Momentum transfer to nanoobjects between isothermal parallel plates
A small-scale, trapezoidal rigid body in the gas-filled gap between two parallel plates at different temperatures is considered. An analytical expression for the thermally induced force onto the body in the direction parallel to the plates valid for an infinite Knudsen number is derived. For this purpose, diffuse reflection of the gas molecules at the solid walls is assumed. Simultaneously, Monte Carlo simulations are performed allowing an extension of the analysis to Knudsen numbers of the order of one. The numerical and the analytical results show excellent agreement, indicating that a temperature gradient orthogonal to the plates can induce a significant force in parallel direction, a phenomenon without analogy in the macroworld. This force is only slightly reduced when a Knudsen number of one is considered. In addition to the diffuse-reflection boundary condition, a mixture of diffuse and specular reflection is studied. The practical relevance of the results is exemplified by considering two scenarios with bodies of a specific geometry, among others a nanoscopic platelet.