Thermal Knudsen forces arise in microsystem in presence of a thermal gradient and a rarefied gas environment due to the non-equilibrium energy exchange between gas molecules and solid surfaces. Knudsen force can be used as an alternative actuation mechanism for microactuators. The purpose of this work is to design and optimize a Knudsen force actuated microbeam using modeling and simulation. The microbeam is heated by an external heat source that causes a thermal gradient between the beam and substrate. The characteristic domain size is small enough so that the rarefied gap effect is present. The study focuses on three major components that influence the Knudsen force significantly, including geometry of microbeam, external heat input to the system, and the radiometric effects generated by Peltier thermoelectric device. A Boltzmann-ESBGK model is implemented to simulate the rarefied gas flow and a continuous Fourier heat transfer model is used to solve the beam temperature field generated by the external heat source, and the fluid and solid regions are coupled using an effective heat convection interface condition.

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