Reversible Tran Formation Of Surface Wettability Under Electric Field Excitation And Its Effect On Lubrication Performance

Regulation of surface wettability has a wide range of applications in the microfluidic system, adjustable liquid lens and lubrication drag reduction and so on. Electrowetting is an effective method to real-time change surface wettability, but wettability reversal of reversible problems still need to be solved. In order to understand the mechanism and influencing factors of the wetting state transition in the electro wetting process, so as to provide theoretical guidance for the controllable transition of wetting state.In this paper, the dynamic process of wettability transition under electric field excitation is studied theoretically and experimentally,major work and conclusions include:Based on the energy minimization method, the influence of external electric field, surface microstructure parameters and surface energy on the transition energy barrier of the wetting state is deduced. The conditions of different surface microstructure and the change of wettability under electric field excitation are given.From the perspective of electrodynamics, the electric field is excited as a theoretical model for the simulation of wetting state transition as electromotive force coupled to a hydrodynamic two-phase flow equation. The theoretical results provide a theoretical basis for numerical calculation and analysis of test results.Based on the phase-field two-phase flow model, the dynamic process of wetting state transition under electric field excitation was numerically simulated. The results show that the driving force of the wetting state transition is mainly due to the electromotive force of the gas -liquid interface and the electrowetting effect due to the influence of the electric field on the interfacial surface tension coefficient. The dynamic process of the wetting state transition and the final result are mainly determined by the gas-liquid interface electric field. Factors that affect the electric field include voltage, dielectric layer and surface microstructure. The surface structure affects the electric field distribution and the wetting state transition energy barrier. The optimization of the surface microstructure can control the wetting state transition process.The microstructures of different geometrical features were prepared by the micro -processing of silicon, and the regularity of the micro - structure was studied. The results show that the complete reversible transformation of surface wettability can not be achieved due to the existence of energy barrier. The control part of the filling state can realize the reversible transformation of surface wettability to a certain extent. There is a certain relationship between the degree of reversibility and the degree of partial filling, and the reversibility of wettability has some controllability.The wear-resistant hydrophobic surface with multi-stage microstructure was prepared by laser processing on the surface of metal substrate, and the friction performance of hydrophobicity was studied. The results show that the hydrophobicity of the friction surface can reduce the friction coefficient under light load condition, but the friction coefficient will increase significantly under heavy load condition.