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Design and calibration of a new compact radiative heat-flux gauge (RHFG) for combustion applications
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): V. Mahendra Reddy , S. Sudheer , S.V. Prabhu , Sudarshan Kumar
It is important to develop an inexpensive and robust gauge for measuring the contribution of radiation heat-flux component while operating in high temperature conditions without the need of cooling water supply. This work presents a new compact radiative heat-flux gauge (RHFG) for measuring the radiative heat-flux from combustion systems operating at high operating temperatures (∼1200K). Various types of total heat-flux meters (convective and radiative) are available for measuring heat-flux. In this study, pure radiative heat-flux measuring gauge (RHFG) is developed. Quartz plate is used as a window of RHFG acting as media to transfer pure radiative heat from the heat source. Copper plate is used as the heat sensing element. A thermocouple is brazed to the copper plate to measure the rate of heat transfer to the sensing element. The mathematical modeling, numerical analysis and construction methodology of RHFG is discussed. Initially, a large sized gauge (G1) is fabricated and calibrated with cone calorimeter. The measured response time of 670s is observed for G1. Numerical analysis is carried out to optimize the size of RHFG and reduce the response time. Four different gauges with various dimensions (G2, G3, G4 and G5) are analyzed numerically and a response time of 208, 17, 14 and 12s respectively is observed. The gauge, G5 is manufactured and calibrated with cone calorimeter with known radiative heat-flux and the experimental response time of 13s is observed. This RHFG is of low cost, simple to manufacture, rugged and requires no water cooling even for high temperature combustion applications.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): V. Mahendra Reddy , S. Sudheer , S.V. Prabhu , Sudarshan Kumar
It is important to develop an inexpensive and robust gauge for measuring the contribution of radiation heat-flux component while operating in high temperature conditions without the need of cooling water supply. This work presents a new compact radiative heat-flux gauge (RHFG) for measuring the radiative heat-flux from combustion systems operating at high operating temperatures (∼1200K). Various types of total heat-flux meters (convective and radiative) are available for measuring heat-flux. In this study, pure radiative heat-flux measuring gauge (RHFG) is developed. Quartz plate is used as a window of RHFG acting as media to transfer pure radiative heat from the heat source. Copper plate is used as the heat sensing element. A thermocouple is brazed to the copper plate to measure the rate of heat transfer to the sensing element. The mathematical modeling, numerical analysis and construction methodology of RHFG is discussed. Initially, a large sized gauge (G1) is fabricated and calibrated with cone calorimeter. The measured response time of 670s is observed for G1. Numerical analysis is carried out to optimize the size of RHFG and reduce the response time. Four different gauges with various dimensions (G2, G3, G4 and G5) are analyzed numerically and a response time of 208, 17, 14 and 12s respectively is observed. The gauge, G5 is manufactured and calibrated with cone calorimeter with known radiative heat-flux and the experimental response time of 13s is observed. This RHFG is of low cost, simple to manufacture, rugged and requires no water cooling even for high temperature combustion applications.
Design and fabrication of SAW pressure, temperature and impedance sensors using novel multiphysics simulation models
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): G.A. Borrero , J.P. Bravo , S.F. Mora , S. Velásquez , F.E. Segura-Quijano
Surface acoustic wave (SAW) devices have been shown to be suitable for many applications. Some of these applications are temperature, pressure and impedance-based sensors. In this study, we investigate the performance of a SAW resonator as temperature and pressure sensors, and a reflective differential delay line (RDDL) structure as an impedance sensor. The SAW sensors were designed using a proposed FEM-based multiphysics model on COMSOL® and fabricated using photolitography over a 128° YX LiNbO3 substrate for an operation frequency of 65MHz. Using a vector network analyzer (VNA), the devices were characterized; frequency shifts on the S 11 parameter of resonators were observed depending on the applied external pressure and temperature changes, and amplitude variations for impedance changes in the case of RDDL. The experimental results were compared with simulation data. The evaluated sensitivities were 87.81 ppm/°C, 0.9 ppm/kPa and 0.0023 dB/Ω.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): G.A. Borrero , J.P. Bravo , S.F. Mora , S. Velásquez , F.E. Segura-Quijano
Surface acoustic wave (SAW) devices have been shown to be suitable for many applications. Some of these applications are temperature, pressure and impedance-based sensors. In this study, we investigate the performance of a SAW resonator as temperature and pressure sensors, and a reflective differential delay line (RDDL) structure as an impedance sensor. The SAW sensors were designed using a proposed FEM-based multiphysics model on COMSOL® and fabricated using photolitography over a 128° YX LiNbO3 substrate for an operation frequency of 65MHz. Using a vector network analyzer (VNA), the devices were characterized; frequency shifts on the S 11 parameter of resonators were observed depending on the applied external pressure and temperature changes, and amplitude variations for impedance changes in the case of RDDL. The experimental results were compared with simulation data. The evaluated sensitivities were 87.81 ppm/°C, 0.9 ppm/kPa and 0.0023 dB/Ω.
A new design method for a strain sensor using the cross-section modification of a coaxial cable
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Pengfei Shi , Renjing Gao , Shutian Liu , Jian Zhao
Strain sensors have been used extensively in structural condition monitoring. In this paper, based upon microwave network theory, a novel design method for a real-time strain monitoring sensor is proposed by using the variable cross section of a coaxial cable to detect the strain-induced frequency shift of the peak frequency at which the S parameter exhibits a peak value. With this method, a dual variable-cross-section sensor is designed and fabricated using coaxial cable as the fabrication element. The S-parameters of the sensor obtained analytically by transmission theory are almost consistent with those obtained by numerical simulation. In experiments, the sensitivity of the sensor achieved 5MHz/mɛ with the original segment length of 10.345mm and peak frequency of 5.0GHz, and the resolution achieved is 140.25μɛ. The relative small deviation of nearly 3.2% from the theoretical results to the experimental results adequately validated the feasibility of the design method. Adjusting the diameter of the dielectric layer, the length and cascaded periods of the variable cross-section, the quality factor and sensitivity of the sensor can be optimized. Due to the simplicity and ruggedness of the cable based sensor it has great potential application in structural condition monitoring compared to existing sensors.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Pengfei Shi , Renjing Gao , Shutian Liu , Jian Zhao
Strain sensors have been used extensively in structural condition monitoring. In this paper, based upon microwave network theory, a novel design method for a real-time strain monitoring sensor is proposed by using the variable cross section of a coaxial cable to detect the strain-induced frequency shift of the peak frequency at which the S parameter exhibits a peak value. With this method, a dual variable-cross-section sensor is designed and fabricated using coaxial cable as the fabrication element. The S-parameters of the sensor obtained analytically by transmission theory are almost consistent with those obtained by numerical simulation. In experiments, the sensitivity of the sensor achieved 5MHz/mɛ with the original segment length of 10.345mm and peak frequency of 5.0GHz, and the resolution achieved is 140.25μɛ. The relative small deviation of nearly 3.2% from the theoretical results to the experimental results adequately validated the feasibility of the design method. Adjusting the diameter of the dielectric layer, the length and cascaded periods of the variable cross-section, the quality factor and sensitivity of the sensor can be optimized. Due to the simplicity and ruggedness of the cable based sensor it has great potential application in structural condition monitoring compared to existing sensors.
Study of the influence of temperature on the optical response of interferometric detector systems
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Thomas Wood , Judikaël Le Rouzo , François Flory , Raphael K. Kribich , Geoffrey Maulion , Philippe Signoret , Paul Coudray , Thomas Mazingue
In this paper, we will demonstrate a theoretical approach to determining the optical response of interferometric detector systems to external stimuli. The wavelength dispersion of the refractive index and the thermo-optic coefficient of transparent polymer blend waveguide materials are inserted into modeling software in order to simulate the optical response of both Multimode Interferometer (MMI) and Bragg grating (BG) architectures. The optical output of such devices is very sensitive to variations in the refractive index of the constituent materials, and they may be used to detect phenomena such as local temperature changes or relative humidity variations [1]. When the input intensity of the sensor system is normalized to unity, we demonstrate theoretical thermal sensitivities of 2×10−4/K for BG architectures and 3×10−5/K for MMI devices. A differential measurement system for BG or MMI components is discussed and simulated. We shall also discuss the use of such systems as gas detectors when a catalyst capable of accelerating the exothermic oxidation of combustible gasses is deposited onto the optical circuit.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Thomas Wood , Judikaël Le Rouzo , François Flory , Raphael K. Kribich , Geoffrey Maulion , Philippe Signoret , Paul Coudray , Thomas Mazingue
In this paper, we will demonstrate a theoretical approach to determining the optical response of interferometric detector systems to external stimuli. The wavelength dispersion of the refractive index and the thermo-optic coefficient of transparent polymer blend waveguide materials are inserted into modeling software in order to simulate the optical response of both Multimode Interferometer (MMI) and Bragg grating (BG) architectures. The optical output of such devices is very sensitive to variations in the refractive index of the constituent materials, and they may be used to detect phenomena such as local temperature changes or relative humidity variations [1]. When the input intensity of the sensor system is normalized to unity, we demonstrate theoretical thermal sensitivities of 2×10−4/K for BG architectures and 3×10−5/K for MMI devices. A differential measurement system for BG or MMI components is discussed and simulated. We shall also discuss the use of such systems as gas detectors when a catalyst capable of accelerating the exothermic oxidation of combustible gasses is deposited onto the optical circuit.
Laser profilometer using a Fabry–Perot etalon and an objective
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Shyh-Tsong Lin , Sheng-Lih Yeh , Yi-Chun Wang , Meng-Zhu Chen
This paper introduces an innovative laser profilometer using a Fabry–Perot etalon and an objective. Following the derivation of the measurement theory, an experimental setup constructed to realize the profilometer is demonstrated, and the experimental results from the uses of this setup are then presented. The experimental setup has a sensitivity, vertical resolution, and stability of 1.62/μm, 2.2nm, and 6.6nm, respectively, and the experimental results agree not only the validity but also the feasibility of the proposed profilometer.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Shyh-Tsong Lin , Sheng-Lih Yeh , Yi-Chun Wang , Meng-Zhu Chen
This paper introduces an innovative laser profilometer using a Fabry–Perot etalon and an objective. Following the derivation of the measurement theory, an experimental setup constructed to realize the profilometer is demonstrated, and the experimental results from the uses of this setup are then presented. The experimental setup has a sensitivity, vertical resolution, and stability of 1.62/μm, 2.2nm, and 6.6nm, respectively, and the experimental results agree not only the validity but also the feasibility of the proposed profilometer.
Synthesis of mesoporous polypyrrole nanowires/nanoparticles for ammonia gas sensing application
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Ishpal Rawal , Amarjeet Kaur
Nanostructured polypyrrole (PPy) has been synthesized in the presence of anionic azo dye {sodium 4-[4-(dimethyl-amino)-phenyldiazo] phenylsulfonate} (MO) and cationic surfactant {cetyltrimethyl ammonium bromide} (CTAB). The synthesis of the prepared PPy samples was confirmed by Fourier transform infrared spectroscopy and structural analysis was carried out using X-ray diffraction technique. Scanning electron microscopy and high resolution transmission electron microscopy investigations confirm the formation of nanostructured PPy. Both the samples have different shapes and dimensions. The sample prepared in the presence of MO has the higher doping level, bipolaron concentration and electrical conductivity (4Scm−1) as compared to the sample prepared in the presence of CTAB (1.69×10−4 Scm−1). The prepared samples were tested for porosity through BET measurements. It has been found that the PPy nanowires (S1) have larger surface area (156,056.0cm2/g) as compared PPy nanoparticles (S2) (11,259.0cm2/g). Moreover, PPy nanowires have shown better gas sensitivity (∼6%) as compared to PPy nanoparticles (∼4%) and well corroborated with porosity, surface morphology, and the Raman investigations carried out under ammonia environment.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Ishpal Rawal , Amarjeet Kaur
Nanostructured polypyrrole (PPy) has been synthesized in the presence of anionic azo dye {sodium 4-[4-(dimethyl-amino)-phenyldiazo] phenylsulfonate} (MO) and cationic surfactant {cetyltrimethyl ammonium bromide} (CTAB). The synthesis of the prepared PPy samples was confirmed by Fourier transform infrared spectroscopy and structural analysis was carried out using X-ray diffraction technique. Scanning electron microscopy and high resolution transmission electron microscopy investigations confirm the formation of nanostructured PPy. Both the samples have different shapes and dimensions. The sample prepared in the presence of MO has the higher doping level, bipolaron concentration and electrical conductivity (4Scm−1) as compared to the sample prepared in the presence of CTAB (1.69×10−4 Scm−1). The prepared samples were tested for porosity through BET measurements. It has been found that the PPy nanowires (S1) have larger surface area (156,056.0cm2/g) as compared PPy nanoparticles (S2) (11,259.0cm2/g). Moreover, PPy nanowires have shown better gas sensitivity (∼6%) as compared to PPy nanoparticles (∼4%) and well corroborated with porosity, surface morphology, and the Raman investigations carried out under ammonia environment.
All fiber curvature sensor based on modal interferometer with waist enlarge splicing
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Haifeng Song , Huaping Gong , Kai Ni , Xinyong Dong
A novel fiber curvature sensor based on modal interferometer with waist-enlarge splicing is proposed. A section of 30mm polarization maintaining fiber (PMF) is spliced with waist enlarge between two conventional single mode fibers (SMFs) to construct an all fiber curvature sensor. The results show that the transmission spectrum has a blue and red shift, corresponding to the opposite curvature directions. The sensitivity coefficient of −10.634nm/m−1 and 10.152nm/m−1 were acquired by concave and convex bending with the range from 0m−1 to 2.054m−1, and the corresponding resolution were 9.4×10−4 m−1 and 9.85×10−4 m−1, respectively. And the influence of different lengths of PMF on the sensitivity was also discussed.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Haifeng Song , Huaping Gong , Kai Ni , Xinyong Dong
A novel fiber curvature sensor based on modal interferometer with waist-enlarge splicing is proposed. A section of 30mm polarization maintaining fiber (PMF) is spliced with waist enlarge between two conventional single mode fibers (SMFs) to construct an all fiber curvature sensor. The results show that the transmission spectrum has a blue and red shift, corresponding to the opposite curvature directions. The sensitivity coefficient of −10.634nm/m−1 and 10.152nm/m−1 were acquired by concave and convex bending with the range from 0m−1 to 2.054m−1, and the corresponding resolution were 9.4×10−4 m−1 and 9.85×10−4 m−1, respectively. And the influence of different lengths of PMF on the sensitivity was also discussed.
A fast response intrinsic humidity sensor based on an etched singlemode polymer fiber Bragg grating
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Ginu Rajan , Yusof Mohd Noor , Bing Liu , Eliathamby Ambikairaja , David J. Webb , Gang-Ding Peng
A simple, low cost and fast response time intrinsic relative humidity sensor system based on an etched singlemode polymer fiber Bragg (POFBG) is presented in this paper. A macro-bend linear edge filter which converts the humidity induced wavelength shift into an intensity change is used as the interrogation technique. The singlemode POFBG is etched to micro-meters in diameter to improve the response time of the humidity sensor. A response time of 4.5s is observed for a polymer FBG with a cladding diameter of 25μm. The overall sensor system sensitivity was 0.23mV/%RH. The etched POFBG humidity sensor shows anexponential decrease in response time with a decrease in fiber diameter. The developed sensor might have potential applications in a wide range of applications where fast and accurate real time humidity control is required.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Ginu Rajan , Yusof Mohd Noor , Bing Liu , Eliathamby Ambikairaja , David J. Webb , Gang-Ding Peng
A simple, low cost and fast response time intrinsic relative humidity sensor system based on an etched singlemode polymer fiber Bragg (POFBG) is presented in this paper. A macro-bend linear edge filter which converts the humidity induced wavelength shift into an intensity change is used as the interrogation technique. The singlemode POFBG is etched to micro-meters in diameter to improve the response time of the humidity sensor. A response time of 4.5s is observed for a polymer FBG with a cladding diameter of 25μm. The overall sensor system sensitivity was 0.23mV/%RH. The etched POFBG humidity sensor shows anexponential decrease in response time with a decrease in fiber diameter. The developed sensor might have potential applications in a wide range of applications where fast and accurate real time humidity control is required.
Capacitive contact lens sensor for continuous non-invasive intraocular pressure monitoring
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Guo-Zhen Chen , Ion-Seng Chan , David C.C. Lam
Intraocular pressure (IOP) is a primary indicative factor in the diagnosis and treatment monitoring of glaucoma. Measurement of IOP during conventional single office consultation is insufficient for determination of the pressure peak, and IOP profile is needed for peak determination. A capacitive wearable contact lens sensor for monitoring of the IOP is developed in this study. A curvature-sensitive inductor–capacitor sensor is fabricated and embedded inside a silicone rubber contact lens, such that the curvature of the lens is correlated with the resonance frequency of the sensor. The curvature of the lens is mechanically related to the IOP in the underlying eye such that the IOP can be determined from the resonance frequency of the sensor. To fit human eyes, the sensor was designed to have an outer diameter of 14mm, radius of curvature of 8.5mm, and operates in human IOP range between 5 and 40mmHg. The frequency responses and the ability of the sensor to track IOP cycles were tested. Tests on model silicone eyes and enucleated porcine eyes showed that the sensors have a linearity R >0.997 and a sensitivity >200ppm/mmHg for IOP monitoring. Together with wireless reading circuitry taped around the eye socket, the new contact lens sensor can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Guo-Zhen Chen , Ion-Seng Chan , David C.C. Lam
Intraocular pressure (IOP) is a primary indicative factor in the diagnosis and treatment monitoring of glaucoma. Measurement of IOP during conventional single office consultation is insufficient for determination of the pressure peak, and IOP profile is needed for peak determination. A capacitive wearable contact lens sensor for monitoring of the IOP is developed in this study. A curvature-sensitive inductor–capacitor sensor is fabricated and embedded inside a silicone rubber contact lens, such that the curvature of the lens is correlated with the resonance frequency of the sensor. The curvature of the lens is mechanically related to the IOP in the underlying eye such that the IOP can be determined from the resonance frequency of the sensor. To fit human eyes, the sensor was designed to have an outer diameter of 14mm, radius of curvature of 8.5mm, and operates in human IOP range between 5 and 40mmHg. The frequency responses and the ability of the sensor to track IOP cycles were tested. Tests on model silicone eyes and enucleated porcine eyes showed that the sensors have a linearity R >0.997 and a sensitivity >200ppm/mmHg for IOP monitoring. Together with wireless reading circuitry taped around the eye socket, the new contact lens sensor can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring.
Stress relaxation measurement of viscoelastic materials using a polymer-based microfluidic device
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Jiayue Shen , Peng Cheng , Wenting Gu , Zhili Hao
This paper presents the stress relaxation measurement of viscoelastic materials using a polymer-based microfluidic device. Comprised of a single polymer rectangular microstructure and a set of electrolyte-enabled distributed resistive transducers, this device is capable of detecting continuous distributed dynamic loads. In a measurement, a rigid cylinder probe is utilized to apply a precisely controlled step displacement input to a material specimen on the device, and consequently the spatially varying stress relaxation behavior of the specimen is translated to time-dependent continuous distributed loads acting on the device, where such loads give rise to time-dependent continuous deflection of the polymer microstructure and register as discrete resistance changes at the locations of the transducers. To account for device-to-device fabrication variations, performance characterization is first conducted on a device as a control experiment, and then a specimen is placed on a characterized device for measurement. Several homogeneous and heterogeneous specimens are measured, and the associated data analysis is conducted for extracting the spatially varying Young's relaxation modulus, which is expressed as the Maxwell model with two relaxation times. The results demonstrate the feasibility of using a single polymer-based microfluidic device to map out the spatially varying stress relaxation behavior of viscoelastic materials.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Jiayue Shen , Peng Cheng , Wenting Gu , Zhili Hao
This paper presents the stress relaxation measurement of viscoelastic materials using a polymer-based microfluidic device. Comprised of a single polymer rectangular microstructure and a set of electrolyte-enabled distributed resistive transducers, this device is capable of detecting continuous distributed dynamic loads. In a measurement, a rigid cylinder probe is utilized to apply a precisely controlled step displacement input to a material specimen on the device, and consequently the spatially varying stress relaxation behavior of the specimen is translated to time-dependent continuous distributed loads acting on the device, where such loads give rise to time-dependent continuous deflection of the polymer microstructure and register as discrete resistance changes at the locations of the transducers. To account for device-to-device fabrication variations, performance characterization is first conducted on a device as a control experiment, and then a specimen is placed on a characterized device for measurement. Several homogeneous and heterogeneous specimens are measured, and the associated data analysis is conducted for extracting the spatially varying Young's relaxation modulus, which is expressed as the Maxwell model with two relaxation times. The results demonstrate the feasibility of using a single polymer-based microfluidic device to map out the spatially varying stress relaxation behavior of viscoelastic materials.
Laser synthesized gold nanoparticles for high sensitive strain gauges
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Salamat Burzhuev , Aykutlu Dâna , Bülend Ortaç
We demonstrate high strain sensitivity property of gold nanoparticle (Au-NP) thin films fabricated on flexible polydimethylsiloxane (PDMS) substrates. This behavior is attributed to quantum tunneling effect that is highly dependent on nanoparticle separation. Au-NPs were synthesized in water by nanosecond laser ablation method. The clean surface providing high tunneling decay constant, size of the Au-NPs and Au-NPs aggregate clusters offer advantages for high sensitivity strain sensor. We prepared Au-NPs films on flexible PDMS substrate by using hands-on drop-cast method. To obtain high gauge factor (g factor), we investigated the nanoparticles concentration on the substrate. Laser-generated Au-NPs films demonstrated g factor of ∼300 for higher than 0.22% strain and ∼80 for the strain lower than 0.22% strain, which is favorably comparable to reported sensitivities for strain sensors based on Au-NPs. Mechanical characterizations for the prolonged working durations suggest long term stability of the strain sensors. We discuss several models describing conductance of films in low and high strain regimes.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Salamat Burzhuev , Aykutlu Dâna , Bülend Ortaç
We demonstrate high strain sensitivity property of gold nanoparticle (Au-NP) thin films fabricated on flexible polydimethylsiloxane (PDMS) substrates. This behavior is attributed to quantum tunneling effect that is highly dependent on nanoparticle separation. Au-NPs were synthesized in water by nanosecond laser ablation method. The clean surface providing high tunneling decay constant, size of the Au-NPs and Au-NPs aggregate clusters offer advantages for high sensitivity strain sensor. We prepared Au-NPs films on flexible PDMS substrate by using hands-on drop-cast method. To obtain high gauge factor (g factor), we investigated the nanoparticles concentration on the substrate. Laser-generated Au-NPs films demonstrated g factor of ∼300 for higher than 0.22% strain and ∼80 for the strain lower than 0.22% strain, which is favorably comparable to reported sensitivities for strain sensors based on Au-NPs. Mechanical characterizations for the prolonged working durations suggest long term stability of the strain sensors. We discuss several models describing conductance of films in low and high strain regimes.
Improving the stability and reproducibility of the carbon nanotube gas ionization sensor by Co–Ti/Ti co-deposited catalyst layer
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Chia-Tsung Chang , Chun-Yu Huang , Yu-Ren Li , Huang-Chung Cheng
A novel gas ionization sensor (GIS) of the carbon nanotube (CNT) film using the Co–Ti/Ti co-deposited catalyst layer had been proposed for the first time to exhibit higher stability and better reproducibility with respect to the CNT film ones with the single catalyst layer. For the proposed CNT GIS, the variation of the breakdown voltage (V br ) was less than 25% for the ten devices with the same structure measurement since the lengths of the CNT synthesized were uniform and aligned. Besides, the fluctuation of the V br was about 14% during 1000 operation times in nitrogen at the pressure of 0.035Torr. It was attributed to the adhesion between CNTs and the substrate could be improved since the co-deposited catalyst layer and Ti adhesion layer would be coalesced so that the Co nanoparticles would be partially immersed into Ti layer after hydrogen pretreatment. Such a CNT GIS with the co-deposited catalyst layer also exhibited high sensitivity and selectivity for different kinds of gases detection as well as the good linearity for detecting the gas mixture.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Chia-Tsung Chang , Chun-Yu Huang , Yu-Ren Li , Huang-Chung Cheng
A novel gas ionization sensor (GIS) of the carbon nanotube (CNT) film using the Co–Ti/Ti co-deposited catalyst layer had been proposed for the first time to exhibit higher stability and better reproducibility with respect to the CNT film ones with the single catalyst layer. For the proposed CNT GIS, the variation of the breakdown voltage (V br ) was less than 25% for the ten devices with the same structure measurement since the lengths of the CNT synthesized were uniform and aligned. Besides, the fluctuation of the V br was about 14% during 1000 operation times in nitrogen at the pressure of 0.035Torr. It was attributed to the adhesion between CNTs and the substrate could be improved since the co-deposited catalyst layer and Ti adhesion layer would be coalesced so that the Co nanoparticles would be partially immersed into Ti layer after hydrogen pretreatment. Such a CNT GIS with the co-deposited catalyst layer also exhibited high sensitivity and selectivity for different kinds of gases detection as well as the good linearity for detecting the gas mixture.
Design and analysis of functional multiwalled carbon nanotubes for infrared sensors
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): R. Afrin , N.A. Shah , M. Abbas , M. Amin , A.S. Bhatti
In this paper, we report the comparison of infrared detection based on buckypapers of chemically modified multiwalled carbon nanotubes by carboxyl and thiol groups. We observed that functionalized carbon nanotube buckypapers had a significant impact on radiation sensing at room temperature. Nanotubes buckypapers were formed by successively increasing cross-linker reagent in carbon nanotubes. It was observed that infrared sensitivity of resistively read-out of carboxylated and thiolated buckypapers increased by increasing the cross-linker reagent up to certain limit. Further increase in cross-linker reagent results in brittleness of buckypaper. The maximum sensitivity of carboxylated and thiolated buckypapers was 3.4% and 16.07% while minimum response time of carboxylated and thiolated buckypapers was 1.29s and 6.09s, respectively. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy were used for analysis of presences of nanotubes, structural morphology and defect density to evaluate all the modifications of the nanotubes structure and the nature of the compounds added to the nanotubes surface by functionalization treatment.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): R. Afrin , N.A. Shah , M. Abbas , M. Amin , A.S. Bhatti
In this paper, we report the comparison of infrared detection based on buckypapers of chemically modified multiwalled carbon nanotubes by carboxyl and thiol groups. We observed that functionalized carbon nanotube buckypapers had a significant impact on radiation sensing at room temperature. Nanotubes buckypapers were formed by successively increasing cross-linker reagent in carbon nanotubes. It was observed that infrared sensitivity of resistively read-out of carboxylated and thiolated buckypapers increased by increasing the cross-linker reagent up to certain limit. Further increase in cross-linker reagent results in brittleness of buckypaper. The maximum sensitivity of carboxylated and thiolated buckypapers was 3.4% and 16.07% while minimum response time of carboxylated and thiolated buckypapers was 1.29s and 6.09s, respectively. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy were used for analysis of presences of nanotubes, structural morphology and defect density to evaluate all the modifications of the nanotubes structure and the nature of the compounds added to the nanotubes surface by functionalization treatment.
Analysis of a concentric coplanar capacitor for epidermal hydration sensing
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Huanyu Cheng , Yihui Zhang , Xian Huang , John A. Rogers , Yonggang Huang
Without conformal contact between hydration sensors and skin, measured signals (either capacitance or impedance) can be susceptible to artifacts associated with motion-induced changes and irreproducibility in contact. Devices with mechanical properties matched to the skin enable conformal contact and adhesion via the action of van der Waals forces alone, thereby facilitating accurate, reproducible measurements. Theoretical investigations of concentric coplanar capacitors in this type of ‘epidermal’ format yield analytic expressions of the impedance for single- and double-layer capacitors. The calculated dependence of impedance on material and geometric parameters agree well with finite element analysis and experiments, thereby providing important insights into the design of epidermal systems for hydration sensing.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Huanyu Cheng , Yihui Zhang , Xian Huang , John A. Rogers , Yonggang Huang
Without conformal contact between hydration sensors and skin, measured signals (either capacitance or impedance) can be susceptible to artifacts associated with motion-induced changes and irreproducibility in contact. Devices with mechanical properties matched to the skin enable conformal contact and adhesion via the action of van der Waals forces alone, thereby facilitating accurate, reproducible measurements. Theoretical investigations of concentric coplanar capacitors in this type of ‘epidermal’ format yield analytic expressions of the impedance for single- and double-layer capacitors. The calculated dependence of impedance on material and geometric parameters agree well with finite element analysis and experiments, thereby providing important insights into the design of epidermal systems for hydration sensing.
Real-time 1D hyperspectral imaging of porous silicon-based photonic crystals with one-dimensional chemical composition gradients undergoing pore-filling-induced spectral shifts
23 October 2013,
09:20:49
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Adam Leacock-Johnson , Adrian Garcia Sega , Adnan Sharief , Michael J. Sailor , Gordon M. Miskelly
A line-scan hyperspectral imager can provide real-time spectral information at many points along a transect of a gradient-modified material. This is demonstrated by monitoring the optical reflectance spectrum of a porous silicon photonic crystal with a hydrophobic/hydrophilic pore-wall surface composition gradient while it is immersed in water to which ethanol is added. The combination of the hyperspectral imager and the pore-wall composition gradient allows a detailed study of the pore filling process. It is observed that even the most hydrophobic pores fill to a small extent when only a small amount of ethanol has been added. This gradient of filling is in contrast to visible observation of the porous silicon samples, which can suggest a step change in pore filling. The pore-filling process can take many minutes when the solution composition allows pores at a given position along the gradient to be about 50% filled. These observations demonstrate the utility of aligning a line-scan hyperspectral imager with a gradient material.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Adam Leacock-Johnson , Adrian Garcia Sega , Adnan Sharief , Michael J. Sailor , Gordon M. Miskelly
A line-scan hyperspectral imager can provide real-time spectral information at many points along a transect of a gradient-modified material. This is demonstrated by monitoring the optical reflectance spectrum of a porous silicon photonic crystal with a hydrophobic/hydrophilic pore-wall surface composition gradient while it is immersed in water to which ethanol is added. The combination of the hyperspectral imager and the pore-wall composition gradient allows a detailed study of the pore filling process. It is observed that even the most hydrophobic pores fill to a small extent when only a small amount of ethanol has been added. This gradient of filling is in contrast to visible observation of the porous silicon samples, which can suggest a step change in pore filling. The pore-filling process can take many minutes when the solution composition allows pores at a given position along the gradient to be about 50% filled. These observations demonstrate the utility of aligning a line-scan hyperspectral imager with a gradient material.
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