Micro- and nanoscale surface texturing effects on surface friction

The surface friction of smooth, microtextured, and nanotextured aluminum substrates against a half-ball shape of polydimethylsiloxane rubber was investigated under different surface humidity conditions. The work of adhesion estimated by the contact angle on nanotextured surfaces having a 250 nm scale dimple structure array was much higher than that on microtextured surfaces having a 3 pin scale dome structure array. Surface textures increased the work of adhesion, thus the surface friction of microtextured and nanotextured surfaces was increased compared to that of a smooth surface under dry conditions. On the other hand, the nanotextured surface considerably reduced the surface friction under wet surface conditions, while the surface friction of the microtextured surface was similar in both dry and wet surface conditions. In dry surface conditions, the measured surface frictions of microtextured and nanotextured aluminum substrates were 1.26 times and 2.69 times higher, respectively, than that of a smooth one. Under water lubricant conditions, the microtextured surface showed approximately 2 times higher surface friction than the smooth one, but the surface friction of the nanotextured surface was only 32% of the smooth surface. (C) 2015 Elsevier B.V. All rights reserved.