Elastocapillary deformation prevents interfacial water trapping in underwater contact

Abstract

Adhering substrates using elastomeric adhesives underwater is challenging due to interfacial water trapping, which hinders intimate contact and weakens adhesion. This issue arises primarily from elastohydrodynamic deformation, where the pressure required to drain interfacial water deforms the adhesive. Here we show that elastocapillary deformation caused by interfacial tension can counteract elastohydrodynamic deformation and prevent interfacial water trapping. This resolves a key contradiction in the design of underwater adhesives: soft adhesives promote conformal contact with the substrate but are prone to elastohydrodynamic deformation, while stiff adhesives resist elastohydrodynamic deformation but limit contact. Using finite element simulations that couple elastic, capillary, and hydrodynamic effects, we quantify the role of elastocapillary deformation in underwater adhesion. Our findings provide a design framework to achieve robust underwater adhesion without being limited by interfacial water trapping using microfibrillar structures.