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papers from the latest issue:
Liquid gate dielectric field effect transistor for a radiation nose
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Jin-Woo Han, M. Meyyappan, Jae-Hyuk Ahn, Yang-Kyu Choi
Radiation sensors are essential to detect illicit radiological materials, nuclear waste management, radiochemistry, nuclear physics, and medical research. Detectors should be capable of uncovering various radiation sources with a good energy resolution and being adaptable to different platforms such as handheld, desktop, and benchtop, which can be easily implemented for security check in harbors and airports. Many of the devices and systems presently in use are bulky and expensive. Herein, we present a new detection method and architecture based on metal oxide semiconductor field effect transistor. Some liquids react to radiation, leading to a change in properties such as dielectric constant. Inspired by such radiation-responsivity, we have constructed a transistor with a radiation-responsive liquid as a gate dielectric. Current–voltage characteristics of the device change upon gamma-ray irradiation. Different types of liquids that specifically interact with target radiations can be used in an array of transistors serving as a radiation nose in the future. Such a radiation nose can be adaptable to different platforms and for implementation as a dosimeter for radiotherapy patients, nuclear plant health and safety inspection, space travel, environmental monitoring, and sensors for security.
Source:Sensors and Actuators A: Physical, Volume 182
Jin-Woo Han, M. Meyyappan, Jae-Hyuk Ahn, Yang-Kyu Choi
Radiation sensors are essential to detect illicit radiological materials, nuclear waste management, radiochemistry, nuclear physics, and medical research. Detectors should be capable of uncovering various radiation sources with a good energy resolution and being adaptable to different platforms such as handheld, desktop, and benchtop, which can be easily implemented for security check in harbors and airports. Many of the devices and systems presently in use are bulky and expensive. Herein, we present a new detection method and architecture based on metal oxide semiconductor field effect transistor. Some liquids react to radiation, leading to a change in properties such as dielectric constant. Inspired by such radiation-responsivity, we have constructed a transistor with a radiation-responsive liquid as a gate dielectric. Current–voltage characteristics of the device change upon gamma-ray irradiation. Different types of liquids that specifically interact with target radiations can be used in an array of transistors serving as a radiation nose in the future. Such a radiation nose can be adaptable to different platforms and for implementation as a dosimeter for radiotherapy patients, nuclear plant health and safety inspection, space travel, environmental monitoring, and sensors for security.
Two-dimensional folded CMOS Hall device with interacting lateral magnetotransistor and magnetoresistor
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Chih-Ping Yu, Guo-Ming Sung
This study investigates a two-dimensional folded Hall device fabricated by standard 0.35-μm CMOS process. The effective conduction length is shortened by folding the device, and the conducting channel is narrowed by using a p+ guard ring. The measurement results show that the maximum supply-current-related magnetosensitivity (S RI ) of lateral magnetotransistor (LMT) integrated with magnetoresistor (MR) is about 5 and 7 times higher than that of singular LMT and singular MR, respectively. Cross-coupling signal is also higher but is easily cancelled since the signal is approximately one fifth of the related measured Hall voltage. Both MR and LMT have poor nonlinearity, especially for two opposing extremes at I bias ≤20mA and I bias ≥80mA. Integrating LMT with MR improves nonlinearity by reducing the total conductive resistance V bias /I bias . The measured optimum S RI , optimum sensitivity S, minimum nonlinearity error (NLE) and minimum offset are 0.385V/AT, 9.564mV/T, 4.03%, and 18.85mV, respectively, at a bias current of 100mA excited with a supply voltage of 2.7V.
Source:Sensors and Actuators A: Physical, Volume 182
Chih-Ping Yu, Guo-Ming Sung
This study investigates a two-dimensional folded Hall device fabricated by standard 0.35-μm CMOS process. The effective conduction length is shortened by folding the device, and the conducting channel is narrowed by using a p+ guard ring. The measurement results show that the maximum supply-current-related magnetosensitivity (S RI ) of lateral magnetotransistor (LMT) integrated with magnetoresistor (MR) is about 5 and 7 times higher than that of singular LMT and singular MR, respectively. Cross-coupling signal is also higher but is easily cancelled since the signal is approximately one fifth of the related measured Hall voltage. Both MR and LMT have poor nonlinearity, especially for two opposing extremes at I bias ≤20mA and I bias ≥80mA. Integrating LMT with MR improves nonlinearity by reducing the total conductive resistance V bias /I bias . The measured optimum S RI , optimum sensitivity S, minimum nonlinearity error (NLE) and minimum offset are 0.385V/AT, 9.564mV/T, 4.03%, and 18.85mV, respectively, at a bias current of 100mA excited with a supply voltage of 2.7V.
A review and evaluation of melt temperature sensors for polymer extrusion
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Chamil Abeykoon, Peter J. Martin, Adrian L. Kelly, Elaine C. Brown
Melt temperature is one of the key variables in polymer extrusion which determines process thermal stability and hence melt quality. Therefore, melt temperature is commonly measured in polymer processing and point/bulk melt temperature measurement methods are widely used in the present industry. Some thermal profile measurement methods have also been attempted in research. This study presents a review of melt temperature measurements in polymer extrusion in research and industry, and describes the results of an experimental evaluation carried out to explore the performance of five melt temperature measurement techniques. In addition, an investigation was carried out on the fully developed melt temperature profile of a cylindrical rod die. Moreover, the existing challenges and possible future applications for extrusion thermal monitoring are discussed. The results confirmed that melt temperature varied significantly at different radial locations within the die. Point/bulk melt temperature measurements were found to provide relatively limited information on process thermal quality close to the die wall. Hence, information provided by these sensors is less representative of actual thermal conditions as they are unable to capture thermal information from the whole melt flow cross-section. Therefore, the importance of the development of industrially compatible thermal profile measurement techniques is emphasised.
Source:Sensors and Actuators A: Physical, Volume 182
Chamil Abeykoon, Peter J. Martin, Adrian L. Kelly, Elaine C. Brown
Melt temperature is one of the key variables in polymer extrusion which determines process thermal stability and hence melt quality. Therefore, melt temperature is commonly measured in polymer processing and point/bulk melt temperature measurement methods are widely used in the present industry. Some thermal profile measurement methods have also been attempted in research. This study presents a review of melt temperature measurements in polymer extrusion in research and industry, and describes the results of an experimental evaluation carried out to explore the performance of five melt temperature measurement techniques. In addition, an investigation was carried out on the fully developed melt temperature profile of a cylindrical rod die. Moreover, the existing challenges and possible future applications for extrusion thermal monitoring are discussed. The results confirmed that melt temperature varied significantly at different radial locations within the die. Point/bulk melt temperature measurements were found to provide relatively limited information on process thermal quality close to the die wall. Hence, information provided by these sensors is less representative of actual thermal conditions as they are unable to capture thermal information from the whole melt flow cross-section. Therefore, the importance of the development of industrially compatible thermal profile measurement techniques is emphasised.
3D force sensor for biomechanical applications
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
R.A. Brookhuis, T.S.J. Lammerink, R.J. Wiegerink, M.J. de Boer, M.C. Elwenspoek
A force sensor with capacitive readout is designed and realized for the measurement of mechanical power transfer. The ultimate aim is to integrate such sensors in a glove that will determine the complete mechanical interaction between the human hand and its environment. The sensor measures the normal force and two perpendicular moments by dividing the read-out into four quadrants. The fabrication process is based on silicon fusion bonding allowing the realization of extremely small gaps (250nm). This, in combination with mechanical amplification due to the sensor structure, results in a large sensitivity of 16pF/N and a full-scale range of 50N.
Source:Sensors and Actuators A: Physical, Volume 182
R.A. Brookhuis, T.S.J. Lammerink, R.J. Wiegerink, M.J. de Boer, M.C. Elwenspoek
A force sensor with capacitive readout is designed and realized for the measurement of mechanical power transfer. The ultimate aim is to integrate such sensors in a glove that will determine the complete mechanical interaction between the human hand and its environment. The sensor measures the normal force and two perpendicular moments by dividing the read-out into four quadrants. The fabrication process is based on silicon fusion bonding allowing the realization of extremely small gaps (250nm). This, in combination with mechanical amplification due to the sensor structure, results in a large sensitivity of 16pF/N and a full-scale range of 50N.
Highlights
► An accurate miniature 3D force sensor is designed and realized. ► Many thin silicon pillars form the spring element of the sensor in all its degree of freedom and carry the load. ► Sensor has a high force range of 50N. ► Small electrode gaps of 250nm are realized using a patterned SOI-wafer as electrode. ► The normal force measurements show a large sensitivity of 16pF/N.Micro-magnetometry for susceptibility measurement of superparamagnetic single bead
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Brajalal Sinha, S. Anandakumar, Sunjong Oh, CheolGi Kim
We have fabricated a micro-planar Hall resistive (PHR) sensor consisting of a thin magnetic multilayer structure, and characterized the magnetic susceptibility of a single superparamagnetic bead (Dynabeads® M-280 of 2.8μm). The sensor arm length with an active sensing junction of 3μm×3μm was optimized using a finite element method (FEM) simulation to minimize its induced field effect over the junction area under an applied field, and the field sensitivity of the fabricated 7μm arm length sensor was measured to be 0.075μV/Am−1 (6.0μV/Oe) in the low field region. An average voltage change of 7.6μV with a standard deviation of 0.26μV was observed in the sensor during the repeated bead droplet-washing procedure. The magnetic susceptibility of a single bead was calculated to be 0.65 (SI), which agreed with the measured susceptibility by a SQUID magnetometer. This novel approach provides an inexpensive micro-magnetometry method for measuring the magnetic susceptibility of magnetic micro-sized objects, which is applicable in widespread laboratories.
Source:Sensors and Actuators A: Physical, Volume 182
Brajalal Sinha, S. Anandakumar, Sunjong Oh, CheolGi Kim
We have fabricated a micro-planar Hall resistive (PHR) sensor consisting of a thin magnetic multilayer structure, and characterized the magnetic susceptibility of a single superparamagnetic bead (Dynabeads® M-280 of 2.8μm). The sensor arm length with an active sensing junction of 3μm×3μm was optimized using a finite element method (FEM) simulation to minimize its induced field effect over the junction area under an applied field, and the field sensitivity of the fabricated 7μm arm length sensor was measured to be 0.075μV/Am−1 (6.0μV/Oe) in the low field region. An average voltage change of 7.6μV with a standard deviation of 0.26μV was observed in the sensor during the repeated bead droplet-washing procedure. The magnetic susceptibility of a single bead was calculated to be 0.65 (SI), which agreed with the measured susceptibility by a SQUID magnetometer. This novel approach provides an inexpensive micro-magnetometry method for measuring the magnetic susceptibility of magnetic micro-sized objects, which is applicable in widespread laboratories.
Novel piezoresistive high-g accelerometer geometry with very high sensitivity-bandwidth product
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Robert Kuells, Siegfried Nau, Manfred Salk, Klaus Thoma
This paper reports on a novel piezoresistive high-g accelerometer design, that partially overcomes a common drawback of shock sensor concepts, namely that their bandwidth, i.e. natural frequency, cannot be increased without sacrificing sensitivity. Its figure of merit (sensitivity multiplied by frequency squared) is about 5×106 m−1. This is one order of magnitude higher than in existing designs in the literature or currently on the market. The increase is made possible by a design approach that focuses on displacements rather than stresses and the utilization of a spring–mass system related parameter called the “geometrical constant”. The concept allows finding initial design geometries, which can be used for further optimization, and may be applied to sensors other than accelerometers. The accelerometer design presented in this paper is implemented as a MEMS device that features self-supporting piezoresistive elements. The first specimens have been characterized for shocks of up to 75,000× g in Hopkinson bar experiments and have sensitivities ranging from 0.035 to 0.23μV/Vexc./g and natural frequencies ranging from 2.7 to 3.7MHz. Also, measurement data from a 200,000× g survivability check is presented.
Source:Sensors and Actuators A: Physical, Volume 182
Robert Kuells, Siegfried Nau, Manfred Salk, Klaus Thoma
This paper reports on a novel piezoresistive high-g accelerometer design, that partially overcomes a common drawback of shock sensor concepts, namely that their bandwidth, i.e. natural frequency, cannot be increased without sacrificing sensitivity. Its figure of merit (sensitivity multiplied by frequency squared) is about 5×106 m−1. This is one order of magnitude higher than in existing designs in the literature or currently on the market. The increase is made possible by a design approach that focuses on displacements rather than stresses and the utilization of a spring–mass system related parameter called the “geometrical constant”. The concept allows finding initial design geometries, which can be used for further optimization, and may be applied to sensors other than accelerometers. The accelerometer design presented in this paper is implemented as a MEMS device that features self-supporting piezoresistive elements. The first specimens have been characterized for shocks of up to 75,000× g in Hopkinson bar experiments and have sensitivities ranging from 0.035 to 0.23μV/Vexc./g and natural frequencies ranging from 2.7 to 3.7MHz. Also, measurement data from a 200,000× g survivability check is presented.
Design and characterization of a photo-sensor based force measurement unit (FMU)
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Gwang Min Gu, Yong Kyun Shin, Jina Son, Jung Kim
This paper presents the design and development of a customizable force measurement unit (FMU). The sensing mechanism is based on a monolithic structure incorporating a flexure with an interrupter and photo-sensors. The FMU is able to measure force by the deformation of the flexure, which results in a difference in the intensity of infrared light detected. Owing to the simplicity of the proposed structure and the sensing method, the FMU is an adaptable sensing platform with high design flexibility. We performed finite element method (FEM) simulations to systematically determine a set of design variables and characterized the static and dynamic properties of the fabricated FMU. We demonstrated that the FMU shows comparable performance to a widely used off-the-shelf sensor (Mini45, ATI) and can be used as a compact and accurate force sensor for various applications.
Source:Sensors and Actuators A: Physical, Volume 182
Gwang Min Gu, Yong Kyun Shin, Jina Son, Jung Kim
This paper presents the design and development of a customizable force measurement unit (FMU). The sensing mechanism is based on a monolithic structure incorporating a flexure with an interrupter and photo-sensors. The FMU is able to measure force by the deformation of the flexure, which results in a difference in the intensity of infrared light detected. Owing to the simplicity of the proposed structure and the sensing method, the FMU is an adaptable sensing platform with high design flexibility. We performed finite element method (FEM) simulations to systematically determine a set of design variables and characterized the static and dynamic properties of the fabricated FMU. We demonstrated that the FMU shows comparable performance to a widely used off-the-shelf sensor (Mini45, ATI) and can be used as a compact and accurate force sensor for various applications.
Highlights
► The proposed force measurement unit (FMU) operates without the use of an external amplifier. ► The FMU is easily customized to various requirements such as capacity, size, and weight. ► The developed FMU was characterized through the experiments under static and dynamic loading conditions. ► The use of dual photo-sensors can effectively cancel out the interference generated by the shear forces. ► The results show comparable performance of both conditions to a widely used off-the-shelf sensor.Composite materials with embedded photonic crystal fiber interferometric sensors
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Ginu Rajan, Manjusha Ramakrishnan, Piotr Lesiak, Yuliya Semenova, Tomasz Wolinski, Anna Boczkowska, Gerald Farrell
A feasibility study of smart composite materials with embedded photonic crystal fiber (PCF) sensors for measurements of local and average strain and temperature is presented in this paper. For this purpose a composite material sample with embedded fiber sensors is fabricated and characterized. For temperature independent local strain measurements a short length PCF modal interferometer is utilized, while for an average strain measurement a polarization maintaining PCF Sagnac interferometric sensor is used. The strain and temperature sensitivities of a buffer coated and a buffer stripped PM-PCF Sagnac fiber loop mirror sensors are measured in free space and compared to those for similar sensors embedded in the composite material. It is found that the Sagnac interferometer with an acrylate coated PCF embedded in the composite material shows the same response as the one in free space while the unbuffered PCF Sagnac interferometric sensor which is temperature insensitive in free space shows significant temperature sensitivity when embedded in the composite material sample. A fiber Bragg grating array is also embedded in the composite material for comparison of the strain and temperature measured by the PCF modal interferometers. The results obtained in this study demonstrate that PCF sensors are a feasible technology that can be adapted for composite material strain measurement.
Source:Sensors and Actuators A: Physical, Volume 182
Ginu Rajan, Manjusha Ramakrishnan, Piotr Lesiak, Yuliya Semenova, Tomasz Wolinski, Anna Boczkowska, Gerald Farrell
A feasibility study of smart composite materials with embedded photonic crystal fiber (PCF) sensors for measurements of local and average strain and temperature is presented in this paper. For this purpose a composite material sample with embedded fiber sensors is fabricated and characterized. For temperature independent local strain measurements a short length PCF modal interferometer is utilized, while for an average strain measurement a polarization maintaining PCF Sagnac interferometric sensor is used. The strain and temperature sensitivities of a buffer coated and a buffer stripped PM-PCF Sagnac fiber loop mirror sensors are measured in free space and compared to those for similar sensors embedded in the composite material. It is found that the Sagnac interferometer with an acrylate coated PCF embedded in the composite material shows the same response as the one in free space while the unbuffered PCF Sagnac interferometric sensor which is temperature insensitive in free space shows significant temperature sensitivity when embedded in the composite material sample. A fiber Bragg grating array is also embedded in the composite material for comparison of the strain and temperature measured by the PCF modal interferometers. The results obtained in this study demonstrate that PCF sensors are a feasible technology that can be adapted for composite material strain measurement.
A three-channel thermoelectric RF MEMS power sensor for GaAs MMIC applications
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Zhiqiang Zhang, Xiaoping Liao
This paper presents an X-band three-channel thermoelectric radio frequency microelectromechanical systems (RF MEMS) power sensor with three inputs and one output, in order to measure the power with up to three RF signals. This power sensor is based on the principle of power–heat–voltage conversion and accomplished with the GaAs monolithic microwave integrated circuit (MMIC) technology. The three inputs are used to transmit RF signals over coplanar waveguide (CPW) lines and the one output collects the thermovoltage. To show good electromagnetic and thermal isolations, signal crosstalks for the three-input and one-output power sensor are quantified by the S-parameters simulation and the power handling measurement, respectively. In addition, the measured power sensor has resulted in three input reflection coefficients of less than −21.5dB for frequencies up to 12GHz. Experiments demonstrate the sensor has the good linearity of the power with respect to the thermovoltage at X-band, with sensitivities of about 53.1μVmW−1, 56.3μVmW−1, 58.9μVmW−1 for the three inputs at 12GHz, respectively.
Source:Sensors and Actuators A: Physical, Volume 182
Zhiqiang Zhang, Xiaoping Liao
This paper presents an X-band three-channel thermoelectric radio frequency microelectromechanical systems (RF MEMS) power sensor with three inputs and one output, in order to measure the power with up to three RF signals. This power sensor is based on the principle of power–heat–voltage conversion and accomplished with the GaAs monolithic microwave integrated circuit (MMIC) technology. The three inputs are used to transmit RF signals over coplanar waveguide (CPW) lines and the one output collects the thermovoltage. To show good electromagnetic and thermal isolations, signal crosstalks for the three-input and one-output power sensor are quantified by the S-parameters simulation and the power handling measurement, respectively. In addition, the measured power sensor has resulted in three input reflection coefficients of less than −21.5dB for frequencies up to 12GHz. Experiments demonstrate the sensor has the good linearity of the power with respect to the thermovoltage at X-band, with sensitivities of about 53.1μVmW−1, 56.3μVmW−1, 58.9μVmW−1 for the three inputs at 12GHz, respectively.
Experimental research on hysteresis effects in GMR sensors for analog measurement applications
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Shen Liu, Qi Huang, Yong Li, Wei Zhen
A Wheatstone bridge GMR sensor can be used for analog magnetic field measurements. This paper deals with hysteresis effects in GMR sensor, which is the major source of measurement error. Experiments are conducted by measuring hysteresis curves between applied magnetic field and sensor output voltage with different typical initial magnetization states. GMR sensor has two operation modes: bipolar and unipolar. Bipolar operation means internal magnetization pattern of GMR sensor changes direction during operation range. This mode is inappropriate for direct measurement, as experimental results indicate that the shape of measured curves with the same range of applied magnetic field may be severely distorted due to different initial magnetization states. Unipolar operation is an intermediate process of bipolar operation with invariant magnetization direction. Its input–output relationship is almost linear that is especially suitable for measurement. The principal measurement error within unipolar operation is DC offset voltage, which is induced by remanence. It can be fixed by saturating GMR sensor before operation.
Source:Sensors and Actuators A: Physical, Volume 182
Shen Liu, Qi Huang, Yong Li, Wei Zhen
A Wheatstone bridge GMR sensor can be used for analog magnetic field measurements. This paper deals with hysteresis effects in GMR sensor, which is the major source of measurement error. Experiments are conducted by measuring hysteresis curves between applied magnetic field and sensor output voltage with different typical initial magnetization states. GMR sensor has two operation modes: bipolar and unipolar. Bipolar operation means internal magnetization pattern of GMR sensor changes direction during operation range. This mode is inappropriate for direct measurement, as experimental results indicate that the shape of measured curves with the same range of applied magnetic field may be severely distorted due to different initial magnetization states. Unipolar operation is an intermediate process of bipolar operation with invariant magnetization direction. Its input–output relationship is almost linear that is especially suitable for measurement. The principal measurement error within unipolar operation is DC offset voltage, which is induced by remanence. It can be fixed by saturating GMR sensor before operation.
Original embedded impedance analyzer for piezoelectric sensors
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Abdulrahman Hamed, Etienne Tisserand, Patrick Schweitzer, Yves Berviller
In this paper we present the design, simulation and implementation of an embedded impedance analyzer primarily intended for use with piezoelectric transducers. It is currently set to perform complex impedance measurements above 1Ω in the range 0–5MHz. The method does not require the current to be measured and allows grounded transducers to be analyzed in real time. It is based on feedback control of the transducer voltage using a digital resistive network R G. Real and imaginary parts of the impedance are determined from R G and the phase during a fast frequency sweeping. The entire digital architecture is implemented in an Field Programmable Gate Array (FPGA) Stratix II board with a 100MHz frequency clock. The system is developed in a virtual environment in which the transducer is modeled by a Butterworth van Dycke structure. The duration of the analysis is optimized in real time by adjusting the sweeping speed according to changes in R G. Further, our analyzer is tested in real time and in a real situation with two 2MHz ultrasonic transducers. The duration of the analysis is equal to 2ms and the measurements are accurate to within 1% within the resonant zone of the transducers.
Source:Sensors and Actuators A: Physical, Volume 182
Abdulrahman Hamed, Etienne Tisserand, Patrick Schweitzer, Yves Berviller
In this paper we present the design, simulation and implementation of an embedded impedance analyzer primarily intended for use with piezoelectric transducers. It is currently set to perform complex impedance measurements above 1Ω in the range 0–5MHz. The method does not require the current to be measured and allows grounded transducers to be analyzed in real time. It is based on feedback control of the transducer voltage using a digital resistive network R G. Real and imaginary parts of the impedance are determined from R G and the phase during a fast frequency sweeping. The entire digital architecture is implemented in an Field Programmable Gate Array (FPGA) Stratix II board with a 100MHz frequency clock. The system is developed in a virtual environment in which the transducer is modeled by a Butterworth van Dycke structure. The duration of the analysis is optimized in real time by adjusting the sweeping speed according to changes in R G. Further, our analyzer is tested in real time and in a real situation with two 2MHz ultrasonic transducers. The duration of the analysis is equal to 2ms and the measurements are accurate to within 1% within the resonant zone of the transducers.
Uniaxial stress dependence of the dielectric permittivity of the Na0.5Bi0.5TiO3–KTaO3 system
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Jakob König, Danilo Suvorov
The dependence of the dielectric permittivity on the uniaxial compressive stress was investigated for the case of Na0.5Bi0.5TiO3–KTaO3 ceramics. Special attention was focused on the reversibility of the permittivity–stress dependence. The results were connected with the transition from the ferroelectric to the relaxor state in the concentration region between 5 and 10mol% of KTaO3. With this transition, the permittivity–stress dependence changes from non-linear, irreversible and time dependent to linear, instantaneous and reversible. In samples with 10–30mol% of KTaO3 some minor relaxations were observed, which were suppressed under a small pre-stress. The stress sensitivity was higher at a lower measuring frequency and the reversible change of the permittivity was the highest in the sample with 20mol% of KTaO3 (the absolute and relative changes of permittivity were 196.5 and 10.3%, respectively, at a pressure change between 8 and 219MPa). The obtained results are discussed in terms of the macrodomains/microdomains’ reorientation under applied pressure and the transition from one to another with a change of the KTaO3 concentration. The use of Na0.5Bi0.5TiO3–KTaO3 ceramics for device applications is described.
Source:Sensors and Actuators A: Physical, Volume 182
Jakob König, Danilo Suvorov
The dependence of the dielectric permittivity on the uniaxial compressive stress was investigated for the case of Na0.5Bi0.5TiO3–KTaO3 ceramics. Special attention was focused on the reversibility of the permittivity–stress dependence. The results were connected with the transition from the ferroelectric to the relaxor state in the concentration region between 5 and 10mol% of KTaO3. With this transition, the permittivity–stress dependence changes from non-linear, irreversible and time dependent to linear, instantaneous and reversible. In samples with 10–30mol% of KTaO3 some minor relaxations were observed, which were suppressed under a small pre-stress. The stress sensitivity was higher at a lower measuring frequency and the reversible change of the permittivity was the highest in the sample with 20mol% of KTaO3 (the absolute and relative changes of permittivity were 196.5 and 10.3%, respectively, at a pressure change between 8 and 219MPa). The obtained results are discussed in terms of the macrodomains/microdomains’ reorientation under applied pressure and the transition from one to another with a change of the KTaO3 concentration. The use of Na0.5Bi0.5TiO3–KTaO3 ceramics for device applications is described.
Highlights
► Lead-free Na0.5Bi0.5TiO3–KTaO3 materials for pressure sensing. ► Dielectric permittivity–uniaxial stress dependence. ► Change in the permittivity–stress dependence with change in domain structure. ► Instantaneous and reversible dependence in relaxor compositions.Lead-free piezoelectric single crystal based 1–3 composites for ultrasonic transducer applications
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Dan Zhou, Kwok Ho Lam, Yan Chen, Qinhui Zhang, Yat Ching Chiu, Haosu Luo, Jiyan Dai, Helen Lai Wa Chan
In this work, lead-free 1–3 composites based on piezoelectric 0.947Na0.5Bi0.5TiO3–0.053BaTiO3 (NBT–0.053BT) single crystal and epoxy are fabricated for ultrasonic transducer applications by a modified dice-and-fill method. Excellent properties for ultrasonic transducer applications have been achieved, such as high electromechanical coupling coefficient (k t =73%), lower acoustic impedance (Z =16MRayl) and moderate dielectric constant. Based on this lead-free piezoelectric single crystal composite, single-element ultrasonic transducer and linear array have been fabricated and characterized. Both types of transducers exhibit similar performance with broad bandwidth of exceeding 100%. The promising results show that these lead-free composites have the potential to be used for high-performance ultrasonic transducers.
Source:Sensors and Actuators A: Physical, Volume 182
Dan Zhou, Kwok Ho Lam, Yan Chen, Qinhui Zhang, Yat Ching Chiu, Haosu Luo, Jiyan Dai, Helen Lai Wa Chan
In this work, lead-free 1–3 composites based on piezoelectric 0.947Na0.5Bi0.5TiO3–0.053BaTiO3 (NBT–0.053BT) single crystal and epoxy are fabricated for ultrasonic transducer applications by a modified dice-and-fill method. Excellent properties for ultrasonic transducer applications have been achieved, such as high electromechanical coupling coefficient (k t =73%), lower acoustic impedance (Z =16MRayl) and moderate dielectric constant. Based on this lead-free piezoelectric single crystal composite, single-element ultrasonic transducer and linear array have been fabricated and characterized. Both types of transducers exhibit similar performance with broad bandwidth of exceeding 100%. The promising results show that these lead-free composites have the potential to be used for high-performance ultrasonic transducers.
Room temperature ultra-sensitive resistive humidity sensor based on single zinc oxide nanowire
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Nima Mohseni Kiasari, Saeid Soltanian, Bobak Gholamkhass, Peyman Servati
A highly sensitive relative humidity (RH) sensor is fabricated by a low-cost and scalable dielectrophoresis method that places a single crystalline zinc oxide nanowire (ZnO NWs) between pre-patterned electrodes in a freestanding device structure. The resistive device demonstrates an exponential sensitivity of more than 5 decades to changes from dry air to 60% RH at room temperature, indebted to a subthreshold carrier modulation due to the high surface-to-volume-ratio and completely exposed NW surface that facilitates surface physisorption of water molecules. Transient and temperature-dependence measurements signify a reproducible sensing performance and an Arrhenius behavior with activation energy of 0.6eV, expected for these metal oxide semiconductors. These results demonstrate the potential of such nanoscale devices for accurate monitoring of RH in different applications, including fuel cells and automotive sensors, smart clothing, smart food packaging and sensor networks.
Source:Sensors and Actuators A: Physical, Volume 182
Nima Mohseni Kiasari, Saeid Soltanian, Bobak Gholamkhass, Peyman Servati
A highly sensitive relative humidity (RH) sensor is fabricated by a low-cost and scalable dielectrophoresis method that places a single crystalline zinc oxide nanowire (ZnO NWs) between pre-patterned electrodes in a freestanding device structure. The resistive device demonstrates an exponential sensitivity of more than 5 decades to changes from dry air to 60% RH at room temperature, indebted to a subthreshold carrier modulation due to the high surface-to-volume-ratio and completely exposed NW surface that facilitates surface physisorption of water molecules. Transient and temperature-dependence measurements signify a reproducible sensing performance and an Arrhenius behavior with activation energy of 0.6eV, expected for these metal oxide semiconductors. These results demonstrate the potential of such nanoscale devices for accurate monitoring of RH in different applications, including fuel cells and automotive sensors, smart clothing, smart food packaging and sensor networks.
Multi-frequency electromagnetic energy harvester using a magnetic spring cantilever
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
Abu Riduan Md. Foisal, Chinsuk Hong, Gwiy-Sang Chung
In this study, an array of four generators is designed and fabricated to demonstrate the possibility of harvesting energy from different environmental frequencies. The magnetic spring technique is used as a cantilever to scavenge energy from low frequency vibrations. Initially, a single frequency energy harvester is optimized in terms of the number of turns, coil width, and coil position. Finally, two configurations of a multi-generator are fabricated. In model A, four individual generators are placed side by side; whereas in model B, the generators are placed one above the other. The experimental results show that both models can operate in the 7–10Hz frequency range. The power densities of model A and model B are 21.92μW/cm3 and 52.02μW/cm3, respectively, at an acceleration of 0.5 g.
Source:Sensors and Actuators A: Physical, Volume 182
Abu Riduan Md. Foisal, Chinsuk Hong, Gwiy-Sang Chung
In this study, an array of four generators is designed and fabricated to demonstrate the possibility of harvesting energy from different environmental frequencies. The magnetic spring technique is used as a cantilever to scavenge energy from low frequency vibrations. Initially, a single frequency energy harvester is optimized in terms of the number of turns, coil width, and coil position. Finally, two configurations of a multi-generator are fabricated. In model A, four individual generators are placed side by side; whereas in model B, the generators are placed one above the other. The experimental results show that both models can operate in the 7–10Hz frequency range. The power densities of model A and model B are 21.92μW/cm3 and 52.02μW/cm3, respectively, at an acceleration of 0.5 g.
A new type of multi-degree-of-freedom miniaturization actuator using symmetric piezoelectric pusher element for a pocket sun-tracking system
03 July 2012,
07:56:06
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 182
S.C. Shen, P.C. Tsai, Y.J. Wang, H.J. Huang
This study presents a 2×2 pocket sun-tracking system that combines a multi-degree-of-freedom motion (multi-DOF) piezoelectric actuator with a hemisphere concentrator lens. The multi-DOF piezoelectric actuator consists of two parallel symmetric piezoelectric pusher elements (SPPEs) and ball-bearing bases. The proposed multi-DOF piezoelectric actuator uses three SPPE vibration modes to rotate a hemisphere concentrator lens along three perpendicular axes. The experiment in this study demonstrates how the 2×2 pocket sun-tracking system is driven by different modes and rotates around the X-, Y-, and Z-axes. When applying 3Vpp to a multi-DOF piezoelectric actuator, the rotating accuracies of the 2×2 pocket sun-tracking system along the X-, Y-, and Z-axes were 0.022°, 0.022°, and 0.007°, respectively, and the driving frequencies along the X-, Y-, and Z-axes were 223.4kHz, 223.2kHz, and 225kHz, respectively. The results confirm that the 2×2 pocket sun-tracking system was accomplished successfully using the multi-DOF piezoelectric actuator.
Source:Sensors and Actuators A: Physical, Volume 182
S.C. Shen, P.C. Tsai, Y.J. Wang, H.J. Huang
This study presents a 2×2 pocket sun-tracking system that combines a multi-degree-of-freedom motion (multi-DOF) piezoelectric actuator with a hemisphere concentrator lens. The multi-DOF piezoelectric actuator consists of two parallel symmetric piezoelectric pusher elements (SPPEs) and ball-bearing bases. The proposed multi-DOF piezoelectric actuator uses three SPPE vibration modes to rotate a hemisphere concentrator lens along three perpendicular axes. The experiment in this study demonstrates how the 2×2 pocket sun-tracking system is driven by different modes and rotates around the X-, Y-, and Z-axes. When applying 3Vpp to a multi-DOF piezoelectric actuator, the rotating accuracies of the 2×2 pocket sun-tracking system along the X-, Y-, and Z-axes were 0.022°, 0.022°, and 0.007°, respectively, and the driving frequencies along the X-, Y-, and Z-axes were 223.4kHz, 223.2kHz, and 225kHz, respectively. The results confirm that the 2×2 pocket sun-tracking system was accomplished successfully using the multi-DOF piezoelectric actuator.
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