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Owing to the advantages of small size and high integration that accelerometers made by MEMS technology, the Pulse Width Modulation (PWM) closed-loop feedback interface circuit of a sandwich capacitive accelerometer based on ARM is designed. Based on the design, a simulation by SIMULINK and a PCB board-level circuit are conducted. Simulation and measurement are provided to support the design. The realization of Proportion Integral Differential (PID) control algorithm and the generation of PWM are performed by STM32 microcontroller instead of the circuit in the design. The output form of the interface circuit is PWM with different duty cycle and filtered DC voltage. According to the measurement results, the output of the PWM duty cycle change is 16.9%/g, and the sensitivity is 1.045 V/g. [ABSTRACT FROM AUTHOR]

This paper analyzes the acoustic and micro seism signal feature of the projectile launching, flight and landing explosion in range test, and puts forward a Landing Point Location method which based on the asynchronous time difference of arrival (ATDOA) method. This method can effectively filter away the signals in launching and flight process, meanwhile get the acoustic and micro seism signal of projectile explosion accurately, and then the explosion location and velocity can be obtained by iterative equations. Comparing with the existing projectile point positioning method, this method can find the arrival time of explosion signal accurately, and establish the composition equations by iterative calculation equation of the respective location without precise synchronization of each sensor. Accordingly, the complexity of the application system is reduced, and positioning precision is improved effectively. [ABSTRACT FROM AUTHOR]

This paper presents a symmetrical double-sided serpentine beam-mass structure design with a convenient and precise process of manufacturing MEMS accelerometers. The symmetrical double-sided serpentine beam-mass structure is fabricated from a single double-device-layer SOI wafer, which has identical buried oxides and device layers on both sides of a thick handle layer. The fabrication process produced proof mass with though wafer thickness (860 μm) to enable formation of a larger proof mass. Two layers of single crystal silicon serpentine beams with highly controllable dimension suspend the proof mass from both sides. A sandwich differential capacitive accelerometer based on symmetrical double-sided serpentine beams-mass structure is fabricated by three layer silicon/silicon wafer direct bonding. The resonance frequency of the accelerometer is measured in open loop system by a network analyzer. The quality factor and the resonant frequency are 14 and 724 Hz, respectively. The differential capacitance sensitivity of the fabricated accelerometer is 15 pF/g. The sensitivity of the device with close loop interface circuit is 2 V/g, and the nonlinearity is 0.6 % over the range of 0-1 g. The measured input referred noise floor of accelerometer with interface circuit is 2 μg /√Hz (0-250 Hz). [ABSTRACT FROM AUTHOR]

Abstract: This paper reports a novel capacitive accelerometer with highly symmetrical double-sided beam-mass structure. The highly symmetrical structure is fabricated from single wafer by a novel vertical sidewall protection technique. The good device performance is obtained by highly symmetrical double-sided beam-mass structure and fabrication process that enable formation of a large proof mass, controllable thickness of beam, and a narrow uniform capacitive gap over a large area. The resonance frequency of the accelerometer is measured in open loop system by a network analyzer. The quality factor and the resonant frequency are 34 and 787Hz, respectively. The accelerometer with closed loop interface circuit is calibrated on B&K Vibration Transducer Calibration System (Type 3629). The typical measurement range of the device is 1g, and the maximum range is 2g. The capacitance sensitivity of the fabricated accelerometer is 11.7pF/g. The sensitivity of the device with closed loop interface circuit is 1V/g, and the nonlinearity is 0.39% over the range of 1g. The cross-sensitivity x/z is 0.72% and y/z is 0.50%, respectively. The accelerometer with closed loop circuit has wide bandwidth of DC to 1kHz (3dB). Also the bias stability is 255μg. The device with closed loop circuit has signal to noise ratio (SNR) of 106dB, the average noise floor is (0–100Hz). [Copyright &y& Elsevier]

Abstract: A simplified, cost-effective flexible micro-electronic-mechanical systems (MEMS) technology has been developed for realizing a temperature-sensing array on a flexible polyimide substrate. The fabrication technique utilized liquid polyimide to form flexible film on the rigid silicon wafer using a temporary carrier during the fabrication. The platinum thin film is employed as temperature sensitive material and 8×8 temperature-sensing arrays were micromachined on the polyimide, from which the silicon wafer carrier was removed at the end of fabrication. The platinum thin film temperature sensor exhibits excellent linearity and its temperature coefficient of resistance reaches 0.00291°C−1. Because of the effective thermal isolation, the flexible temperature sensors show a high sensitivity of 1.12Ω/°C at 10mA to the constant drive current. The flexible MEMS technology based on liquid polyimide enables the development of flexible, compliant, robust, and multi-modal sensor skins for many other important applications, such as robotics, biomedicine, and wearable microsystems. [Copyright &y& Elsevier]

Abstract: The combs of the comb capacitive inertial sensors fabricated by a deep reactive ion etching are usually not parallel. This non-ideal feature is greater in high aspect ratio structure and significantly affects the capacitance and electrostatic force. In this paper, the effects of non-parallel combs on the reliable operation range for step and pulse signals in three capacitive configurations are investigated when alternative electronic testing signals are applied on the sensors for detecting the variation of capacitance. Analytical expressions of the critical step acceleration and the critical time duration of pulse acceleration of the capacitive sensor whose comb electrodes have little angle of the decline are obtained. Results show that for a step inertial signal, even the angle of the decline is 0.5°, the reliable operation ranges of the sensor with single-sided structure, double-sided structure and double-sided structure with feedback voltage are diminished to 0.34, 0.44 and 0.54 of the ones whose comb electrodes are parallel, respectively, for pulse inertial signal, the reliable operation ranges with single-sided structure and double-sided structure are diminished to 0.45 and 0.56, respectively, and the ones of double-sided capacitive sensor with feedback voltage are diminished to 0.95 as the angle is changed from 0.1° to 0.15°, which show that the effects of the non-parallel can not also been ignored. Results also show that the reliable dynamic operation ranges of the sensor with double-sided comb capacitive structure are least affected by the effects of non-parallel plates and its merit is more evident as the angle of the decline of the comb electrodes increases. Compared to the effects of non-parallel comb electrodes on the reliable operation range for step inertial signal, the effects for pulse inertial signal are smaller. [Copyright &y& Elsevier]

For capacitive sensing, a driving signal with a dc bias voltage and an ac voltage is usually necessary for the measurement of capacitance. The electrostatic forces caused by the driving signal on the mechanical capacitor may interfere significantly with the measurement and the normal operation of the devices. In this paper, quantitative analyses on the effects of driving signal with different bias voltage polarities are made for double-sided driving and double-sided driving with voltage feedback. For double-sided driving, the effects of the dc bias voltage with different polarities on devices are the same. For double-sided driving with voltage feedback, positive–positive and positive–negative bias voltage configurations may improve the measurement linearity of the device and mostly eliminate the pull-in effect caused by the driving signal, while negative–negative and negative–positive bias voltage configurations maximize the side effects of the driving signal and reduce largely the safe operation range of the device. [Copyright &y& Elsevier]

Design, fabrication and testing of a novel silicon micromachined gyroscope prototype with slots structure are presented. The device structure which we called “slots gyroscope” consists of a proof mass with slots linked up to substrate by suspend springs and is fabricated by silicon–glass bonding and deep reactive ion etching (DRIE). The gyroscope makes use of electrostatic driving and capacitive sensing. As the proof mass used as the movable electrodes is parallel to the plane of fixed driving and sensing electrodes, there is only slide film damping in the driving and sensing mode. The gyroscope can operate at atmospheric pressure due to almost same high quality factor in the sensing direction and driving direction. The experiment result shows that the drive and sense mode resonant frequencies are 460.4 and 549.6 Hz, respectively, and the quality factor of the drive and sense are 102.5 and 106.5, respectively at atmospheric pressure. The scale factor and non-linearity of the micromachined gyroscope are 20 mV/(° s) and 0.56%, respectively at atmospheric pressure. [Copyright &y& Elsevier]

Protection suits are vital for firefighters' safety. Traditional protection suits physically protect firemen from burns, but cannot locate the position of bodily injuries caused by impact debris. Herein, we present a wearable impact debris positioning system for firefighter protection suits based on an accelerometer array. Wearable piezoelectric accelerometers are distributed regularly on the suit to detect the vibration on different body parts, which is conducive to determining the position of injured body parts. In addition, the injured parts can be displayed on a dummy body model on the upper computer with a higher localization accuracy of 4 cm. The positioning alarm system has a rapid response time of 0.11 ms, attributed to the smart signal processing method. This work provides a reliable and smart method for locating and assessing the position of bodily injuries caused by impact debris, which is significant because it enables fire commanders to rescue injured firefighters in time. [ABSTRACT FROM AUTHOR]

Harvesting energy from natural water evaporation has been proposed as a promising alternative to supply power for self‐powered and low‐power devices and systems, owing to its spontaneous, ubiquitous, and sustainability. Herein, an approach is presented for harvesting water‐evaporation‐induced electricity based on liquid–solid triboelectric nanogenerators (LS‐TENGs), which has various advantages of easy preparation, substrate needless, and robustness. This developed harvester with porous Al2O3 ceramic sheet can generate a continuous and stable direct current of ≈0.3 µA and voltage of ≈0.7 V by optimizing the sheet physical dimensions and ambient parameters such as relative humidity, temperature, wind velocity, and ion concentration. The output power also can be improved significantly by series or parallel connection the harvesters, which has superior electrical compatibility and environmental suitability. The development of the water‐evaporation‐induced electricity harvesting shows many application prospects including power supply for digital calculator and charging capacitor. This research provides an in‐depth experimental study on water‐evaporation‐induced electricity harvesting based on LS‐TENGs and an efficient approach to supply electricity for low‐power devices. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors play a significant role in wearable devices and electronic skin. Iontronic pressure sensors with high sensitivity, wide measurement range, and high resolution can meet requirements. Based on the significant deformation characteristics of alveoli to improve compressibility, and the ability of the arch to disperse vertical pressure into horizontal thrust to increase contact area, a graded hollow ball arch (GHBA) microstructure is proposed, greatly improving sensitivity. The fabrication of GHBA ingeniously employs a double‐sided structure. One side uses mold casting to create convex structures, while the other utilizes the evaporation of moisture during the curing process to form concave structures. At the same time, a novel side‐by‐side package structure is proposed, ensuring pressure on flexible substrate is maximally transferred to the GHBA microstructure. Within the range of 0.2 Pa–300 kPa, the iontronic pressure sensor achieves a maximum sensitivity of 10 420.8 kPa−1, pressure resolution of 0.1% under the pressure of 100 kPa, and rapid response/recovery time of 40/35 ms. In wearable devices, it is capable of monitoring dumbbell curl exercises and wirelessly correcting sitting positions. In electronic skin, it can non‐contactly detect the location of the wind source and achieve object classification prediction when combined with the CNN model. [ABSTRACT FROM AUTHOR]

Real-time monitoring of rainwater is a critical issue in the development of autonomous vehicles and smart homes, while the corresponding sensors play a pivotal role in ensuring their sensitivity. Here, we study a self-powered intelligent water droplet monitoring sensor based on a solid–liquid triboelectric nanogenerator (SL-TENG). The sensor comprises a SL-TENG, a signal acquisition module, a central processing unit (CPU), and a wireless transmission module, facilitating the real-time monitoring of water droplet signals. It is worth noting that the SL-TENG has self-powering characteristics and can convert the kinetic energy of water droplets into electrical energy. The excellent output performance, with open-circuit voltage of 9 V and short-circuit current of 2 μA without any treatment of the SL-TENG, can provide an effective solution to the problem that traditional sensor need battery replacement. In addition, the SL-TENG can generate stable amplitude electrical signals through water droplets, exemplified by the absence of decay in a short-circuit current within 7 days. More importantly, the sensor is equipped with intelligent analytical capabilities, allowing it to assess rainfall based on variables such as amplitude and frequency. Due to its excellent stability and intelligent analysis, this sensor can be used for roof rainwater monitoring, intravenous administration monitoring, and especially in automobile automatic wipers and other fields. [ABSTRACT FROM AUTHOR]

Sound as a ubiquitous energy in our surroundings is clean and sustainable, and carries abundant information in a wide frequency bandwidth. However, effectively harvesting and utilizing acoustic energy is still hindered by the limitations such as low energy density of acoustic energy and lack of novel application. In this paper, we successfully present a self-powered acoustic sensor, which is composed of an adjustable spacing structure and sound-driven triboelectric nanogenerator (TENG). The acoustic sensor exhibits excellent electric output properties because of the poriferous electrode structure, ultrathin vibrating membrane as well as high-quality triboelectric materials. The sensor can deliver a maximal output voltage of 6.28 V with the sound frequency of 350 Hz and sound pressure of 110 dB. In addition, the electric output frequency is closely related to the applied acoustic wave and the corresponding directional dependence pattern as a butterfly is highly symmetrical. Our approach presents a cost-effective strategy to develop self-powered acoustic sensor and shows great potentials in home automation, self-powered microphone, sensor network and artificial intelligence. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have excellent properties in harvesting tiny environmental energy and self-powered sensor systems with extensive application prospects. Here, we report a high sensitivity self-powered wind speed sensor based on triboelectric nanogenerators (TENGs). The sensor consists of the upper and lower two identical TENGs. The output electrical signal of each TENG can be used to detect wind speed so that we can make sure that the measurement is correct by two TENGs. We study the influence of different geometrical parameters on its sensitivity and then select a set of parameters with a relatively good output electrical signal. The sensitivity of the wind speed sensor with this set of parameters is 1.79 μA/(m/s) under a wind speed range from 15 m/s to 25 m/s. The sensor can light 50 LEDs at the wind speed of 15 m/s. This work not only advances the development of self-powered wind sensor systems but also promotes the application of wind speed sensing. [ABSTRACT FROM AUTHOR]

Water droplets are ubiquitous in nature and harvesting droplet kinetic energy has attracted a great deal of attention to meet the increasing worldwide energy demands. In this work, we report a water droplet motion energy harvester with the wafer-level fabrication method, which is based on the water–solid surface contact electrical double layer effect. A theoretical model is established to illuminate the water droplet motion energy harvesting mechanism. Guided by the model, an energy harvester is developed based on Micro Electro-Mechanical Systems compatible process technology, which achieve a wafer-level fabrication. The output performance of the energy harvester has been optimized by decreasing the electrode width and its interval. Experimental results also show that the output voltage can be improved by increasing the droplet volume and decreasing the ionic concentration. The optimized energy harvester exhibits an open circuit output peak voltage of 57.5 mV. This research provides an in-depth theoretical study and a practical guidance on water droplet kinetic energy harvesting. [ABSTRACT FROM AUTHOR]

The last two decades have witnessed an explosion of interest in the field of droplet-based microfluidics for their multifarious applications. Despite rapid innovations in strategies to generate small-scale liquid transport on these devices, the speed of motion is usually slow, the transport distance is limited, and the flow direction is not well controlled because of unwanted pinning of contact lines by defects on the surface. We report a new method of microscopic liquid transport based on a unique topological structure. This method breaks the con tact line pinning through efficient conversion of excess surface energy to kinetic energy at the advancing edge of the droplet while simultaneously arresting the reverse motion of the droplet via strong pinning. This results in a novel topological fluid diode that allows for a rapid, directional, and long-distance transport of virtually any kind of liquid without the need for an external energy input. [ABSTRACT FROM AUTHOR]

Based on the challenge of high-Q capacitive accelerometer, the analysis of the structure and the dynamic response of an all-silicon sandwich accelerometer are conducted. An analog closed-loop interface circuit based on proportional-differential feedback compensation is designed and simulated by SIMULINK/SIMSCAPE in order to stabilize the sensor and increase the closed-loop damping. Based on the design, a printed circuit board level circuit and an ASIC circuit are made for the test. Simulation and measurement are provided to support the design. Measurement results show that the circuit effectively improves the dynamic response time of the system. The accelerometer with ASIC circuit has the scale factor of 0.9976 V/g and the second order non-linearity of −400 ppm g/g in the range of ±1 g, the average noise floor is 2 μg/√Hz (0-200 Hz). [ABSTRACT FROM AUTHOR]

Highlights: [•] The proof mass is suspended symmetrically by double-sided 16 straight beams. [•] The highly symmetrical beam-mass structure is fabricated from a single wafer. [•] The accelerometer is designed reasonably and can be fabricated easily. [•] The fabricated accelerometer is measured within the range of 30g. [ABSTRACT FROM AUTHOR]

A novel method is presented to fabricate a self-aligned electrostatic vertical actuator using plastic deformation technology. The model of the vertical actuator is proposed and simulated using finite element analysis method. The fixed combs and movable combs, and spring beams are patterned using one mask and fabricated by DRIE technology simultaneously. The fixed combs and movable combs have staggered distance of 21.8 μm in the vertical direction on the condition of self-alignment using plastic deformation technology. The electrostatic vertical actuator has achieved large vertical drive displacement at low voltage. The measurement results show that the maximum drive displacement runs up to 17 μm at 17 V voltage between the fixed combs and movable combs. Experimental results verify the usefulness of the guidelines obtained from simulation and calculation. [ABSTRACT FROM AUTHOR]

The effect of fabrication process error on the nonlinearity of sandwich MEMS capacitive accelerometer is analyzed in the paper. Firstly, after the packaging of the accelerometer, the displacement offset and torsion angle of the sensitive proof mass are obtained by CV testing. The gravitational field rolling four-position testing method is used to calibrate the bias, the scale factor, and the second-order nonlinearity coefficient of the accelerometer under different compensation capacitance. Testing results show that the second-order nonlinearity coefficient has a linear relationship with the compensation capacitance. A physical model of the accelerometer is built to analyze the effect of fabrication process error on the nonlinearity of the accelerometer, justifying the experimental linear relationship. Using the relationship, the capacitance compensation method is optimized, thus improving the efficiency of compensation. In the optimal case, the second-order nonlinearity coefficient of the accelerometer can be reduced to the order of 10−4 only by three capacitance compensations. [Display omitted] • The displacement offset and torsion angle are obtained by CV testing. • A physical model is built to explore effect of displacement offset on nonlinearity. • 2nd-order nonlinearity coefficient is linearly related to compensation capacitance. • 2nd-order nonlinearity coefficient is reduced to the order of 10−4 by compensation. [ABSTRACT FROM AUTHOR]