Experimental Investigation on the Use of Photostrictive Optical Actuator for MEMS Devices and Verification With the FEA Modeling Results

Abstract

Photostrictive materials are lanthanum-modified lead zirconate titanate (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, called PLZT, exhibit large photostriction under uniform illumination of high-energy light. Photostrictive materials are ferrodielectric ceramics that have a photostrictive effect. Photostriction arises from a superposition of the photovoltaic effect, i.e. the generation of large voltage from the irradiation of light, and the converse-piezoelectric effect, i.e. expansion or contraction under the voltage applied. When non-centrosymmetric materials, such as ferroelectric single crystals or polarized ferroelectric ceramics, are uniformly illuminated, a high voltage, considerably exceeding the band gap energy, is generated. Along with this photovoltage, mechanical strain is also induced due to the converse piezoelectric effect. Photostrictive materials offer the potential for actuators with many advantages over traditional transducing electromechanical actuators made of shape memory alloys and electroceramics (piezoelectric and electrostrictive). Drawback of traditional actuators is that they require hard-wired connections to transmit the control signals which introduce electrical noise into the control signals; on the other hand PLZT actuators offer non-contact actuation, remote control, and immune from electric/magnetic disturbances. Some experimental research has been conducted on the use of PLZT materials, such as optical motor as an electromechanical device suitable for miniaturization, micro-waking machine, photo driven relay device using PLZT bimorphs and high speed (less than 10 ns), low-voltage, low power consumption optical switch. Authors have developed a computational method and implemented in an in-house finite element code which will be useful for designing systems incorporating thin film photostrictive actuators. The purpose of this current research work is to design and develop an experimental test set-up for photostriction effect measurement of PLZT thin film of different thickness, size and location on silicon wafer as smart beams, which may be useful for various MEMS device as optical actuator. The experimental results will be verified by comparing with the FEA modeling results.