Effect of geometrical parameters on radiometric force in low-pressure MEMS gas actuator

In this paper, comprehensive numerical studies are performed to investigate the effects of the geometrical factors on the performance of the low-pressure gas actuator. The flow feature and force generation mechanism inside a rectangular enclosure with heat and cold arms as the non-isothermal walls are inclusively discussed. Also, comprehensive parametric studies are done to reveal the effects of physical parameters on the performance and characteristics of this device in different operating conditions. In this study, the Knudsen number is varied from 0.1 to 4.5 to investigate all characteristics of the thermal-driven force inside the MEMS sensor. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equations are applied to obtain high precision results. To solve these equations, Direct Simulation Monte Carlo approach is used as a robust method for the non-equilibrium flow field. The effects of length, thickness and length ratio of arms are comprehensively investigated in different ambient pressures. Our findings show that maximum force increases approximately 3.66 times when the length of the arms is increased from 50 to 150 A mu m. In addition, the obtained results demonstrate that the geometrical parameters of arm induce complex structure in rarefied pressure, and the mechanism of force generation highly varies in the different pressure conditions.