(562b) Investigating The Effect Of Gold Nanoparticle Deposition Via CO2-Expanded Liquids On Micromachine Reliability

The technology to fabricate microeletromechanical systems (MEMS) and micromachines has been around for over 20 years. Unfortunately, due to persistent reliability issues such as stiction, friction, and structural wear, only the most basic MEMS are currently used in commercial applications.

In order to moderate the interfacial forces which cause reliability issues in MEMS, the contact area between microscale components must be controlled. One approach is to increase the surface roughness by depositing nanoscale particles with specified size and surface number density. Although the tribological effects of metallic nanoparticles on MEMS are essentially unexplored, we may expect to achieve insight into the surface interactions (capillary force, van der Waals force, solid-bridging, etc.) that may only be obtained by controlling the contact mechanics.

In this work, ligand-stabilized gold nanoparticles dispersed in n-hexane were deposited onto the surface of various micromachined structures using a CO₂-expanded liquid process previously developed by Roberts et al. Transitioning the liquid CO₂ to the supercritical phase then allows for the drying of MEMS in absence of a liquid-vapor interface, negating the effect of destructive capillary forces. Following deposition, the operation of micromachined devices was observed and the effects of metallic nanoparticles on adhesion were studied.