Effect of air confinement on thermal contact resistance in nanoscale heat transfer

Abstract

Here, we report a detailed analysis of thermal contact resistance (Rc) of nano-size contact formed between a Wollaston wire thermal probe and the used samples (fused silica and titanium) as a function of air pressure (from 1 Pa to 105 Pa). Moreover, we suggest an analytical model using experimental data to extract Rc. We found that for both samples, the thermal contact resistance decreases with increasing air pressure. We also showed that Rc strongly depends on the thermal conductivity of materials keeping other parameters the same, such as roughness of the probe and samples, as well as the contact force. We provide a physical explanation of the Rc trend with pressure and thermal conductivity of the materials: Rc is ascribed to the heat transfer through solid–solid (probe-sample) contact and confined air at nanoscale cavities, due to the rough nature of the materials in contact. The contribution of confined air on heat transfer through the probe sample contact is significant at atmospheric pressure but decreases as the pressure decreases. In vacuum, only the solid–solid contact contributes to Rc. In addition, theoretical calculations using the well-known acoustic and diffuse mismatch models showed a high thermal conductivity material that exhibits high heat transmission and consequently low Rc, supporting our findings.