Lubrication and tribological performance optimizations for micro-electro-mechanical systems

Abstract

Lubricants and lubrication have been of great interest to mankind since the introduction of machines with sliding/rolling surfaces into everyday life. With the recent trend of miniaturization, Micro-Electro-Mechanical Systems (MEMS) have taken centre stage, featuring components with scales in dimensions as small as nanometres. In this PhD study, two approaches to solving MEMS tribology problems have been pursued. First, a novel direct lubrication method using well-known lubricants such as perfluoropolyether (PFPE) and multiply alkylated cyclopentane (MAC) was developed and tested using reciprocating sliding and actual MEMS tribometry. The second approach utilized the concept of hydrodynamic lubrication and selective surface modification for MEMS. To combat spreading and starvation of lubricants in small contacts such as in MEMS, selective modification of the silicon surface with hydrophobic (non-wetting) and hydrophilic (wetting) portions was carried out and found to increase the force required to move a droplet of lubricant from a designated location on the surface. Octadecylamine and dodecylamine were also used as additives to successfully induce autophobicity in hexadecane, and the various spreading behaviours investigated. In conclusion, several new approaches to tackling tribological problems in MEMS have been researched. These methods are easily adapted to suitable MEMS devices and greatly reduce adhesion and friction, and increase wear and device life by several orders of magnitude.