Wet adhesion of graphene

Abstract

Interfacial adhesion between graphene and various substrate materials is essential for practical applications of graphene. To date, most of the studies on adhesion of graphene have assumed dry adhesion of van der Waals type. In this paper, we conduct molecular dynamics simulations to study the traction–separation behaviors for wet adhesion of graphene on amorphous silicon oxide covered by a thin layer of water. Three stages of the traction–separation relations are identified and they are analyzed by simple, approximate continuum models. The work of separation is found to be close to the theoretical value dictated by the interaction potential between graphene and water. The maximum traction is found to be set by the critical stress for cavitation at the water/graphene interface. With morphological evolution of water from cavitation to capillary bridging, the range of interaction extends to about 3 nm before complete separation of graphene. Compared to van der Waals interactions for dry adhesion of graphene, the work of separation for wet adhesion is smaller, the maximum traction is lower, but the interaction range is longer. It is noted that the properties of wet adhesion depend sensitively on the graphene–water interactions, which may vary considerably from hydrophobic to hydrophilic interactions.