Optically-driven actuator using photo-induced phase-transition material

The authors propose a new optically driven actuator which utilizes photo-induced phase-transition (PIPT) material. This actuator is expected to be useful for micromechanical systems, since it provides a wireless energy supply by light. In these PIPT materials the material phase is changed by irradiation of light, as well as by temperature or external fields. In this report, a kind of polydiacetylene (PDA) substituted with alkyl-urethane is investigated. This material is known to exhibit reversible PIPT around 125/spl deg/C between the 'blue' phase and 'red' phase. The authors measured the induced macroscopic elongation of PDA crystal using a displacement meter. The induced strains due to thermal phase transition were measured to be 2%, 0.03%, and 0.9% at 125/spl deg/C for the a-, b-, and c-axes, respectively. These values are larger than that of the piezoelectric or thermal-expansion materials conventionally used for microactuators. Material deformation due to light-pulse irradiation was demonstrated for the first time. The observed bending was explained by bimorph formation induced by phase transition at the irradiated surface.