In this paper, we presents a MEMS pressure sensor integrated with a readout circuit on a chip for an on-chip signal processing. The capacitive pressure sensor is formed on a CMOS chip by using a post-CMOS MEMS processes. The proposed device consists of a sensing capacitor that is square in shape, a reference capacitor and a readout circuitry based on a switched-capacitor scheme to detect capacitance change at various environmental pressures. The readout circuit was implemented by using a commercial 0.35 μm CMOS process with 2 polysilicon and 4 metal layers. Then, the pressure sensor was formed by wet etching of metal 2 layer through via hole structures. Experimental results show that the MEMS pressure sensor has a sensitivity of 11 mV/100 kPa at the pressure range of 100-400 kPa.

In this study, we propose and demonstrate a piezoelectric energy harvester with a shell cantilever for mechanical frequency up-conversion to generate electric power in a low-frequency vibration environment. The proposed device is composed of a clamped semicylindrical shell cantilever as a driving beam and a piezoelectric cantilever attached to the proof mass of the shell cantilever as a generating beam. The shell cantilever bends downward when the external acceleration is over the threshold value for buckling transition. When the acceleration direction is reversed, the shell cantilever makes abrupt stop at its initial position, inducing impact-like force on the generating beam and resulting in free vibration at high resonance frequencies. Experimental results show that a maximum power of 101 µW at 20 Hz can be obtained.