Reversible Underwater Dry Adhesion of a Shape Memory Polymer

Abstract

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.

Barnacle Cement Proteins‐Inspired Tough Hydrogels with Robust, Long‐Lasting, and Repeatable Underwater Adhesion

“…The former are liquid solutions (e.g., coacervates, [ 2 ] polymer solutions, [ 3 ] liquid polymers, [ 4 ] and monomer solutions [ 5 ] ) that require a curing process to achieve interfacial bonding in water. The latter are solid materials (e.g., polymer films, [ 6 ] rubbers, [ 7 ] and hydrogels [ 8 ] ) that can directly adhere to the substrates underwater. The bonding strengths of glue‐type adhesives are usually robust (>100 kPa) but require long curing times (hours to days) and they cannot be reused.…”

Elastic Energy Storage Enabled Magnetically Actuated, Octopus‐Inspired Smart Adhesive

“…Despite extensive existing studies on artificial adhesives, [ 28–30,32,57–62 ] a rapidly tunable and highly reversible smart dry/wet adhesive has been rarely reported before. The concept of the smart adhesion system reported in this article can provide significant benefits in a wide range of adhesion applications requiring switchable adhesion in both dry and wet conditions, including transfer printing for flexible electronics [ 63–65 ] (Figure S5, Supporting Information) and amphibious soft robotic manipulators capable of gripping and releasing a variety of rigid and deformable substrates ranging in roughness and curvature.…”

A Review of Shape Memory Polymers and Composites: Mechanisms, Materials, and Applications

“…As a fast‐growing innovative technology, numerous innovative SMP dry adhesive systems have been explored to develop soft grippers. [ 234–237 ] The conventional wet adhesive systems comprising multicomponent with glue are not reusable. As a consequence, they cannot be used to grasp and drop an object.…”