Hair-like airflow sensing with piezoelectric vibrating diaphragm

Inspired by filiform hairs, we propose a three dimensional (3D) microelectromechanical systems (MEMS) airflow sensing structure for wind velocity measurement. The piezoelectric Pb(Zr,Ti)O₃ (PZT) diaphragm vibrating at its resonant frequency is used as the sensing element to mimic the neuron. The standing beam on the diaphragm behaves like the hair to collect the airflow drag force. The bending of the standing beam can induce the mechanical strain, resulting the changes in the diaphragm stiffness and subsequently the resonant frequency. Then the airflow velocity can be characterized by the resonant frequency shift of the piezoelectric diaphragm. The microstructure design, fabrication and packaging sequence are described. A specific electronic printed circuit, which converts the resonant frequency shift to a voltage (conversion rate of 0.7 mV/Hz) and enables the data communication to a PC, has been developed. Testing result shows that a 25Hz resonant frequency shift is found when the packaged device is subjected to a wind speed of 10 m/s.