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The effect of water vapor on n-pentanol vapor phase lubrication (VPL) was studied with a microelectromechanical system (MEMS) side-wall tribometer, a pin-on-disc tribometer, and attenuated total reflection infrared (ATR-IR) spectroscopy. The n-pentanol vapor pressure was fixed at 50 % relative to its saturation vapor pressure (P sat = ~2.2 Torr at room temperature), which is sufficient to maintain a monolayer of n-pentanol on a SiO2 surface in a dry Ar environment. As the relative humidity (RH) was increased from zero to 30 %, ATR-IR measurements showed that the water adsorption on the surface increases and the adsorbed pentanol thickness decreases by 60 %. These changes in the adsorption isotherm were manifested as higher, and more scattered friction coefficients observed during the MEMS tribometer operation. The maximum RH tolerance appeared to be 25–30 % RH above which the MEMS tribometer failed to operate reliably. In contrast, the n-pentanol VPL efficiency was not affected significantly during the macro-scale pin-on-disc tribometer tests. These results imply that the friction behavior of the asperity contacts in MEMS is more susceptible to co-adsorption of water than the friction behavior of macro-scale contacts.

We have fabricated, tested and analyzed the reliability of Pt- and RuO2-coated ohmic microrelays in ultra-high purity gas environments. RuO2-coated relays could survive 3 × 108 contact cycles without electrical degradation, while Pt-coated devices degraded after 105 cycles. Thermally actuated microrelays were fabricated using a process that employed a polysilicon surface-micromachined substructure. After releasing the devices, just a few blanket metal depositions were required to create the different coatings. This method allowed direct comparisons between different coating materials, and was enabled by a self-aligned shadow mask that provides electrical isolation between different traces. Testing was performed in a clean environment achieved through in situ ultra-high vacuum bakeouts, chamber cooling to