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This study reports the design architecture to embed piezoresistive pressure sensor into accelerometer (PinG sensor) on a single chip by using the cavity-SOI process. The monolithic sensing chip can find various applications such as tire pressure monitoring system (TPMS), etc. The merits of the presented design includes significant chip size reduction by integrating the diaphragm of pressure sensor into the proof-mass of accelerometer, as well as better manufacturability through combining piezoresistor (PZR) process and CSOI process. Preliminary tests demonstrated the feasibility of detecting both pressure and acceleration using the presented PinG sensor. This design architecture is also applicable for other sensors integration.

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This study presents a novel dual-axis capacitive-type accelerometer design consists of a pendulum-proofmass (bulk Si), a gimbal-spring (poly-Si film), and vertical-combs sensing electrodes. This design has three merits, (1) pendulum-proofmass to produce torque by in-plane acceleration (offset-axis inertial force), (2) gimbal-springs enable the detection of dual-axis accelerations, and (3) high-aspect-ratio-micromachined (HARM) vertical-combs as the differential sensing electrodes to detect angular motion. In short, applying the HARM vertical-combs for differential capacitive sensing to detect the offset-axis inertial force is firstly implemented in this work. Measurement results show that sensitivities (non-linearity) of etch direction are 2.44mV/G (0.04%) of X-axis, and 51.99mV/G (0.11%) of Y-axis (measurement range: 0.05G~2G). The resolution is 50mG for both axes. The cross-axis errors range from 0.005% to 11%.

This study presents the design and realization of a piezoelectric MEMS microspeaker for high-frequency enhancement. Based on piezoelectric thin film actuation, designs of cantilever diaphragms are conducted by modal analysis. Under a die size of 2.5 mm (w) × 5 mm (l) × 0.4 mm (t), the diaphragms are designed to include mid-range and tweeter units with regard to the balance of radiation area and sound pressure contribution. Furthermore, the out-of-phase driving of the proposed device can ensure that the superposition of the sound pressure level (SPL) is within the target frequency range (8–13 kHz) while reducing the SPL outside the target range. In pressure-field measurements, the proposed multi-shape cantilever array can produce high average SPL (91.6 dB) in the target frequency range from 8 kHz to 13 kHz and has a low total harmonic distortion (THD) of <1.4% under a 0.707 Vrms input signal. The performance can be further improved by biasing the input signal. With a 9 V bias, the average SPL of the proposed microspeaker in the target frequency range is enhanced to 99.4 dB, and the average THD is reduced to <0.7%. In addition, the THD from 7.7 kHz to 18 kHz is below 2.5%. This study shows the great potential of piezoelectric MEMS microspeakers for in-ear applications.