Near Axisymmetric Partial Wetting Using Interface-Localized Liquid Dielectrophoresis.
The wetting of solid surfaces can be modified by altering the surface free energy balance between the solid, liquid, and vapor phases. Liquid dielectrophoresis (L-DEP) can produce wetting on normally nonwetting surfaces, without modification of the surface topography or chemistry. L-DEP is a bulk force acting on the dipoles of a dielectric liquid and is not normally considered to be a localized effect acting at the interface between the liquid and a solid or other fluid. However, if this force is induced by a nonuniform electric field across a solid-liquid interface, it can be used to enhance and control the wetting of a dielectric liquid. Recently, it was reported theoretically and experimentally that this approach can cause a droplet of oil to spread along parallel interdigitated electrodes thus forming a stripe of liquid. Here we show that by using spiral-shaped electrodes actuated with four 90° successive phase-shifted signals, a near axisymmetric spreading of droplets can be achieved. Experimental observations show that the induced wetting can achieve film formation, an effect not possible with electrowetting. We show that the spreading is reversible thus enabling a wide range of partial wetting droplet states to be achieved in a controllable manner. Furthermore, we find that the cosine of the contact angle has a quadratic dependence on applied voltage during spreading and deduce a scaling law for the dependence of the strength of the effect on the electrode size.
Smart Materials and Surfaces Laboratory, Faculty of Engineering & Environment, Northumbria University , Ellison Place, Newcastle upon Tyne NE1 8ST, United Kingdom.
Zuzana
Z
Brabcova
Smart Materials and Surfaces Laboratory, Faculty of Engineering & Environment, Northumbria University , Ellison Place, Newcastle upon Tyne NE1 8ST, United Kingdom.
Glen
G
McHale
Smart Materials and Surfaces Laboratory, Faculty of Engineering & Environment, Northumbria University , Ellison Place, Newcastle upon Tyne NE1 8ST, United Kingdom.
Gary G
GG
Wells
School of Science and Technology, Nottingham Trent University , Clifton Lane, Nottingham NG11 8NS, United Kingdom.
Carl V
CV
Brown
School of Science and Technology, Nottingham Trent University , Clifton Lane, Nottingham NG11 8NS, United Kingdom.
Michael I
MI
Newton
School of Science and Technology, Nottingham Trent University , Clifton Lane, Nottingham NG11 8NS, United Kingdom.
Andrew M J
AM
Edwards