Importance of Pico-Scale Topography of Surfaces for Adhesion, Friction, and Failure

This article is an edited transcript based on the MRS Medal Award presentation given by Jacob N. Israelachvili on December 1, 2004. at the Materials Research Society Fall Meeting in Boston. An expanded article on this topic will be published in the August 2005 issue of the Journal of Materials Research. Recent experimental results have shown how surface texture, surface energy, and the bulk properties of materials can affect their adhesion and friction and, in turn, determine some of the fundamental differences between modes of failure of materials. Theoretical modeling and computer simulations. among other methods. provide examples and comparisons of surfaces that are rough or smooth, hard or soft (for example, viscoelastic), adhesive or non-adhesive, and dry (unlubricated) or lubricated. Such studies clarify the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations, revealing insights and relationships between nanoscale (molecular) and macroscale processes. Also of critical importance are the effects that occur at the sub-nanoscale, that is, in the sub-angstrom or picoscale regime. It is demonstrated and argued that the ultrafine picoscale details of a surface lattice, or its roughness. can be the most important factor in determining its friction (and mode II fracture), whereas such effects are quantitatively less important for adhesion and mode I fracture processes.