The receding contact line cools down during dynamic wetting

TL;DR

This study uses molecular dynamics simulations to show that during dynamic wetting, the receding contact line cools down contrary to the advancing line, revealing new thermal behaviors important for nanofluidic modeling.

Contribution

It uncovers the temperature drop at receding contact lines and introduces a macroscopic energy balance framework for analyzing heat transport in dynamic wetting.

Findings

Temperature drops at receding contact lines during wetting.

Internal energy changes cause temperature decrease similar to latent heat.

Framework applicable to various nanofluidic systems.

Abstract

When a contact line (CL) -- where a liquid-vapor interface meets a substrate -- is put into motion, it is well known that the contact angle differs between advancing and receding CLs. Using non-equilibrium molecular dynamics simulations, we reveal another intriguing distinction between advancing and receding CLs: while temperature increases at an advancing CL -- as expected from viscous dissipation, we show that temperature can drop at a receding CL. Detailed quantitative analysis based on the macroscopic energy balance around the dynamic CL showed that the internal energy change of the fluid along the pathline induced a remarkable temperature drop around the receding CL, in a manner similar to latent heat upon phase changes. This result provides new insights for modeling the dynamic CL, and the framework for heat transport analysis introduced here can be applied to a wide range of nanofluidic systems.