(4q) Nanoparticle-Based Thin Films for Tribology Control in MEMS

Due to inherent interfacial forces that cause strong adhesion and friction in microelectromechanical systems (MEMS), only the most mechanically simple MEMS devices are currently used commercially. In the past, several approaches have been examined to overcome the inherent forces leading to stiction and friction. Chemical surface alterations have been extensively studied in order to reduce the surface energy, increase hydrophobicity, and reduce unwanted adhesion. Another approach has been to create surface roughness in situ during the microfabrication process and effectively reduce the real area of contact between contacting components on a MEMS device. Both methods have been proven to successfully reduce microstructure adhesion, however, some issues with film durability still remain.

This work utilized a novel CO₂-expanded liquid nanoparticle deposition process to conformally coat silicon surfaces and MEMS surfaces with rough nanoparticle coatings. Various liquid- and vapor-based film deposition techniques were also used to couple nanoparticle-based rough surfaces with low surface energy thin films, effectively reducing the surface energy even further. A unique water erosion technique was used to examine the durability of these nanoparticle-based composite thin films, while tribological devices and interferometric techniques were incorporated to examine the effect of the thin films on microstructure adhesion in MEMS. The results conclude that rough nanoparticle surfaces do indeed provide relief to the strong adhesion exhibited in MEMS devices.