Characterisation of PZT thin film micro-actuators using a silicon micro-force sensor

Abstract

This paper reports on the measurements of displacement and blocking force of piezoelectric micro-cantilevers. The free displacement was studied using a surface profiler and a laser vibrometer. The experimental data were compared with an analytical model which showed that the PZT thin film has a Young's modulus of 110 GPa and a piezoelectric coefficient d31,f of 30 pC/N. The blocking force was investigated by means of a micro-machined silicon force sensor based on the silicon piezoresistive effect. The generated force was detected by measuring a change in voltage within a piezoresistors bridge. The sensor was calibrated using a commercial nano-indenter as a force and displacement standard. Application of the method showed that a 700 μm long micro-cantilever showed a maximum displacement of 800 nm and a blocking force of 0.1 mN at an actuation voltage of 5 V, within experimental error of the theoretical predictions based on the known piezoelectric and elastic properties of the PZT film.