Spreading of a dielectric droplet through an interfacial electric pressure

Abstract

A corona discharge-assisted technique for spreading of a gently deposited dielectric droplet into a uniform thin film over a dry isothermal conductive substrate is proposed. The surface charge was built up over the droplet interface through ion bombardment using a sharp emitter electrode. Interaction of the surface charge density and intense electric field generates an interfacial electrical pressure and leads to a uniform axisymmetric spreading of the droplet in the radial direction. It was shown that the droplet expansion process can be controlled through variation of the ion injection current and/or discharge exposure time. It is also demonstrated that the proposed technique can be analogous to the classical Stefan's squeezing liquid flow between two separated parallel discs. The dynamics of the film spreading owing to the corona discharge can be predicted through a simplified analytical model based on this analogy.

On the corona discharge spreading of dielectric liquid films

“…It has been demonstrated that the electrostatic forces can be used for spreading of dielectric layers [2,3]. A selective spreading of silicone oil due to the tangential component of electric forces over dielectric substrates was demonstrated in Ref.…”

“…[2]. Very recently, it was also shown that a dielectric droplet exposed to a perpendicular corona discharge expands uniformly over the grounded substrate [3]. The corona discharge accelerates the ionic clouds toward the substrate and develops a surface charge over the droplet interface.…”

Simulation of Motion of Micrometer Sized Droplets of Dielectric Water-based Paint under Air Flow and Electric Field

“…Reference [10] reported that there was a linear relation between the contact line velocity and the relationship between fall speed and fall height by using a high-speed video camera. Reference [11] demonstrated that the droplet expansion process can be controlled through variation of the ion injection current and /or discharge exposure time. Reference [12] and under a uniform electric field.…”

Instability of Dielectric Liquid Surface under the Action of HV Corona Discharge Pulses

“…Electrohydrodynamic instabilities formed on the surface of dielectric liquids are caused by extrusion of the latter from the discharge region. Two physical mechanisms of such an extrusion can be distinguished: the discharge ionic wind pressure [2] [3] and the electrostatic repulsion on the charged surface [4]- [14]. The ionic wind pressure is detected in dielectrics with a relatively high electrical conductivity, which ensures passage of a sufficiently high current of the barrier discharge through them.…”