SIMPLE SYNTHESIS OF ELASTOMERIC PHOTOMECHANICAL SWITCHES THAT SELF-HEAL

Soft robots, composed of intrinsically soft materials, have continuously deformable structures that help them generate muscle-like actuators. Most conventional soft robots utilize compressed air/liquid to actuate, which involves bulky power sources that may sacrifice their flexibility. This work introduces a new class of light-induced actuation to the field of soft robotics by using light to reversibly trigger a bending/unbending motion. This new actuation mechanism is enabled by the trans-cis isomerization of azobenzene molecules. Based on this mechanism, photomechanical switches were made by covalently incorporating these molecules into a polyurethane-polyurea copolymer via a two-stage step-growth polymerization. The synthesized elastomeric photomechanical switches demonstrate good optical and mechanical properties: under the actuation wavelength (UV 385nm), they can generate maximum bending angle of 70 degrees with the photomechanical stress of 17 kPa. In addition, the supramolecular network in the switches realizes autonomous self-healing at room temperature with high efficiency (recovers 70% of maximum strain at break of the pristine sample). We envision this new material with simple molecular design will provide new directions for research in bio-inspired materials and future soft robotics