Shuyu He

The fabrication of high-performance flexible humidity sensors using biocompatible materials is crucial for expanding their application scope. Herein, a humidity sensor using silk fibroin (SF) as the sensing material is proposed and fabricated, accompanying with a systematical investigation of the effects of interdigital electrode geometry (the shape and spacing) and thickness of sensing layer on sensor performance. The prepared sensors were characterized by high sensitivity (3580%) at 95% RH (Relative Humidity), with a detection limit (LOD) of 1.34 × 10⁻³ %RH and a quantification limit (LOQ) of 4.48 × 10⁻³ %RH. It features a short response/recovery time of 37.81/1.15s, excellent repeatability, outstanding flexibility, and minimal hysteresis (5.81%). The proposed flexible humidity sensors show pleasing applicability in many scenarios, amongst which there are three primary functions presented in this paper, i.e. the real-time respiratory status monitoring, skin perspiration moisture monitoring, and non-contact interactive switching. The experimental results reveal its broad application prospects in the areas of health monitoring and smart human-computer interactions. This work demonstrates a viable strategy for developing biocompatible humidity sensors with high performance and multifunctional applicability in next-generation wearable electronic devices.

By establishing the nonlinear vibration model of a resonant accelerometer, this article analyzes the effects of mechanical nonlinearity and electrostatic nonlinearity on the output frequency offset of the resonant accelerometer. It is found that these two types of nonlinearities affect the nonlinear coefficient oppositely. Thereby, a nonlinearity compensation model is proposed and built by using electrostatic nonlinearity to counteract mechanical nonlinearity. Subsequently, polarization voltage conditions aiming for zero nonlinear coefficient are investigated, so that to decrease the output frequency offset of the resonant accelerometer, improving the stability of the output frequency. Finally, through theoretical calculations and numerical simulations, it is figured out that under the compensation voltage, the output frequency offset is less than 0.001%. According to the principles of electromechanical equivalence, the nonlinear vibration compensation model is equivalently represented by an electrical circuit model. The output frequencies of the equivalent circuit turned out to be consistent with that obtained by numerical analysis of the nonlinear vibration compensation model. The linearity of the accelerometer output curve before and after compensation is compared, and the results certify the feasibility of the proposed nonlinear vibration compensation method.