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 degreesC 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 degreesC 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.