A study of ‘thermophoresis-like’ force on a heated trapezoidal nano-object confined between parallel plates

Abstract

A small scale, trapezoidal rigid nano-body in the gas filled gap between two parallel plates at different temperatures is considered. Direct Simulation Monte Carlo (DSMC) technique is used to determine the ‘thermophoresis-like’ force on the body in a direction perpendicular to the temperature gradient. The present numerical and analytical results of Hardt et al. (2009) [1] show good agreement, indicating that a temperature gradient orthogonal to the plates can induce a significant force in parallel direction, a phenomenon without analogy in the macro-world. Thereafter, the force external to the object which has more practical applications is studied. The effects of Knudsen number, asymmetry of the nano-object, temperature gradient and pitch on the force are studied. The force is found to increase with the increase in Knudsen number and it is negligible at lower Knudsen numbers (Kn=0.1). Also, the force is found to increase with increase in asymmetry of the nano-object about a direction parallel to the temperature gradient and it vanishes when the object is symmetrical. It can be concluded that the primary factor behind the force inducement is asymmetry in the nano-object while the temperature gradient tends to enhance the magnitude of this force. The force interaction in the presence of two identical objects is studied by varying the distance between them in terms of pitch. As the pitch decreases, the force on the object located towards right end of the channel is decreased and the force on the object located towards left end of the channel is increased by approximately the same amount.