Reversible Underwater Dry Adhesion of a Shape Memory Polymer

Dry adhesives are believed to be inadequate to achieve high adhesion to a wet or submerged surface due to liquid layers intercalated at the contact interface. Here, the reversible dry adhesion of a thermoresponsive shape memory polymer (SMP) performing under water and other liquids such as oil is presented. It is revealed that applying pressure to the SMP in its compliant rubbery state enables to squeeze out the liquid from its contact interface, and that the interface is then maintained by fixing the SMPs shape in its glassy state. During this conformal and hermetic contact condition, the rigidity of the glassy state SMP provides remarkably high (≈18 atm, atmosphere) underwater yet dry adhesion. Lastly, the permanent shape recovery of the SMP allows a surrounding liquid to quickly squeeze in and separate the contact interface, which makes the SMP almost adhesiveless. These findings pave the way for inexpensive reversible dry adhesives working on submerged surfaces.