Solvation forces in confined molecular liquids

Abstract

Solvation forces in confined liquids have been studied using the atomic force microscope (AFM), and in particular using sample modulation techniques. Measurements involving liquids of differing molecular structure reveal force oscillations, which agree with computer simulations but can differ markedly from surface force apparatus (i.e. branched liquids) observations due to the smaller confinement area and the different chemical nature of the surfaces in AFM. Results show that surface roughness and liquid molecular structure can affect the magnitude of force measurements. Force measurements in solutions and liquid mixtures show that discrete co-existent molecular layers with one molecular species being preferentially adsorbed can form at the solid-liquid interface. High-resolution imaging showing in-plane ordering of the adsorbed layer is possible by controlling the force to within the measured force range of the first solvation layer.