Dielectrophoretic Levitation of Small Metallic Particles

Small uncharged metallic spheres have been levitated in a nonuniform electric field using a microprocessor-based active feedback control system. The particle is centered horizontally in an axisymmetric time-varying electric field. The vertical gravitational force is balanced by the dielectrophoretic force; however, the resulting equilibrium is unstable. To achieve stable levitation the vertical particle position is sensed optically and an error voltage is applied to the electrodes. Experimental results with the levitator are in good agreement with the equilibrium force balance model.