Bio-inspired dual surface modification to improve tribological properties at small-scale

Abstract

In miniaturized devices like micro/nano-electro-mechanical systems (MEMS/NEMS), the critical forces, namely adhesion and friction restrict the smooth operation of the elements that are in relative motion. MEMS/NEMS are traditionally made of silicon, whose tribological properties are not good. In this paper, we present an investigation on the approach of dual surface modi. cation of silicon surfaces and their tribological properties at micro-scale. The dual surface modi. cation is a combination of topographical and chemical modi. cations. As the topographical modi. cation, micro-patterns with varying shapes of pillars and channels were fabricated on Si(100) wafer surfaces using photolithography method. Chemical modi. cation included the coating of micro-patterns with diamond-like carbon (DLC) and Z-DOL (perfluoropolyether, PFPE) thin. films. The surfaces with combined modi. cation were evaluated for their micro-friction behavior in comparison with those of bare Si(100). at surfaces and the topographically/chemically modified silicon surfaces. Results showed that the surfaces with dual modi. cation exhibited superior tribological properties. These results indicate that a combination of topographical and chemical modi. cation is very effective in enhancing tribological properties at small-scale. The combined surface treatments such as the ones investigated in the current work could be useful for tribological applications in small-scale devices such as MEMS/NEMS. The motivation for undertaking the dual modi. cation approach comes from an earlier observation made on the significant influence of the surface characteristics of lotus leaf on its micro-friction behavior. (C) 2008 Elsevier B. V. All rights reserved.