Small-scale surface engineering problems

This chapter begins by providing a theoretical framework for the various interfacial forces that lead to adhesion of micromechanical structures. Next, a number of test structures used to quantify adhesion between micromachined surfaces are reviewed. Adhesion results for both horizontal and vertical surfaces are presented, with particular emphasis placed on the role of surface roughness, relative humidity, surface chemistry and contact pressure. Finally, several techniques for reducing the work of adhesion are examined. Initial attempts to decrease adhesion have focused on reducing the real contact area by physically altering the surfaces via dimples, spacers and surface roughening techniques, while more recent work has focused on chemically modifying the surfaces to control roughness and surface energy via hydrogen-terminating treatments, self-assembled monolayers and wear-resistant coatings. © 2010 Woodhead Publishing Limited. All rights reserved.