LUBRICATION OF SILICON MICROMECHANISMS BY CHEMICAL GRAFTING OF LONG-CHAIN MOLECULES

A method involving the grafting of long-chain molecules on hydroxylate d ceramic surfaces like silica is proposed to improve lubrication in m icroactuators. Preliminary experiments show that one monolayer of octa decyl and docosyl silane molecules does improve the sliding properties of silica. The friction tests are performed on a reciprocating tribom eter, in a sphere and plane geometry with a contact pressure of 340 MP a. The friction-reduction effect is clearly evidenced, the value of th e friction coefficient decreasing from 0.6-0.7 to nearly 0.1 in the pr esence of the grafted molecule layer. The lifetime of the effect is es timated as one hundred cycles. In a prospective view, these results ar e extended to contacts in micromechanisms.