Liquid transport based on electrostatic deformation of fluid interfaces

We have developed a method for moving liquid along a surface using purely electrostatic effects, without the need for mechanically moving parts. In this approach, liquid drops are confined to specific regions of the substrate by a printed pattern that has the appropriate hydrophilic and hydrophobic wetting characteristics. Using a variation of well-known electrowetting techniques, the shape of the droplet can be changed by applying an electric field that changes the surface energy relationship. Specifically, a bead of oil confined to a hydrophobic region of the surface can be pinched into drops using localized electrostatic fields, and by changing the applied field pattern, these oil drops can be moved to cause net liquid flow. This approach may have useful applications in heat transfer. We have demonstrated that with drops traveling at approximately 15 cm/s, it is possible to transport heat more effectively than by using an equivalent volume of solid copper. (c) 2006 American Institute of Physics.