Ultralow friction of confined thin films

The ultralow friction of thin film lubrication systems attracts more and more scientific and practical interests. However, so far the understanding of such processes is still at its infancy. In this work, two tightly confined thin films (oil-based and water-based) were investigated to discover thin film lubrication mechanisms. 1. Tribochemical reactions between certain diketone lubricants and steel sliding surfaces induce self-limiting wear processes which lead to highly conformal surfaces. This polishing together with the formation of an ordered lubricant layer results in ultralow friction (µ˜ 0.005). 2. Surface-attached hydrogels were characterized by indentation and friction tests. Studies of the influence of compression rates, film thicknesses, and crosslink densities result in a model which describes lubrication in systems comparable to natural synovial joints.