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An improved peninsula-island structured pressure sensor was presented with the novel dry-wet combination etching process. There were four pairs of segmented mass blocks attaching on the back of the diaphragm. Each segmented mass block was composed of a peninsula structure and an island structure with anisotropic-etching-induced sidewalls. The improved structure not only inherited the stress concentration feature of low strain energy dissipation but also improved the comprehensive ability of the sensor chip, including low fabrication cost, high etching uniformity, good temperature performance and low residual stress in the diaphragm. Also, the fabrication method combining DRIE (Deep Reactive Ion Etching) and anisotropic wet etching was verified by the simulation based on the Sentaurus 2013. The fabrication error caused by anisotropic wet etching was analyzed. Compared with the flat film of the same size, the proposed structure can increase the sensitivity by 225%, reduce the nonlinearity by 80.3%, and increase resonance frequency by 11%. In addition, the sensor structure can also be applied to pressure sensors with different working range, which will be helpful to design the pressure sensors with high efficiency and accuracy.

Lumped element model (LEM) for resonant chemical sensors based on the capacitive micromachined ultrasonic transducers (CMUTs) was developed and analyzed with electrical characterization. The CMUTs chip were functionalized with the electrospinning technology. Two Butterworth Van-Dyke (BvD) models for functionalized CMUTs were proposed and analyzed with different DC voltages. Considering the electrical phase with parasitic capacitance, the modified BvD model can be used to illustrate more comprehensive features for both mechanical impedance and phase properties. The parallel capacitance was measured accurately using an impedance analyzer, and the quality factor was calculated based on the proposed model under different DC voltages. These models will provide important theoretical basis for CMUTs-based chemical sensors to further electrical analysis and oscillator design.

A micro electromechanical systems (MEMS) resonant sensing chip with microcantilever has been developed to measure gas pressure by immersing it in gaseous environment. The microcantilever was designed to sense surrounding gas molecules loading, owing to the gas density sensitive to the pressure, then the resonant frequency shifts of sensing chip were induced under different pressures. Especially, the sensing chip featuring no diaphragm realized embedded package and installation for the immersive measurement. The resonance response of the sensing chip for target pressure was theoretically analyzed and simulated, and a packaged pressure sensor with the proposed sensing chip was tested under flexural and torsional modes of the microcantilever. The experimental results proved that the proposed sensor had preferable measuring performance under the torsional mode with the RSS (root sum square) accuracy of 0.21%FS in the working range of 10–560 kPa. The temperature compensation was presented to alleviate the temperature disturbance for the sensor, and the maximum deviation of the frequency was 59 ppm over the full pressure and the temperature range of 26–55 ℃. The proposed sensing chip is potentially a better choice for pressure sensors with measurement demand for immersive gas pressure.