Photoswitchable Liquid Crystal Elastomer Adhesives Operating at Room Temperature

The ability to toggle adhesion between two surfaces on demand using reusable "smart" plastics would enable a myriad of applications requiring temporary bonding, such as in dry transfer of materials for electronics applications. To this end, light is an attractive stimulus owing to its modularity, low energy consumption, and spatiotemporal control. However, a lack of materials capable of reversible light-triggered adhesion at room temperature exists. Herein, a systematic examination of azobenzene-containing liquid crystal elastomers (LCEs) revealed design principles that relate processing and composition to the performance of photoswitchable adhesives. This led to LCEs capable of reversibly picking up and releasing objects through a simple "flip of the switch" on UV and blue LEDs. Moreover, detailed optical and thermomechanical characterization outlined the modular scope of the present platform and provided insight into the governing mechanism(s) for photoswitchable adhesion, which will serve to inform further optimization. Such stimuli-responsive materials have the potential to advance applications in electronics and soft robotics that can benefit from programmable and dynamic adhesion.