Prof. Robert Evans FRS from the HH Wills Physics Laboratory, University of Bristol, UK will give a seminar at the School of Mathematics and Physics, on Wednesday 10th of February 2016, 3 pm (room MB1019 in the Minerva Building, no 1 on the university map). Please join us in attending this interesting talk.

A physicist’s view of hydrophobicity: drying and the role of density fluctuations

All physical scientists would agree that for water (liquid) at a flat substrate a contact angle θ > 90º defines the substrate as hydrophobic (solvophobic): it prefers gas to liquid. A controversial question is whether there is an effective indicator of local ordering of the liquid, manifest at microscopic distances from the substrate, that correlates with the macroscopic (thermodynamic) contact angle. I argue that an important indicator is the local compressibility which measures fluctuations in the local density of the adsorbed liquid. For distances within one or two molecular diameters of a weakly adsorbing substrate, where θ approaches 180º (drying), classical Density Functional Theory and intelligent Monte Carlo simulations show that the local compressibility takes values which are orders of magnitude times that of the bulk liquid. Such behaviour is characteristic of a critical drying transition.

R. Evans & N. B. Wilding Phys. Rev. Letters, 115, 016103 (2015)