Dielectric Constant Measurements Using Dielectrophoretic Levitation

Abstract

A dielectrophoretic levitation scheme is used to measure the dielectric constant of insulating dieletric liquids and small solid spherical particles. The fixed ring-disk electrode system is first calibrated against a known standard dielectric liquid by levitating a small gas bubble in the liquid at a fixed location. The measurements are then performed by measuring the voltage required to levitate a gas bubble in the unknown liquid at the same location with respect to the electrode structure. A similar procedure is used for solid spherical particles. The system is unique because it requires no detailed knowledge of the electric field. Fabrication of the electrodes does not require precision machining, and the structure is relatively insensitive to leveling. The size of the gas bubble or solid particle is not critical as long as it is much smaller than the electrode structure. The measurement precision is limited by the accuracy of the voltage measurements and by the accuracy to which the dielectric constant (of the standard) and the specific gravities (of the unknown and the standard) are known. The measurements presented support the contention that this method is a simple and reliable method of measuring the dielectric constant of insulating dielectric liquids.