Experimental observation of attractive and repulsive thermal forces on microcantilevers

Abstract

We report measurements of thermal forces acting on a microcantilever near a substrate surface in air. In magnitude and direction, the observed force depends on the temperatures of substrate and cantilever, which were varied independently. The data are explained by considering interface scattering at the substrate surface as expressed by an accommodation coefficient of less than unity. The observed forces effectively act in the direction of the thermal gradient-opposite to thermophoresis of free particles suspended in a gas. The observation thus exhibits similarities with the so-called negative thermophoresis. © 2005 American Institute of Physics.