Photoswitchable\nLiquid Crystal Elastomer Adhesives\nOperating at Room Temperature

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