Showing papers in "IEEE Sensors Journal in 2007"
TL;DR: A detailed mechanism of the surface plasmon resonance (SPR) technique for sensing purposes has been discussed in this paper, where different new techniques and models in this area that have been introduced are discussed in quite a detail.
Abstract: Since the introduction of optical fiber technology in the field of sensor based on the technique of surface plasmon resonance (SPR), fiber-optic SPR sensors have witnessed a lot of advancements. This paper reports on the past, present, and future scope of fiber-optic SPR sensors in the field of sensing of different chemical, physical, and biochemical parameters. A detailed mechanism of the SPR technique for sensing purposes has been discussed. Different new techniques and models in this area that have been introduced are discussed in quite a detail. We have tried to put the different advancements in the order of their chronological evolution. The content of the review article may be of great importance for the research community who are to take the field of fiber-optic SPR sensors as its research endeavors.
824 citations
TL;DR: This paper discusses a complementary approach to provide power autonomy to devices on a human body, i.e., thermoelectric conversion of human heat, based on custom-design small-size BiTe thermopiles.
Abstract: Solar cells are the most commonly used devices in customer products to achieve power autonomy. This paper discusses a complementary approach to provide power autonomy to devices on a human body, i.e., thermoelectric conversion of human heat. In indoor applications, thermoelectric converters on the skin can provide more power per square centimeter than solar cells, particularly in adverse illumination conditions. Moreover, they work day and night. The first sensor nodes powered by human heat have been demonstrated and tested on people in 2004-2005. They used the state-of-the-art 100-muW watch-size thermoelectric wrist generators fabricated at IMEC and based on custom-design small-size BiTe thermopiles. The sensor node is completed with a power conditioning module, a microcontroller, and a wireless transceiver mounted on a watchstrap
373 citations
TL;DR: In this article, the electrical, mechanical, and electromechanical properties of carbon nanotubes (CNTs) have been investigated for nanoelectromechanical sensors.
Abstract: Carbon nanotubes (CNTs) have shown great promise as sensing elements in nanoelectromechanical sensors. In this review paper, we discuss the electrical, mechanical, and electromechanical properties of CNTs that are used in such applications. This investigation indicates which nanotube properties should be carefully considered when designing nanotube-based sensors. We then present the primary techniques that have been used for the integration of nanotubes into devices and proceed to give a description of sensors that have been developed using CNTs as active sensing elements
265 citations
TL;DR: In this article, a novel high-temperature temperature resistance fiber bragg grating temperature sensor based on hydrogen-loaded germanium-doped fiber grating was developed. But the results of the experiments have shown that the stability of the device is substantially increased at high temperature range.
Abstract: Fiber Bragg grating (FBG) temperature sensor and sensor arrays were applied widespread particularly in harsh environments. Although FBGs are often referring to permanent refractive index modulation in the fiber core, exposure to high-temperature environments usually results in the bleach of the refractive index modulation. The maximum temperature reported for the conventional FBG temperature sensor is around 600 degC due to its weak bonds of germanium and oxygen. In this paper, we report design and development of a novel high-temperature resistance FBG temperature sensor, based on the hydrogen-loaded germanium-doped FBG. The refractive index modulation in the FBG is induced by the molecular water. The results of our experiments have shown that the stability of the device is substantially increased at high temperature range. Due to the high bonds energy of hydroxyl and the low diffusivity of the molecular water, the thermal testing results of this temperature sensor show the thermal stability of hydrogen-loaded FBG can be increased by using annealing treatment; moreover, the highest erasing temperature for the device could reach to 1100 degC or more. The reflectivity of this new FBG depends on the concentration of Si-OH and indirectly related to the reflectivity of hydrogen-loaded FBG. Furthermore, the experimental results have provided a better understanding of the formation of the hydrogen-loaded FBGs and the chemical transfers at elevated temperatures in the fiber core
251 citations
TL;DR: A dynamic volume imaging based on the principle of electrical capacitance tomography (ECT), namely, ECVT, has been developed in this study and has been successfully verified over actual objects in the experimental conditions.
Abstract: A dynamic volume imaging based on the principle of electrical capacitance tomography (ECT), namely, electrical capacitance volume tomography (ECVT), has been developed in this study. The technique generates, from the measured capacitance, a whole volumetric image of the region enclosed by the geometrically three-dimensional capacitance sensor. This development enables a real-time, 3-D imaging of a moving object or a real-time volume imaging (4-D) to be realized. Moreover, it allows total interrogation of the whole volume within the domain (vessel or conduit) of an arbitrary shape or geometry. The development of the ECVT imaging technique primarily encloses the 3-D capacitance sensor design and the volume image reconstruction technique. The electrical field variation in three-dimensional space forms a basis for volume imaging through different shapes and configurations of ECT sensor electrodes. The image reconstruction scheme is established by implementing the neural-network multicriterion optimization image reconstruction (NN-MOIRT), developed earlier by the authors for the 2-D ECT. The image reconstruction technique is modified by introducing into the algorithm a 3-D sensitivity matrix to replace the 2-D sensitivity matrix in conventional 2-D ECT, and providing additional network constraints including 3-to-2-D image matching function. The additional constraints further enhance the accuracy of the image reconstruction algorithm. The technique has been successfully verified over actual objects in the experimental conditions
240 citations
TL;DR: In this paper, a conductometric H2, NO2, and hydrocarbon gas sensor based on single-crystalline zinc oxide (ZnO) nanobelts has been developed.
Abstract: A conductometric H2, NO2, and hydrocarbon gas sensor based on single-crystalline zinc oxide (ZnO) nanobelts has been developed. The nanobelt sensitive layer was deposited using a radio frequency (RF) magnetron sputterer. The microcharacterization study reveals that the nanobelts have a single crystal hexagonal structure with average thickness and width of about 10 and 50nm, respectively. The sensor was exposed to H2, NO2 and propene gases at operating temperatures between 150 degC and 450 degC. The study showed that optimum operating temperatures for the sensor are in the range of 300 degC-400degC for H2, 300 degC-350 degC for NO2, and 350 degC-420 degC for propene sensing
234 citations
TL;DR: A novel scheme called the adaptive fuzzy strong tracking Kalman filter (AFSTKF) is carried out, which is essentially a nonlinear smoother algorithm that employs suboptimal multiple fading factors, in which the softening factors are involved.
Abstract: The well-known extended Kalman filter (EKF) has been widely applied to the Global Positioning System (GPS) navigation processing. The adaptive algorithm has been one of the approaches to prevent the divergence problem of the EKF when precise knowledge on the system models are not available. One of the adaptive methods is called the strong tracking Kalman filter (STKF), which is essentially a nonlinear smoother algorithm that employs suboptimal multiple fading factors, in which the softening factors are involved. Traditional approach for selecting the softening factors heavily relies on personal experience or computer simulation. In order to resolve this shortcoming, a novel scheme called the adaptive fuzzy strong tracking Kalman filter (AFSTKF) is carried out. In the AFSTKF, the fuzzy logic reasoning system based on the Takagi-Sugeno (T-S) model is incorporated into the STKF. By monitoring the degree of divergence (DOD) parameters based on the innovation information, the fuzzy logic adaptive system (FLAS) is designed for dynamically adjusting the softening factor according to the change in vehicle dynamics. GPS navigation processing using the AFSTKF will be simulated to validate the effectiveness of the proposed strategy. The performance of the proposed scheme will be assessed and compared with those of conventional EKF and STKF
170 citations
TL;DR: A wireless smart sensor platform targeted for instrumentation and predictive maintenance systems is presented, which supports hardware interface, payload and communications needs of multiple inertial and position sensors, and actuators, using a RF link for communications, in a point-to-point topology.
Abstract: A wireless smart sensor platform (based on patent pending technologies, Ramamurthy ) targeted for instrumentation and predictive maintenance systems is presented. The generic smart sensor platform with "plug-and-play" capability supports hardware interface, payload and communications needs of multiple inertial and position sensors, and actuators, using a RF link (Wi-Fi, Bluetooth, or RFID) for communications, in a point-to-point topology. The design also provides means to update operating and monitoring parameters as well as sensor/RF link specific firmware modules "over-the-air." Sample implementations for industrial applications and system performance are discussed
162 citations
TL;DR: In this paper, a balanced-mass double-ended tuning fork (BDETF) was fabricated from 3C-SiC on a silicon substrate, achieving a selectivity of 5:1 and etch rate of 2500 Aring/min.
Abstract: In this paper, we present a silicon carbide MEMS resonant strain sensor for harsh environment applications. The sensor is a balanced-mass double-ended tuning fork (BDETF) fabricated from 3C-SiC deposited on a silicon substrate. The SiC was etched in a plasma etch chamber using a silicon oxide mask, achieving a selectivity of 5:1 and etch rate of 2500 Aring/min. The device resonates at atmospheric pressure and operates from room temperature to above 300degC. The device was also subjected to 10 000 g shock (out-of-plane) without damage or shift in resonant frequency. The BDETF exhibits a strain sensitivity of 66 Hz/muepsiv and achieves a strain resolution of 0.11 muepsiv in a bandwidth from 10 to 20 kHz, comparable to state-of-the-art silicon sensors
160 citations
TL;DR: In this article, the design, modeling, and simulation of a novel micromachined magnetic field sensor is discussed, which uses an electrostatic resonator whose fundamental resonant frequency is modified by a Lorentz force generated from the interaction of the sensor structure and the present magnetic field.
Abstract: The design, modeling, and simulation of a novel micromachined magnetic field sensor are discussed. The sensor uses an electrostatic resonator whose fundamental resonant frequency is modified by a Lorentz force generated from the interaction of the sensor structure and the present magnetic field. The sensor was fabricated in a standard bulk micromachining process without the need for any additional processing steps. Since the sensor does not employ any magnetic materials, it does not exhibit hysteresis. A comprehensive model of the sensor behavior is derived which encompasses the interactions of the involved physical domains. Validity of the modeling results was verified by finite-element simulations, and later, through experiments. The sensitivities of the fabricated sensors are in the range of 48-87 Hz/T, depending on sensor structure and dimensions. The design of the sensor allows for its fabrication in many standard microelectromechanical system processes and is compatible with CMOS processes. The theoretical minimum detectable signal with current devices is on the order of 217 nT. Methods to improve the sensitivity of the current sensors are suggested. A linear response to a wide range of magnetic fields makes this design suitable for applications where large fields need to be measured with high resolution.
156 citations
TL;DR: In this paper, a new type of CMOS time-of-flight (TOF) range image sensor using single-layer gates on field oxide structure for photo conversion and charge transfer is presented.
Abstract: This paper presents a new type of CMOS time-of-flight (TOF) range image sensor using single-layer gates on field oxide structure for photo conversion and charge transfer. This simple structure allows the realization of a dense TOF range imaging array with 1515 mum2 pixels in a standard CMOS process. Only an additional process step to create an n-type buried layer which is necessary for high-speed charge transfer is added to the fabrication process. The sensor operates based on time-delay dependent modulation of photocharge induced by back reflected infrared light pulses from an active illumination light source. To reduce the influence of background light, a small duty cycle light pulse is used and charge draining structures are included in the pixel. The TOF sensor chip fabricated measures a range resolution of 2.35 cm at 30 frames per second and an improvement to 0.74 cm at three frames per second with a pulsewidth of 100 ns.
TL;DR: In this paper, the effects of synchronous demodulation and electrostatic quadrature compensation performed with a dc voltage on the final zero-rate output (ZRO) of a vibratory microgyroscope are studied.
Abstract: In this paper, issues related to the zero-rate output (ZRO) of a vibratory microgyroscope are studied. Different sources of the ZRO are discussed and how the effect of each source can be minimized and their stability improved is described. The effects of synchronous demodulation and electrostatic quadrature compensation performed with a dc voltage on the final ZRO are analyzed. Ways to implement the control loop for electrostatic quadrature compensation performed with a dc voltage are described, concentrating on a case where the compensation voltage is generated with a digital-to-analog converter and the controller is digital. In particular, extending the resolution with SigmaDelta techniques is studied. The experimental work shows the feasibility of the implemented quadrature compensation loop and analyzes the ZRO sources of one particular gyroscope implementation. How to perform the ZRO measurements in such a way that the various sources can be distinguished from each other is also described.
TL;DR: The feasibility of sending wireless power to a buried sensor antenna within concrete was studied and DC power at the rectenna was measured within dry and wet concrete samples with various cover thicknesses and air-gaps.
Abstract: The feasibility of sending wireless power to a buried sensor antenna within concrete was studied. A receive patch rectenna with 75.8% conversion efficiency was designed for operation at 5.7 GHz. The received DC power at the rectenna was measured within dry and wet concrete samples with various cover thicknesses and air-gaps. For the rectenna buried within 30 mm of the concrete, the received DC power was 10.37 mW, which was about 70% of the received DC power in free-space.
TL;DR: In this paper, the authors present the recent development, now the third generation, of micromachined angular rate sensors at Robert Bosch GmbH, which exhibit outstanding performance compared to similar designs, especially in terms of resolution, noise and insensitivity against external perturbations.
Abstract: Micromachined angular rate sensors are key elements in several automotive systems, thus enabling highly sophisticated applications like rollover detection and mitigation, navigation systems, electronic stability program, and other future vehicle stabilizing and dynamics control systems. New automotive systems are demanding higher accuracy, better signal-to-noise ratio, higher robustness and insensitivity against external perturbations, better system availability and reliability, as well as easy application of the gyros. This paper is presenting the recent development, now the third generation, of micromachined angular rate sensors at Robert Bosch GmbH. Mass production was started in spring 2005. These surface micromachined gyroscopes exhibit outstanding performance compared to similar designs, especially in term of resolution, noise, and insensitivity against external perturbations
TL;DR: In this paper, a thin-film piezoelectric sensor was used to mimic the tactile feedback exhibited by the human hand in an artificial limb to detect object slip and provide information to a controller, which automatically adjusts the grip force applied to a held object to prevent it from falling.
Abstract: The ability to mimic the tactile feedback exhibited by the human hand in an artificial limb is considered advantageous in the automatic control of new multifunctional prosthetic hands. The role of a slip sensor in this tactile feedback is to detect object slip and thus provide information to a controller, which automatically adjusts the grip force applied to a held object to prevent it from falling. This system reduces the cognitive load experienced by the user by not having to visually assess the stability of an object, as well as giving them the confidence not to apply unnecessarily excessive grip forces. A candidate for such a sensor is a thick-film piezoelectric sensor. The method of fabricating a thick-film piezoelectric slip sensor on a prototype fingertip is described. The construction of experimental apparatus to mimic slip has been designed and analyzed to allow the coefficient of friction between the fingertip and the material in contact with the fingertip to be calculated. Finally, results show that for a coefficient of friction between the fingertip and grade P100 sandpaper of approximately 0.3, an object velocity of 0.025plusmn0.008 ms-1 was reached before a slip signal from the piezoelectric sensor was able to be used to detect slip. It is anticipated that this limiting velocity will be lowered (improved) in the intended application where the sensor electronics will be powered from a battery, connections will be appropriately screened, and if necessary a filter employed. This will remove mains interference and reduce other extraneous noise sources with the consequence of an improved signal-to-noise ratio, allowing lower threshold values to be used in the detection software
TL;DR: In this paper, an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror was presented, and the length of the sensing head was 380 mm and its corresponding wavelength spacing between two interferometer minima was 8 nm.
Abstract: This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 ) when compared with coated Hi-Bi PCF (1.21 ). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).
TL;DR: The proposed method exhibits significantly higher performance than the basic ICA algorithm and also shows improvement over other state-of-the-art algorithms.
Abstract: In this paper, we present a novel multimodal image fusion algorithm in the independent component analysis (ICA) domain. Region-based fusion of ICA coefficients is implemented, where segmentation is performed in the spatial domain and ICA coefficients from separate regions are fused separately. The ICA coefficients from given regions are consequently weighted using the Piella fusion metric in order to maximize the quality of the fused image. The proposed method exhibits significantly higher performance than the basic ICA algorithm and also shows improvement over other state-of-the-art algorithms
TL;DR: In this paper, the authors demonstrate refractive index measurement of liquids using two sensor system designs, both based on microring resonators, and they achieve a sensitivity of 30 nm/RIU and a resulting detection limit on the order of 10-7 RIU.
Abstract: We demonstrate refractive index measurement of liquids using two sensor system designs, both based on microring resonators. Evanescent sensors based on microrings utilize the resonating nature of the light to dramatically decrease the required size and sample consumption volume, which are requirements of lab-on-a-chip sensor systems. The first design, which utilizes an optical microsphere, exhibits a sensitivity of 30 nm/RIU and a resulting detection limit on the order of 10-7 RIU. The second approach is a novel design called a liquid core optical ring resonator (LCORR). This concept uses a quartz capillary as the fluidics and as the ring resonator and achieves a sensitivity of 16.1 nm/RIU. The detection limit of this system is around 5times10-6 RIU. Both of these systems have the potential to be incorporated with advanced microfluidic systems for lab-on-a-chip applications. In particular, the LCORR combines high sensitivity, performance stability, and microfluidic compatibility, making it an excellent choice for lab-on-a-chip development
TL;DR: In this article, nonlinear responses and dynamics of the electrostatically actuated MEMS resonant sensors under two-frequency parametric and external excitations are presented and the results showing the effect of varying the dc bias, the squeeze film damping, cubic stiffness, and ac excitation amplitude on the frequency response curves, resonant frequencies and nonlinear dynamic characteristics are given in detail.
Abstract: Electrostatically actuated resonant microelectromechanical systems (MEMS) sensors have gotten significant attention due to their geometric simplicity and broad applicability. In this paper, nonlinear responses and dynamics of the electrostatically actuated MEMS resonant sensors under two-frequency parametric and external excitations are presented. The presented model and methodology enable simulation of the steady-state dynamics of electrostatic MEMS undergoing small motions. Response and dynamics of the MEMS resonator to a combination resonance are studied. The responses of the system at steady-state conditions and their stability are investigated using the method of multiple scales. The results showing the effect of varying the dc bias, the squeeze film damping, cubic stiffness, and ac excitation amplitude on the frequency response curves, resonant frequencies and nonlinear dynamic characteristics are given in detail. Frequency response, resonant frequency and peak amplitude are examined for variation of the dynamic parameters involved. This investigation provides an understanding of the nonlinear dynamic characteristics of microbeam-based resonant sensors in MEMS
TL;DR: GMR is a fully localized algorithm that efficiently delivers multicast data messages to multiple destinations that outperforms position based multicast in terms of cost of the trees and computation time over a variety of networking scenarios.
Abstract: We present geographic multicast routing (GMR), a new multicast routing protocol for wireless sensor networks. It is a fully localized algorithm that efficiently delivers multicast data messages to multiple destinations. It does not require any type of flooding throughout the network. Each node propagating a multicast data message needs to select a subset of its neighbors as relay nodes towards destinations. GMR optimizes the cost over progress ratio where the cost is equal to the number of neighbors selected for relaying and the progress is the overall reduction of the remaining distances to destinations. Such neighbor selection achieves a good tradeoff between the bandwidth of the multicast tree and the effectiveness of the data distribution. Our cost-aware neighbor selection is based on a greedy set merging scheme achieving a O(Dnmin(D,n)3) computation time, where n is the number of neighbors of current node and D is the number of destinations. As in traditional geographic routing algorithms, delivery to all destinations is guaranteed by applying face routing when necessary. Our simulation results show that GMR outperforms position based multicast in terms of cost of the trees and computation time over a variety of networking scenarios
TL;DR: In this paper, the authors present a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications.
Abstract: Noncontacting inductive sensors are applicable on a large scale for position detection or travel measurement in industrial applications. Reasons for such broad acceptance in many sectors of industry are noncontact and wear-free sensing of the target (any metal object), reliability and robustness, resistance to fouling, water tightness and compact size. The present work is intended to be a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications. It starts with the fundamentals of inductive sensing and presents the physical basics gained by modern analytic and simulation methods, as well as high-level integrated circuits for inductive sensors. The following sections deal with present-day inductive analog proximity sensors and with the distinctive technological innovation offered by the new inductive linear displacement sensors and with miniaturization results achieved through consistent integration.
TL;DR: In this article, the authors present a new technique for continuously calibrating the sensitivity of a current measurement microsystem based on a Hall magnetic field sensor using a variant of the chopper modulation, combined with a second modulation of the reference signal.
Abstract: This paper presents a new technique for continuously calibrating the sensitivity of a current measurement microsystem based on a Hall magnetic field sensor. An integrated reference coil generates a magnetic field for calibration. Using a variant of the chopper modulation, the spinning current technique, combined with a second modulation of the reference signal, the sensitivity of the complete system is continuously measured without interrupting normal operation. Modulation and demodulation schemes allowing the joint processing of both external and reference magnetic fields are proposed. Additional techniques for extracting the very low reference signal are presented. The implementation of the microsystem is then discussed. Finally, measurements validate the calibration principle. A thermal drift lower than 50 ppm/degC is achieved. This is 6-10 times less than in state-of-the-art implementations. Furthermore, the calibration technique also compensates drifts due to mechanical stresses and ageing
TL;DR: In this article, a microfabricated DNA chip for fully electronic, label-free DNA recognition based on capacitance measurements has been presented, which is fabricated in 0.5mum CMOS technology and it features an array of individually addressable sensing sites consisting of pairs of gold electrodes and addressing logic.
Abstract: This paper presents a microfabricated DNA chip for fully electronic, label-free DNA recognition based on capacitance measurements. The chip has been fabricated in 0.5-mum CMOS technology and it features an array of individually addressable sensing sites consisting of pairs of gold electrodes and addressing logic. Read-out circuitry is built externally using standard components to provide increased experimental flexibility. The chip has been electrically characterized and tested with various solutions containing DNA samples. Significant capacitance variations due to DNA hybridization have been measured, thus showing that the approach represents a viable solution for a single chip DNA sensor array
TL;DR: In this paper, an ambulatory and non-invasive method using microelectromechanical systems (MEMS) accelerometers is presented to estimate energy expenditure of elite athletes.
Abstract: Fitness development and performance assessment of elite athletes requires an understanding of many physiological factors, many of these are direct and indirect measures of athlete energy expenditure. Many methods are physiological factor assessments and require the athlete to be constrained by laboratory equipment or periodic interruption of activity to take measurements such as blood samples are required to be taken. This paper presents a method that is entirely ambulatory and noninvasive, using microelectromechanical systems (MEMS) accelerometers. The commonly used output of commercial accelerometer-based devices (known as "counts") cannot discriminate activity intensity for the activities of interest. This, in conjunction with variability in output from different systems and lack of commonality across manufacturers, limits the usefulness of commercial devices. This paper identifies anthropometric and kinematic sources of inter-athlete variability in accelerometer output, leading to an alternate energy expenditure estimator based mainly on step frequency modified by anthropometric measures. This energy expenditure estimator is more robust and not influenced by many sources of variability that affect the currently used estimator. In this system, low-power signal processing was implemented to extract both the energy estimator and other information of physiological and statistical interest
TL;DR: In this article, a nonlinear regression model of a microelectromechanical system capacitive accelerometer, targeted to be used in tilt sensing and low-g motion tracking applications, is proposed.
Abstract: This paper proposes a nonlinear regression model of a microelectromechanical systems capacitive accelerometer, targeted to be used in tilt sensing and low-g motion-tracking applications. The proposed model for the accelerometer's deterministic errors includes common physical parameters used to rate an accelerometer: scale factor, bias, and misalignment. Simple experiments used to reveal the behavior and characteristics of these parameters are described. A phenomenological modeling method is used to establish mathematical representations of these parameters in relation to errors such as nonlinearity and cross-axis effect, without requiring a complete understanding of the underlying physics. Tilt and motion-sensing experiments show that the proposed model reduces sensing errors to a level close to the residual stochastic noise
TL;DR: A new noninvasive system for multimodal electrical tomography based on electrical capacitance tomography (ECT) sensor hardware is proposed that has the advantage of using already established reconstruction techniques, and the potential for combination with new reconstruction techniques by taking advantage of combined conductivity/permittivity data.
Abstract: A new noninvasive system for multimodal electrical tomography based on electrical capacitance tomography (ECT) sensor hardware is proposed. Quasistatic electromagnetic fields are produced by ECT sensors and used for interrogating the sensing domain. The new system is noninvasive and based on capacitance measurements for permittivity and power balance measurements for conductivity (impedance) imaging. A dual sensitivity map of perturbations in permittivity and conductivity is constructed. The measured data along with the sensitivity matrix are used for the actual image reconstruction. The new multimodal tomography system has the advantage of using already established reconstruction techniques, and the potential for combination with new reconstruction techniques by taking advantage of combined conductivity/permittivity data. Moreover, it does not require direct contact between the sensor and the region of interest. The system performance has been tested on representative data, producing good results
TL;DR: In this article, two different pH sensors based on the deposition of nanometric scale polymeric films onto the surface of a long-period fiber grating (LPFG) have been studied and compared.
Abstract: In this paper, two different pH sensors based on the deposition of nanometric scale polymeric films onto the surface of a long-period fiber grating (LPFG) have been studied and compared. An electrostatic self-assembled (ESA) method has been used to create sensitive films with an optimal overlay thickness. Two types of sensors have been designed: The first one is based on polyallylamine hydrochloride (PAH), polyacrylic acid (PAA), and the second one was done incorporating the pigment Prussian blue (PB) in the PAH/PAA matrix. A theoretical model of multilayer cylindrical waveguides based on coupled-mode theory has been used to predict the position of the attenuation bands as a function of the overlay thickness. Both sensors were tested and compared in terms of sensitivity and response time. A faster response was obtained with the introduction of PB particles in the polymeric matrix. Linear sensors in the pH range 4-7 were obtained, showing good repeatability and high sensitivity
TL;DR: In this paper, a portable noncontact heartbeat and respiration monitoring system operating in 5GHz band is reported, which can be used for various applications in biology, medicine, and security.
Abstract: A portable noncontact heartbeat and respiration monitoring system operating in 5-GHz band is reported in this letter. Compared with the previously reported system operating at Ka-band, this system has been simplified to include only two PCB antennas, a palm-size PCB radio module, a data acquisition module, and a laptop. The system, powered by the laptop battery through USB connection, is compact, low-cost, and convenient for field test. A detection accuracy of better than 80% has been achieved at a distance of 2.8 m and at a low transmitted power of 20 muW. The system can be used for various applications in biology, medicine, and security.
TL;DR: In this article, a template-free rapidly mixed reaction was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline and Camphor sulfonic acid (CSA).
Abstract: A template-free rapidly mixed reaction was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline. Hydrochloric acid (HCl) and camphor sulfonic acid (CSA) were used in the synthesis to obtain 30- and 50-nm average diameter polyaniline nanofibers. The nanofibers were deposited onto layered ZnO/64deg YX LiNbO3 surface-acoustic-wave transducers. The sensors were tested toward hydrogen (H2) gas while operating at room temperature. The dopant for the polyaniline nanofiber synthesis was found to have a significant effect on the device sensitivity. The sensor response was found to be larger for the 50-nm diameter CSA-doped nanofiber based sensors, while the response and recovery times were faster for the 30-nm diameter HCl-doped nanofibers
TL;DR: In this paper, the authors present a system that continuously measures the relevant stress components, estimates the sensitivity drift, and corrects for it digitally, which can keep the drift of magnetic sensitivity well below 1%.
Abstract: Silicon Hall sensors are known to suffer from a long-term drift in the magnetic sensitivity between 1% and 4%, depending on the degree of moisture in the mold compound of the package. This drift is mainly caused by changes of mechanical stress exerted by the plastic package onto the die. We present a system, which continuously measures the relevant stress components, estimates the sensitivity drift, and corrects for it digitally. An individual precalibration versus temperature is necessary to achieve the required level of accuracy. Results from laboratory characterization with pressure cells and lifetime drift during qualification runs show that this system can keep the drift of magnetic sensitivity well below 1%.