Linking Surface Wettability to Interfacial Thermal Transport at Ti-Water Interfaces: A Molecular Dynamics Study

Solid-liquid interfacial heat transfer plays a key role in microelectronic devices, energy systems, and liquid cooling technologies. However, the vibrational mismatch at solid-liquid interfaces produces an interfacial thermal resistance (ITR) that limits the heat-dissipation efficiency. Herein, molecular dynamics (MD) simulations were used to study the regulation of heat transfer at Ti-water interfaces by the Ti-O interaction strength. As the interaction strength increased, the Ti surface changed from strongly hydrophobic to complete wetting, with the contact angle spanning 153° to θ < 5° over the full droplet series. Over the range where the interfacial thermal conductance (ITC) was computed, the contact angle decreased from about 143° to 15°, and the ITC increased from 35.71 ± 4.26 to 231.97 ± 14.17 MW/m²·K. This increase originated from changes in the interfacial water structure, as the stronger interaction led to a denser and more ordered near-wall water structure that became more tightly bound to the surface, which enhanced the solid-liquid vibrational coupling. From the phonon perspective, the spectral overlap increased by only about 2%, from 0.01973 to 0.02008 THz^-1, while the ITC increased by a factor of 6.5, indicating that the spectral overlap is not the controlling factor. Instead, the phonon lifetime of the interfacial Ti shortened markedly while the phonon heat capacity remained stable, showing that the enhancement originates from the stronger interfacial coupling rather than from an increase in the spectral overlap. This work clarifies how wettability regulates the microscopic structure of interfacial water and interfacial vibrational coupling, and provides a basis for understanding heat transfer at metal-water interfaces.