Organic crystal photoactuators

Abstract

Mechanically responsive materials that exhibit macroscopic motions by external stimuli such as light and heat have attracted much attention over the past two decades, both in terms of fundamentals and applications. Such mechanical materials are expected to be applicable to sensors, switches, actuators, and soft robots. Many mechanical crystals that show bending, twisting, jumping, and locomotion have already been developed, based on mainly photoisomerization and some phase transitions. We have also developed various mechanical crystals over the past decade. Herein, our recent works are shortly reviewed, including crystal locomotion and the new photo-triggered phase transition. In particular, the discovery of high-speed crystal actuation by the photothermal effect is the most important topic. Most crystals that absorb light have their own photothermal effect. It is expected that actuation of any crystals will be possible via photothermal effect, which cannot be realized by photoisomerization, and the potential and versatility of crystals as actuation materials will expand.