Spreading Characteristics Of Droplet In The Presence Of Electric Field

In recent years, the development of MEMS technology attracts much attention on the fields of microscale and even nanoscale droplet/film flows in the field of fluid mechanics. With the decrease of scale, the application of the electric field, the topography feature of the substrate and variations of surface tension due to interfacial charge density will have significant effects on the dynamic characteristics of liquid flows,which determines the quality and application performance of products.In this paper, for the movement of conductive droplet on different substrates,oscillation and spreading evolution model was established basing on the lubrication theory and leaky dielectric model to analyze the dynamics of a droplet between two electrode plates in the presence of electric field. The PDECOL code was used to model and investigate the dynamics of a droplet and the effects of important parameters under different types of electric potential, and the change rate of main characteristics was discussed. The main contents of the paper are listed as follows:(1) For movement of conductive droplet on flat substrate, the evolution equations of liquid film thickness and interfacial charge density are derived. The dynamics of droplet under different types of electric potential which contains linearly potential, nonlinear potential and alternating current potential are simulated with PDECOL code, and the change of droplet's free interface morphological under different electric field is also examined. By discussing the change rate of main feature amounts over time under different electrical capillary C and the electrode distance ?, specifically to reveal the effect of electric field on the spreading of droplet.(2) For movement of conductive droplet on uneven substrate, the evolution equation of thin liquid film thickness under steady state is formulated. The spreading speed of droplet under different topography surfaces and different values of constant potential are investigated based on the numerical simulation with PDECOL code. The effects of the topography structure and different types of electric field on the variations of ultrathin liquid film thickness and droplet spreading velocity are also discussed. By introducing disjoining pressure model, the unique characteristics of droplet spreading on uneven substrate are simulated and compared.