Atomic Force Microscopy for Low-Adhesion Surfaces: Thermodynamic Criteria, Critical Surface Tension, and Intermolecular Forces

Designing low-adhesive surfaces is a challenging task made difficult in part by a lack of understanding of the fundamental intermolecular forces underlying adhesion. Atomic force microscopy was used to measure the adhesion energy between a well-known marine mussel adhesive protein, Mytilus edulis foot protein 1 (Mefp-1), and seven polymeric surfaces characterized by their critical surface tension (γ c ) and wettability (cos θ w ) in simulated and natural seawater. On the basis of their attractive binding (adhesive) energy during separation, the surfaces were divided in two groups, those that exhibited γ c -values greater than and less than that of the model protein. The γ c -value of the adsorbing protein determines the thermodynamic criteria for which substrates exhibit low and invariant adhesive energy or high and increased adhesive energy. The dominant interactions appear to be polar in nature (and possibly chemically specific π−π interactions for one of the surfaces) and not dispersive. Unusually close predictions between the Johnson−Kendall−Roberts theory and measurements were obtained.