Effects of Sub-ångstrom (pico-scale) Structure of Surfaces on Adhesion, Friction, and Bulk Mechanical Properties

We review experimental results—over the past 10–15 years and more recent theoretical modeling and computer simulations—on the effects of surface subnanoscale texture on adhesion and friction and the implications for certain mechanical properties of materials such as Mode I and Mode II failure. Examples and comparisons include surfaces that are adhesive or nonadhesive, rough or smooth, hard or soft (e.g., viscoelastic polymers), dry (unlubricated) or lubricated. One important conclusion is that the ultrafine picoscale details of a surface lattice or its roughness (“texture”) can be the most important factor in determining its friction and Mode II fracture, whereas such effects are less important for determining adhesion forces and Mode I fracture processes. Such studies are also clarifying the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations and are revealing new fundamental insights and relationships between nanoscale (molecular) and macroscale processes.