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papers from the latest issue:
Interaction between gas flow and a Lamb waves based microsensor
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Lianqun Zhou, Jean-François Manceau, François Bastien
The interaction between the gas flow and Lamb waves is investigated in this paper. Depending on the fact that the phase velocity is higher or lower than the gas sound velocity, we will get evanescent waves (EW) or leaky Lamb waves (LLW) in the gas along the solid–gas interface. In the LLW case, experiments showed that gas flow had not evident effects on Lamb waves’ propagations. In the EW case, the interaction between the gas flow and the Lamb waves was observed clearly when the Lamb wave phase velocity is close to the gas sound velocity. This interaction is related with the gas flow velocity profile within the boundary layer. The experimental results show that this sensor is very promising for many experiments involving gas flows such in wind tunnels, micro channels characterization, and can lead to multi-parameters measurements.
Source:Sensors and Actuators A: Physical, Volume 181
Lianqun Zhou, Jean-François Manceau, François Bastien
The interaction between the gas flow and Lamb waves is investigated in this paper. Depending on the fact that the phase velocity is higher or lower than the gas sound velocity, we will get evanescent waves (EW) or leaky Lamb waves (LLW) in the gas along the solid–gas interface. In the LLW case, experiments showed that gas flow had not evident effects on Lamb waves’ propagations. In the EW case, the interaction between the gas flow and the Lamb waves was observed clearly when the Lamb wave phase velocity is close to the gas sound velocity. This interaction is related with the gas flow velocity profile within the boundary layer. The experimental results show that this sensor is very promising for many experiments involving gas flows such in wind tunnels, micro channels characterization, and can lead to multi-parameters measurements.
Study of the photoconductive ZnO UV detector based on the electrically floated nanowire array
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Yongning He, Wen Zhang, Songchang Zhang, Xue Kang, Wenbo Peng, Youlong Xu
ZnO nanowires have been shown to have high sensitivity for detecting UV light. In this paper, we report a low-cost fabricated metal–semiconductor–metal (MSM) structure, consisting of ZnO nanowire array as outer-layer photo absorber supported by a ZnO nanocrystalline film. The ZnO film is bridged between two electrically interdigitated metal electrodes for collecting photo-generated charges. Different from previous approaches, in which nanowires were directly connected with two metal electrodes [1,2], our MSM structure allows direct exposure of dense ZnO nanowires to UV light. In such a way, the outer ZnO nanowires serve as antireflective traps, and the ZnO film are used for both charge transport and seeding ZnO nanowire array self-assembly growth. The photoresponse characteristics for the detector were measured in detail and then the carriers transport model was given to explain the theoretical mechanism for the enhanced photocurrent. The oxygen exchange processes were suggested to be responsible for the slow transient properties. Finally, nanowire surfaces were modified using surface passivation with polymer and Ar ion bombardment to verify the surface depletion effect. It has been shown that transient response for the detector with the polymer passivation become much faster than that original one without the passivation.
Source:Sensors and Actuators A: Physical, Volume 181
Yongning He, Wen Zhang, Songchang Zhang, Xue Kang, Wenbo Peng, Youlong Xu
ZnO nanowires have been shown to have high sensitivity for detecting UV light. In this paper, we report a low-cost fabricated metal–semiconductor–metal (MSM) structure, consisting of ZnO nanowire array as outer-layer photo absorber supported by a ZnO nanocrystalline film. The ZnO film is bridged between two electrically interdigitated metal electrodes for collecting photo-generated charges. Different from previous approaches, in which nanowires were directly connected with two metal electrodes [1,2], our MSM structure allows direct exposure of dense ZnO nanowires to UV light. In such a way, the outer ZnO nanowires serve as antireflective traps, and the ZnO film are used for both charge transport and seeding ZnO nanowire array self-assembly growth. The photoresponse characteristics for the detector were measured in detail and then the carriers transport model was given to explain the theoretical mechanism for the enhanced photocurrent. The oxygen exchange processes were suggested to be responsible for the slow transient properties. Finally, nanowire surfaces were modified using surface passivation with polymer and Ar ion bombardment to verify the surface depletion effect. It has been shown that transient response for the detector with the polymer passivation become much faster than that original one without the passivation.
Highlights
► When using the electrically floated ZnO nanowire array as light absorb layer, the UV detector based on MSM structure obtains excellent photoconductivity and repeatability as well as the yield production can be easily carried out. ► The oxygen exchange mechanism including the oxygen absorption and desorption due to the surface defects and the oxygen exchange process with the ZnO point defects was suggested to responsible for the slow transient properties of the detector. ► Using the transparent polymer as the top passivation layer, the transient performance of the detector is improved greatly with little expense of photocurrent decrease.A method for high accuracy determination of equilibrium relative humidity
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
O.M. Jensen
This paper treats a new method for measuring equilibrium relative humidity and equilibrium dew-point temperature of a material sample. The developed measuring device is described – a Dew-point Meter – which by means of so-called Dynamic Dew-point Analysis permits quick and very accurate determination of the equilibrium relative humidity. Potentially, the method can also be used for measuring air relative humidity.
Source:Sensors and Actuators A: Physical, Volume 181
O.M. Jensen
This paper treats a new method for measuring equilibrium relative humidity and equilibrium dew-point temperature of a material sample. The developed measuring device is described – a Dew-point Meter – which by means of so-called Dynamic Dew-point Analysis permits quick and very accurate determination of the equilibrium relative humidity. Potentially, the method can also be used for measuring air relative humidity.
Response behavior of a palladium nanoparticle array based hydrogen sensor in hydrogen–nitrogen mixture
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Bo Xie, SiShi Zhang, Fei Liu, Xing Peng, Fengqi Song, Guanghou Wang, Min Han
Closely spaced palladium nanoparticle arrays were fabricated in between a pair of interdigital electrodes by means of gas phase cluster beam deposition with controlled coverage. The quantum conductance change induced by hydrogen absorption was used for hydrogen sensing. The hydrogen response behavior of a sensor chip was investigated in N2 +H2 mixture gas. The sensor could be calibrated with three linear response hydrogen concentration regimes. A sub-second fast response was shown at 2.2% H2 concentration. The influence of the temperature variation to the quantitative hydrogen concentration measurement with this sensor was discussed.
Source:Sensors and Actuators A: Physical, Volume 181
Bo Xie, SiShi Zhang, Fei Liu, Xing Peng, Fengqi Song, Guanghou Wang, Min Han
Closely spaced palladium nanoparticle arrays were fabricated in between a pair of interdigital electrodes by means of gas phase cluster beam deposition with controlled coverage. The quantum conductance change induced by hydrogen absorption was used for hydrogen sensing. The hydrogen response behavior of a sensor chip was investigated in N2 +H2 mixture gas. The sensor could be calibrated with three linear response hydrogen concentration regimes. A sub-second fast response was shown at 2.2% H2 concentration. The influence of the temperature variation to the quantitative hydrogen concentration measurement with this sensor was discussed.
Closed-loop compensation of the cross-coupling error in a quartz Coriolis Vibrating Gyro
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Mélanie Descharles, Jean Guérard, Hamid Kokabi, Olivier Le Traon
In this paper, the issue related to the quadrature error in a piezoelectric angular rate gyro is studied. Fabrication process and anisoelasticity of the material are known to reduce the performance of the bias stability of micromachined gyros. However, solutions exist to compensate for the quadrature error in silicon-based gyros: DC voltage, parallel capacitance. The principle of operation presented in this paper is based on charge injection in opposite phase to balance the charges induced by the quadrature error in quartz Coriolis Vibrating Gyros. The concept is experimentally tested first with an open-loop circuit. The result of this experiment showed a bias stability of 96°/h RMS over the temperature range. An additional closed-loop feedback circuit is designed and experimented. The active compensation of the quadrature error then improves the bias stability by 5 times, leading to a performance of 20°/h RMS over temperature.
Source:Sensors and Actuators A: Physical, Volume 181
Mélanie Descharles, Jean Guérard, Hamid Kokabi, Olivier Le Traon
In this paper, the issue related to the quadrature error in a piezoelectric angular rate gyro is studied. Fabrication process and anisoelasticity of the material are known to reduce the performance of the bias stability of micromachined gyros. However, solutions exist to compensate for the quadrature error in silicon-based gyros: DC voltage, parallel capacitance. The principle of operation presented in this paper is based on charge injection in opposite phase to balance the charges induced by the quadrature error in quartz Coriolis Vibrating Gyros. The concept is experimentally tested first with an open-loop circuit. The result of this experiment showed a bias stability of 96°/h RMS over the temperature range. An additional closed-loop feedback circuit is designed and experimented. The active compensation of the quadrature error then improves the bias stability by 5 times, leading to a performance of 20°/h RMS over temperature.
Highlights
► Quadrature error compensation in quartz Coriolis Vibrating Gyros. ► Passive charge re-injection leads to a bias stability of 96°/h RMS over the temperature range (−25 to +75°C). ► Active compensation by controlling the charge re-injection from a double phase/quadrature demodulation. ► Active charge re-injection leads to a bias stability of 20°/h RMS over the temperature range (−25 to +75°C).Long-term retention of hydrophilic behavior of plasma treated polydimethylsiloxane (PDMS) surfaces stored under water and Luria-Bertani broth
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Li Hong Zhao, Jennifer Lee, Pabitra N. Sen
Polydimethylsiloxane (PDMS) is inherently hydrophobic. Oxygen plasma treatment is a non-toxic, low cost method to render PDMS hydrophilic. Storing PDMS samples, immediately after plasma treatment, under water and Luria-Bertani broth (LB broth), a common growth medium for bacteria, retards hydrophobic recovery considerably. PDMS samples stored in LB broth retain hydrophilic behavior the longest period (contact angle about 10–20° after a week) and the samples stored in water also remained hydrophilic for 7 days (around 20–30°), whereas, the samples stored in air recovered hydrophobicity quickly (above 100° after a week). Scanning electron microscopy (SEM) reveals no clear correlation between wettability and cracks, but changes in surface properties that are not visible through SEM are seen in the drying pattern left on PDMS by the fluid. We show that bacteria (E. coli strain MG1655 and any air borne) and the biofilm produced by them have minimal effect on wettability, however sealing the petri dishes during storage further reduce the contact angle.
Source:Sensors and Actuators A: Physical, Volume 181
Li Hong Zhao, Jennifer Lee, Pabitra N. Sen
Polydimethylsiloxane (PDMS) is inherently hydrophobic. Oxygen plasma treatment is a non-toxic, low cost method to render PDMS hydrophilic. Storing PDMS samples, immediately after plasma treatment, under water and Luria-Bertani broth (LB broth), a common growth medium for bacteria, retards hydrophobic recovery considerably. PDMS samples stored in LB broth retain hydrophilic behavior the longest period (contact angle about 10–20° after a week) and the samples stored in water also remained hydrophilic for 7 days (around 20–30°), whereas, the samples stored in air recovered hydrophobicity quickly (above 100° after a week). Scanning electron microscopy (SEM) reveals no clear correlation between wettability and cracks, but changes in surface properties that are not visible through SEM are seen in the drying pattern left on PDMS by the fluid. We show that bacteria (E. coli strain MG1655 and any air borne) and the biofilm produced by them have minimal effect on wettability, however sealing the petri dishes during storage further reduce the contact angle.
Role of interface states and depletion layer in NO2 sensing mechanism of n-InP epitaxial layers
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
K. Wierzbowska, B. Adamowicz, B. Lauron, L. Bideux
The electronic properties of n-type InP epitaxial layers covered by their native oxides have been investigated in order to explain the NO2 gas sensing mechanism. The impact of interface states on the interface Fermi level, E F, carrier concentration in-depth profiles, n(x), and resistance, R, of n-InP layers has been studied by means of numerical analysis. The U-shaped interface state continuum, with the density minimum, N SS0, from 1010 to 1013 eV−1 cm−2, has been assumed at the InP interface according to the disordered-induced gap state model. Moreover, the surface fixed charge, Q FC, representing adsorbed ions at the semiconductor surface has been introduced. Also the influence of temperature on the electron distribution n(x) has been analysed. The n-InP layer resistance and Hall-effect measurements (using the Van der Pauw method) have been performed for the InP sensors before and upon NO2 action in order to assess the influence of gas adsorption on the electron concentration and mobility as well as on the depletion layer width, W. On this basis the influence of interface states and near-surface region on the InP layer response to NO2 adsorption has been determined. In addition, the conclusions for optimising the InP-based resistive sensor structure (in terms of the layer thickness and doping) have been obtained.
Source:Sensors and Actuators A: Physical, Volume 181
K. Wierzbowska, B. Adamowicz, B. Lauron, L. Bideux
The electronic properties of n-type InP epitaxial layers covered by their native oxides have been investigated in order to explain the NO2 gas sensing mechanism. The impact of interface states on the interface Fermi level, E F, carrier concentration in-depth profiles, n(x), and resistance, R, of n-InP layers has been studied by means of numerical analysis. The U-shaped interface state continuum, with the density minimum, N SS0, from 1010 to 1013 eV−1 cm−2, has been assumed at the InP interface according to the disordered-induced gap state model. Moreover, the surface fixed charge, Q FC, representing adsorbed ions at the semiconductor surface has been introduced. Also the influence of temperature on the electron distribution n(x) has been analysed. The n-InP layer resistance and Hall-effect measurements (using the Van der Pauw method) have been performed for the InP sensors before and upon NO2 action in order to assess the influence of gas adsorption on the electron concentration and mobility as well as on the depletion layer width, W. On this basis the influence of interface states and near-surface region on the InP layer response to NO2 adsorption has been determined. In addition, the conclusions for optimising the InP-based resistive sensor structure (in terms of the layer thickness and doping) have been obtained.
Non-symmetrical Bouc–Wen model for piezoelectric ceramic actuators
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Wei Zhu, Dai-hua Wang
The existing Bouc–Wen models for piezoelectric ceramic actuators (PCAs) possess the symmetrical characteristic of the hysteretic component and can be categorized as symmetrical Bouc–Wen models. When modeling PCAs with non-symmetrical hysteresis by a symmetrical Bouc–Wen model, large modeling errors will occur. In this paper, a non-symmetrical Bouc–Wen hysteresis operator for modeling the non-symmetrical hysteresis of PCAs is established by introducing a non-symmetrical formula into the Bouc–Wen hysteresis operator. Accordingly, a non-symmetrical Bouc–Wen model for PCAs is proposed and established by modeling the non-symmetrical hysteresis component of PCAs with the non-symmetrical Bouc–Wen hysteresis operator. A corresponding parameter identification method, which can identify the parameters by obtaining analytical solutions with a set of input–output experimental data to and from a PCA with an applied periodic voltage under the zero initial condition, is established. In the parameter identification, the least-squares method is used to reduce external random disturbances. The performance of the non-symmetrical Bouc–Wen model with the corresponding parameter identification method is experimentally verified by the established experimental setup. The research results show that the non-symmetrical Bouc–Wen model can simulate the PCA with the non-symmetrical hysteresis more accurately than the symmetrical Bouc–Wen models, and the modeling errors are decreased by about 30%. In addition, the established parameter identification method can be used to identify the parameters of the non-symmetrical and symmetrical Bouc–Wen models effectively and quickly.
Source:Sensors and Actuators A: Physical, Volume 181
Wei Zhu, Dai-hua Wang
The existing Bouc–Wen models for piezoelectric ceramic actuators (PCAs) possess the symmetrical characteristic of the hysteretic component and can be categorized as symmetrical Bouc–Wen models. When modeling PCAs with non-symmetrical hysteresis by a symmetrical Bouc–Wen model, large modeling errors will occur. In this paper, a non-symmetrical Bouc–Wen hysteresis operator for modeling the non-symmetrical hysteresis of PCAs is established by introducing a non-symmetrical formula into the Bouc–Wen hysteresis operator. Accordingly, a non-symmetrical Bouc–Wen model for PCAs is proposed and established by modeling the non-symmetrical hysteresis component of PCAs with the non-symmetrical Bouc–Wen hysteresis operator. A corresponding parameter identification method, which can identify the parameters by obtaining analytical solutions with a set of input–output experimental data to and from a PCA with an applied periodic voltage under the zero initial condition, is established. In the parameter identification, the least-squares method is used to reduce external random disturbances. The performance of the non-symmetrical Bouc–Wen model with the corresponding parameter identification method is experimentally verified by the established experimental setup. The research results show that the non-symmetrical Bouc–Wen model can simulate the PCA with the non-symmetrical hysteresis more accurately than the symmetrical Bouc–Wen models, and the modeling errors are decreased by about 30%. In addition, the established parameter identification method can be used to identify the parameters of the non-symmetrical and symmetrical Bouc–Wen models effectively and quickly.
Vertical comb-drive MEMS mirror with sensing function for phase-shift device
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Kentaro Oda, Hidekuni Takao, Kyohei Terao, Takaaki Suzuki, Fusao Shimokawa, Ichirou Ishimaru, Fumikazu Oohira
We aim to develop a MEMS mirror fabricated by micro-fabrication technology to realize a phase-shift device, which is a key component of a two-dimensional Fourier spectrometer. This MEMS mirror is capable of high-precision movement in the vertical direction parallel to the reference plane. In this study, a vertical electrostatic comb-drive actuator and capacitance sensor were fabricated monolithically on a single chip, and then four of them were mounted around the movable mirror. We fabricated a MEMS mirror that was able to move in the vertical direction while sensing the tilting angle. As a result, it would be feasible to use this vertical comb-drive MEMS mirror with a sensing function for a phase-shift device that was able to control the vertical displacement and the tilting angle of a movable mirror.
Source:Sensors and Actuators A: Physical, Volume 181
Kentaro Oda, Hidekuni Takao, Kyohei Terao, Takaaki Suzuki, Fusao Shimokawa, Ichirou Ishimaru, Fumikazu Oohira
We aim to develop a MEMS mirror fabricated by micro-fabrication technology to realize a phase-shift device, which is a key component of a two-dimensional Fourier spectrometer. This MEMS mirror is capable of high-precision movement in the vertical direction parallel to the reference plane. In this study, a vertical electrostatic comb-drive actuator and capacitance sensor were fabricated monolithically on a single chip, and then four of them were mounted around the movable mirror. We fabricated a MEMS mirror that was able to move in the vertical direction while sensing the tilting angle. As a result, it would be feasible to use this vertical comb-drive MEMS mirror with a sensing function for a phase-shift device that was able to control the vertical displacement and the tilting angle of a movable mirror.
Equivalent circuit modeling of ionomer and ionic polymer conductive network composite actuators containing ionic liquids
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Yang Liu, Ran Zhao, Mehdi Ghaffari, Junhong Lin, Sheng Liu, Hülya Cebeci, Roberto Guzmán de Villoria, Reza Montazami, Dong Wang, Brian L. Wardle, James R. Heflin, Q.M. Zhang
In this study, we demonstrate electrical equivalent circuits that model the complex frequency-dependent impedance of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) containing electro-active polymer membranes and ionic polymer conductor network composite (IPCNC) devices. The devices include Nafion membrane actuators, Nafion coated with layer-by-layer (LbL) Au nanoparticle/poly(allylamine hydrochloride) (PAH) composite actuators, and Nafion with vertically aligned carbon nanotube (VA-CNT)/Nafion composite actuators. It is found that the low frequency responses of these devices indicate Warburg diffusion. Therefore, Warburg impedance is utilized to model the low frequency diffusion behavior of the devices, while the electric double layer capacitance (C dl ) represents the storage of drifting ions under electric field at high frequencies. It is found that C dl for Nafion with 40wt% EMI-Tf is 7.5μF/cm2 and increases to 11.4μF/cm2 with increasing surface area of the LbL composite electrode. C dl increases further to above 3×103 μF/cm2 for an actuator with 12μm VA-CNT/Nafion composite electrodes, while the Warburg coefficient A W remains nearly the same for all the devices. As a result, the actuation magnitude and speed increase with charges accumulated due to higher C dl , without much increase in the contribution from the slow ion diffusion process.
Source:Sensors and Actuators A: Physical, Volume 181
Yang Liu, Ran Zhao, Mehdi Ghaffari, Junhong Lin, Sheng Liu, Hülya Cebeci, Roberto Guzmán de Villoria, Reza Montazami, Dong Wang, Brian L. Wardle, James R. Heflin, Q.M. Zhang
In this study, we demonstrate electrical equivalent circuits that model the complex frequency-dependent impedance of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) containing electro-active polymer membranes and ionic polymer conductor network composite (IPCNC) devices. The devices include Nafion membrane actuators, Nafion coated with layer-by-layer (LbL) Au nanoparticle/poly(allylamine hydrochloride) (PAH) composite actuators, and Nafion with vertically aligned carbon nanotube (VA-CNT)/Nafion composite actuators. It is found that the low frequency responses of these devices indicate Warburg diffusion. Therefore, Warburg impedance is utilized to model the low frequency diffusion behavior of the devices, while the electric double layer capacitance (C dl ) represents the storage of drifting ions under electric field at high frequencies. It is found that C dl for Nafion with 40wt% EMI-Tf is 7.5μF/cm2 and increases to 11.4μF/cm2 with increasing surface area of the LbL composite electrode. C dl increases further to above 3×103 μF/cm2 for an actuator with 12μm VA-CNT/Nafion composite electrodes, while the Warburg coefficient A W remains nearly the same for all the devices. As a result, the actuation magnitude and speed increase with charges accumulated due to higher C dl , without much increase in the contribution from the slow ion diffusion process.
RF-MEMS switch with through-silicon via by the molten solder ejection method
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Shinpei Ogawa, Shinnosuke Soda, Sang-Seok Lee, Shinichi Izuo, Yukihisa Yoshida
A radio frequency-microelectromechanical system (RF-MEMS) switch with through-silicon via (TSV) technology for hermetic packaging was designed and developed using the molten solder ejection method (MSEM). High frequency simulation was used to determine the lowest loss of the shift-aligned ground-signal-ground (GSG) TSV structure. The RF-MEMS with shift-aligned TSV was successfully developed by integrating surface micromachining with MSEM. The electrical properties of RF-MEMS switches with the shift-aligned TSV were measured, and a low insertion loss of 0.1dB at 15GHz was achieved for a GSG TSV configuration.
Source:Sensors and Actuators A: Physical, Volume 181
Shinpei Ogawa, Shinnosuke Soda, Sang-Seok Lee, Shinichi Izuo, Yukihisa Yoshida
A radio frequency-microelectromechanical system (RF-MEMS) switch with through-silicon via (TSV) technology for hermetic packaging was designed and developed using the molten solder ejection method (MSEM). High frequency simulation was used to determine the lowest loss of the shift-aligned ground-signal-ground (GSG) TSV structure. The RF-MEMS with shift-aligned TSV was successfully developed by integrating surface micromachining with MSEM. The electrical properties of RF-MEMS switches with the shift-aligned TSV were measured, and a low insertion loss of 0.1dB at 15GHz was achieved for a GSG TSV configuration.
A normally closed electrostatic parylene microvalve for micro total analysis systems
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Ender Yıldırım, M.A. Sahir Arıkan, Haluk Külah
This paper presents an electrostatically actuated, normally closed microvalve for parylene microfluidics. The proposed valve structure isolates the fluid from the electric field, and hence results in relatively low actuation potentials (<60V) irrespective of the working fluid. Hereby, the microvalve solves electrolysis or electrode shielding problems observed in electrostatic actuation in micro total analysis systems. To investigate leakage properties, microvalves were tested under pressurized flow with de-ionized (DI) water. No detectable leakage ratio was observed up to 20kPa inlet pressure, due to the unique semi-circular valve seat design. It was shown that the valve seat could be reconfigured to enable sealing at various pressure levels for different applications.
Source:Sensors and Actuators A: Physical, Volume 181
Ender Yıldırım, M.A. Sahir Arıkan, Haluk Külah
This paper presents an electrostatically actuated, normally closed microvalve for parylene microfluidics. The proposed valve structure isolates the fluid from the electric field, and hence results in relatively low actuation potentials (<60V) irrespective of the working fluid. Hereby, the microvalve solves electrolysis or electrode shielding problems observed in electrostatic actuation in micro total analysis systems. To investigate leakage properties, microvalves were tested under pressurized flow with de-ionized (DI) water. No detectable leakage ratio was observed up to 20kPa inlet pressure, due to the unique semi-circular valve seat design. It was shown that the valve seat could be reconfigured to enable sealing at various pressure levels for different applications.
Development of a grating based multi-degree-of-freedom laser linear encoder using diffracted light
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Chien-Hung Liu, Chung-Hsiang Cheng
A multi-degree-of-freedom laser linear encoder that can simultaneously measure the position, straightness, pitch, roll, and yaw errors of a linear stage is developed. The proposed laser encoder uses the phase and spatial information of diffracted light. When the light is reflected from a grating and diffracts, the relative movement makes the orders of diffracted light have both phase and spatial geometric variations. The proposed encoder design makes the ±1 order diffracted light interfere and outputs pure sine and cosine wave signals for linear displacement. The ±2 order diffracted light spots are received by two quadrant photodiode detectors and analyzed to inversely calculate the other motion errors. The experimental results show that the measurement error is ±0.6μm for straightness, ±0.8 arcsec for angular error, and ±1.2μm for linear displacement.
Source:Sensors and Actuators A: Physical, Volume 181
Chien-Hung Liu, Chung-Hsiang Cheng
A multi-degree-of-freedom laser linear encoder that can simultaneously measure the position, straightness, pitch, roll, and yaw errors of a linear stage is developed. The proposed laser encoder uses the phase and spatial information of diffracted light. When the light is reflected from a grating and diffracts, the relative movement makes the orders of diffracted light have both phase and spatial geometric variations. The proposed encoder design makes the ±1 order diffracted light interfere and outputs pure sine and cosine wave signals for linear displacement. The ±2 order diffracted light spots are received by two quadrant photodiode detectors and analyzed to inversely calculate the other motion errors. The experimental results show that the measurement error is ±0.6μm for straightness, ±0.8 arcsec for angular error, and ±1.2μm for linear displacement.
SMA-based bionic integration design of self-sensor–actuator-structure for artificial skeletal muscle
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 181
Jianjun Zhang, Yuehong Yin
This paper presents a novel shape memory alloy (SMA)-based artificial skeletal muscle (AM) with functions of actuating, energy-storing and self-sensing. The design is based on the comparison of skeletal muscle and SMA wire mechanical properties that are described by force–velocity and force–length relationships. Experimental results have shown that SMA wires can initially imitate force–velocity properties of skeletal muscles, but cannot imitate their force–length properties, which is improved by adding an anti-overstretching flexible body. Besides, a simple but effective artificial tendon is utilized to achieve energy storage like human tendon. In order to realize the self-sensing function of the AM, self-sensing properties of SMA wires are explored and modeled based on the experimental study of resistivity variations. The AM self-sensing capability is further demonstrated by its application to a 1 degree of freedom (DOF) robotic ankle-foot.
Source:Sensors and Actuators A: Physical, Volume 181
Jianjun Zhang, Yuehong Yin
This paper presents a novel shape memory alloy (SMA)-based artificial skeletal muscle (AM) with functions of actuating, energy-storing and self-sensing. The design is based on the comparison of skeletal muscle and SMA wire mechanical properties that are described by force–velocity and force–length relationships. Experimental results have shown that SMA wires can initially imitate force–velocity properties of skeletal muscles, but cannot imitate their force–length properties, which is improved by adding an anti-overstretching flexible body. Besides, a simple but effective artificial tendon is utilized to achieve energy storage like human tendon. In order to realize the self-sensing function of the AM, self-sensing properties of SMA wires are explored and modeled based on the experimental study of resistivity variations. The AM self-sensing capability is further demonstrated by its application to a 1 degree of freedom (DOF) robotic ankle-foot.
Increase Buoyancy of a Solid Fragment Using Micropillars
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical
Lei Qiao, Mingming Xiang, Cheng Luo
When a solid fragment has a higher density than water, it may still float on water surface due to the support of surface tension. However, once the solid fragment is completely immersed inside water, it sinks down to water bottom due to elimination of the surface tension. In this work, we demonstrated that, after the incorporation of micropillars on such a solid fragment, it may still get back to water surface. Air is trapped between micropillars. This increases the space that the solid fragment occupies under water. Accordingly, the buoyancy is increased. The critical values of trapped air, micropillar-covered area, micropillar height and water depth for a micropillar-covered fragment to rise up to water surface were formulated. Four micropillar-incorporated SU-8 fragments were fabricated and tested to validate the derived relationships. Experimentally determined critical values of micropillar-covered areas and trapped air volumes had good match with theoretically predicted ones. In addition, through force analysis, we showed that surface tension at the triple lines between water, micropillars and trapped air retains the volume of the trapped air but does not provide any lifting force to make the fragment rise up to water surface. Since the incorporation of the micropillars may make a completely immersed fragment get back to water surface from under water, the presented results have potential applications in developing miniaturized devices, such as submarines and water robots, that may need to rise up to water surface.
Source:Sensors and Actuators A: Physical
Lei Qiao, Mingming Xiang, Cheng Luo
When a solid fragment has a higher density than water, it may still float on water surface due to the support of surface tension. However, once the solid fragment is completely immersed inside water, it sinks down to water bottom due to elimination of the surface tension. In this work, we demonstrated that, after the incorporation of micropillars on such a solid fragment, it may still get back to water surface. Air is trapped between micropillars. This increases the space that the solid fragment occupies under water. Accordingly, the buoyancy is increased. The critical values of trapped air, micropillar-covered area, micropillar height and water depth for a micropillar-covered fragment to rise up to water surface were formulated. Four micropillar-incorporated SU-8 fragments were fabricated and tested to validate the derived relationships. Experimentally determined critical values of micropillar-covered areas and trapped air volumes had good match with theoretically predicted ones. In addition, through force analysis, we showed that surface tension at the triple lines between water, micropillars and trapped air retains the volume of the trapped air but does not provide any lifting force to make the fragment rise up to water surface. Since the incorporation of the micropillars may make a completely immersed fragment get back to water surface from under water, the presented results have potential applications in developing miniaturized devices, such as submarines and water robots, that may need to rise up to water surface.
Static crack growth and fatigue modeling for silicon MEMS
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical
W. Merlijn van Spengen
Fatigue in silicon microstructures has been widely observed but is currently not well understood. In this paper, it is shown that typical silicon MEMS fatigue can be described by a ‘classic’ stress corrosion cracking (SCC) model for glass fracture. The model can be used to describe the slow crack propagation and ultimate failure of MEMS structures due to mechanical stress under different conditions. With this SCC model it is possible to do full lifetime predictions, and these correspond very well with measured fatigue data from literature, as a function of applied stress and temperature. This suggests that at least part of the literature data available can be explained by static fatigue, which is better described by a time to failure than cycles to failure. However, not all failures can be explained by SCC alone, a notable exception being those of MEMS devices with very thin surface oxides.
Source:Sensors and Actuators A: Physical
W. Merlijn van Spengen
Fatigue in silicon microstructures has been widely observed but is currently not well understood. In this paper, it is shown that typical silicon MEMS fatigue can be described by a ‘classic’ stress corrosion cracking (SCC) model for glass fracture. The model can be used to describe the slow crack propagation and ultimate failure of MEMS structures due to mechanical stress under different conditions. With this SCC model it is possible to do full lifetime predictions, and these correspond very well with measured fatigue data from literature, as a function of applied stress and temperature. This suggests that at least part of the literature data available can be explained by static fatigue, which is better described by a time to failure than cycles to failure. However, not all failures can be explained by SCC alone, a notable exception being those of MEMS devices with very thin surface oxides.
Multi-Point Force Sensor Based on Crossed Optical Fibers
14 June 2012,
18:26:56
Publication year:
2012
Source:Sensors and Actuators A: Physical
S. Pirozzi
The objective of this paper is to present a sensor concept based on optical fibers suitable crossed in order to obtain a multi-point force sensor. The working principle exploits the optical power losses due to the fiber bending. The bending losses highly depend on the curvature of the fiber. Firstly, an analytical model that relate bending losses to fiber curvature is introduced and experimentally validated. After the demonstration of the proposed concept potentiality, a design procedure based on the simultaneous use of the analytical model and a Finite Element (FE) model is described. The procedure is experimentally validated for a single crossing of fibers and it is used to realize a complete sensor prototype. Finally, the sensor prototype is experimentally calibrated as a multi-point force sensor.
Source:Sensors and Actuators A: Physical
S. Pirozzi
The objective of this paper is to present a sensor concept based on optical fibers suitable crossed in order to obtain a multi-point force sensor. The working principle exploits the optical power losses due to the fiber bending. The bending losses highly depend on the curvature of the fiber. Firstly, an analytical model that relate bending losses to fiber curvature is introduced and experimentally validated. After the demonstration of the proposed concept potentiality, a design procedure based on the simultaneous use of the analytical model and a Finite Element (FE) model is described. The procedure is experimentally validated for a single crossing of fibers and it is used to realize a complete sensor prototype. Finally, the sensor prototype is experimentally calibrated as a multi-point force sensor.
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