Study on Contact Microforce Measurement Based on Piezoelectric PZT Thin Film

PZT thin film sensors are widely used in microsensor because of its simple structure, high sensitivity and good linearity. The sol-gel method is used for the PZT thin film deposition on the silicon cantilever structure, actuation and sensing electrodes are made on the PZT micro-cantilever by the bulk micromachining technology. AC voltage is applied to the actuation electrode to make the micro-cantilever oscillate at 70 Hz, and the charge on the sensing electrode serves as sensor signal. When contact force is applied to the tip of the micro-cantilever, the amplitude variation of the induced charge is collected by a charge amplifier and a digital lock-in amplifier. Experiments have shown that the PZT thin film sensors with the micro-cantilever structure are able to sense contact force whether the PZT thin film is in the state of stretching stress or compressive stress. The resolution of the microforce sensor is 3 muN at the stretching stress, and 3.75 muN at the compressive stress