Anisotropic Liquid Dielectrophoresis and Interfacial Forces

There is a growing technology-driven interest in using external influences to move or shape small quantities of liquids, a process that is referred to as "microfluidic actuation". Using electrical, rather than mechanical, forces to achieve this actuation is convenient because this involves relatively simple device architectures that contain no moving parts. Existing non-mechanical microfluidic actuation techniques that are driven by the application of a voltage include electrowetting, which only works with conducting liquids, and dielectrophoresis, which works with both conducting and non-conducting liquids. We have previously shown how dielectrophoresis forces in non-conducting isotropic liquids can be used to create not only forced wetting and liquid spreading, but also liquid film wrinkling in which an engineered electric field distribution imprints a replica of itself as a distortion pattern at the liquid-air interface of the film. In this proposal the possibility that liquid dielectrophoresis can lead to added functionality and greater control within a pure anisotropic liquid, i.e. a nematic liquid crystal rather than a simple isotropic liquid, will be investigated. Liquid dielectrophoresis in pure anisotropic liquids has not been studied before, either experimentally or theoretically. Our proposed integrated collaborative experimental and theoretical research approach aims to understand and exploit the forces that can be created within, and at the surface of, free and confined anisotropic liquids when they are subject to electric fields. The proposed research will investigate an exciting new possibility of using anisotropic liquids along with particular confinement geometries which allow voltage controlled actuated microfluidic pumping to be produced even with simplified electrode architectures. Our industrial supporters include Merck Chemicals Ltd, the world-leading researcher, developer and manufacturer of liquid crystals and reactive mesogens, together with Hewlett-Packard and ADT, who are developing the next generation of information displays based on liquid crystal and microfluidic effects.