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Photofield effect and photoresponse properties of the transparent oxide-based BaInZnO thin-film transistors
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
The photoresponse properties of the BaInZnO (BIZO) thin film transistors were investigated by the output and transfer characteristics. The drain current of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-on and turn-off states is significantly increased with light illumination. The photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 4.56 and 6.27, respectively, while the photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 6.14 and 11.714, respectively. The photoresponse values of the transistors in turn-off state are lower than that of turn-on state. This indicates that the dominant photocurrent mechanism of the BIZO transistors is based on photovoltaic effects. The photoresponse properties of the BIZO transistors were improved with the increasing doping ratio of Ba. The obtained results indicate that BIZO transistors could be used as a photosensor for optoelectronic applications.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
The photoresponse properties of the BaInZnO (BIZO) thin film transistors were investigated by the output and transfer characteristics. The drain current of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-on and turn-off states is significantly increased with light illumination. The photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 4.56 and 6.27, respectively, while the photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 6.14 and 11.714, respectively. The photoresponse values of the transistors in turn-off state are lower than that of turn-on state. This indicates that the dominant photocurrent mechanism of the BIZO transistors is based on photovoltaic effects. The photoresponse properties of the BIZO transistors were improved with the increasing doping ratio of Ba. The obtained results indicate that BIZO transistors could be used as a photosensor for optoelectronic applications.
Fabrication and characterization of a double-heater based MEMS thermal flow sensor
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This paper presents a micro flow sensor based on two heaters acting also as temperature sensors. The two heating/sensing elements of the sensor are arranged in the diagonal arms of the Wheatstone bridge and suspended in an airflow channel by solid beams. The length of the heater and the distance between the heaters were optimized by numerical modeling. The solid beams were fabricated by a heavily doped p-type silicon layer and a silicon nitride layer, which was immune to airflow disturbances and thermal noises. The experimental results indicated that the micro flow sensor with a high sensitivity of 0.30mV/(ml/min) exhibited an excellent linear response within the range of 0.5–6sccm. This micro sensor demonstrated great potentials in biological applications, micro gas chromatography systems, medical instrumentation and process control.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This paper presents a micro flow sensor based on two heaters acting also as temperature sensors. The two heating/sensing elements of the sensor are arranged in the diagonal arms of the Wheatstone bridge and suspended in an airflow channel by solid beams. The length of the heater and the distance between the heaters were optimized by numerical modeling. The solid beams were fabricated by a heavily doped p-type silicon layer and a silicon nitride layer, which was immune to airflow disturbances and thermal noises. The experimental results indicated that the micro flow sensor with a high sensitivity of 0.30mV/(ml/min) exhibited an excellent linear response within the range of 0.5–6sccm. This micro sensor demonstrated great potentials in biological applications, micro gas chromatography systems, medical instrumentation and process control.
Highlights
► The device with two heaters working as temperature sensing elements is proposed for the first time. ► The fabrication process of the MEMS based gas flow sensor with optimum heater length and the heaters distance was presented. ► The micro gas flow sensor was applied to flow rate measurement with characterization results described and discussed.Piezoelectric properties of PVDF/MWCNT nanofiber using near-field electrospinning
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This study reports the use of near-field electrospinning to fabricate polyvinylidene fluoride (PVDF) piezoelectric nanofibers mixed with multiwalled-carbon nanotubes (MWCNT). This study also investigates the mechanical strength and piezoelectric characteristics of a single PVDF/MWCNT nanofiber. The morphology and polarization intensity of piezoelectric fiber can be controlled by adjusting the traveling velocity of the X–Y stage, the DC voltage, and the gap between the needle and collection plate. The optimal parameters of the PVDF solution, such as the PVDF powder weight percentage and MWCNT content, were also determined. X-ray diffraction (XRD) analysis shows a high diffraction peak at 2θ =20.8° in the piezoelectric crystal β-phase structure. ANSYS finite element analysis (FEA) software with coupled field analysis was used to realize piezoelectric actuation behavior of the PVDF fibers. A nano-indentation test (NanoIndenter XP System, MTS co.) was used to investigate Young's modulus of the PVDF fiber. Finally, the fixed–fixed beam structures of PVDF composite fibers were tested using a DC voltage supply. Comparing the polarized fiber with non-polarized fibers, the measurement of the center displacements as a function of electric field was conducted and characterized.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This study reports the use of near-field electrospinning to fabricate polyvinylidene fluoride (PVDF) piezoelectric nanofibers mixed with multiwalled-carbon nanotubes (MWCNT). This study also investigates the mechanical strength and piezoelectric characteristics of a single PVDF/MWCNT nanofiber. The morphology and polarization intensity of piezoelectric fiber can be controlled by adjusting the traveling velocity of the X–Y stage, the DC voltage, and the gap between the needle and collection plate. The optimal parameters of the PVDF solution, such as the PVDF powder weight percentage and MWCNT content, were also determined. X-ray diffraction (XRD) analysis shows a high diffraction peak at 2θ =20.8° in the piezoelectric crystal β-phase structure. ANSYS finite element analysis (FEA) software with coupled field analysis was used to realize piezoelectric actuation behavior of the PVDF fibers. A nano-indentation test (NanoIndenter XP System, MTS co.) was used to investigate Young's modulus of the PVDF fiber. Finally, the fixed–fixed beam structures of PVDF composite fibers were tested using a DC voltage supply. Comparing the polarized fiber with non-polarized fibers, the measurement of the center displacements as a function of electric field was conducted and characterized.
Comparative displacement study of bilayer actuators comprising of conducting polymers, fabricated from polypyrrole, poly(3,4-ethylenedioxythiophene) or poly(3,4-propylenedioxythiophene)
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
The stress gradient generated due to electrochemical oxidation/reduction of a conducting polymer in a bilayer actuator causes a bending movement. Here we report a comparative study of the displacement of bilayer actuators prepared using different conducting polymers. The effects of conducting polymers obtained from electrochemical or chemical synthesis route: different polymers (polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) PEDOT and poly(3,3-dihexyl-3-4-dihydro-2H-thieno[3,4b][1,4]-dioxepine [PProDOT(Hx)2]); and different electrolytes (0.1M lithium trifluromethanesulfonate/propylenecarbonate (LiTFSI/PC) and 1-ethyl-3-methyl imidazolium trifluromethanesulfonate (EMITFSI)) on the displacement amplitude and displacement patterns of these actuators were investigated and compared. The results indicate that the bilayer actuator consisting of an electrochemically synthesized conducting polymer exhibits far greater displacements compared to chemically synthesized polymers at the same stimulating voltage. Similarly, amongst the three conducting polymers considered, the PPY actuator showed greater displacement followed by PProDOT and PEDOT. Furthermore, the use of different electrolyte solution during polymerization as well as during actuation was found to affect not only displacement distance but also its pattern.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
The stress gradient generated due to electrochemical oxidation/reduction of a conducting polymer in a bilayer actuator causes a bending movement. Here we report a comparative study of the displacement of bilayer actuators prepared using different conducting polymers. The effects of conducting polymers obtained from electrochemical or chemical synthesis route: different polymers (polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) PEDOT and poly(3,3-dihexyl-3-4-dihydro-2H-thieno[3,4b][1,4]-dioxepine [PProDOT(Hx)2]); and different electrolytes (0.1M lithium trifluromethanesulfonate/propylenecarbonate (LiTFSI/PC) and 1-ethyl-3-methyl imidazolium trifluromethanesulfonate (EMITFSI)) on the displacement amplitude and displacement patterns of these actuators were investigated and compared. The results indicate that the bilayer actuator consisting of an electrochemically synthesized conducting polymer exhibits far greater displacements compared to chemically synthesized polymers at the same stimulating voltage. Similarly, amongst the three conducting polymers considered, the PPY actuator showed greater displacement followed by PProDOT and PEDOT. Furthermore, the use of different electrolyte solution during polymerization as well as during actuation was found to affect not only displacement distance but also its pattern.
NiTi/Pb(Zr0.52Ti0.48)O3 thin film heterostructures for vibration damping in MEMS
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
We report on the damping properties of NiTi/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructures using nanoindentation technique. Creep and impact tests were performed to obtain hardness (H), elastic modulus (E r ), damping factor (tan δ) and figure of merit (FOM. A hold time of 30s during creep test shows significant improvement in damping factor for NiTi/PZT (0.046) and CrTiN/NiTi/PZT (0.050). Impact test demonstrates highest damping capacity with lowest coefficient of restitution (0.30) in CrTiN/NiTi/PZT. Higher hardness (19.8GPa) and excellent figure of merit (0.751) in CrTiN/NiTi/PZT makes them very attractive damping material for microelectromechanical systems (MEMS).
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
We report on the damping properties of NiTi/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructures using nanoindentation technique. Creep and impact tests were performed to obtain hardness (H), elastic modulus (E r ), damping factor (tan δ) and figure of merit (FOM. A hold time of 30s during creep test shows significant improvement in damping factor for NiTi/PZT (0.046) and CrTiN/NiTi/PZT (0.050). Impact test demonstrates highest damping capacity with lowest coefficient of restitution (0.30) in CrTiN/NiTi/PZT. Higher hardness (19.8GPa) and excellent figure of merit (0.751) in CrTiN/NiTi/PZT makes them very attractive damping material for microelectromechanical systems (MEMS).
Development of a multilayer microfluidic device integrated with a PDMS-cellulose composite film for sample pre-treatment and immunoassay
31 January 2013,
09:35:13
15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This work presents an integrated multilayer microfluidic device enabling raw sample pre-treatment and immunoassay based detection where a polydimethylsiloxane (PDMS)-cellulose composite film was used to isolate plasma from raw samples based on the cross-flow principle. The PDMS-cellulose composite film was prepared by the dip-coating method and its morphologies were studied by the SEM technology and the bonding strength was quantified by atmospheric pressure experiments. The integrated microfluidic device was used to detect human immunoglobulin (IgG) in rat whole blood samples, with a quantified detection range of 0.5–5μg/mL and a correlation coefficient of 0.978. A raw urine sample was also tested by the integrated microfluidic device, producing a detection range of 0.6–25μg/mL with a correlation coefficient of 0.969 for human IgG. This integrated microfluidic device may function as a platform technology, enabling on-site detection of raw clinical samples.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193
This work presents an integrated multilayer microfluidic device enabling raw sample pre-treatment and immunoassay based detection where a polydimethylsiloxane (PDMS)-cellulose composite film was used to isolate plasma from raw samples based on the cross-flow principle. The PDMS-cellulose composite film was prepared by the dip-coating method and its morphologies were studied by the SEM technology and the bonding strength was quantified by atmospheric pressure experiments. The integrated microfluidic device was used to detect human immunoglobulin (IgG) in rat whole blood samples, with a quantified detection range of 0.5–5μg/mL and a correlation coefficient of 0.978. A raw urine sample was also tested by the integrated microfluidic device, producing a detection range of 0.6–25μg/mL with a correlation coefficient of 0.969 for human IgG. This integrated microfluidic device may function as a platform technology, enabling on-site detection of raw clinical samples.
Sensitive electro-optic sensor using KTa1−xNbxO3 crystal
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
KTa1−x Nb x O3 (KTN) is well-known as a crystal having very large EO coefficients. High-quality KTN crystal growth technology has been recently developed, and several applications of KTN are being investigated. We tried to use KTN to make an electric field sensor and, studied its electro-optic properties for this purpose. The modulation depth of the sensor was about 20 times deeper than that of the ZnTe sensor used in our previous system in the frequency range from DC to 1.5MHz.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
KTa1−x Nb x O3 (KTN) is well-known as a crystal having very large EO coefficients. High-quality KTN crystal growth technology has been recently developed, and several applications of KTN are being investigated. We tried to use KTN to make an electric field sensor and, studied its electro-optic properties for this purpose. The modulation depth of the sensor was about 20 times deeper than that of the ZnTe sensor used in our previous system in the frequency range from DC to 1.5MHz.
Low power UV photodetection characteristics of cross-linked ZnO nanorods/nanotetrapods grown on silicon chip
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
High-quality cross-linked ZnO nanorods/nanotetrapods have been successfully synthesized via thermal evaporation of Zn metal grains on Si (100) substrates. The growth mechanism for the formation of such cross-linked ZnO nanorods is discussed. The morphological, structural and optical properties of the nanorods have been investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence techniques. Cross-linked ZnO nanorods-based metal-semiconductor-metal UV detectors (Ag-ZnONRs-Ag MSM PD) were fabricated. The device showed a sensitivity of 595. The responsivity (R) of the device is 0.63AW−1, which is 10 times higher than that reported for ZnO-based PDs. Under low power illumination (365nm, 1.5mW/cm2), the device showed a relatively fast response and baseline recovery for UV detection. The prototype device shows a simple method for cross-linked nanorods synthesis and demonstrates the possibility of constructing nanoscale photodetectors for nano-optics applications.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
High-quality cross-linked ZnO nanorods/nanotetrapods have been successfully synthesized via thermal evaporation of Zn metal grains on Si (100) substrates. The growth mechanism for the formation of such cross-linked ZnO nanorods is discussed. The morphological, structural and optical properties of the nanorods have been investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence techniques. Cross-linked ZnO nanorods-based metal-semiconductor-metal UV detectors (Ag-ZnONRs-Ag MSM PD) were fabricated. The device showed a sensitivity of 595. The responsivity (R) of the device is 0.63AW−1, which is 10 times higher than that reported for ZnO-based PDs. Under low power illumination (365nm, 1.5mW/cm2), the device showed a relatively fast response and baseline recovery for UV detection. The prototype device shows a simple method for cross-linked nanorods synthesis and demonstrates the possibility of constructing nanoscale photodetectors for nano-optics applications.
Fully differential current-mode MEMS dual-axis optical inclination sensor
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
We demonstrate a tilt sensor fabricated in the MultiMEMS SensoNor process. The system uses an array of four photodiodes to determine the position of a bubble fluid pendulum and the tilt angle with respect to gravity. The entire sensing structure was manufactured in the commercial MultiMEMS process so it can be easily reproduced in large quantities. The device was tested across a range of inclinations to verify performance in sensing two axis tilt. Results for tilt measurements from −45° to +45° show correlation to expected values with an R 2 value of 0.99595. The resolution of the device is 0.5° at zero degrees of inclination. The outputs of the sensor are mapped to a fit equation to allow calculation of inclination angle. The small size, simple structure, and minimal power consumption make it well-suited for a number of research and industrial applications.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
We demonstrate a tilt sensor fabricated in the MultiMEMS SensoNor process. The system uses an array of four photodiodes to determine the position of a bubble fluid pendulum and the tilt angle with respect to gravity. The entire sensing structure was manufactured in the commercial MultiMEMS process so it can be easily reproduced in large quantities. The device was tested across a range of inclinations to verify performance in sensing two axis tilt. Results for tilt measurements from −45° to +45° show correlation to expected values with an R 2 value of 0.99595. The resolution of the device is 0.5° at zero degrees of inclination. The outputs of the sensor are mapped to a fit equation to allow calculation of inclination angle. The small size, simple structure, and minimal power consumption make it well-suited for a number of research and industrial applications.
Highlights
► Design and testing of a MEMS inclination sensor. ► A fluid pendulum affects light transmission to photodiodes. ► Small size, robust operation, and straightforward post-processing. ► Four quadrant design leads to differential measurement and translinear readout. ► Commercial process and minimal post-processing allow for high volume production scaling.Current sensor based on inline microfiber Mach–Zehnder interferometer
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A compact inline microfiber Mach–Zehnder interferometer (MMZI) is proposed for current sensor application. The MMZI is fabricated using flame-brushing technique where both transition parts of a microfiber are tapered to reduce the waist diameter and form an interference region. The fabricated MMZI shows a good interference fringes with a high extinction ratio of 15dB. The fringe spacing can be tuned from 3.95nm to 3.36nm as the length of the interference region is varied from 4.5mm to 6mm. The shift in the interference fringes is observed to be linearly proportional to the square of the amount of the flowing current and the slope efficiency of the sensor is obtained at 140.26pm/A2 with a correlation coefficient of 0.99. Since the refractive index of the fiber core has a different temperature coefficient than that of air, the interferometer can be used as a current sensor by placing the current carrying wire in contact with the waist region of the second part of the tapered fiber.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A compact inline microfiber Mach–Zehnder interferometer (MMZI) is proposed for current sensor application. The MMZI is fabricated using flame-brushing technique where both transition parts of a microfiber are tapered to reduce the waist diameter and form an interference region. The fabricated MMZI shows a good interference fringes with a high extinction ratio of 15dB. The fringe spacing can be tuned from 3.95nm to 3.36nm as the length of the interference region is varied from 4.5mm to 6mm. The shift in the interference fringes is observed to be linearly proportional to the square of the amount of the flowing current and the slope efficiency of the sensor is obtained at 140.26pm/A2 with a correlation coefficient of 0.99. Since the refractive index of the fiber core has a different temperature coefficient than that of air, the interferometer can be used as a current sensor by placing the current carrying wire in contact with the waist region of the second part of the tapered fiber.
Ion beam sputtered Ge–Si–O amorphous thin films for microbolometer infrared detectors and their application in earth sensors
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
Ge–Si–O thin films are prepared by ion beam sputtering technique with argon (Ar) alone and argon and oxygen as sputtering species, using sputtering targets of different compositions of Ge and SiO2. The deposited thin films are amorphous in nature and have chemical compositions close to that of the target. The study of electrical properties has shown that the activation energy and hence the thermistor constant (β) and electrical resistivity (ρ) are sensitive to oxygen flow rate, and they are the least for thin films prepared with Ar alone as the sputtering species. Different thermal isolation structures (TIS), consisting of silicon nitride (Si3N4) membrane of different thicknesses, Ge–Si–O thin film and, chromium coating on the rear side of the membrane, are prepared by bulk micro-machining technique, whose thermal conductance (G th) properties are evaluated from the experimentally determined current–voltage (I–V) characteristics. G th shows non-linear dependence with respect to raise in temperature of thin film thermistor due to Joule heating. The infrared micro-bolometer detectors, fabricated using one of the TIS structures have shown responsivity (ℜ) close to 115V/W at a bias voltage of 1.5V and chopping frequency of 10Hz, thermal time constant (τ) of 2.5ms and noise voltage of 255nV/Hz1/2 against the corresponding thermal properties of G th and thermal capacitance C th equal to 9.0×10−5 W/K and 1.95×10−7 J/K respectively. The detectors are found to have uniform spectral response in the infrared region from 2 to 20μm, and NEDT in the range from 108 to 574mK when used with an F/1 optical system. The detector, in an infrared earth sensor system, is tested before an extended black body which simulates the earth disc in the laboratory and the results are discussed.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
Ge–Si–O thin films are prepared by ion beam sputtering technique with argon (Ar) alone and argon and oxygen as sputtering species, using sputtering targets of different compositions of Ge and SiO2. The deposited thin films are amorphous in nature and have chemical compositions close to that of the target. The study of electrical properties has shown that the activation energy and hence the thermistor constant (β) and electrical resistivity (ρ) are sensitive to oxygen flow rate, and they are the least for thin films prepared with Ar alone as the sputtering species. Different thermal isolation structures (TIS), consisting of silicon nitride (Si3N4) membrane of different thicknesses, Ge–Si–O thin film and, chromium coating on the rear side of the membrane, are prepared by bulk micro-machining technique, whose thermal conductance (G th) properties are evaluated from the experimentally determined current–voltage (I–V) characteristics. G th shows non-linear dependence with respect to raise in temperature of thin film thermistor due to Joule heating. The infrared micro-bolometer detectors, fabricated using one of the TIS structures have shown responsivity (ℜ) close to 115V/W at a bias voltage of 1.5V and chopping frequency of 10Hz, thermal time constant (τ) of 2.5ms and noise voltage of 255nV/Hz1/2 against the corresponding thermal properties of G th and thermal capacitance C th equal to 9.0×10−5 W/K and 1.95×10−7 J/K respectively. The detectors are found to have uniform spectral response in the infrared region from 2 to 20μm, and NEDT in the range from 108 to 574mK when used with an F/1 optical system. The detector, in an infrared earth sensor system, is tested before an extended black body which simulates the earth disc in the laboratory and the results are discussed.
Design and characterization of a novel, robust, tri-axial force sensor
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A novel, robust, tri-axial force sensor has been developed that can be integrated into biomedical and robotic devices thanks to its size and accuracy. It features a titanium alloy body, the components of the force are separated by four basic strain sensing elements. The sensor was modeled by finite element method and the results were validated by experimental data. The sensor's diameter is 2.6mm, its height is 2mm. Proper signal conditioning tools were realized in software and hardware to achieve a sensitivity of 29.63mV/N and minimum detectable force of 4.87mN. The sensing element's structure fits electrical discharge machining technologies. The sensor was calibrated with a Nano 17 force sensor and we found that its performance is comparable to the commercial device.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A novel, robust, tri-axial force sensor has been developed that can be integrated into biomedical and robotic devices thanks to its size and accuracy. It features a titanium alloy body, the components of the force are separated by four basic strain sensing elements. The sensor was modeled by finite element method and the results were validated by experimental data. The sensor's diameter is 2.6mm, its height is 2mm. Proper signal conditioning tools were realized in software and hardware to achieve a sensitivity of 29.63mV/N and minimum detectable force of 4.87mN. The sensing element's structure fits electrical discharge machining technologies. The sensor was calibrated with a Nano 17 force sensor and we found that its performance is comparable to the commercial device.
Single axis accelerometer fabricated using printed circuit board techniques and laser ablation
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
Low-cost accelerometers could be used in applications where extremely good characteristics are not a requirement. This paper presents an accelerometer fabricated using printed circuit board (PCB) processing techniques, and laser ablation. Laser is used to remove part of the PCB substrate, releasing a mass suspended by copper beams. The structure is easily bonded to another PCB, creating a variable parallel-plate capacitor with a small gap, which capacitance varies with the movement of the mass, caused by external acceleration. The fabricated accelerometer has been compared to a commercial silicon one, showing good agreement in the measurements. The measured sensitivity was 81fF/g.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
Low-cost accelerometers could be used in applications where extremely good characteristics are not a requirement. This paper presents an accelerometer fabricated using printed circuit board (PCB) processing techniques, and laser ablation. Laser is used to remove part of the PCB substrate, releasing a mass suspended by copper beams. The structure is easily bonded to another PCB, creating a variable parallel-plate capacitor with a small gap, which capacitance varies with the movement of the mass, caused by external acceleration. The fabricated accelerometer has been compared to a commercial silicon one, showing good agreement in the measurements. The measured sensitivity was 81fF/g.
Non-adiabatic silica microfiber for strain and temperature sensors
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A non-adiabatic silica microfiber is proposed for displacement or strain and high temperature sensing for the first time. The spectral response of the microfiber depends on the difference of the effective refractive indices of the core and the cladding modes, which induces resonant wavelength shift against the strain and temperature. It is observed that the peak wavelength of the transmitted comb spectrum is blue-shifted against displacement at a rate of 4.2pm/μm. The temperature sensitivity of the device was measured to be 12.1pm/°C with an excellent linearity for temperature measurement up to 800°C.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A non-adiabatic silica microfiber is proposed for displacement or strain and high temperature sensing for the first time. The spectral response of the microfiber depends on the difference of the effective refractive indices of the core and the cladding modes, which induces resonant wavelength shift against the strain and temperature. It is observed that the peak wavelength of the transmitted comb spectrum is blue-shifted against displacement at a rate of 4.2pm/μm. The temperature sensitivity of the device was measured to be 12.1pm/°C with an excellent linearity for temperature measurement up to 800°C.
Highlights
► Non-adiabatic silica microfiber for strain and high temperature sensors. ► Strain and temperature variation induces resonant wavelength shift. ► Resonant wavelength is blue-shifted against displacement at a rate of 4.2pm/μm. ► Temperature sensitivity of the device was measured to be 12.1pm/°C.Nanogaps controlled by liquid nitrogen freezing and the effects on hydrogen gas sensor performance
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A practical strategy for the reduction of nanogap width has been investigated using liquid nitrogen freezing of Pd-sputtered elastomeric substrates. Two types of hydrogen gas sensors, in which no pre-strain and 25% elongation were applied to Pd films on the elastomeric substrates, showed extremely low detection limits of less than 300 and 200ppm, respectively, after liquid nitrogen freezing and recovery to room temperature. For the non-strained sensors, the nanogap width was measured to be about 90nm, whereas it was more reduced to 25nm on the elongated sensors. Both sensors exhibited perfect On–Off switching, fast response, and good reversibility, which are based on the nanogap open–close mechanism upon exposure to hydrogen gas. These results provide a valuable clue for reducing nanogap width, thereby improving the hydrogen-sensing capabilities of nanogap-based On–Off hydrogen sensors.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
A practical strategy for the reduction of nanogap width has been investigated using liquid nitrogen freezing of Pd-sputtered elastomeric substrates. Two types of hydrogen gas sensors, in which no pre-strain and 25% elongation were applied to Pd films on the elastomeric substrates, showed extremely low detection limits of less than 300 and 200ppm, respectively, after liquid nitrogen freezing and recovery to room temperature. For the non-strained sensors, the nanogap width was measured to be about 90nm, whereas it was more reduced to 25nm on the elongated sensors. Both sensors exhibited perfect On–Off switching, fast response, and good reversibility, which are based on the nanogap open–close mechanism upon exposure to hydrogen gas. These results provide a valuable clue for reducing nanogap width, thereby improving the hydrogen-sensing capabilities of nanogap-based On–Off hydrogen sensors.
TNT detection using a voltammetric electronic tongue based on neural networks
31 January 2013,
09:35:13
1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
We report here the use of a voltammetric electronic tongue based on simple metallic electrodes for the detection and discrimination of different concentrations of 2,4,6-trinitrotoluene (TNT) in acetonitrile:water 1:1 (v/v) mixtures. The tongue consisted of noble working electrodes made of iridium, rhodium, platinum and gold and non-noble electrodes including silver, copper, cobalt and nickel. Both the self-organizing map (SOM) and multi-layer feed-forward network (MLFN) neural networks were applied to the data obtained from the electronic tongue and TNT solutions. From SOM analysis it was established that a suitable response in terms of a correct classification of the TNT concentration was observed when using only noble metal electrodes and only 5 selected pulses. Similar good classifications were found when using MLFN. Moreover, the algorithm of neural network MLFN was embedded in a microcontroller in order to obtain a smart portable system for discrimination of TNT. In this case an R 2 of 0.993 was obtained for predicted vs observed graphs of concentrations of TNT concentrations.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192
We report here the use of a voltammetric electronic tongue based on simple metallic electrodes for the detection and discrimination of different concentrations of 2,4,6-trinitrotoluene (TNT) in acetonitrile:water 1:1 (v/v) mixtures. The tongue consisted of noble working electrodes made of iridium, rhodium, platinum and gold and non-noble electrodes including silver, copper, cobalt and nickel. Both the self-organizing map (SOM) and multi-layer feed-forward network (MLFN) neural networks were applied to the data obtained from the electronic tongue and TNT solutions. From SOM analysis it was established that a suitable response in terms of a correct classification of the TNT concentration was observed when using only noble metal electrodes and only 5 selected pulses. Similar good classifications were found when using MLFN. Moreover, the algorithm of neural network MLFN was embedded in a microcontroller in order to obtain a smart portable system for discrimination of TNT. In this case an R 2 of 0.993 was obtained for predicted vs observed graphs of concentrations of TNT concentrations.
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