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 par t by a lack of understanding of the fundamental intermolecular forces under lying adhesion. Atomic force microscopy was used to measure the adhesion en ergy between a well-known marine mussel adhesive protein, Mytilus edulis fo ot protein 1 (Mefp-1), and seven polymeric surfaces characterized by their critical surface tension (gamma (c)) and wettability (cos theta (w) ) in si mulated and natural seawater. On the basis of their attractive binding (adh esive) Energy during separation, the surfaces were divided in two groups, t hose that exhibited gamma (c)-values greater than and less than that of the model protein. The gamma (c)-value of the adsorbing protein determines the thermodynamic criteria for which substrates exhibit low and invariant adhe sive energy or high and increased adhesive energy. The dominant interaction s appear to be polar in nature (and possibly chemically specific pi-pi inte ractions for one of the surfaces) and not dispersive. Unusually close predi ctions between the Johnson-Kendall-Roberts theory and measurements were obt ained.