Hybrid Organic Inorganic Photon-Powered Actuators Based on Aligned Diarylethene Nanocrystals

When photochromic molecules are organized in a crystal, the small-scale forces generated by molecular photoisomerization events can combine together to generate work on micro- or macroscopic length scales. In this work, photomechanical nanocrystals themselves are organized on macroscopic length scales using a porous inorganic template. The organic diarylethene component provides the reversible photoresponse, whereas the porous alumina component provides structural support and directionality. This hybrid organic-inorganic photomechanical material acts as a bending actuator. Using ultraviolet and visible photons as power inputs, as little as 0.1 mg of reacted material generates enough force to tilt a 1.28 g mirror and steer a laser beam. The motion can be cycled multiple times in air and under water. Actuator figures-of-merit such as energy-to-work conversion efficiency and stiffness are probably limited by the high elastic modulus of the inorganic template, providing an obvious pathway for optimization.