I study the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. I derive a relation between the (average) interfacial separation $u$ and the applied normal squeezing pressure $p$. I show that, for nonadhesive interaction and small applied pressure, $p\sim \exp (-u/u_0)$, in good agreement with recent experimental observations.

• Received 19 June 2007

DOI:https://doi.org/10.1103/PhysRevLett.99.125502