Tribology of self-lubricating SU-8 composites for micro-electro mechanical systems (MEMS) applications

Abstract

The photo-resistive property of epoxy-based SU-8 polymer makes it a potential structural material for micro-fabrication of MEMS devices using the photo-lithography process. However, its poor tribological and mechanical properties are major concerns, if SU-8 has to replace Si, which is the mainstay structural material for making MEMS. Low modulii and hardness present problems in the fabrication and functioning of the micro-machines. Poor tribology will lead to adhesion, friction, wear and early failure of the components. This thesis deals with the preparation of novel SU-8 based composites to enhance the tribological and mechanical properties of the base polymer. It is observed that adding liquid PFPE (Perfluoropolyether; Z-dol 4000) lubricant to SU-8 as filler promotes chemical reactions between the molecules of SU-8 and PFPE, which helps in forming a physical boundary lubrication layer (~10 nm) when this composite is subjected to tribological contacts. This enhances the wear durability of SU-8 by more than four orders of magnitude over its pure form.