Electrowetting A Nanoparticle Suspension

Steven      J. Grisafi

Abstract

Kinetic theory is used to predict the pressure within a sessile droplet containing a suspension of nanometer sized particles. The effect of an applied electric field upon the contact angle is examined. The applied electric field decreases the contact angle of the droplet by lowering the pressure within the droplet. The phenomenon of contact angle saturation is not predicted. It is seen that the pressure reductions required to decrease the contact angle below approximately 30deg grow rapidly. This requires a rapidly increasing electric field. The model assumes that the electric field induces electric dipoles on the nanoparticles. By doing so it decreases their kinetic contribution to the fluid pressure within the droplet. A simple analytical expression for the contact angle as a function of fluid pressure and the applied electric field is derived.

Keywords: Wetting, contact angle, surface tension, electrostatics, pressure, kinetic theory, nanoparticle suspension, electrowetting, solid-vapor interface, thermodynamics