Mechanics Modelsand Experiments Of Piezoelectric Microcantilever Used For Gas Detection

As a kind of the simplest MEMS devices, microcantilever was firstly used in SPM as a tool to measure surface morphology or small force. Recently, microcantilever has also been widely used as micro/nano sensors due to their advantages of reduced size, high sensitivity, fast response and low costs. Microcantilever has two kinds of operational mode: static mode and dynamic mode. The microcantilever can be used to kinds of detections by detecting its static deflection or change of resonant frequency.Though microcantilever has been widely used and researched because of its some significant advantages, the mechanism of biological and chemical microcantilever sensor hasn't been fully understood. Additionally, optical leverage is highly sensitive, but it is complicated and not feasible for the miniaturization of the sensing system. Base on the piezoelectric effect of piezoelectric materials, the piezoelectric microcantilever gas sensors are researched in this paper. Because the piezoelectricity can not only be used for microcantilever actuation but also for detection of microcantilever signals, it can effectively solve the problem of miniaturization of the sensing system.In this paper, the piezoelectric microcantilever gas sensors are studied and the theoretical models are established. First, the change of neutral layer position caused by adsorption-induced surface stress is introduced in the modeling and the static bending model of piezoelectric microcantilever gas sensors is established, and piezoelectric microcantilever adsorbed with water molecules is used to analyze the static bending performancies and investigate the relationship of static deflection of piezoelectric microcantilever gas sensor with thickness of microcantilever and adsorbed gas.Second, the dynamic models of piezoelectric microcantilever gas sensor without considering the piezoelectric effect and gas adsorption, only considering the adsorption,only considering the piezoelectric effect and considering both the piezoelectric effect and gas adsorption are established, then the effect of piezoelectric effect and adsorption on resonant frequency of microcantilever is analyzed.The piezoelectric microcantilever adsorbed with water molecules is also used to analyze the dynamic performancies and investigate the relationship of resonant frequency of piezoelectric microcantilever gas sensor with driven voltage and adsorbed gas. In the end, an experimental platform including Agilent 4294A impedance analyzer, DMASP piezoelectric microcantilever and CHL-156 dry box is built to detect humidity. The experimental results show that the theoretical model is in good agreement with the experimental results.