  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 force onto the body in the direction parallel to the plates
valid for an infinite Knudsen number is derived. Simultaneously, Monte-Carlo
simulations are performed allowing to extend 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. This force is only slightly
reduced when a Knudsen number of one is considered. In the future, the
discovered effect may be exploited for the conversion of thermal into
mechanical energy in nanomachines.
