Modeling and quantifying thermal Knudsen forces on microcantilevers

Mizuki Wada, Purdue University

Abstract

Thermal Knudsen forces arise in microsystem in a rarefied gas environment with a thermal gradient. They are caused by non-equilibrium energy exchange between gas molecules and solid surfaces. This study explores the possibility of utilizing the Knudsen force to deflect microstructures and trigger contact for applications in microelectromechanical systems (MEMS). Actuation experiments performed in a low-pressure environment by creating a significant thermal gradient across a thin beam suspended over a substrate are presented and used to validate a computational framework. The computational framework solves an approximate form of the Boltzmann equation using a parallel, unstructured finite volume solver developed in C++. The experiments show that the magnitude of the Knudsen force produced on a beam with a thermal gradient across it is significantly higher than that on a uniformly heated beam with both sides of the beam at the same temperature. It is also demonstrated that the direction of force on the beam is controllable making it a suitable candidate for MEMS applications. The validated numerical framework presents a design tool for bi-directional actuators using a wide range of thermal configurations and ambient gas pressures.

Degree

M.S.A.A.

Advisors

Sun, Purdue University.

Subject Area

Aerospace engineering

COinS