EFFECT OF NANOTEXTURING ON INTERFACIAL ADHESION IN MEMS

We demonstrate that the interfacial adhesion between microelectromechanical systems (MEMS) surfaces is in a regime not previously considered by standard models of rough surfaces such as the Fuller-Tabor [1] or Maugis [2] extensions of the theory of elastic contact of rough surfaces [3]. Our experiments and models show that at small roughness values, adhesion is mainly due to van der Waals forces across extensive non-contacting areas and is proportional to 1/(average surface separation) 2 . At large roughness values, asperities that nearly bridge the gap become the dominating contributor to the adhesion. These van der Waals contributions to adhesion have been ignored in the above models. They cannot be ignored in MEMS because the surfaces are in close proximity over a long range as a result of the planar deposition technology.