Liquid-to-solid transitions in thin liquid films induced by confinement

The mechanical properties of confined thin films of simple liquids were measured via a surface force balance as a function of the film thickness. We find an abrupt transition from liquid-like to a solid-like behaviour at a confinement alone and does not require external applied pressure. At the transition the effective viscosity increases by at least seven orders of magnitude. It is proposed that this is a cooperative effect, reminiscent of a Lindemann-like mechanism, originating in the suppression of the freedom of the confined molecules to move.