 Expressions for the van der Waals forces for many different geometries using the Lifshitz theory have likewise been published.The ability of geckos – which can hang on a glass surface using only one toe – to climb on sheer surfaces has been for many years mainly attributed to the van der Waals forces between these surfaces and the spatulae, or microscopic projections, which cover the hair-like setae found on their footpads.A later study suggested that capillary adhesion might play a role, but that hypothesis has been rejected by more recent studies.