Protein layers may act as protective/lubricant barriers where their resistance to wear is of relevance. Despite this, little research has been performed on wear of protein layers due to the lack of experimental techniques. Recently, we showed how the Atomic Force Microscope (AFM) operated in the Friction Force Spectroscopy (FFS) mode can be used to follow the dynamics of the scratching of protein layers. Specifically, this method allows monitoring of the evolution of topography (in the nm range) and of the friction between tip and sample (in the nN range) while varying the applied load. We show how parameters of the layers such as the yield strength, and even information on the lateral diffusion of the proteins within the layers, can be provided. Results are presented for layers formed by globular proteins (BSA), and for layers formed by amphiphilic unordered proteins (�-casein). FFS measurements on salivary films are also presented.

Friction force spectroscopy as a tool to study the strength, lateral diffusion, and structure of proteinaceous layers

243rd National Meeting (2012)

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