In-situ vapor-phase lubrication of MEMS

In-situ vapor-phase lubrication of sidewall MicroElectroMechanical System (MEMS) devices is investigated with 1-pentanol vapor. The 1-pentanol vapor successfully maintains lubricating properties between silicon contacts of MEMS devices. This is attributed to the ability of alcohol to adsorb on the silicon surface and sustain a lubricating layer, which prevents wear of the MEMS surfaces and minimizes friction. In the presence of these vapors, MEMS devices with sliding contacts operated without failure for up to a factor of 1.7 x 10(4) longer than in dry N-2 gas alone, representing a dramatic improvement in operating life. Adhesion and friction were also investigated as a function of alcohol vapor pressure. The adhesive force between microfabricated MEMS sidewall surfaces increases from similar to 30 to similar to 60 nN as the alcohol vapor pressure is increased from 0 to 20% of saturation, and then only slightly increases to similar to 75 nN at 95% of saturation vapor pressure. This increase in force is well within the capabilities of even the lowest force on-chip actuators, such as electrostatic comb drives which can typically generate a few mu N of force. The static friction force was found to be independent of alcohol vapor pressure within the uncertainties in the measurement.