title: Negative Knudsen force on heated microbeams.
abstract: Knudsen force acting on a heated microbeam adjacent to a cold substrate in a rarefied gas is a mechanical force created by unbalanced thermal gradients. The measured force has its direction pointing towards the side with a lower thermal gradient and its magnitude vanishes in both continuum and free-molecule limits. In our previous study, negative Knudsen forces were discovered at the high Knudsen regime before diminishing in the free-molecule limit. Such a phenomenon was, however, neither observed in experiment [A. Passian et al., Phys. Rev. Lett. 90, 124503 (2003)], nor captured in the latest numerical study [J. Nabeth et al., Phys. Rev. E 83, 066306 (2011)]. In this paper, the existence of such a negative Knudsen force is further confirmed using both numerical simulation and theoretical analysis. The asymptotic order of the Knudsen force near the collisionless limit is analyzed and the analytical expression of its leading term is provided, from which approaches for the enhancement of negative Knudsen forces are proposed. The discovered phenomenon could find its applications in novel mechanisms for pressure sensing and actuation.
authors.affiliation: Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong.
authors.forename: Taishan
authors.initials: T
authors.lastname: Zhu
authors.forename: Wenjing
authors.initials: W
authors.lastname: Ye
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D005740:Gases; D006358:Hot Temperature; D007700:Kinetics; D015233:Models, Statistical; D008962:Models, Theoretical; D009010:Monte Carlo Method; D010825:Physics / Q000379:methods*; D011312:Pressure; D013499:Surface Properties; D013696:Temperature
chemical_list: D005740:Gases