Texture-Dependent Adhesion in Polydopamine Nanomembranes.

The conformal nature of in situ polymerization of adhesive dopamine molecules permits the strong underwater adhesion between polydopamine (PDA) nanomembranes and the target substrates. However, the adhesive interaction between the postdeposit PDA nanomembranes and other macrobodies is strongly influenced by the texture of PDA nanomembranes. Here we report the texture-dependent adhesion of PDA nanomembranes both in air and aqueous environments. Despite the nanometer-scale roughness of PDA nanomembranes, interfacial adhesion between PDA nanomembranes and elastomeric bodies are the strong function of the root-mean-square roughness of PDA nanomembranes, root-mean-square gradient of PDA nanomembranes, and the elasticity of the bulk materials. Reduced adhesion due to increased texture is intensified in hydrated conditions, possibly hinting that the conventional explanation of the negative effect of water to adhesion from a molecular level needs to be revisited. These findings can inform the role of adhesive interaction in conformal coatings and provide an explanation for the differential adhesion observed in freestanding PDA nanomembranes.