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

A method involving the grafting of long-chain molecules on hydroxylated ceramic surfaces like silica is proposed to improve lubrication in microactuators. Preliminary experiments show that one monolayer of octadecyl and docosyl silane molecules does improve the sliding properties of silica. The friction tests are performed on a reciprocating tribometer, in a sphere and plane geometry with a contact pressure of 340 MPa. The friction-reduction effect is clearly evidenced, the value of the friction coefficient decreasing from 0.6-0.7 to nearly 0.1 in the presence of the grafted molecule layer. The lifetime of the effect is estimated as one hundred cycles. In a prospective view, these results are extended to contacts in micromechanisms.