Light-activated piezoelectric linear motor by using a serial bimorph made of an optopiezoelectric composite

© 2018 IOP Publishing Ltd. In this paper, we report a new method to activate and control a piezoelectric linear motor using a switching light source through two transparent electrodes and a photoconductive coating. This coating is composed of titanium oxide phthalocyanine (TiOPc), electron transport materials, hole transport materials, and polyvinyl butyral binder. It is used to replace one of the surface electrodes of a piezoelectric serial bimorph to provide an optical interface and to construct an optopiezoelectric composite. The weight percentage of TiOPc nanoparticles, solvent compositions, and film thickness are studied to identify the optimal coating to match the electrical impedance of the piezoelectric serial bimorph in both on and off states. Experimental results show that the photoconductive coating has a good on-off ratio and low electrical impedance under conditions of high concentration of TiOPc, small film thickness, high light intensity, and low frequency. To design this motor based on a one-frequency-two-mode driving method, an analytical solution is derived and an optopiezoelectric linear motor (OP-LM) is developed. Our analytical analysis, finite element simulation, and experimental results demonstrate that traveling waves can be generated by driving this motor at a frequency between the first and the second bending modes with a 90° phase difference between two designed actuating areas. The optimal condition is to match the driving frequency and light switching frequency. The moving direction and velocity of objects in different weight can be optically controlled by illuminating different areas of an optopiezoelectric motor with two 10 W power LEDs and masks. Discussions on the developed theory, simulation, and experimental studies of the OP-LM are provided in this paper.