Phase‐Change Induced Capacitive Response in Lubricating Nanocapsules for In Situ Monitoring of Tribological Interface Temperature

ABSTRACT High‐precision in situ monitoring of tribological interface temperature is essential for the reliable operation of aerospace and advanced tribological systems, yet conventional thermocouples and infrared methods suffer from implantation difficulties, delayed response, and environmental interference. Here, we report a novel multifunctional lubricated nanocapsule that leverages the phase‐change behavior of deep eutectic solvents (DES) to overcome these limitations. Structural characterization was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and tribological tests were conducted to evaluate both tribological behavior and capacitance‐temperature response mechanisms. Experimental results demonstrate that when the interface temperature reaches the melting point of the DES, the capacitance of the tribological system undergoes an abrupt transition, while both the coefficient of friction (COF) and the wear rate decrease to a certain extent. The improvement in dielectric properties is ascribed to the ion polarization effect generated by the molten DES, whereas the enhancement of tribological performance arises from the lubrication protection provided by its liquid phase. This work demonstrates a materials‐based strategy for real‐time temperature sensing at dynamic tribological interfaces, offering new opportunities for intelligent lubrication and fault prediction in high‐end equipment.