Study On Microforce Sensor Based On Piezoelectric Thin Film

Piezoelectric sensors and actuators with many advantages including simple structure, fast response, high frequency, and simple driving and measuring circuit, have been extensively applied to ultrasonic devices, precision positioning, detecting of acoustics and mechanic parameters, etc. Piezoelectric material is used as MEMS function material extensively. PZT thin film as one type of piezoelectric material with excellent piezoelectricity is studied by lots of scholar.The main work includes building the experiment system to measure microforce, characterization of the microcantilever's frequency, measuring the two-segment and two-layer PZT thin film microcantilever's sensing and actuating capability, characterization of the microcantilever as a structure integrated microsensor and microactuator.Microforce sensor's dimension is several hundreds of μm, the generation and control of the microforce is very difficult at μN level, and the charge signal generated by the piezoelectric material at μN force is very weak. In the microforce measurement system, a microprobe adhered on bimoph is used to generate the microforce, electric balance is used to calibrate microforce, a 3D positioning stage is used to precious position and a microscope is used to observe the microcosmic.The measurement of the piezoelectric microcantilever's sensing and actuating capability is carried out. The calculation formula of piezoelectric constant d₃₁ is deduced based on direct or converse piezoelectric effect, respectively. Calculation indicates that the values of d₃₁ by two methods are approximately equal. The frequency characteristic of the microcantilever is tested by optical method and impulse exciting method, and the results are close to the theoretic calculation.The measurements of the microforce sensor and microactuator based on piezoelectric microcantilevers are carried out, the sensitivity, resolution, stability, hysteresis, repetitiveness, linearity and so on are studied.The two-segment microcantilever is measured as a structure integrated microsensor and microactuator. The simulation of microoperation process is performed, using the NI-DAQPad6015 by LabVIEW programme controlled D/A and A/D port.