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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]

Tactile force sensor has attracted considerable interests owing to its great application prospects in human-computer interaction systems, intelligent robots, wearable medical devices and other fields. The key to achieve this sensor is (1) high sensitivity and low crosstalk, (2) fast response time and (3) the economy of fabricating macroscopic sensors on flexible substrates. However, low-cost tactile sensors reported hitherto cannot simultaneously achieve high sensitivity, low crosstalk and fast response time. In this study, we report an all-printed 4 × 4 capacitive array tactile sensors using PDMS with innovative island-structure and printable nanocomposite inks as dielectric layer and electrodes, respectively. By changing the geometry parameters of the island-structure of the dielectric layer, the sensors can achieve adjustable sensitivity while effectively reducing crosstalk between sensing elements, leading to accurate position perception of the applied pressure. The sensitivity of the sensor can reach 0.76 kPa−1 in the range of 0–1 kPa, and 0.2 kPa−1 in the range of 1–15 kPa. Moreover, the sensor exhibits a fast response time (∼50 ms) and low detection limit (∼2 Pa). These achievements have rarely been reported in a fully printed tactile force sensor. As a proof of concept for fully printed high sensitivity and low crosstalk sensor, human motion and sound signal detection were finally demonstrated. The advantages of the array sensors afford several applications, including low-cost, wide-range flexible wearable devices for measuring signals from a user, rehabilitation training and human-computer interaction, etc. [Display omitted] • Circular radiation-shaped microstructures dielectric layer that prevents crosstalk between sensing elements is proposed. • Capacitive array tactile force sensors with tunable sensitivity are fabricated by full printing technology. • A low-cost manufacturing progress and procedure to fabricate the array tactile force sensors is proposed. [ABSTRACT FROM AUTHOR]

Impact-based vibration energy harvesters (VEHs) with a rolling proof mass are promising candidates for scavenging ambient low-level, broadband, and low-frequency vibration energy. This paper derives the mathematical model of a VEH with two piezoelectric cantilevers symmetrically located at two open ends of a guiding channel with a rolling steel ball inside as the proof mass. The model includes the equation of motion and coupled electrical circuit equation of the bimorphs under base excitation, the equations of motion of the rolling proof mass under base excitation, and the collision equations between the bimorphs and the proof mass. Simulation results show that the scavenging efficiency of low-level vibration can be improved by introducing the rolling proof mass. The numerical results agree well with the experiments when the harvester prototype is horizontally fixed on the base. Under the base excitation of 1 g(=9.8 m/s 2 ), the maximum output power of one bimorph is about 511 μW at 18.4 Hz. [ABSTRACT FROM AUTHOR]

Active SIW-based sensor terminated with negative resistance circuit. • A microwave sensor based on SIW technology for characterization of MD materials is for the first time reported. • The proposed sensor has the ability for measuring both complex permittivity and complex permeability. • By virtue of negative resistance circuit, the sensor exhibits higher quality factor than previous reported sensors. A high-Q sensor based on substrate integrated waveguide (SIW) technology is designed to fully characterize magneto-dielectric materials. By utilizing the negative resistance circuit, the quality factor is further increased to an ultrahigh value of 13,399. By virtue of the improved complementary split ring resonator (CSRR), the complex permittivity, as well as the complex permeability, can be extracted from variations of the resonant frequency and magnitude. A prototype of the designed active SIW-based sensor is fabricated and validated experimentally. A good agreement can be achieved between the measured values and the reference data. [ABSTRACT FROM AUTHOR]