPa, and its linearity can reach 0.999. The pressure sensor has potential to be applied to pipeline pressure measurement.
       
  • Stretchable strain sensors based on PDMS composites with cellulose sponges
           containing one- and two-dimensional nanocarbons
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Shuying Wu, Shuhua Peng, Chun H. Wang Here we present a new technique to create stretchable strain sensors by using porous cellulose composites with a low content of nanocarbon materials. In this method, highly porous cellulous microfibre sponges containing nanocarbon materials are first created by a freeze-drying method. The resullting cellulose sponges are highly conductive due to the spatial confinement of the reduced graphene oxide (rGO) or its hybrid with carbon nanofibers (CNFs) in the fibrous skeleton. Infiltrating this highly porous sponge with polydimethylsiloxane (PDMS) then creates a stretchable composite containing hierarchical conductive network with a very low loading of nanocarbons (∼0.1 wt% in the resultant PDMS composites). Experimental results reveal that the hybridisation of rGO with a small amount of CNFs increases the electrical conductivity and piezoresistive sensitivity of the composite sensor. Moreover, upon increasing the CNFs content (rGO:CNFs mass ratio varies from 1:0 to 1:1), the electrical conductivity increases up to 9.2 × 10−3 S/m, the modulus increases while strength and elongation at break decrease, and the gauge factor increases initially from approximately 3.4 to 9.4 (at rGO:CNFs = 1:0.1) then decreases thereafter. When subjected to cyclic loading-unloading up to 10 000 cycles, the new composite sensors show excellent durability with very little drift over a large number of cycles. The piezoresistive response exhibits negligible strain-rate dependence up to 0.2 s−1. Finally, an example is presented to highlight the potentials of the composite sensor as wearables in monitoring the movement of human joints, e.g., the bending of a finger joint.
       
  • Effect of local-action on electro-birefringence in bilayer composite and
           micro-displacement sensing
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Jiansen Gao, Xiaobin Luo, Ning Zhang A bilayer composite with electro-birefringence effect was fabricated using ferroelectric and stress-birefringence medium. Its electro-optical response was studied. The transmission light intensity was found to change with displacement of the incident beam to the elastic-optical layer in two dimensions perpendicular to the beam. The effects of local-action and interfacial elastic coupling on the stress distribution in the elastic-optical material were analyzed. Starting from the basic equations of elasticity, a physical model of electro-stress birefringence for the bilayer composite was derived. It was found that the theoretical calculations in general accord with the experimental results without considering ferroelectric relaxation. And the micro-displacement sensing of two-dimension was realized with the bilayer composite of electro-stress birefringence.
       
  • Modeling the analog response of passive infrared sensor
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Bodhibrata Mukhopadhyay, Seshan Srirangarajan, Subrat Kar Passive infrared (PIR) sensors are sensitive to infrared (IR) rays and are mostly used for motion detection. In this paper we propose a mathematical model that enables better understanding of the analog response of the PIR sensor, the Fresnel lens, and the associated electronic circuitry. The proposed model relates the sensor's analog output waveform to the width of sensing element, and speed of movement and distance of the subject from the PIR sensor. Experiments were performed to capture the sensor's analog output waveform corresponding to the subject's movement through the sensor's field of view (FoV) at different distances, and the relationship of the sensor's peak-to-peak output voltage with distance and speed of the subject. The simulation results are shown to match reasonably well with the experimental results.
       
  • Piezoelectric MEMS acoustic emission sensors
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Minoo Kabir, Hanie Kazari, Didem Ozevin In this paper, piezoelectric MEMS (piezo-MEMS) sensors are designed and characterized for detecting elastic waves released by active flaws, known as acoustic emission (AE). The designed sensors operate in plate flexural mode or rigid body mode driven by the vibration of silicon diaphragm where piezoelectric layer is deposited on. The designed device contains two different frequency sensors tuned to 40 kHz and 200 kHz. The microstructural layers consist of doped silicon, aluminum nitride (AlN) and metal layer, which function as the bottom electrode, sensing layer and top electrode, respectively. The silicon layer also functions as a mass-spring system where a movable plate is connected with four partially clamped beams to the substrate. As the geometry sizes are restricted by the design rules of the manufacturing process, an additional mass is provided for the 40 kHz sensor through the substrate etching process. The sensors are numerically modeled using COMSOL Multiphysics software to obtain the frequency response and the dynamic response under excitation. Afterwards, the sensors are manufactured using Piezoelectric Multi-User MEMS Process (PiezoMUMPs) provided by MEMSCAP foundry. The performance of the designed sensors is demonstrated through electromechanical characterization experiments. A face-to-face response is obtained for each sensor, and the performance of the designed sensors is compared with the conventional piezoelectric AE sensors. The developed piezo-MEMS AE sensors have advantages of small foot-print, low cost and no need for bias voltage for operation.
       
  • Piezoresistive stretchable strain sensors with human machine interface
           demonstrations
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Yichuan Wu, Ilbey Karakurt, Levent Beker, Yoshihiro Kubota, Renxiao Xu, Kong Yin Ho, Shilong Zhao, Junwen Zhong, Min Zhang, Xiaohao Wang, Liwei Lin Stretchable strain sensors are important elements in flexible and skin-mountable electronics typically fabricated using semiconductor materials in cleanroom-based manufacturing processes. This work demonstrates piezoresistive strain sensors with both strain and pressure sensing capabilities by a cost-effective and versatile process utilizing a laser patterning, graphite conversion, and polymeric transfer process. The resulting sensing systems exhibit high gauge factor of 37 and pressure sensitivity of 0.088kPa-1 with high sustainable strain up to 70%. These exceptional performances are explained and observed by deforming the sensor under an in-situ SEM to show self-healing characteristics of films under large deformations. The highly sensitive strain sensors have been shown in human interface demonstrations, such as measuring the physiological signal of the human pulses, finger pressure and bending of fingers as well as assisting a robotic arm for gripping and releasing operations.Graphical abstractGraphical abstract for this article
       
  • A carbon nanotube based NTC thermistor using additive print manufacturing
           processes
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Vikram S. Turkani, Dinesh Maddipatla, Binu B. Narakathu, Bradley J. Bazuin, Massood Z. Atashbar A fully printed carbon nanotube (CNT) based negative temperature coefficient (NTC) thermistor was developed for temperature sensing applications. The multi-layer NTC thermistor was fabricated using additive print manufacturing processes on a flexible polyethylene terephthalate (PET) substrate. Two silver (Ag) electrodes were printed using screen printing process. CNT based active layer was deposited by means of gravure printing. Organic and silver encapsulation layers were deposited using screen printing. The capability of the fabricated thermistor was investigated by measuring its response towards temperatures varying from −40 °C to 100 °C, in steps of 10 °C. As the temperature was increased from −40 °C to 100 °C, the resistive response of the thermistor decreased exponentially with an overall percentage change of 53% with the temperature coefficient of resistance (TCR) of −0.4%/°C. The stability of the printed thermistor towards relative humidity (RH) varying from 20% RH to 70% RH, in steps of 10% RH at two constant temperatures of 30 °C and 50 °C, was also studied. A maximum change of 0.34% and 0.1% was observed at 30 °C and 50 °C, respectively when compared to its base resistance at 20% RH. In addition, a response time of ≈300 ms and a recovery time of 4 s were measured for the printed thermistor with an accuracy of ± 0.5 °C.
       
  • Fully integrated wearable humidity sensor based on hydrothermally
           synthesized partially reduced graphene oxide
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): M. Shojaee, Sh. Nasresfahani, M.K. Dordane, M.H. Sheikhi In this paper, partially reduced graphene oxide (PRGO) nanosheets were prepared by an environmentally friendly hydrothermal route and their morphology, structure and humidity sensing performance were investigated. The sensor structure with gold interdigitated electrodes was fabricated on flexible polyimide substrate via standard lithography technology. The integration of a commercial Bluetooth module enabled real-time wireless transmission of sensing data to the smart phone application. Characterization data showed a decrease in the amount of oxygen functional groups attached to the PRGO nanosheets when the hydrothermal reduction time was increased. It was found that the flexible PRGO-4h sensor exhibits impressive response and quick response/recovery times over a wide range of RH levels. According to the experimental results, the enhanced response of PRGO-4h is attributed to the considerable oxygen functional groups and the improved response/recovery times are attributed to the restoration of sp2 carbon network. The performance of sensor remained nearly unchanged under bending condition. Taking the advantage of fast response/recovery time and flexibility, the sensor can monitor human respiration in real time. This work demonstrates that the potential application of PRGO-4h as a sensitive material for indication of environmental humidity as well as future generation of wearable humidity sensors.
       
  • An improved sensor for the magnetic susceptibility imaging technique for
           detecting impurities in non-ferromagnetic materials
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Xiucheng Liu, Pengfei Xing, Bhaawan Gupta, Bin Wu, Jieming Yang, Jiaying Zhang, Benjamin Ducharne, Ningxiang Yang, Cunfu He A cantilever-based sensor of magnetic force is a potential tool for magnetic susceptibility imaging in bulky materials. To solve the limitations of the previously reported sensors, in this study, a Hall device is employed to measure the magnetic field variation caused by the displacement of sensing magnet attached to the free end of the cantilever. The improved sensor has the smaller size and the higher lateral resolution and the adopted permanent magnet can be attached onto the cantilever’s free end to improve its sensitivity to the magnetic susceptibility. Based on the improved sensor configuration, two types of sensors are presented and their performances are experimentally investigated. Type-1 sensor with the cylindrical sensing magnet with a diameter of 5 mm is capable of detecting a cubic impurity (with a side length of 1 mm) of 304 stainless steel or aluminum with a depth of 1 mm in a photosensitive resin block. Type-2 sensor employs a sensing magnet with a diameter of 1.2 mm and possesses higher lateral resolution than Type-1 sensor. The estimated sensitivity of Type-2 sensor is about one third of that of Type-1 sensor. Although the impurity of aluminum and even resin cannot be distinguished from the air background in the magnetic susceptibility imaging results obtained by Type-2 sensor, the cubic impurity of 304 stainless steel can be successfully detected by Type-2 sensor.Graphical abstractPhoto of the cantilever-based sensor.Graphical abstract for this article
       
  • Miniature orthogonal fluxgate sensor in rotation magnetization mode:
           Modeling and characterization
    • Abstract: Publication date: 15 August 2018Source: Sensors and Actuators A: Physical, Volume 279Author(s): Tobias Heimfarth, Marcelo Mulato Orthogonal fluxgates operated with a dc bias can achieve lower noise levels by suppressing Barkhausen jumps. We constructed and mathematically modeled a small orthogonal fluxgate consisting of a NiFe electroplated Cu wire, surrounded by a pick-up solenoid. A large dc current was applied through the wire to keep the core in constant saturation. This ensures that the main permeability modulation mechanism is magnetization rotation. Several output parameters were analyzed: sensitivity, noise and the perming error amplitude, all with respect to two input parameters, constant and alternating excitation field component. A good agreement between the experimental data and the theoretical model was found, with higher deviations appearing when the excitation field was not high enough to saturate the core and domain wall movement becomes relevant. Measured sensitivities were highly dependent on the excitation amplitudes, but mostly in the hundreds of V/T, and noise levels of about 0.75 nT in the 0.1–10 Hz range were found. As for the perming, the sensor zero readout can vary about 20 μT if subjected to magnetic shocks of up to 4.8 mT.
       
  • Influence of key factors on Eddy current testing sensitivity and
           monotonicity on subsurface depth for ferromagnetic and non-ferromagnetic
           materials
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Deqiang Zhou, Xiang Chang, Yunze He, Hua Wang, Piyu Cao, Li Yang Studies on key influencing factors (coil’s size and excitation frequency) of eddy current testing (ECT) sensitivity, monotonicity and defect detectability have been carried out for detection of subsurface defects in ferromagnetic and non-ferromagnetic plate materials. A set of ECT finite element models and experiments have been accomplished and the detection performance has been analyzed and compared. The simulation and experiment results have indicated that for ferromagnetic material, the amplitude response of low frequency excitation has lower sensitivity but better monotonicity than high frequency. The phase response of low frequency excitation has higher sensitivity and better monotonicity than high frequency. For the non-ferromagnetic plate material, the lower the excitation frequency is, the smaller the detection sensitivity of the amplitude response is. Outside a defined excitation frequency, the defect monotonicity of the amplitude response reduces. For phase response, the lower the excitation frequency is, the smaller the detection sensitivity and the greater the monotonicity. The coil’s size has a certain extent influence on the detection sensitivity. For ferromagnetic and non-ferromagnetic plate materials, it is effective to enhance the detection sensitivity of amplitude response by increasing the size of the exciter coil and the detector coil within a certain range; and it is effective to enhance the detection sensitivity of phase response by decreasing the size of the detector coil or increasing the size of exciter coil within a certain range.
       
  • Magnetic anomaly detection based on stochastic resonance
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Chengbiao Wan, Mengchun Pan, Qi Zhang, Fenghe Wu, Long Pan, Xiaoyong Sun Orthonormal basis function (OBF) decomposition method and minimum entropy (ME) detector are two typical methods of magnetic anomaly detection. The OBF detector works effectively only when the assumptions of the target signal and noise are appropriate, and the ME detector is limited by low signal-to-noise ratio (SNR). In order to improve magnetic anomaly detection performance in the case of low SNR and no prior information of the target signal, we proposed a novel detector by using stochastic resonance (SR) method and named it SR detector in the paper. The SR detector consists of a bistable SR system and a corresponding receiver. Firstly, the noise is used to enhance the magnetic anomaly signal with the help of SR system, instead of being suppressed in a traditional method; then the anomaly signal can be detected more effectively by the receiver. Experimental results show that the SR detector did work well, its detection probability approximated to 70% even if the input SNR was −3 dB, and was about 100% if the input SNR was 0dB, when the false alarm rate (FAR) was 1.5%. Furthermore, the SR detector provided higher detection probability than the ME detector under the same basis. In a word, due to the good detection performance and simple implementation, the SR detector would be more attractive in practice.
       
  • Design and evaluation of a micro linear ultrasonic motor
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Shunsuke Izuhara, Tomoaki Mashimo We propose a micro linear ultrasonic motor, which is one of the smallest linear actuators that can generate practical force. Such a small actuation mechanism can be used for a wide range of applications, such as auto-focus systems used in thinner cell phones and smaller endoscopes. In this paper, we design the micro linear ultrasonic motor and evaluate the performance of the prototype motor. The size of the prototype stator with piezoelectric elements measures 2.6 mm in height, 2.6 mm in width, and 2.2 mm in depth (the length in slider travel direction). There is a hole of 1.4 mm in diameter at the stator center, and the slider inserted into the hole moves back and forth when voltages are applied to the piezoelectric elements. By optimizing the preload between the stator and slider experimentally, the motor thrust force has been improved to over 10 mN, which is a practical force for moving small objects. Experiments clarify the output characteristics in response to the input voltages. Finally, a maximum thrust force of 20 mN has been obtained at applied voltages with an amplitude of 150 Vp−p.
       
  • Ultrasensitive zinc magnesium oxide nanorods based micro-sensor platform
           for UV detection and light trapping
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Hemant Ghadi, Punam Murkute, Anupam Ghosh, Shyam Murli Manohar Dhar Dwivedi, Aniruddha Mondal, Subhananda Chakrabarti A cost effective unique approach has been employed to realize high quality zinc magnesium oxide (Zn1-xMgxO) based nanostructures which can replace conventional material i.e. Zinc oxide (ZnO) in detector and sensor applications. High resolution structural studies showed the formation of vertically aligned hexagonal and truncated hexagonal nanorods on RF sputtered ZnO and Zn1-xMgxO seed layer. Single crystal Zn1-xMgxO and ZnO nanorods with dominant c-axis growth along (002) crystal axis and d-spacing of 0.262 and 0.266 nm, respectively were obtained from high resolution transmission electron microscopy, selective area diffraction pattern and high resolution X-ray diffraction spectra. The high external quantum efficiency of 12.054% with narrow full width half maxima of 12.63 nm was achieved from photoluminescence spectroscopy (Zn1-xMgxO nanorods) performed at room temperature. Approximately two order of enhancement in current density was observed from photodetector fabricated using Zn1-xMgxO nanorods. A state of art peak responsivity of 62.19 A/W at 350 nm attributed to near band edge emission peak and high current rectification capability with a maximum internal gain of 185 was measured from Zn1-xMgxO detector. Zn1-xMgxO detector exhibited temporal response with reasonable rise and fall time constants along with three order higher detectivity values in comparison to ZnO detector. A DC current based humidity sensor was fabricated and characterized using sample synthesized for longer growth duration. High sensitivity of 1.612 /% RH was achieved and low recovery time was observed as the sample was subjected to annealing treatment.
       
  • Biaxial flexure testing of free-standing thin film membrane with
           nanoindentation system
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Takashi Ozaki, Tomoyuki Koga, Norio Fujitsuka, Hiroaki Makino, Hiroshi Hohjo, Hiroaki Kadoura The advent of microelectromechanical devices has increased the demand for biaxial flexure testing at the micro- and nanoscale. However, testing at these scales is challenging owing to difficulties in manipulating very small samples and applying highly symmetric biaxial loads to them. In this study, we developed a facile technique for on-chip biaxial flexure testing. The principle of the technique was inspired by ball-on-ring biaxial testing commonly employed for macroscopic flexure analysis of ceramics. In our technique, the specimen is tested as a circular membrane fixed at its edges to a substrate. The center of the membrane is pushed from above by a rounded conical nanoindenter (NI) until the membrane fractures. Since this method does not require microscale specimen manipulation involving the securing of microscale components and/or samples by external fixtures, the test procedure is relatively easy to perform. In addition, the load and displacement curves obtained using the NI are high resolution, enabling precise strength evaluation and application to very weak structures such as nanoscale membranes. To demonstrate the test system, we designed and fabricated polysilicon membranes with diameters of 20 μm and thicknesses of 80 nm. The most likely source of error in the system is misalignment between the indenter and the membrane center. Accordingly, its effect was numerically analyzed. The results showed that a misalignment of less than 3.0 μm causes a 0.32% error in the first principal stress. Since the NI tester can easily attain this alignment accuracy, highly accurate stress estimates can be achieved. The measured fracture strengths of the polysilicon membranes were fitted to the Weibull distribution, revealing an average strength of 8.11 ± 0.31 GPa and a shape parameter of 13.9 ± 5.4, both of which agree well with the results from previous research. The fracture origins were observed near the center of the membranes. These results confirm the viability of our concept.Graphical abstractGraphical abstract for this article
       
  • Optimization of both Perturb & Observe and Open Circuit Voltage MPPT
           Techniques for Resonant Piezoelectric Vibration Harvesters feeding bridge
           rectifiers
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Marco Balato, Luigi Costanzo, Alessandro Lo Schiavo, Massimo Vitelli When the characteristics of the input vibrations change with time, also the optimal operating point of a Resonant Piezoelectric Vibration Energy Harvester (RPVEH) changes with time. Such an optimal operating point is characterized by the highest value of the extracted electrical power and is called Maximum Power Point (MPP). This paper is focused on MPP Tracking (MPPT) techniques for RPVEHs. In the most widespread RPVEH AC/DC architecture, which is based on the use of a diode bridge rectifier cascaded by a DC/DC converter, MPPT requires that the voltage V0 at the output of the bridge rectifier is properly regulated. The first issue that is addressed in this paper is the derivation of a simple closed form expression of the power extracted by a RPVEH as a function of the voltage V0 as well as of the optimal value of V0. Moreover, a complete set of general guidelines leading to the proper choice of the values of the parameters of the two most widely used MPPT techniques for RPVEHs applications (the Perturb & Observe technique and the Open Circuit Voltage technique) are provided and experimentally validated. It is experimentally shown that, if the above MPPT techniques are not properly and carefully customized to the particular RPVEH application of interest, they may lead to very poor performances of the system.
       
  • Phase derivative thermo-spatiogram for distributed temperature sensing
           based on chirped grating-Michelson Interferometer
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Daryl Tan, Kok-Sing Lim, Muhammad Khairol Annuar Zaini, Chai-Hong Yeong, Yin-How Wong, Hang-Zhou Yang, Harith Ahmad A novel thermometric measurement based on chirped fiber Bragg grating (CFBG) and Michelson Interferometer is proposed. The interrogation technique is based on the linear relation between the temperature and the phase derivative function of the grating, which is determined through Fourier transformation of the output spectrum. The Michelson interferometer configuration offers the flexibility in adjusting the position of coupling coefficient curve in the spatiogram, enabling the interrogation to be done at a shorter optical spectrum record length which can reduce the interrogation time and computation load.
       
  • Design and analysis of an elliptical-shaped linear ultrasonic motor
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Hamed Sanikhani, Javad Akbari A linear ultrasonic motor (LUSM) with an elliptical-shaped metallic stator and two orthogonal vibration modes is presented in this research. The driving tip’s desired vibration is generated by the excitation of two piezoelectric actuators installed inside the stator by two sinusoidal voltages with ±π2 phase difference. The working principle of the motor is described and mathematically formulated. Furthermore, finite element analysis and parametric optimization are performed to finalize the motor design. A prototype of the motor is fabricated and evaluated by identification and operation tests. The experimental and numerical characteristic curves of the motor are presented and compared. Based on the experimental results, the prototype has a no-load speed of 40 mm/s and maximum thrust force of 1.55 N under excitation voltage of 70 Vp and preload of 12 N.
       
  • Electrically tunable long period gratings temperature sensor based on
           liquid crystal infiltrated photonic crystal fibers
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Chao Du, Qi Wang, Yong Zhao A novel high sensitivity temperature sensor has been proposed and theoretically investigated based on a photonic crystal fiber (PCF) infiltrated with liquid crystal (LC). The LC is infiltrated into the core of PCF, and the refractive index (RI) of LC will be periodically altered due to the electro-optic effect when external voltage is applied on the comb electrodes, which satisfies the formation principle of long period fiber gratings (LPFGs) and thus the attenuation bands can be observed in transmission spectrum. The resonance wavelength is more sensitive to the temperature variations due to incident light interacts with the internal infiltrated LC which has a high thermo-optic coefficient (TOC). Meanwhile, the simulation of theoretical optimization is further carried out in order that the sensor is good performance with narrow full width at half maximum (FWHM) and high sensitivity in the temperature change from 15 °C to 58 °C. To the best of our knowledge, the sensing performance of temperature variation is superior to previous optical fibers infiltrated by LC material. It is imperative to realize that there is non-linear relationship between the temperature variation and resonant wavelength shift. Nevertheless, the excellent temperature performance that is reliable could be expected to be utilized in the biochemical reaction and cell culture where the high sensitivity measurement within a small temperature change range is needed.
       
  • Microfabricated sensor platform with through-glass vias for bidirectional
           3-omega thermal characterization of solid and liquid samples
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Corinna Grosse, Mohamad Abo Ras, Aapo Varpula, Kestutis Grigoras, Daniel May, Bernhard Wunderle, Pierre-Olivier Chapuis, Séverine Gomès, Mika Prunnila A novel microfabricated, all-electrical measurement platform is presented for a direct, accurate and rapid determination of the thermal conductivity and diffusivity of liquid and solid materials. The measurement approach is based on the bidirectional 3-omega method. The platform is composed of glass substrates on which sensor structures and a very thin dielectric nanolaminate passivation layer are fabricated. Using through-glass vias for contacting the sensors from the chip back side leaves the top side of the platform free for deposition, manipulation and optical inspection of the sample during 3-omega measurements. The thin passivation layer, which is deposited by atomic layer deposition on the platform surface, provides superior chemical resistance and allows for the measurement of electrically conductive samples, while maintaining the conditions for a simple thermal analysis. We demonstrate the measurement of thermal conductivities of borosilicate glass, pure water, glycerol, 2-propanol, PDMS, cured epoxy, and heat-sink compounds. The results compare well with both literature values and values obtained with the steady-state divided bar method. Small sample volumes (∼0.02 mm³) suffice for accurate measurements using the platform, allowing rapid temperature-dependent measurements of thermal properties, which can be useful for the development, optimization and quality testing of many materials, such as liquids, gels, pastes and solids.
       
  • A novel exposure sensor based on reverse series memristor
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Changbao Wen, Jitong Hong, Shipeng Yao, Taotao Niu, Yongfeng Ju In order to expand the measuring range of the exposure sensor and solve the current fluctuation caused by the memristor resistance, a novel exposure sensor based on reverse series memristor is proposed. The exposure sensor mainly consists of the photoresistor, the current limiting resistor and the reverse series memristor. The resistance of photoresistor varies with the illuminance, causing the loop current change. Based on the memory feature of the memristor, its resistance can be used to characterize the integral value of the illuminance for a period of time. Thus the measurement of the exposure can be realized by the exposure sensor based on reverse series memristor. In the exposure sensor, two series memristors constitute the reverse series memristor and they are connected in serial oppositely. And the sum of their normalized thicknesses is 1. Experimental results show that the exposure sensor based on reverse series memristor can measure the exposure and its measuring range is larger than other measurement methods. The measuring range is from 0 to 600 lx·s when the illuminance is 100 lx. With the increase of illuminance, the measuring range of the sensor will expand while the sensitivity will decrease. Because the resistance of the reverse series memristor almost remains unchanged during measuring exposure (the standard deviation of the change is only 0.43 Ω), the influence of the total resistance’ increase on the loop current can be avoided. Thus it can avoid the impact on the measurement of the exposure and reduce the error introduced by the change of the memristors resistance. As the number of memristors increases, the measuring range will expand and the sensitivity will improve, but the symmetry of the reverse series memristor will deteriorate. Hence the number of memristors can’t be excessively large. The variation tendency of the memristor resistance curve and the normalized thickness curve are consistent, and they rise along with the increase of the exposure. In addition, the measuring range of the exposure sensor will expand gradually while the sensitivity will decrease as the resistance of the current limiting resistor increases.
       
  • Effect of structural parameters and stability of constituent materials on
           the performance of 1–3 spherical crown piezocomposite and transducer
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Yongchen Wang, Xiujuan Lin, Jianan Li, Shifeng Huang, Xin Cheng Transducer is the main instrument for signal transmitting and receiving. As the core component of the transducer, the preparation and performance of piezocomposite directly affect the efficiency of the transducer. The novel 1–3 spherical crown piezocomposites with resonance frequency higher than 320 kHz was prepared via arrangement-casting technique. And the effect of structure parameters on properties of piezocomposite was studied in this paper. The results showed that PZT aspect ratio had a significant effect on the resonance frequency of the piezocomposite. Resonance frequency varied from 322 kHz to 457 kHz as the PZT aspect ratio increased from 0.57 to 0.74. While resonance frequency slightly increased from 347 kHz to 368 kHz as the PZT volume fraction varied from 27.0% to 70.6%. Resonance frequency of piezocomposites were merely dependent on the temperature varying from −20 °C to 60 °C, revealing a great thermal stability. The -3 dB opening angle of the transducer was respectively 42° and 39° in horizontal and vertical directions. And the increasing PZT volume fraction was beneficial for enhancing the peak value of transmitting voltage response from 157 dB to 164 dB with -3 dB bandwidth of 42 kHz.Graphical abstractGraphical abstract for this article
       
  • High-resolution flexible temperature sensor based graphite-filled
           polyethylene oxide and polyvinylidene fluoride composites for body
           temperature monitoring
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Ying Huang, Xiao Zeng, Wendong Wang, Xiaohui Guo, Chao Hao, Weidong Pan, Ping Liu, Caixia Liu, Yuanming Ma, Yugang Zhang, Xiaoming Yang Flexible and high accurate temperature sensors have great potential toward applications such as medical diagnosis and body temperature monitoring. Here, we demonstrated a flexible temperature sensor based on graphite-filled polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) composites exhibiting a high accuracy of 0.1 °C and high repeatability nearly 2000 times, in the sensing temperature range of 25–42 °C. Device performance is hardly affected in different curvature, which allows for conformal application to human skin. Especially, subtle temperature change on the skin surface was also measured to validate the accuracy and anti-interference ability. Under physiological conditions, the temperature sensor based on positive temperature coefficient showed a high-speed response time of 26 s with relatively simple fabrication technology. These results demonstrated the possibility and feasibility of fully using the sensors in body temperature sensing for medical use as well as sensing function of body temperature measuring.
       
  • Sensitivity of compositional measurement of high-pressure fluid mixtures
           using microcantilever frequency response
    • Abstract: Publication date: 1 August 2018Source: Sensors and Actuators A: Physical, Volume 278Author(s): Shadi Khan Baloch, Alexandr Jonáš, Alper Kiraz, B. Erdem Alaca, Can Erkey Frequency response of an oscillating microcantilever immersed in a fluid mixture can be used to determine the composition of the mixture over a wide range of temperatures and pressures. The Limit of Detection (LOD) in such measurements carried out at high pressures is of great interest for monitoring technologically important processes such as supercritical drying of aerogels. We studied compositional measurement sensitivity of cantilevers defined as the derivative of the cantilever resonant frequency or quality factor with respect to the fluid mixture composition. On the basis of Sader’s model of hydrodynamic interaction of an oscillating immersed cantilever with the surrounding fluid, we derived analytical expressions for the sensitivity that were found to be complex functions of the density and viscosity of the mixture as well as the length, width, thickness, and density of the cantilever. We measured the frequency response of cantilevers immersed in ethanol−CO2 mixtures containing 0 – 0.04 wt fraction of ethanol at 318 K and within the pressure range 10–21 MPa. Using the measured resonant frequency and quality factor together with previously published density and viscosity data for ethanol−CO2 mixtures of various compositions, we calculated the sensitivity at each pressure and temperature and determined the LOD of the measurement. In particular, with our current setup, the LOD ranged from 0.0009 to 0.0071 wt fraction of ethanol in the mixture in the pressure range 10–21 MPa for a 150 μm long cantilever. Our results convincingly illustrate the potential of miniature cantilever-based probes for fast and sensitive in-situ detection of the composition of fluid mixtures in practical technological processes carried out at high pressures.
       
  • Built-in thin film thermocouples in surface textures of cemented carbide
           tools for cutting temperature measurement
    • Abstract: Publication date: Available online 11 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Jindang Li, Bo Tao, Shuwen Huang, Zhouping Yin Cemented carbide tools embedded with thin film thermocouples are presented in this paper, to monitor the tool temperature distribution in machining of titanium alloys. In order to protect the thin film sensors from the flowing chips, the fabrication processes which include preparation of micro-grooves on the rake face of commercial tungsten carbide cutting inserts and installation of the thin film sensors in the grooves are proposed. Six K-type thin film thermocouples are implanted in the grooves at a depth of about 100 μm with a 100 μm × 50 μm hot junction area. The tests show that the sensors are reliably insulated with the alloy substrate and have good linearity and uniformity in the measurement. The performance of the fabricated inserts are evaluated in a titanium alloy (Ti6 Al4V) turning process with the cutting temperature close to the tool-chip interface obtained online for both continuous and interrupted cutting experiments. The fabricated sensors show good sensitivity and improved durability during the cutting processes.
       
  • Investigation of fast and sizeable photostriction effect in tellurium thin
           films using fiber Bragg grating sensors
    • Abstract: Publication date: Available online 11 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Sivakumar Gayathri, Sridevi S, Gagandeep Singh, B.N. Shivananju, Sundarrajan Asokan We report a sizeable photoinduced strain in 90 nm tellurium (Te) thin film, coated on a fiber Bragg grating (FBG) sensor. The Bragg wavelength shift of the FBG sensor is used as the probe, to understand the photostrictive properties of Te thin film under illumination with laser light of visible wavelengths (405, 532 and 633 nm), at varying optical power density (5 to 161 mW/mm2), and also during cyclic exposure. An induced elastic strain of the order of 10-5 to 10-4 has been observed which is found to increase with increasing wavelength of laser illumination. The high (1 picometer) resolution of the FBG interrogator used facilitates the accurate detection of the elastic strain induced in Te thin films even at a short exposure time of 0.1 s.
       
  • Theory, Technology and Applications of Piezoresistive Sensors: a Review
    • Abstract: Publication date: Available online 9 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): A.S. Fiorillo, C.D. Critello, A.S. Pullano Sensors based on the detection of small resistance variations are universally recognized as piezoresistive. Being one of the simplest, most common and most investigated classes of sensors, continuous efforts are focused on creating improved devices with higher performance that can be used in many commercial and non–commercial applications (e.g. evaluation of strain, pressure, acceleration, force etc.). Consequently, despite the fact that more than 150 years have passed since the discovery of the piezoresistive effect in some classes of metals and semiconductors, the development of such sensors remains interesting and topical. Moreover, with the advent of second–generation robotics, research on piezoresistive sensors has undergone a massive increase. This paper aims to be a short, self–consistent vademecum which would be useful to researchers and engineers, since it focuses on the fundamentals of theory, materials, and readout–circuit design pertinent to the most recent developments in the field of piezoresistive sensors.
       
  • Role of Ca2+ co-dopants on structural and optical properties of YF3:Tm3+
           /Yb3+ upconversion phosphor for improved optical thermometry
    • Abstract: Publication date: Available online 7 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): A. Kumar, S.P. Tiwari, A. Sardar, K. Kumar, Joaquim C.G. Esteves da Silva This work describes the synthesis, structural and optical properties of Tm3+/Yb3 doped and Ca2+ co-doped YF3 upconversion phosphor material. The effect of Ca2+ ions co-dopant concentration is varied at 0, 10, 20 and 30 mol % to observe it’s effect on YF3:Tm3+/Yb3+ through different characterizations like XRD, XPS, FE-SEM, FTIR, UV-vis and upconversion measurements. Dominant upconversion emission bands are found at 450, 476, 645 and 696 nm emission wavelengths corresponding to the 1D2→3F4, 1G4→3H6, 1G4→3F4 and 3F3→3H6 transitions within Tm3+ activator center on 976 nm excitation. Finally, prepared samples are utilized in temperature sensing application demonstrations with Ca2+ ions co-dopants concentration variations.Graphical abstractGraphical abstract for this article
       
  • LANGASITE CRYSTAL BASED PRESSURE SENSOR WITH TEMPERATURE COMPENSATION
    • Abstract: Publication date: Available online 7 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Sujan Yenuganti, Haifeng Zhang, Chen ZhangABSTRACTThis paper presents the design and testing of a new pressure sensor utilizing a doubly rotated cut piezoelectric langasite (LGS) crystal resonator with temperature compensation. The sensor can measure temperature and pressure simultaneously by using the dual mode nature of the doubly rotated cut langasite resonator (SBTC). The sensor is designed using CAD software, fabricated and tested experimentally in the laboratory for a pressure range from 0-45 PSI. Before fabrication the sensing principle was verified performing a force frequency analysis on the langasite resonator using a special apparatus. The experimental results on the sensor shows a good linear relationship between applied pressure and C-mode frequency. Temperature compensation is also achieved by utilizing the dual mode behavior of the LGS crystal resonator. The comparison between our experiment and Peer’s theoretical modelling results shows a reasonable consistency. The sensor structure is very compact, robust, low cost and temperature compensation can be achieved at high temperatures particularly in nuclear applications.
       
  • Experimental Investigation of the Aeroacoustics of Synthetic Jet Actuators
           in Quiescent Conditions
    • Abstract: Publication date: Available online 6 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Jonne Jeyalingam, Mark Jabbal In this paper, the aeroacoustic characteristics of a circular orifice, synthetic jet actuator in quiescent conditions is investigated. Electromagnetic actuation, in the form of a shaker-driven actuator with latex diaphragm, proved to be desirable over piezoelectric actuation for this work due to the reduced diaphragm noise contribution to overall actuator self-noise, hence making it easier to identify jet-related noise. Acoustic and velocity data, collected from microphone measurements in an anechoic chamber and hotwire measurements respectively, were compared for correlation. Schlieren visualization was also used to show synthetic jet development near the orifice. Flow-induced sound in the form of an audible whistling was found to occur for a Strouhal number range of 0.24
       
  • Low-temperature hermetic thermo-compression bonding using electroplated
           copper sealing frame planarized by fly-cutting for wafer-level MEMS
           packaging
    • Abstract: Publication date: Available online 5 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Muhammad Salman Al Farisi, Hideki Hirano, Shuji Tanaka Hermetic packaging plays an important role for optimizing the functionality and reliability of a wide variety of micro-electro-mechanical systems (MEMS). In this paper, we propose a low-temperature wafer-level hermetic packaging method based on the thermo-compression bonding process using an electroplated Cu sealing frame planarized by a single-point diamond mechanical fly-cutting. This technology has an inherent possibility of hermetic sealing and electrical contact as well as a capability of integration of micro-structured wafers. Hermetic sealing can be realized with the sealing frame as narrow as 30 μm at a temperature as low as 250 °C. At such a low bonding temperature, a less amount of gases is desorbed, resulting in a sealed cavity pressure lower than 100 Pa. The leak rate into the packages is estimated by a long-term sealed cavity pressure measurement for 7 months to be less than 1.67 × 10−15 Pa m3 s−1. In addition, the bonding shear strength is also evaluated to be higher than 100 MPa.
       
  • Effect of Elastic Element on Self-excited Electrostatic Actuator
    • Abstract: Publication date: Available online 4 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Hiroyuki Nabae, Koichi Ikeda Self-excited electrostatic actuators, which are also called Franklin bells or Gordon bells, are one of the simplest oscillators among various types of actuators. The actuators oscillate with DC voltage and simple structures mainly composed of only two electrodes and a conductive armature. These features seem suitable for micro mechatronic devices, including micro robots; however, these actuators only have small number of practical applications. The high voltage for actuation, damage by electrical discharge, and mechanical loss with collisions between the armature and electrodes keep the actuators away from practical usages. This research focuses on the mechanical loss with collisions between the armature and electrodes and proposes a method for decreasing this loss by energy recovery with elastic elements. This study first conducts a model-based analysis of the behavior of the proposed system that combines the electrostatic self-excitation and the elastic elements. The results are then compared with the experimental results of a prototype actuator. The simple analysis predicted the increase of the oscillating frequency with the elastic elements, limiting the condition of the self-excitation caused by the energy loss of the damping factor. The results of the experimental verification showed the same tendency as the analytical predictions: increase of the oscillating frequency and existence of a critical value for the oscillation limit. Although comparatively large errors were confirmed between the simulation and the experiment under a lower applied voltage, experimentally obtained frequencies have errors less than 6.4% compared with the analytical result under the applied voltage of over 1.3 kV.
       
  • Sensor and actuator simulation training system for en-route intravenous
           procedure
    • Abstract: Publication date: Available online 4 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Darren McMorran, Sewminda Kalana Samarasinghe, Murat Muradoglu, Dwayne Chung Kim Chung, Brett Williams, Oi Wah Liew, Tuck Wah Ng A system has been developed to simulate transport in a medical emergency vehicle with the intent of assisting paramedics improve their skills in en-route cannulation. En-route cannulation makes pre-hospital venous access possible, which in turns helps to minimize the risk of lengthening transfer times. The system is designed to attain full monitoring of transport conditions, not just in the spatial but also in the temporal sense, and to physically recreate these parameters on a fabricated six degree of freedom simulator system. Tests conducted revealed the viability of applying an inertial measurement unit board sensor to collect data from a vehicle during transport and to subsequently reproduce the exact motions encountered on the simulator. It was found that a smartphone could be used to collect transport data that are dominated by perturbations in the O(101) Hertz scale. With a training arm for venipuncture placed on the simulator, a preliminary study conducted with six participants showed more pronounced performance deterioration amongst those who were untrained in cannulation when the simulator was switched on. The demonstrated system has features that make it amenable for incorporation into a clinical skills laboratory setting.
       
  • Controllable magnetorheological fluid based actuators for
           6-degree-of-freedom haptic master applicable to robot-assisted surgery
    • Abstract: Publication date: Available online 3 July 2018Source: Sensors and Actuators A: PhysicalAuthor(s): Seok-Rae Kang, Seung-Woo Cha, Yong-Hoon Hwang, Yang-Sup Lee, Seung-Bok Choi This work presents controllable magnetorheological (MR) fluid based actuators for the design of a new 6-degree-of-freedom haptic master which can be applicable to robot-assisted surgery. In this work, two different actuators are used. One actuator is controllable MR clutch for the translational motion in three directions of the haptic master body, while the other actuator is controllable MR brake for the rotational motion to reflect the end-effector of the surgical slave robot. The overall mechanism of the proposed haptic master is designed to have a symmetric structure so that the translation and rotation motion becomes independently. This leads to a simple structure with decoupled dynamics between the translation and rotational motions resulting in a fast computation time. In addition, a gravity compensator is designed and integrated with the haptic master to reduce the effect of the inertia. A proportional-integral-derivative controller is then designed and experimentally implemented for the tracking control of the repulsive torque/force of the haptic master. The tracking control result of each axis motion is shown in time domain.
       
 
 
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