| AVS 59th Annual International Symposium and Exhibition | |
| Tribology Focus Topic | Wednesday Sessions |
| Session TR+SE-WeM |
| Session: | Tribology and Wear of Low-Friction Coatings and Materials |
| Presenter: | E.E. Flater, Luther College |
| Authors: | N. Ansari, Auburn University S. Barkley, St. Olaf College C. Bouxsein, St. Olaf College M. Deram, St. Olaf College N. Eigenfeld, St. Olaf College O. Matthews, Luther College A. Poda, Auburn University W.R. Ashurst, Auburn University B.P. Borovsky, St. Olaf College E. Linn-Molin, Luther College E.E. Flater, Luther College |
| Correspondent: | Click to Email |
Since microelectromechanical systems (MEMS) are critically-limited by interfacial phenomena such as friction and adhesion, strategies have been developed to reduce friction in these systems. One common strategy is to coat MEMS surfaces with molecularly-thin self-assembled monolayer (SAM) coatings. Silicon MEMS are most commonly coated with silane-based SAMs, such as octadecyltrichlorosilane (OTS). Continued development of MEMS technology may require new material systems to be employed. Therefore, in this study, we investigate the frictional properties of octadecylphosphonic acid (ODP) monolayers deposited on aluminum oxide surfaces. Measurements using an atomic force microscope (AFM) and separately using a nanoindenter-quartz crystal microbalance system were performed each with a microsphere-terminated probe, allowing for a comparative study between different velocity regimes using contacts with similar sizes, surface roughnesses, and interfacial chemistries. AFM colloidal probe friction measurements indicate that while the frictional properties of aluminum oxide can be reduced with the use of an ODP monolayer, a more dramatic rubbing-induced modification is clearly evident for both bare and SAM-coated aluminum oxide substrates. These modification effects depend on scanning duration and environmental conditions such as humidity. We hypothesize that a tribochemical reaction occurs between aluminum oxide and ambient water, which has also been observed in macroscopic tribological studies of aluminum oxide published in the literature.