An in-situ heating effect study on tribological behavior of SU-8+PFPE composite

Abstract

SU-8 polymer is an emerging structural material for micro-fabrication of MEMS/NEMS devices using photo-lithography process. However, poor tribological properties of SU-8 restrict its wide applications as a very reliable MEMS material. In our earlier work [1], we have developed SU-8 composites which reduced friction and enhanced wear life of SU-8 by more than four orders of magnitude. The improvements in the properties were attributed to the self-lubricating nature of the composite by continuous supply of the lubricant into the worn areas, the lubricious nature of the filler lubricant perfluoropolyether (PFPE), and possible chemical bonding between SU-8 and PFPE. In this current work, we further investigated the effect of in-situ heating on the tribological performances of the SU-8+PFPE composite. In-situ heating from room temperature (25°C) to 100°C showed a strong effect on the tribological behavior of SU-8+PFPE composite by reducing its initial and steady-state friction coefficients by ~2 and ~7 times, respectively. Wear life (n) increased by more than three times due to in-situ heating. Greater surface area coverage by the spreading of PFPE lubricant and migration of PFPE from the bulk to surface are found responsible for this superior tribological performance of the composite at high temperatures.