Pressure Gradient-Induced Precursor Film Transition Bridges Dynamic Wetting and Interfacial Thermal Transport for Electronics Cooling

Abstract As heat flux densities in electronic devices continue to increase, dynamic liquid spreading and solid−liquid interfacial thermal transport have become critical to cooling performance, yet the intrinsic coupling between these two processes remains poorly understood. Here, we demonstrate that a pressure gradient-induced precursor film transition establishes a molecular-scale connection between dynamic wetting and interfacial thermal transport. During droplet spreading, a confined near-wall water layer spontaneously separates from the bulk droplet and evolves into a precursor film. We establish a geometric criterion to quantitatively identify the onset of this transition and reveal that the localized pressure buildup arising from near-wall molecular accumulation drives the outward migration of the interfacial water layer. The resulting precursor film further reconstructs the interfacial water network, establishes a continuous solid−liquid contact pathway, and strengthens low-frequency vibrational coupling. These synergistic changes collectively reduce the interfacial thermal resistance by approximately 38.8%. These results identify precursor film formation as a distinct nonequilibrium interfacial transition and establish a unified molecular mechanism linking dynamic wetting, interfacial restructuring, and thermal transport, providing molecular-level guidance for liquid-based cooling of high-heat-flux electronic devices.