Programmable Photothermal Actuators Using Donor Acceptor Stenhouse Adducts Photoswitches

The demonstration of programmable actuation performance by the simple remodeling of material properties advances the field of light responsive materials one step closer to the development of “life-like” actuators. We introduce a novel approach for programmable actuation using negatively photochromic molecular photoswitches, termed donor-acceptor Stenhouse adducts (DASAs), capable of generating programmed mechanical energy using photochemically programmed logic. We report a modular Diels-Alder click chemistry approach that enables attachment of different concentrations of DASA conjugates to polymers. We present a visible light-responsive bilayer actuator that can lift weight against gravity, as well as a simple light-powered crawler, that exploits photothermal energy conversion. Slowly converting a highly-absorbing DASA photochrome into a non-absorbing form upon light illumination enables us to demonstrate programmed mechanical energy generation that can be attenuated or terminated when the actuator decolorizes. The absorbance is analogous to a photochemical fuel that can be recharged at elevated temperatures for reprogramming.