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papers from the latest issue:
Carbon nanotube thermal probe for quantitative temperature sensing
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Jun Hirotani , Juo Amano , Tatsuya Ikuta , Takashi Nishiyama , Koji Takahashi
Quantitative temperature sensing at the nanoscale point contact is developed using a platinum hot film sensor with a carbon nanotube (CNT) as a thermal probe. High spatial resolution and robustness is achieved because of the small tip radius and high stiffness of the CNT. The quantitative local temperature at the CNT probe contact point is determined by bringing the probe in and out of contact and controlling the amount of heat of the Pt hot film in high vacuum environment. Using this method, we overcome the problems of thermal contact resistance (TCR) between the CNT and sample surface. Sensor sensitivity for TCR and thermal conductivity measurement of a CNT is analyzed and the sensor configuration is optimized.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Jun Hirotani , Juo Amano , Tatsuya Ikuta , Takashi Nishiyama , Koji Takahashi
Quantitative temperature sensing at the nanoscale point contact is developed using a platinum hot film sensor with a carbon nanotube (CNT) as a thermal probe. High spatial resolution and robustness is achieved because of the small tip radius and high stiffness of the CNT. The quantitative local temperature at the CNT probe contact point is determined by bringing the probe in and out of contact and controlling the amount of heat of the Pt hot film in high vacuum environment. Using this method, we overcome the problems of thermal contact resistance (TCR) between the CNT and sample surface. Sensor sensitivity for TCR and thermal conductivity measurement of a CNT is analyzed and the sensor configuration is optimized.
Response time scales of anodized-aluminum pressure-sensitive paints
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hirotaka Sakaue , Katsuaki Morita , Yoshimi Iijima , Yoshitaka Sakamura
The response time scales of anodized-aluminum pressure-sensitive paints (AA-PSPs) are characterized by measuring their luminescent lifetimes and response times to a step-like pressure change. The luminescent lifetime is measured by a picosecond fluorescence measurement system at atmospheric conditions. The results show that the twelve AA-PSPs tested fall into two groups according to their luminescent lifetimes; one group includes AA-PSPs with organic luminophores and the other one includes AA-PSPs with metal complex luminophores. The former possesses the lifetime on the order of one nanosecond and the latter possesses that on the order of hundred nanoseconds. The AA-PSPs are also characterized by the response time to a step change in pressure generated in a shock tube. It is observed that the 90% rise times to a step change in pressure are on the order of 10μs and range from 30μs to 50μs, which lie within the tolerance caused by the thickness uncertainty in fabricating the anodized-aluminum layer. It is also found that the luminescent lifetimes are 2–4 orders of magnitude shorter than the step response times.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hirotaka Sakaue , Katsuaki Morita , Yoshimi Iijima , Yoshitaka Sakamura
The response time scales of anodized-aluminum pressure-sensitive paints (AA-PSPs) are characterized by measuring their luminescent lifetimes and response times to a step-like pressure change. The luminescent lifetime is measured by a picosecond fluorescence measurement system at atmospheric conditions. The results show that the twelve AA-PSPs tested fall into two groups according to their luminescent lifetimes; one group includes AA-PSPs with organic luminophores and the other one includes AA-PSPs with metal complex luminophores. The former possesses the lifetime on the order of one nanosecond and the latter possesses that on the order of hundred nanoseconds. The AA-PSPs are also characterized by the response time to a step change in pressure generated in a shock tube. It is observed that the 90% rise times to a step change in pressure are on the order of 10μs and range from 30μs to 50μs, which lie within the tolerance caused by the thickness uncertainty in fabricating the anodized-aluminum layer. It is also found that the luminescent lifetimes are 2–4 orders of magnitude shorter than the step response times.
A layered sensor for simultaneous, spatially coincident softness and moisture measurements
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Akira Kimoto , Daisuke Aoki
This paper proposes a layered sensor for the simultaneous measurement of the softness and surface moisture of an object, at the same position. In the proposed sensor, a thin stainless steel film is pasted on a polyvinylidene difluoride (PVDF) film. The voltages in the stainless steel and PVDF films are generated because of electrostatic and piezoelectric effects, and the resulting waveforms can be measured while the proposed sensor repeatedly contacts and releases the object. The voltages in the films depend on the softness and surface moisture conditions of the object. The proposed sensor therefore makes it possible to measure the softness and surface moisture of the object using the voltage waveforms. Here, we present the relationship between the measured voltages obtained using the proposed sensor and the volume of distilled water infiltrated into the filter paper on the surface of the object, and the relationship between the voltages and the softness of the object. In addition, the potential of the proposed sensor for applications is discussed.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Akira Kimoto , Daisuke Aoki
This paper proposes a layered sensor for the simultaneous measurement of the softness and surface moisture of an object, at the same position. In the proposed sensor, a thin stainless steel film is pasted on a polyvinylidene difluoride (PVDF) film. The voltages in the stainless steel and PVDF films are generated because of electrostatic and piezoelectric effects, and the resulting waveforms can be measured while the proposed sensor repeatedly contacts and releases the object. The voltages in the films depend on the softness and surface moisture conditions of the object. The proposed sensor therefore makes it possible to measure the softness and surface moisture of the object using the voltage waveforms. Here, we present the relationship between the measured voltages obtained using the proposed sensor and the volume of distilled water infiltrated into the filter paper on the surface of the object, and the relationship between the voltages and the softness of the object. In addition, the potential of the proposed sensor for applications is discussed.
Transparent film heaters using multi-walled carbon nanotube sheets
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Daewoong Jung , Donghyun Kim , Kyung H. Lee , Lawrence J. Overzet , Gil S. Lee
This paper presents carbon nanotubes (CNTs) used as transparent heaters, which offer great advantages in miniaturization, high efficiency, low power consumption, and rapid response. Previously proposed transparent single-walled carbon nanotube (SWCNT) based heaters used to replace indium tin oxide (ITO) heaters were fabricated either by dielectrophoresis or the piece-wise alignment of read-out electronics around randomly dispersed CNTs. These methods require steps for purification, separation, and dispersion in a liquid or polymer in order to improve their electrical and optical properties. We studied a transparent film used for heating, fabricated by employing a multi-walled carbon nanotube (MWCNT) sheet. The sheet was made from a super-aligned MWCNT forest; the heater was fabricated by direct coating onto a glass substrate. The characteristics of the MWCNT sheet, i.e. a high transmittance of ∼90% and a sheet resistance of ∼756Ω/sq, are comparable to previously reported SWCNT-based transparent films. These properties are directly applicable to applications such as window tinting and defrosters in production vehicles.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Daewoong Jung , Donghyun Kim , Kyung H. Lee , Lawrence J. Overzet , Gil S. Lee
This paper presents carbon nanotubes (CNTs) used as transparent heaters, which offer great advantages in miniaturization, high efficiency, low power consumption, and rapid response. Previously proposed transparent single-walled carbon nanotube (SWCNT) based heaters used to replace indium tin oxide (ITO) heaters were fabricated either by dielectrophoresis or the piece-wise alignment of read-out electronics around randomly dispersed CNTs. These methods require steps for purification, separation, and dispersion in a liquid or polymer in order to improve their electrical and optical properties. We studied a transparent film used for heating, fabricated by employing a multi-walled carbon nanotube (MWCNT) sheet. The sheet was made from a super-aligned MWCNT forest; the heater was fabricated by direct coating onto a glass substrate. The characteristics of the MWCNT sheet, i.e. a high transmittance of ∼90% and a sheet resistance of ∼756Ω/sq, are comparable to previously reported SWCNT-based transparent films. These properties are directly applicable to applications such as window tinting and defrosters in production vehicles.
Characterisation of thermal barrier sensor coatings synthesised by sol–gel route
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Lisa Pin , Christopher Pilgrim , Jörg Feist , Yannick Le Maoult , Florence Ansart , Philippe Lours
Further improvements in the efficiency of gas turbines are recognised to come from increases in turbine entry temperatures. Accurate temperature measurements are crucial to achieve these increases whilst maintaining reliability and economic component life. The combination of phosphor thermometry and thermal barrier coating (TBC) technology has led to the development of functional temperature sensor coatings which have several advantages over conventional temperature measurement techniques. Developments in sol–gel processing indicate that this method could be used for the production, or particularly, the repair of TBCs in the future. This paper demonstrates, for the first time, that sol–gel processing can be used to make sensor TBCs. The optimum concentration of SmO1.5 was 2wt.% in YSZ to achieve the brightest phosphorescence emission. Above this concentration the overall intensity of the emission reduces and the transitions from 4F3/2 were suppressed. Furthermore, a similar suppression of these transitions was observed when the product of the sol–gel was heat treated to 1100°C. This was concluded to be due to a higher degree of crystallinity allowing a greater interaction between the dopant ions. The dependence of the phosphorescence spectrum on heat treatment temperature provides the first indication that YSZ produced through sol–gel could be used to detect historic temperatures. An evaluation of the subsurface measurement and temperature capabilities has shown that the phosphorescence can be detected from relatively thin layers, 20μm, even under 50μm of undoped YSZ coating. Although the temperature detection range, 400–700°C, is too low for advanced TBCs the material could be used in low temperature regimes or for health monitoring purposes.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Lisa Pin , Christopher Pilgrim , Jörg Feist , Yannick Le Maoult , Florence Ansart , Philippe Lours
Further improvements in the efficiency of gas turbines are recognised to come from increases in turbine entry temperatures. Accurate temperature measurements are crucial to achieve these increases whilst maintaining reliability and economic component life. The combination of phosphor thermometry and thermal barrier coating (TBC) technology has led to the development of functional temperature sensor coatings which have several advantages over conventional temperature measurement techniques. Developments in sol–gel processing indicate that this method could be used for the production, or particularly, the repair of TBCs in the future. This paper demonstrates, for the first time, that sol–gel processing can be used to make sensor TBCs. The optimum concentration of SmO1.5 was 2wt.% in YSZ to achieve the brightest phosphorescence emission. Above this concentration the overall intensity of the emission reduces and the transitions from 4F3/2 were suppressed. Furthermore, a similar suppression of these transitions was observed when the product of the sol–gel was heat treated to 1100°C. This was concluded to be due to a higher degree of crystallinity allowing a greater interaction between the dopant ions. The dependence of the phosphorescence spectrum on heat treatment temperature provides the first indication that YSZ produced through sol–gel could be used to detect historic temperatures. An evaluation of the subsurface measurement and temperature capabilities has shown that the phosphorescence can be detected from relatively thin layers, 20μm, even under 50μm of undoped YSZ coating. Although the temperature detection range, 400–700°C, is too low for advanced TBCs the material could be used in low temperature regimes or for health monitoring purposes.
Experimental and numerical design of a long-waist cone flow meter
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Chao Tan , Hao Wu , Can Wei , Feng Dong
A long-waist cone flow meter is designed for steady differential pressure measurement and relatively small overall pressure drop. A constant-diameter annular flow channel is formed between cone element and pipe wall. The flow field of water flows through cone element is studied with 3-D CFD simulations. The constant-diameter annular channel is found being able to adjust the incoming fluid, and small rear angle of cone element could reduce flow separation and overall pressure difference. An optimized structure of long-waist cone flow meters, referred as LWC, is proposed based on the investigations on flow field analysis. A steady contracting differential pressure and an overall differential pressure can be tapped from a LWC. A set of LWCs was fabricated with diameter ratio β ranging from 0.55 to 0.75, and waist length L from 20 to 60mm when β =0.65 for experimental tests and CFD verifications. A decreasing trend of dimensionless differential pressure Δp* and δp* and an increasing trend of discharge coefficient C d of LWCs under different Reynolds number are observed and analyzed, and flow rate prediction of different Newtonian single phase flow is experimentally studied. A case study of oil–water two-phase flow is then presented with a selected LWC and an average error below 5% is achieved when treating the mixture a homogeneous flow.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Chao Tan , Hao Wu , Can Wei , Feng Dong
A long-waist cone flow meter is designed for steady differential pressure measurement and relatively small overall pressure drop. A constant-diameter annular flow channel is formed between cone element and pipe wall. The flow field of water flows through cone element is studied with 3-D CFD simulations. The constant-diameter annular channel is found being able to adjust the incoming fluid, and small rear angle of cone element could reduce flow separation and overall pressure difference. An optimized structure of long-waist cone flow meters, referred as LWC, is proposed based on the investigations on flow field analysis. A steady contracting differential pressure and an overall differential pressure can be tapped from a LWC. A set of LWCs was fabricated with diameter ratio β ranging from 0.55 to 0.75, and waist length L from 20 to 60mm when β =0.65 for experimental tests and CFD verifications. A decreasing trend of dimensionless differential pressure Δp* and δp* and an increasing trend of discharge coefficient C d of LWCs under different Reynolds number are observed and analyzed, and flow rate prediction of different Newtonian single phase flow is experimentally studied. A case study of oil–water two-phase flow is then presented with a selected LWC and an average error below 5% is achieved when treating the mixture a homogeneous flow.
Nanoscale torsion-free photonic crystal pressure sensor with ultra-high sensitivity based on side-coupled piston-type microcavity
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Daquan Yang , Huiping Tian , Nannan Wu , Yi Yang , Yuefeng Ji
A novel nanoscale torsion-free photonic crystal pressure sensor is demonstrated and its performances are theoretically investigated. The proposed sensor device consists of PhC waveguide and side-coupled piston-type microcacity. By using finite-element method (FEM) and three dimensional finite difference time domain technologies (3D-FDTD), the dependence of optical properties of resonant mode on the applied strain is systematically studied. Linear relationships between the applied strain and the shift in the resonant wavelength of the cavity are obtained. The pressure sensitivity as high as 0.50nm/nN is observed. The minimum detectable pressure variation is estimated to be as small as 0.68nN. Compared to ring-resonator based pressure sensor achieved an equivalent sensitivity, the sensor size presented in this work is reduced by three orders of magnitude. In addition, a flexible design of pressure sensor array is demonstrated in the end.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Daquan Yang , Huiping Tian , Nannan Wu , Yi Yang , Yuefeng Ji
A novel nanoscale torsion-free photonic crystal pressure sensor is demonstrated and its performances are theoretically investigated. The proposed sensor device consists of PhC waveguide and side-coupled piston-type microcacity. By using finite-element method (FEM) and three dimensional finite difference time domain technologies (3D-FDTD), the dependence of optical properties of resonant mode on the applied strain is systematically studied. Linear relationships between the applied strain and the shift in the resonant wavelength of the cavity are obtained. The pressure sensitivity as high as 0.50nm/nN is observed. The minimum detectable pressure variation is estimated to be as small as 0.68nN. Compared to ring-resonator based pressure sensor achieved an equivalent sensitivity, the sensor size presented in this work is reduced by three orders of magnitude. In addition, a flexible design of pressure sensor array is demonstrated in the end.
Design of a non-contact strain sensor based on amorphous ribbons
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hung-Yih Tsai , Rong-Shine Lin , Jeng-Shyong Chen , Cheng-Ta Chung , Yung-Hoh Sheu
Based on the magnetoelastic effect, this study develops a non-contact strain sensor consisting of a magnetoelastic film by using low-priced and highly-sensitive Metglas 2826MB (Fe40Ni38Mo4B18) amorphous ribbons as the strain measure material. Furthermore, a planar spiral coil combined in a Colpitts oscillator circuit is used to excite the magnetoelastic film. Under a tensile load, a mechanical deformation of the amorphous ribbons occurs and alters its permeability and conductivity, and induces an eddy current on the surface of the amorphous ribbons. This results in a variation of impedance on the film coupled with the planar spiral coil as well as in the corresponding voltage output to be measured. The experimental results show that the measurement sensitivity can reach 6.9mV/MPa, and the corresponding gauge factor is approximately 5167. The advantages are a simplified manufacturing process, uniformity in coil characteristics, compactness, uncomplicated circuit architecture, and low manufacturing cost. Moreover, a promising potential for further improvement makes the designed sensor suitable for future practical applications.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hung-Yih Tsai , Rong-Shine Lin , Jeng-Shyong Chen , Cheng-Ta Chung , Yung-Hoh Sheu
Based on the magnetoelastic effect, this study develops a non-contact strain sensor consisting of a magnetoelastic film by using low-priced and highly-sensitive Metglas 2826MB (Fe40Ni38Mo4B18) amorphous ribbons as the strain measure material. Furthermore, a planar spiral coil combined in a Colpitts oscillator circuit is used to excite the magnetoelastic film. Under a tensile load, a mechanical deformation of the amorphous ribbons occurs and alters its permeability and conductivity, and induces an eddy current on the surface of the amorphous ribbons. This results in a variation of impedance on the film coupled with the planar spiral coil as well as in the corresponding voltage output to be measured. The experimental results show that the measurement sensitivity can reach 6.9mV/MPa, and the corresponding gauge factor is approximately 5167. The advantages are a simplified manufacturing process, uniformity in coil characteristics, compactness, uncomplicated circuit architecture, and low manufacturing cost. Moreover, a promising potential for further improvement makes the designed sensor suitable for future practical applications.
A triaxial tactile sensor without crosstalk using pairs of piezoresistive beams with sidewall doping
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hidetoshi Takahashi , Akihito Nakai , Nguyen Thanh-Vinh , Kiyoshi Matsumoto , Isao Shimoyama
This paper reports on a triaxial tactile sensor using piezoresistive beams. The sensor chip is composed of two pairs of sidewall-doped Si beams for shear stress sensing and one pair of surface-doped Si beams for normal stress sensing. The sizes of the shear- and pressure-sensing beams are 180μm×15μm×20μm and 250μm×50μm×20μm (length×width×thickness), respectively. The sensor chip is embedded in a PDMS sheet 10mm×10mm×2mm in size. Because the simple beam structure can be fabricated easily, the proposed sensor is compatible with semiconductor device fabrication. The fabricated sensor was evaluated for normal and shear stress (0–400kPa and 0–100kPa, respectively). The responses of the corresponding beam pairs were found to be proportional to the magnitude of the applied stresses without the influence of the other stresses. The relationship between the angle of shear stress and the responses of each beam pair was also evaluated. Each beam pair detects only one axis's shear stress and showed little reaction to the other axes’ shear stress. As a result, the proposed sensor can measure the three axial components of normal and shear stress independently.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Hidetoshi Takahashi , Akihito Nakai , Nguyen Thanh-Vinh , Kiyoshi Matsumoto , Isao Shimoyama
This paper reports on a triaxial tactile sensor using piezoresistive beams. The sensor chip is composed of two pairs of sidewall-doped Si beams for shear stress sensing and one pair of surface-doped Si beams for normal stress sensing. The sizes of the shear- and pressure-sensing beams are 180μm×15μm×20μm and 250μm×50μm×20μm (length×width×thickness), respectively. The sensor chip is embedded in a PDMS sheet 10mm×10mm×2mm in size. Because the simple beam structure can be fabricated easily, the proposed sensor is compatible with semiconductor device fabrication. The fabricated sensor was evaluated for normal and shear stress (0–400kPa and 0–100kPa, respectively). The responses of the corresponding beam pairs were found to be proportional to the magnitude of the applied stresses without the influence of the other stresses. The relationship between the angle of shear stress and the responses of each beam pair was also evaluated. Each beam pair detects only one axis's shear stress and showed little reaction to the other axes’ shear stress. As a result, the proposed sensor can measure the three axial components of normal and shear stress independently.
Film-thickness and composition dependence of epitaxial thin-film PZT-based mass-sensors
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Minh Duc Nguyen , Matthijn Dekkers , Hung Ngoc Vu , Guus Rijnders
The transverse piezoelectric coefficient e 31,f and mass-sensitivity were measured on piezoelectric cantilevers based on epitaxial PZT thin-films with film-thicknesses ranging from 100 to 2000nm. The highest values of e 31,f and mass-sensitivity were observed at a film thickness of 500–750nm, while the observed remnant polarization P r and longitudinal piezoelectric coefficient d 33,f values become saturated with a film thickness of 750–1000nm. To obtain high performance by making use of its optimal film thickness, PZT thin films with various Zr/Ti ratios from 20/80 to 80/20 were studied. The experimental results indicated that the ferroelectric property reached a highest remnant polarization P r at a Zr/Ti ratio of 20/80, while the longitudinal piezoelectric coefficient d 33,f increased with increasing Zr content and reaches a maximum at a Zr/Ti ratio of 52/48. The findings suggest that the optimal composition for mass-sensitivity and transverse piezoelectric coefficient e 31,f was shifted to the tetragonal part of the phase diagram with the Zr/Ti ratios of 45/55 and 40/60, respectively.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Minh Duc Nguyen , Matthijn Dekkers , Hung Ngoc Vu , Guus Rijnders
The transverse piezoelectric coefficient e 31,f and mass-sensitivity were measured on piezoelectric cantilevers based on epitaxial PZT thin-films with film-thicknesses ranging from 100 to 2000nm. The highest values of e 31,f and mass-sensitivity were observed at a film thickness of 500–750nm, while the observed remnant polarization P r and longitudinal piezoelectric coefficient d 33,f values become saturated with a film thickness of 750–1000nm. To obtain high performance by making use of its optimal film thickness, PZT thin films with various Zr/Ti ratios from 20/80 to 80/20 were studied. The experimental results indicated that the ferroelectric property reached a highest remnant polarization P r at a Zr/Ti ratio of 20/80, while the longitudinal piezoelectric coefficient d 33,f increased with increasing Zr content and reaches a maximum at a Zr/Ti ratio of 52/48. The findings suggest that the optimal composition for mass-sensitivity and transverse piezoelectric coefficient e 31,f was shifted to the tetragonal part of the phase diagram with the Zr/Ti ratios of 45/55 and 40/60, respectively.
A MEMS-based microthermal analysis of explosive materials
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Asaf Zuck , Doron Kaplan , Shai Kendler
An upgraded microcalorimeter comprising a MEMS-based thermal conductivity vacuum gauge with a ∼1.3mV/K thermopile sensor and a thin Si3N x film heater was constructed. The improved features relative to a previous design are linear rise of the temperature with time and rapid heating of up to ∼500°C/s. The device was used for thermal analysis of micrometer-size particles of the explosives TNT, RDX and PETN by measuring temperature changes while heating the film heater. The TNT thermogram features a single exotherm that is well separated from the endotherm. The area and position of the melting and decomposition peaks in the RDX thermogram are proportional to the particle mass. The observed heats of melting agree with known thermodynamic data. The observed heat of deflagration is less than 1% of the calculated value, because a large fraction of the heated sample was sputtered from the heater and most of the heat was lost to the surrounding. Monitoring the air temperature above the heater with an ultrathin thermocouple yielded identifiable thermograms in accord with the surface thermograms. Such contactless sensing above the heater can detect the decomposition of micrometer-size particles and offers potential for the development of an inexpensive, simple to use field explosive detector.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Asaf Zuck , Doron Kaplan , Shai Kendler
An upgraded microcalorimeter comprising a MEMS-based thermal conductivity vacuum gauge with a ∼1.3mV/K thermopile sensor and a thin Si3N x film heater was constructed. The improved features relative to a previous design are linear rise of the temperature with time and rapid heating of up to ∼500°C/s. The device was used for thermal analysis of micrometer-size particles of the explosives TNT, RDX and PETN by measuring temperature changes while heating the film heater. The TNT thermogram features a single exotherm that is well separated from the endotherm. The area and position of the melting and decomposition peaks in the RDX thermogram are proportional to the particle mass. The observed heats of melting agree with known thermodynamic data. The observed heat of deflagration is less than 1% of the calculated value, because a large fraction of the heated sample was sputtered from the heater and most of the heat was lost to the surrounding. Monitoring the air temperature above the heater with an ultrathin thermocouple yielded identifiable thermograms in accord with the surface thermograms. Such contactless sensing above the heater can detect the decomposition of micrometer-size particles and offers potential for the development of an inexpensive, simple to use field explosive detector.
Bimaterial microcantilevers with black silicon nanocone arrays
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Beomjin Kwon , Jing Jiang , Matthew V. Schulmerich , Zhida Xu , Rohit Bhargava , Gang Logan Liu , William P. King
The performance of infrared (IR) sensing bimaterial cantilevers depends upon the thermal, mechanical and optical properties of the cantilever materials. This paper presents bimaterial cantilevers that have a layer of black silicon nanocone arrays, which has larger optical absorbance and mechanical compliance than single crystal silicon. The black silicon consists of nanometer-scale silicon cones of height 104–336nm, fabricated using a three-step O2–CHF3–Ar+Cl2 plasma process. The average cantilever absorbance was 0.16 over the 3–10μm wavelength region, measured using a Fourier transform infrared (FTIR) microspectrometer. The measured cantilever responsivity to incident IR light compares well to a model of cantilever behavior that relate the spectral absorbance, heat transfer, and thermal expansion. The model also provides further insights into the influence of the nanocone height on the absorbance and responsivity of the cantilever. Compared to a cantilever with smooth single crystal silicon, the cantilever with black silicon has about 2× increased responsivity. The nanocone array fabrication technique for silicon bimaterial cantilevers presented here could be applied to other IR sensors.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Beomjin Kwon , Jing Jiang , Matthew V. Schulmerich , Zhida Xu , Rohit Bhargava , Gang Logan Liu , William P. King
The performance of infrared (IR) sensing bimaterial cantilevers depends upon the thermal, mechanical and optical properties of the cantilever materials. This paper presents bimaterial cantilevers that have a layer of black silicon nanocone arrays, which has larger optical absorbance and mechanical compliance than single crystal silicon. The black silicon consists of nanometer-scale silicon cones of height 104–336nm, fabricated using a three-step O2–CHF3–Ar+Cl2 plasma process. The average cantilever absorbance was 0.16 over the 3–10μm wavelength region, measured using a Fourier transform infrared (FTIR) microspectrometer. The measured cantilever responsivity to incident IR light compares well to a model of cantilever behavior that relate the spectral absorbance, heat transfer, and thermal expansion. The model also provides further insights into the influence of the nanocone height on the absorbance and responsivity of the cantilever. Compared to a cantilever with smooth single crystal silicon, the cantilever with black silicon has about 2× increased responsivity. The nanocone array fabrication technique for silicon bimaterial cantilevers presented here could be applied to other IR sensors.
Performance improvement of ZnO nanowire based surface acoustic wave ultraviolet detector via poly(3,4-ethylenedioxythiophene) surface coating
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Wenbo Peng , Yongning He , Youlong Xu , Shaohua Jin , Ke Ma , Xiaolong Zhao , Xue Kang , Changbao Wen
ZnO nanowire based surface acoustic wave ultraviolet (UV) detector is highly desirable for UV radiation detection. However, its slow recovery process due to the surface effect of ZnO nanowires has become a crucial issue. In this paper, a simple method of poly(3,4-ethylenedioxythiophene) (PEDOT) surface coating by the chemical polymerization is proposed and experimentally proved to improve the recovery process significantly. According to the photoconductive effect and the acoustoelectric effect, the suppression of ZnO nanowires’ surface effect and the fast recombination approach of excess carriers provided by the PEDOT layer are responsible for the improvement of the recovery process.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Wenbo Peng , Yongning He , Youlong Xu , Shaohua Jin , Ke Ma , Xiaolong Zhao , Xue Kang , Changbao Wen
ZnO nanowire based surface acoustic wave ultraviolet (UV) detector is highly desirable for UV radiation detection. However, its slow recovery process due to the surface effect of ZnO nanowires has become a crucial issue. In this paper, a simple method of poly(3,4-ethylenedioxythiophene) (PEDOT) surface coating by the chemical polymerization is proposed and experimentally proved to improve the recovery process significantly. According to the photoconductive effect and the acoustoelectric effect, the suppression of ZnO nanowires’ surface effect and the fast recombination approach of excess carriers provided by the PEDOT layer are responsible for the improvement of the recovery process.
Cross-layerly embedded FBG in carbon fiber composites for self-modulated, intensity referenced and temperature insensitive microdisplacement measurement
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Bo Dong , Long Xiao , Yandong Gong , Yixin Wang
A novel temperature insensitive and intensity modulated microdisplacement sensor is demonstrated by cross-layerly embedding an FBG in carbon fiber composites. The reflection spectrum of the FBG is selfmodulated to be chirped spectrum if a microdisplacement is applied to the center of the sensor structure. By monitoring the optical power change due to the above chirped spectrum variation, the microdisplacement can be measured. Experimental results show that there are quasilinear relationships between the microdisplacement and optical power, the maximum measurement resolution of the sensor reaches 10.7μm within the displacement range of 0–1050μm, and the dynamic measurement range is within the range of 0–200Hz.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Bo Dong , Long Xiao , Yandong Gong , Yixin Wang
A novel temperature insensitive and intensity modulated microdisplacement sensor is demonstrated by cross-layerly embedding an FBG in carbon fiber composites. The reflection spectrum of the FBG is selfmodulated to be chirped spectrum if a microdisplacement is applied to the center of the sensor structure. By monitoring the optical power change due to the above chirped spectrum variation, the microdisplacement can be measured. Experimental results show that there are quasilinear relationships between the microdisplacement and optical power, the maximum measurement resolution of the sensor reaches 10.7μm within the displacement range of 0–1050μm, and the dynamic measurement range is within the range of 0–200Hz.
An experimental study of pH optical sensor using a section of no-core fiber
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Wei Li , Hu Cheng , Min Xia , Kecheng Yang
A simple optical fiber structure with a section of no-core fiber for measuring pH is presented. Precursor TEOS and pH-sensitive indicators are used to form the pH coating on the no-core fiber by dip-coating method. The pH induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output power. The results show that a high pH sensitivity of 0.6dBm/pH at 1550nm and a good linear response with a wide pH operation range, from 1 to 13, are obtained. Through monitoring the optical output powers, the responses demonstrate the good stability and repeatability of our proposed structure. At last, the measured data can be obtained with a rapid response time of less than 40s.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Wei Li , Hu Cheng , Min Xia , Kecheng Yang
A simple optical fiber structure with a section of no-core fiber for measuring pH is presented. Precursor TEOS and pH-sensitive indicators are used to form the pH coating on the no-core fiber by dip-coating method. The pH induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output power. The results show that a high pH sensitivity of 0.6dBm/pH at 1550nm and a good linear response with a wide pH operation range, from 1 to 13, are obtained. Through monitoring the optical output powers, the responses demonstrate the good stability and repeatability of our proposed structure. At last, the measured data can be obtained with a rapid response time of less than 40s.
Fabrication and characterization of carbon nanotube–polyimide composite based high temperature flexible thin film piezoresistive strain sensor
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Yizhong Wang , Allen X. Wang , Ying Wang , Minking K. Chyu , Qing-Ming Wang
A high temperature strain sensor based on polyimide/single-wall carbon nanotube (SWCNT) composites was proposed. Sensors with different SWCNT contents ranging from 0.07 to 2.0wt% were prepared. The electrical property of the composites was investigated by direct current (DC) resistance and electrical impedance spectroscopy. A simple equivalent model was used to estimate the resistance of the composite, and percolation theory was adopted to analyze the electrical property transition from insulator to conductor. The experiment results suggested the percolation threshold to be 1wt%. Several strain sensors with different CNT concentrations in and above the percolation threshold range are characterized, and the test results show the optimum CNT concentration for the sensor to be 1.4wt%. The strain sensors are also characterized under different temperature up to 265°C for future high temperature application.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Yizhong Wang , Allen X. Wang , Ying Wang , Minking K. Chyu , Qing-Ming Wang
A high temperature strain sensor based on polyimide/single-wall carbon nanotube (SWCNT) composites was proposed. Sensors with different SWCNT contents ranging from 0.07 to 2.0wt% were prepared. The electrical property of the composites was investigated by direct current (DC) resistance and electrical impedance spectroscopy. A simple equivalent model was used to estimate the resistance of the composite, and percolation theory was adopted to analyze the electrical property transition from insulator to conductor. The experiment results suggested the percolation threshold to be 1wt%. Several strain sensors with different CNT concentrations in and above the percolation threshold range are characterized, and the test results show the optimum CNT concentration for the sensor to be 1.4wt%. The strain sensors are also characterized under different temperature up to 265°C for future high temperature application.
A novel piezoelectric thin film impact sensor: Application in non-destructive material discrimination
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Sudeep Joshi , G.M. Hegde , M.M. Nayak , K. Rajanna
We report on the design, development, and performance study of a packaged piezoelectric thin film impact sensor, and its potential application in non-destructive material discrimination. The impact sensing element employed was a thin circular diaphragm of flexible Phynox alloy. Piezoelectric ZnO thin film as an impact sensing layer was deposited on to the Phynox alloy diaphragm by RF reactive magnetron sputtering. Deposited ZnO thin film was characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM) techniques. The d 31 piezoelectric coefficient value of ZnO thin film was 4.7pmV−1, as measured by 4-point bending method. ZnO film deposited diaphragm based sensing element was properly packaged in a suitable housing made of High Density Polyethylene (HDPE) material. Packaged impact sensor was used in an experimental set-up, which was designed and developed in-house for non-destructive material discrimination studies. Materials of different densities (iron, glass, wood, and plastic) were used as test specimens for material discrimination studies. The analysis of output voltage waveforms obtained reveals lots of valuable information about the impacted material. Impact sensor was able to discriminate the test materials on the basis of the difference in their densities. The output response of packaged impact sensor shows high linearity and repeatability. The packaged impact sensor discussed in this paper is highly sensitive, reliable, and cost-effective.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Sudeep Joshi , G.M. Hegde , M.M. Nayak , K. Rajanna
We report on the design, development, and performance study of a packaged piezoelectric thin film impact sensor, and its potential application in non-destructive material discrimination. The impact sensing element employed was a thin circular diaphragm of flexible Phynox alloy. Piezoelectric ZnO thin film as an impact sensing layer was deposited on to the Phynox alloy diaphragm by RF reactive magnetron sputtering. Deposited ZnO thin film was characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM) techniques. The d 31 piezoelectric coefficient value of ZnO thin film was 4.7pmV−1, as measured by 4-point bending method. ZnO film deposited diaphragm based sensing element was properly packaged in a suitable housing made of High Density Polyethylene (HDPE) material. Packaged impact sensor was used in an experimental set-up, which was designed and developed in-house for non-destructive material discrimination studies. Materials of different densities (iron, glass, wood, and plastic) were used as test specimens for material discrimination studies. The analysis of output voltage waveforms obtained reveals lots of valuable information about the impacted material. Impact sensor was able to discriminate the test materials on the basis of the difference in their densities. The output response of packaged impact sensor shows high linearity and repeatability. The packaged impact sensor discussed in this paper is highly sensitive, reliable, and cost-effective.
FM-based piezoelectric strain voltage sensor at ultra-low frequencies with wireless capability
11 July 2013,
09:43:22
Publication date: 1 September
2013
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Anthony N. Laskovski , Mehmet R. Yuce , S.O. Reza Moheimani
An FM-based ultra low frequency piezoelectric strain voltage sensing system is proposed. The sensing frequencies possible in this system are orders of magnitude lower than those of traditional methods. This method involves the conversion of changes in piezoelectric device's strain voltage to changes in capacitance with a varactor diode. This diode forms part of a feedback network in a Colpitts oscillator, converting variations in capacitance to variations in frequency. The frequency variations are demodulated using an FM demodulator. Demodulated signals as low as 1mHz were achieved and measured. The system was also implemented and measured with a wireless transmission and demodulation of the FM signal.
Source:Sensors and Actuators A: Physical, Volume 199
Author(s): Anthony N. Laskovski , Mehmet R. Yuce , S.O. Reza Moheimani
An FM-based ultra low frequency piezoelectric strain voltage sensing system is proposed. The sensing frequencies possible in this system are orders of magnitude lower than those of traditional methods. This method involves the conversion of changes in piezoelectric device's strain voltage to changes in capacitance with a varactor diode. This diode forms part of a feedback network in a Colpitts oscillator, converting variations in capacitance to variations in frequency. The frequency variations are demodulated using an FM demodulator. Demodulated signals as low as 1mHz were achieved and measured. The system was also implemented and measured with a wireless transmission and demodulation of the FM signal.
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