Showing papers on "Capacitive sensing published in 2016"

Flexible Capacitive Tactile Sensor Based on Micropatterned Dielectric Layer.

Abstract: Flexible tactile sensors are considered as an effective way to realize the sense of touch, which can perform the synchronized interactions with surrounding environment. Here, the utilization of bionic microstructures on natural lotus leaves is demonstrated to design and fabricate new-type of high-performance flexible capacitive tactile sensors. Taking advantage of unique surface micropattern of lotus leave as the template for electrodes and using polystyrene microspheres as the dielectric layer, the proposed devices present stable and high sensing performance, such as high sensitivity (0.815 kPa-1 ), wide dynamic response range (from 0 to 50 N), and fast response time (≈38 ms). In addition, the flexible capacitive sensor is not only applicable to pressure (touch of a single hair), but also to bending and stretching forces. The results indicate that the proposed capacitive tactile sensor is a promising candidate for the future applications in electronic skins, wearable robotics, and biomedical devices.

A Four-Plate Compact Capacitive Coupler Design and LCL -Compensated Topology for Capacitive Power Transfer in Electric Vehicle Charging Application

Abstract: This paper proposes a four-plate compact capacitive coupler and its circuit model for large air-gap distance capacitive power transfer (CPT). The four plates are arranged vertically, instead of horizontally, to save space in the electric vehicle charging application. The two plates that are on the same side are placed close to each other to maintain a large coupling capacitance, and they are of different sizes to maintain the coupling between the primary and secondary sides. The circuit model of the coupler is presented, considering all six coupling capacitors. The LCL compensation topology is used to resonate with the coupler and provide high voltage on the plates to transfer high power. The circuit model of the coupler is simplified to design the parameters of the compensation circuit. Finite-element analysis is employed to simulate the coupling capacitance and design the dimensions of the coupler. The circuit performance is simulated in LTspice to design the specific parameter values. A prototype of the CPT system was designed and constructed with the proposed vertical plate structure. The prototype achieved an efficiency of 85.87% at 1.88-kW output power with a 150-mm air-gap distance.

Highly Sensitive Pressure Sensor Based on Bioinspired Porous Structure for Real‐Time Tactile Sensing

Abstract: A flexible pressure sensor with high performances is one of the promising candidates for achieving electronic skins (E-skin) related to various applications such as wearable devices, health monitoring systems, and artificial robot arms. The sensitive response for external mechanical stimulation is fundamentally required to develop the E-skin which imitates the function of human skin. The performance of capacitive pressure sensors can be improved using morphologies and structures occurring in nature. In this work, highly sensitive capacitive pressure sensors based on a porous structure of polydimethylsiloxane (PDMS) thin film, inspired on the natural multilayered porous structures seen in mushrooms, diatoms, and spongia offilinalis, have been developed and evaluated. A bioinspired porous dielectric layer is used, resulting in high-performance pressure sensors with high sensitivity (0.63 kPa−1), high stability over 10 000 cycles, fast response and relaxation times, and extremely low-pressure detection of 2.42 Pa. Additionally, the resulting pressure sensors are demonstrated to fabricate multipixel arrays, thus achieving successful real-time tactile sensing of various touch shapes. The developed high-performance flexible pressure sensors may open new opportunities for innovative applications in advanced human-machine interface systems, robotic sensory systems, and various wearable health monitoring devices.

Twistable and Stretchable Sandwich Structured Fiber for Wearable Sensors and Supercapacitors

Abstract: Twistable and stretchable fiber-based electrochemical devices having high performance are needed for future applications, including emerging wearable electronics. Weavable fiber redox supercapacitors and strain sensors are here introduced, which comprise a dielectric layer sandwiched between functionalized buckled carbon nanotube electrodes. On the macroscopic scale, the sandwiched core rubber of the fiber acts as a dielectric layer for capacitive strain sensing and as an elastomeric substrate that prevents electrical shorting and irreversible structural changes during severe mechanical deformations. On the microscopic scale, the buckled CNT electrodes effectively absorb tensile or shear stresses, providing an essentially constant electrical conductance. Consequently, the sandwich fibers provide the dual functions of (1) strain sensing, by generating approximately 115.7% and 26% capacitance changes during stretching (200%) and giant twist (1700 rad·m–1 or 270 turns·m–1), respectively, and (2) electrochemi...

Large Area One-Step Facile Processing of Microstructured Elastomeric Dielectric Film for High Sensitivity and Durable Sensing over Wide Pressure Range

Abstract: Once the requirement of sensitivity has been met, to enable a flexible pressure sensor technology to be widely adopted as an economic and convenient way for sensing diverse human body motions, critical factors need to be considered including low manufacturing cost, a large pressure detection range, and low power consumption. In this work, a facile approach is developed for one-step processing of a large area microstructured elastomer film with high density microfeatures of air voids, which can be seamlessly integrated into the process flow for fabricating flexible capacitive sensors. The fabricated sensors exhibit fast response and high sensitivity in the low pressure range to be able to detect very weak pressure down to 1 Pa and perform reliable wrist pulse monitoring. Compared to previous work, more advantageous features of this sensor are relatively high sensitivity being maintained in a wide pressure range up to 250 kPa and excellent durability under heavy load larger than 1 MPa, attributed to the formed dense air voids inside the film. A smart insole made with the sensor can accurately monitor the real-time walking or running behaviors and even a small weight change less than 1 kg under a heavy load of a 70 kg adult. For both application examples of wrist pulse monitoring and smart insole, the sensors are operated in a 3.3 V electronic system powered by a Li-ion battery, showing the potential for power-constrained wearable applications.

An Inductive and Capacitive Combined Wireless Power Transfer System With LC -Compensated Topology

Abstract: This paper proposes a combined inductive and capacitive wireless power transfer (WPT) system with LC -compensated topology for electric vehicle charging application. The circuit topology is a combination of the LCC -compensated inductive power transfer (IPT) system and the LCLC -compensated capacitive power transfer (CPT) system. The working principle of the combined circuit topology is analyzed in detail, providing the relationship between the circuit parameters and the system power. The design of the inductive and capacitive coupling is implemented by the finite-element analysis. The equivalent circuit model of the coupling plates is derived. A 3.0-kW WPT system is designed and implemented as an example of combined inductive and capacitive coupling. The inductive coupler size is 300 mm × 300 mm and the capacitive coupler is 610 mm × 610 mm. The air-gap distance is 150 mm for both couplers. The output power of the combined system is the sum of the IPT and CPT system. The prototype has achieved 2.84-kW output power with 94.5% efficiency at 1-MHz switching frequency, and performs better under misalignment than the IPT System. This demonstrates that the inductive–capacitive combined WPT system is a potential solution to the electric vehicle charging application.

Capacitive Power Transfer Through a Conformal Bumper for Electric Vehicle Charging

Abstract: Wireless power transfer (WPT) is emerging as a practical means for electric vehicle (EV) charging. Of the most common approaches to WPT, inductive coupling, and capacitive coupling, capacitive power transfer (CPT) is proposed to charge an EV at a kilowatt scale power level. CPT implementation replaces copper coils and permeable focusing/shielding materials of inductive approaches with foil surfaces, making CPT a cost effective and structurally simple system to implement while maintaining efficient power transfer capability. This paper addresses the primary technical hurdles to kilowatt scale CPT system development, namely, safe field confinement by achieving high coupling capacitance between the vehicle and the charging station. High capacitive coupling is achieved through a conformal (flexible and compressive) transmitter bumper that molds and contours itself to the vehicle. This minimizes the air gap and confines the field during charging. Here, a conformal surface demonstrates 3–5 times more coupling capacitance than its rigid counterpart of equal area. The associated power electronics are also discussed in detail, utilizing a Class $\text{E}^{2}$ amplifier/rectifier. An experimental docking station was built to charge the 156 V battery pack of a Corbin Sparrow EV and measured throughput power is demonstrated at $>1$ kW at $\sim 90$ % efficiency via a coupling capacitance of 10 nF operating at 530 kHz.

Design and fabrication of capacitive nanosensor based on MOF nanoparticles as sensing layer for VOCs detection

Abstract: Due to high porosity and increased surface area; metal organic frameworks (MOFs) have been widely used in gas storage applications as well as volatile organic compounds (VOCs) detection. Most of these sensors are electromechanical or electrochemical based; however there are few works in which capacitive sensors were developed using micrometer MOFs. In the present study, for the first time, MOF (Cu-BTC) nanoparticles were used to develop capacitive sensor device for detecting VOCs (e.g. methanol, ethanol, isopropanol, and acetone). The studied capacitive sensors were performed in a moderate environment (10% relative humidity and 25 °C). Capacitive sensors were fabricated in a sandwich form or parallel plate by using copper plate as a back electrode, MOF nanoparticles layer as the dielectric, and interconnected silver spots as the upper electrode of the capacitor. Linearity of the response versus LCR meter frequency, reusability, reversibility, response time, and limit of detection (LOD) of the capacitive sensor were determined to evaluate the sensor performance. The results showed high ability of Cu-BTC nanoparticles synthesized as dielectric layer of a capacitive nanosensor to determine VOCs.

Capacitive wearable tactile sensor based on smart textile substrate with carbon black /silicone rubber composite dielectric

Abstract: To achieve the wearable comfort of electronic skin (e-skin), a capacitive sensor printed on a flexible textile substrate with a carbon black (CB)/silicone rubber (SR) composite dielectric was demonstrated in this paper. Organo-silicone conductive silver adhesive serves as a flexible electrodes/shielding layer. The structure design, sensing mechanism and the influence of the conductive filler content and temperature variations on the sensor performance were investigated. The proposed device can effectively enhance the flexibility and comfort of wearing the device asthe sensing element has achieved a sensitivity of 0.02536%/KPa, a hysteresis error of 5.6%, and a dynamic response time of ~89 ms at the range of 0–700 KPa. The drift induced by temperature variations has been calibrated by presenting the temperature compensation model. The research on the time–space distribution of plantar pressure information and the experiment of the manipulator soft-grasping were implemented with the introduced device, and the experimental results indicate that the capacitive flexible textile tactile sensor has good stability and tactile perception capacity. This study provides a good candidate for wearable artificial skin.

Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

Abstract: Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors.

Activated carbon fiber paper with exceptional capacitive performance as a robust electrode for supercapacitors

Abstract: Herein, a facile and available electrochemical activation approach has been developed to markedly boost the capacitive performance of carbon fiber paper (CFP). The activated CFP could deliver a significant areal capacitance of 1.56 F cm−2 at a high current density of 5 mA cm−2 with excellent rate capability and cycling performance.

Self-Powered Piezoionic Strain Sensor toward the Monitoring of Human Activities

Abstract: Wearable sensors for the detection of human activities including subtle physiological signals and large-scale body motion as well as distinguishing the motion direction are highly desirable, but still a challenge. A flexible wearable piezoionic strain sensor based on the ionic polymer membrane sandwiched between two conductive electrodes is developed. This ionic polymer sensor can generate electrical signal output (≈mV) with rapid response (≈50 ms) under the applied bending deformation due to the internal mobile ion redistribution. Compared with the currently studied resistive and capacitive sensors, this sensor can generate sensing signals without the requirement of additional power supply, and is able to distinguish the direction of the bending strain by observing the direction of generated electrical signals. For the sensor with metallic electrode, an output voltage of 1.3 mV is generated under a bending-induced strain of 1.8%, and this voltage can be largely increased when replacing the metallic electrodes by graphene composites. After simple encapsulation of the piezoionic sensor, a wearable sensor is constructed and succeeded in monitoring the diverse human activities ranging from complex large scale multidimensional motions to subtle signals, including wrist bending with different directions, sitting posture sensing, pulse wave, and finger touch.

Fabrication of capacitive sensor based on Cu-BTC (MOF-199) nanoporous film for detection of ethanol and methanol vapors

Abstract: Metal–organic framework (MOF), a nanoporous compound, has been used as sensing material to fabricate capacitive nanosensor. The proposed nanosensor was fabricated by growing a Cu-BTC (MOF-199) film on a copper substrate using electrochemical method. 1-Methyl-3-octylimidazolium chloride, an ionic liquid (IL), was used as conducting salt in the electrochemical cell. Scanning electron microscopy (SEM), FTIR spectroscopy, X-ray diffraction analysis, and BET techniques were used to characterize the prepared MOF which shows a thin film (about 5 μm) of Cu-BTC layer with particle size of 2–3 μm. In order to fabricate the upper electrode of capacitor some interconnected Ag paste dots were patterned on the MOF layer which was coated on the copper surface as back electrode. This fabricated sensor was used for investigation of the capacitance variations in the presence of different amounts of introduced ethanol and methanol vapors. The capacitive sensing parameters were measured by a LCR meter. Relative capacitance variations were measured to verify the potential of the Cu-BTC films for using as dielectric layer in this capacitive sensor. The linear range of the signal vs. concentration is 0–1000 ppm for ethanol and methanol. Limit of detection of the fabricated sensors were 130.0 ppm and 39.1 ppm for ethanol and methanol, respectively. The selectivity of the sensor for polar and nonpolar VOCs was examined by introducing n-hexane in sensing chamber.

Three-dimensional freestanding hierarchically porous carbon materials as binder-free electrodes for supercapacitors: high capacitive property and long-term cycling stability

Abstract: Recently, hierarchically porous carbon materials with advantages of hierarchical porosity and large specific surface areas exhibiting desirable capacitive performance have been widely investigated. Herein, a facile and template-free phase separation methodology has been presented to prepare three-dimensional freestanding hierarchically porous carbon (HPC) materials. Importantly, the as-fabricated HPC with highly uniform and well-interconnected pores can afford plentiful transport channels for rapid diffusion of more ions, and the highly conductive cross-linked backbones ensure fast electron transfer, both of which can greatly reduce the internal resistance and improve the electrochemical properties. As expected, the as-fabricated HPC-based supercapacitor has achieved outstanding electrochemical performance with a high cell capacitance of 51 F g−1 at a current density of 0.5 A g−1, good rate capability with 75% capacitance retention of initial capacitance at 32 A g−1 as well as a maximum energy density of 4.5 W h kg−1 at 200 W kg−1 and a maximum power density of 15100 W kg−1 at 3.4 W h kg−1. More significantly, a remarkable cycling stability almost without capacitance loss after the 50000 charge/discharge test at 5 A g−1 has been achieved for the HPC-based supercapacitors. All these results suggest that the as-synthesized HPC has great potential for application not only as a supercapacitor electrode but also as a substrate for supporting capacitive materials.

Glove-based hand gesture recognition sign language translator using capacitive touch sensor

Abstract: The sign language translator is a bridge between those who comprehend sign languages and those who do not which is the majority of humanity. However, conventional signa language translators are bulky and expensive, limiting their wide adoption. In this paper, we present a gesture recognition glove based on charge-transfer touch sensors for the translation of the American Sign Language. The device is portable and can be implemented with low-cost hardware. The prototype recognize gestures for the numbers 0 to 9 and the 26 English alphabets, A to Z. The glove experimentally achieved, based on 1080 trials, an overall detection accuracies of over 92 %, which is comparable with current high-end counterparts. The proposed device i expected to bridge the communication gap between the hearing and speech impaired and members of the general public.

Distinction between Capacitive and Noncapacitive Hysteretic Currents in Operation and Degradation of Perovskite Solar Cells

Abstract: Perovskite solar cells suffer from significant performance distortions under working conditions, usually known by the generic label of hysteretic effects. A classification of the fluctuations associated with current–voltage curves, centered on capacitance analysis, including measurements in voltage sweep, is provided here. Scan rate constitutes an easy-to-implement probing technique able to differentiate between capacitive and noncapacitive contributions to the overall hysteretic response. Capacitive hysteresis shows a distinctive response with scan rate and mainly originates at TiO2 interfaces contacting perovskite materials. It relies on the interfacial ability to accommodate both ionic and electronic charges in a highly reversible way. Noncapacitive hysteresis points to the occurrence of interfacial energetics modification or contact reactivity caused by perovskite ionic motion. It exhibits positive values for reverse scans, in opposition to what is observed for capacitive currents. Connections between...

Capacitive flexible pressure sensor based on composite material dielectric layer and preparation method of capacitive flexible pressure sensor

Abstract: The invention relates to a capacitive flexible pressure sensor based on microstructural dielectric layers and a preparation method of the capacitive flexible pressure sensor and belongs to the technical field of sensors. The capacitive flexible pressure sensor comprises an upper flexible substrate, a lower flexible substrate, an upper conducting layer and a lower conducting layer, wherein the upper conducting layer is attached to the inner surface of the upper flexible substrate, the lower conducting layer is attached to the inner surface of the lower flexible substrate, and the microstructural dielectric layers are arranged between the upper conducting layer and the lower conducting layer. Compared with the prior art, different microstructural dielectric layers are designed for the capacitive flexible pressure sensor, the sensor performance can be effectively regulated according to change of conditions such as shape, size, distribution and the like of each dielectric layer microstructure, and preparation of the capacitive flexible pressure sensors with different sensitivity and test ranges is realized. Besides, the microstructures prepared with methods such as microcapsule foaming, impressing, replica transfer, 3D printing and the like are low in cost, high in efficiency, low in energy consumption and particularly suitable for large-area and large-scale production, and application and popularization of the sensor are facilitated.

Capacitance Modeling in Dual Field-Plate Power GaN HEMT for Accurate Switching Behavior

Abstract: In this paper, a surface-potential-based compact model is proposed for the capacitance of an AlGaN/GaN high-electron mobility transistor (HEMT) dual field-plate (FP) structure, i.e., with gate and source FPs. FP incorporation in a HEMT gives an improvement in terms of enhanced breakdown voltage, reduced gate leakage, and so on, but it affects the capacitive nature of the device, particularly by bringing into existence in a subthreshold region of operation, a feedback miller capacitance between the gate and the drain, and also a capacitance between the drain and the source, therefore, affecting switching characteristics. Here, we model the bias dependence of the terminal capacitances, wherein the expressions developed for intrinsic charges required for capacitance derivation are analytical and physics-based in nature and valid for all regions of device operation. The proposed model, implemented in Verilog-A, is in excellent agreement with the measured data for different temperatures.

Fabrication, modeling and simulation of high sensitivity capacitive humidity sensors based on ZnO nanorods

Abstract: Recently, humidity sensors due to their broad applications in meteorology, health science, food science, and agriculture have been under extensive investigation. We report fabrication and characterization of high sensitivity capacitive humidity sensors based on ZnO nanorods. ZnO nanorods have been grown by means of chemical bath deposition. We have observed that by changing the seed layer thickness, nanorods with different aspect ratios and densities could be achieved. Furthermore, it is demonstrated that decreasing the density of nanorods has a positive effect on the response of the sensor. Moreover, an equivalent circuit model is proposed to explain the sensing mechanism. The devices were also simulated with COMSOL Multiphysics and a very good agreement with experimental data was observed. Finally a solution for increasing the sensitivity of the sensors is proposed.

Oscillator-Based Reactance Sensors With Injection Locking for High-Throughput Flow Cytometry Using Microwave Dielectric Spectroscopy

Abstract: This paper presents the analysis and design of oscillator-based reactance sensors employing injection locking for high-throughput label-free single-cell analysis using dielectric spectroscopy at microwave frequencies. By injection-locking two sensing LC-oscillators with an I/Q excitation source, the measurement of the sample-induced frequency shift caused by the interaction with the electromagnetic fields is performed through phase detection with injection-strength-dependent transducer gain. Such inherent phase amplification offered by the injection locking not only relaxes the design requirement for the readout circuits but also maintains the highest rejection against common-mode errors associated with the drift of the supply voltage and the environmental parameters. To reduce flicker noise contribution, a chopping technique employing phase modulation is exploited. In addition, this paper presents a novel ping-pong chopping approach to alleviate chopping-induced dc offset. In this prototype, four sensing channels, covering frequencies between 6.5 and 30 GHz, are distributed along a microfluidic channel fabricated with standard photolithography. Measurements show that the proposed microwave capacitive sensors achieve a ${sub}{- }{a}{{F}_{{rms}}}$ of noise sensitivity at 100 kHz filtering bandwidth, enabling measurement throughput exceeding 1 k cells/s. The sensor prototype is implemented in 65 nm CMOS technology and consumes 65 mW at 1 V supply.

Analytical Switching Loss Model for Superjunction MOSFET With Capacitive Nonlinearities and Displacement Currents for DC–DC Power Converters

Abstract: A new analytical model is presented in this study to predict power losses and waveforms of high-voltage silicon superjunction MOSFET during hard-switching operation. This model depends on datasheet parameters of the semiconductors, as well as the parasitics obtained from the printed circuit board characterization. It is important to note that it also includes original features accounting for strong capacitive nonlinearities and displacement currents. Moreover, these features demand unusual extraction of electrical characteristics from regular datasheets. A detailed analysis on how to obtain this electrical characteristic is included in this study. Finally, the high accuracy of the model is validated with experimental measurements in a double-pulse buck converter setup by using commercial SJ MOSFET, as well as advanced device prototypes under development.

All Inorganic Spin-Coated Nanoparticle-Based Capacitive Memory Devices

Abstract: We demonstrate all inorganic, robust, cost-effective, spin-coated, two-terminal capacitive memory metal–oxide nanoparticle-oxide–semiconductor devices with cadmium telluride nanoparticles sandwiched between aluminum oxide phosphate layers to form the dielectric memory stack. Using a novel high-speed circuit to decouple reading and writing, experimentally measured memory windows, programming voltages, retention times, and endurance are comparable with or better than the two-terminal memory devices realized using other fabrication techniques.

A New Capacitive Displacement Sensor With Nanometer Accuracy and Long Range

Abstract: A highly stable motion with orthogonally alternating electric field is established to build the relationship between spatial displacement and time standards. Displacement is measured by counting the time pulses that serve as measurement standards. Thus, a displacement method is called time grating. An orthogonally alternating electric field is generated using two rows of differential capacitive sensing electrodes excited by four sinusoidal voltages. Sine-shaped grating planes rather than hyperfine grating lines are used to pick up the displacement signals. Electrode lead wires are designed below the middle of the electrodes and fabricated using multilayer thin-film technology to suppress the cross-sensitivity effect. A time-grating sensor has been fabricated to evaluate the proposed method. The range of measurement is 200 mm, the width of the electrode is 0.2 mm, the interval between two adjacent electrodes is 20 $\mu \text{m}$ , and the gap for capacitive sensing is 0.3 mm. Experimental results indicate that the measurement accuracy reaches ±200 nm with 1-nm resolution. Nanometer accuracy and resolution are achieved using sensing units with sub-millimeter periods. So, the cost for manufacturing the time-grating sensor can be decreased effectively in comparison to traditional nanometrology displacement sensors, and it may be a suitable low-cost alternative to long-range nanometrology.

Substrate-decoupled, bulk-acoustic wave gyroscopes: Design and evaluation of next-generation environmentally robust devices.

Abstract: This paper reports on a new type of high-frequency mode-matched gyroscope with significantly reduced dependencies on environmental stimuli such as temperature, vibration, and shock. A novel stress-isolation system is used to effectively decouple an axis-symmetric bulk-acoustic wave (BAW) vibratory gyro from its substrate, minimizing the effect that external sources of error have on the offset and scale factor of the device. Substrate-decoupled (SD) BAW gyros with a resonance frequency of 4.3 MHz and Q values near 60 000 were implemented using the high aspect ratio poly and single-crystal silicon (HARPSS) process to achieve ultra-narrow capacitive gaps. Wafer-level packaged sensors were interfaced with a customized application-specific integrated circuit (ASIC) to achieve low variations in the offset across temperature (±26° s−1 from −40 to 85 °C), supreme random-vibration immunity (0.012° s−1 gRMS−1) and excellent shock rejection. With a scale factor of 800 μV (°s−1)−1, the SD-BAW gyro system attains a large full-scale range (±1250° s−1) with a non-linearity of less than 0.07%. A measured angle-random walk (ARW) of 0.39°/√h and a bias instability of 10.5°h−1 are dominated by the thermal and flicker noise of the integrated circuit (IC), respectively. Additional measurements using external electronics show bias-instability values as low as 3.5°h−1, which are limited by feed-through signals coupled from the drive loop to the sense channel, which can be further reduced through proper re-routing of the gyroscope pin-out configuration. Scientists in the USA have developed a device for measuring rotation that is resilient against shock and vibration. A team led by Diego Serrano at Qualtre Inc. fabricated a micrometer-scale gyroscope that is decoupled from motion in the substrate on which it is built. Micromachined gyroscopes usually comprise a low-frequency resonant cantilever or membrane, and rotation is detected through a corresponding change in the resonance pattern of the resonator. However, such devices are susceptible to external sources of vibrations. Serrano’s team created a device known as a bulk acoustic wave gyroscope that is made of a disk of silicon and supports high frequency resonance inherently resistant to random external vibrations. The disk is surrounded by a series of electrodes that can fine tune the properties of the disk to further improve performance.

Printed electrodes structures as capacitive humidity sensors: A comparison

Abstract: This work discusses about four planar printed capacitive sensors with different geometrical layouts, fabricated by inkjet printing on a flexible substrate and used as humidity sensors. In particular, we show a comparison among interdigitated electrodes, meandered electrodes, spiral electrodes, and serpentine electrodes in terms of fabrication yields, sensitivities to relative humidity as well as thermal drift taking into account frequency dependencies. In addition, numerical simulations have been performed to further investigate the characteristics of these sensors. All sensors present similar behavior in frequency with humidity. Taking into account sensitivity within the same sensing area, the highest value is achieved by serpentine electrodes, followed by spiral electrodes, interdigitated and meandered electrodes, in this order. The best configuration will be dependent on the specific application and its requirements.

Rapid and sensitive detection of small biomolecule by capacitive sensing and low field AC electrothermal effect

Abstract: Conventional affinity biosensor typically relies on passive diffusion of analytes for binding reaction, which in many cases leads to long response time and lack of sensitivity. Recent research showed that directed particle motion towards sensor electrodes could be induced in sample matrix by applying a non-uniform AC electric field, often with AC dielectrophoresis as the responsible mechanism. As a result, shorter assay time and higher sensitivity can be achieved. Previously, we demonstrated a rapid and sensitive AC capacitive affinity sensor, which integrates low voltage AC dielectrophoresis into label-free capacitive measurement to achieve a single-step operation without any wash steps for clinical samples. However, dielectrophoretic force is rather short-ranged, and is also proportional to the size of target biomolecules/particles. Therefore, to detect target molecule at diluted concentrations or small molecule, improvement in sensitivity by dielectrophoresis could be quite limited. Alternatively, AC electric field can also produce microfluidic movement to carry biomolecules to sensors, which is of long range and size independent. This work demonstrates the use of low voltage AC electrothermal effect to enhance and accelerate the detection of low abundance and small target molecules by AC capacitive sensing with simultaneous AC electrokinetic enrichment. Electrode designs were studied for their effectiveness in AC electrothermal capacitive sensing. Electrodes with larger characteristic length were found to be more amenable to inducing AC electrothermal convection and were successfully used to detect low abundance protein and femto-molar level small molecules.

A 16 $\times$ 16 CMOS Capacitive Biosensor Array Towards Detection of Single Bacterial Cell

Abstract: We present a 16 $\times$ 16 CMOS biosensor array aiming at impedance detection of whole-cell bacteria. Each ${14}~\mu {\rm m}\times{16}~\mu {\rm m}$ pixel comprises high-sensitive passivated microelectrodes connected to an innovative readout interface based on charge sharing principle for capacitance-to-voltage conversion and subthreshold gain stage to boost the sensitivity. Fabricated in a ${0.25}~\mu {\rm m}$ CMOS process, the capacitive array was experimentally shown to perform accurate dielectric measurements of the electrolyte up to electrical conductivities of 0.05 S/m, with maximal sensitivity of 55 mV/fF and signal-to-noise ratio (SNR) of 37 dB. As biosensing proof of concept, real-time detection of Staphylococcus epidermidis binding events was experimentally demonstrated and provides detection limit of ca. 7 bacteria per pixel and sensitivity of 2.18 mV per bacterial cell. Models and simulations show good matching with experimental results and provide a comprehensive analysis of the sensor and circuit system. Advantages, challenges and limits of the proposed capacitive biosensor array are finally described with regards to literature. With its small area and low power consumption, the present capacitive array is particularly suitable for portable point-of-care (PoC) diagnosis tools and lab-on-chip (LoC) systems.

A Capacitive-Type Novel Six-Axis Force/Torque Sensor for Robotic Applications

Abstract: This paper presents an innovative design of a six-axis force/torque sensor, which enables ease of manufacturing, cost reduction, and ruggedness in operation. The advantages are realized by simplifying the structure of the sensor and reducing manual labor during the manufacturing process. In order to achieve a simple sensor structure, we propose a capacitive-type force sensing scheme in which the sensing elements are aligned in-plane. By using this method, all the sensing elements can be fabricated on single printed circuit board, and thus, manual tasks, such as bonding and coating the sensing elements, can be eliminated. In order to verify the feasibility of the idea, a prototype six-axis force/torque sensor was manufactured, and its performances were evaluated. The characteristics of the prototype are analyzed in terms of condition number, static response, time domain response, hysteresis, repeatability, and time drift.