Individual Role of the Physicochemical Characteristics of Nanopatterns on Tribological Surfaces

Individual Role of the Physicochemical Characteristics of Nanopatterns on Tribological Surfaces
윤의성조일주김홍남Prashant PendyalaHarpreet S. Grewal
surface energy; friction; nanopatterns; nanopillar geometry; adhesion
Issue Date
ACS Applied Materials & Interfaces
VOL 8, NO 44-30600
Nanoscale patterns have dimensions that are comparable to the length scales affected by intermolecular and surface forces. In this study, we systematically investigated the individual roles of curvature, surface energy, lateral stiffness, material, pattern density on the characteristics of the adhesion and friction of nanopatterns. For this purpose, we used a combination of capillary force lithography and nanodrawing methods to fabricate cylindrical and mushroom-shaped pillars with flat- and round-top morphologies. We showed that the curvature, the surface energy and the density of the patterns predominantly influenced the adhesive interactions, whereas lateral stiffness dominated friction by controlling the geometrical interaction between the indenter and pillar during sliding. Interestingly, in contrast to previous studies, cylindrical and mushroom-shaped pillars showed similar adhesion characteristics but very different frictional properties. Using fracture mechanics analysis, we showed that this is due to a larger ratio of the mushroom flange thickness (t) to the radius of the pillar stem (ρ), and we have proposed a design criterion for mushroom patterns to exhibit a gecko-like effect. The most important result of our work is the discovery of a linear master curve in the graph of adhesion vs. friction for pillars with similar lateral stiffness values, which is independent of curvature, material, surface energy, and pattern density. These results will help in the identification of simple pattern parameters, which can be scaled to tune adhesion and friction in addition to broadening the understanding of the nanoscale topographical interactions.
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