Limits to Lubrication Theory in Microsystems

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. However, in a wide range of conditions applicable to many researchers in microelectromechanical systems (MEMS), experimental results seem to indicate that forces separating squeezing surfaces vary according to film thickness to the power minus one, rather than minus three, as lubrication theory requires. Hydrodynamic forces arise incidentally, and are usually the largest source of parasitic losses. The motivation of this research is thus to resolve the contradiction between experimental results and theoretical predictions concerning squeeze film dampers. The objective is to develop an improved theory of hydrodynamic lubrication at the microscale. These goals have important implications in the design of MEMS devices. A combined experimental and theoretical/modeling approach will be followed. The damping coefficient will be directly determined as opposed to indirect measurements in the existing MEMS experiments. A theoretical framework for corrections or modifications to lubrication theory will be proposed and tested both by experimental and numerical studies. Employing active MEMS for actuation and sensing in a liquid environment has potential applications in many technologies of industry and medicine. However, the current lack of understanding of lubrication in microscale systems hinders the development of liquid immersed MEMS. There is a real need for developing trusted accurate verified models liquid damping in microscale systems in order to design reliable devices, able to perform as expected. In addition, the PI and co-PI will outreach to K-12 students by building a portable macro scale squeeze film test rig, as dynamically similar to the microscale research device as possible. Bringing theory to life, K-12 students can perform simple experiments and compare their measured effects to the microscale, by visiting the lab, or by web interaction with laboratory results.