Adhesive and corrosive wear at microscales in different vapor environments

Abstract

Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems (MEMS). By analyzing the oscillation decay characteristics in different vapor environments, we find that wear is dominated by asperity adhesion during the initial stages of rubbing in dry N 2 or O 2 /N 2 mixtures; in these situations the transient wear rate is inversely proportional to the wear depth. But in water or ethanol vapors, chemical reactions between the corrosive adsorbed layer and the silicon substrate limit the wear rate to a constant. These observations are consistent with atomic explanations. The differences between adhesive and corrosive wear explain the advantages offered by lubricating with alcohol vapors rather than using dry environments for tribo-MEMS devices. Compared to ethanol, the relatively poor anti-wear effect of water vapor is explained by aggressive and rapid tribo-reactions.

Boundary lubrication by adsorption film

“…The first is MEMS devices, which are utilized in a large number of successful products such as accelerometers, gyroscopes, and pressure sensors. The study of the nanotribology of SAMs is in fact closely related to the development of MEMS, where the high surface-to-volume ratio makes the interfacial interactions a main factor in the wear and lifetime of such devices [110,111]. The materials used in MEMS are mainly silicon based, the fabrication process of which was developed from the microelectronics industry; thus, mass production can be achieved.…”

Production of a superhydrophobic frame-cone structure by laser etching and Ni electrodeposition

“…In a wet environment, water vapour condenses spontaneously on the surfaces due to the capillary effect, which easily leads to the failure of the relevant components of the MEMS owing to interfacial adhesion [5,6]. Meanwhile, droplet adhesion accelerates the corrosion of metal devices based on MEMS [7] and shortens their service lives. Preparing superhydrophobic structures on the surfaces of MEMS devices may significantly reduce droplet adhesion and improve service reliability.…”