Temperature-Switchable Adhesives Enabled by Thermo-Responsive Soft Active Materials

Many biological systems, such as gecko feet, are capable of reversibly and repeatably switching their surface adherence to various external objects. By contrast, no engineering system has yet reached the same level of both robust adherence and versatile switching. This gap severely limits the capability and adaptivity of the latter to fulfil the emergent economic and societal needs in complex environments. This talk will discuss our recent progress in developing switchable adhesives with high adhesion toughness, large switching ratio, fast switching speed, and good reversibility. We start with a hypothesis of combining a PSA(Pressure Sensitive Adhesive)-like polymer network and its stimuli-responsive phase transition to achieve switchable adhesives. To test this hypothesis, we investigate the switchable adhesion of a thermo-responsive hydrogel with its polymer network containing many free-end dangling polymer chains. The hydrogel forms tough adhesion with various surfaces at ambient environment, and becomes completely non-adhering at an elevated temperature due to the thermo-induced phase separation. The adhesion switching is reversible for many cycles while maintaining a high adhesion toughness. We further study the effects of compositions and mechanical dissipation on the adhesion toughness and switching performance. We discuss the possibility of extending the general design principle to other similar polymer systems.