Control of cell elution from a dielectrophoresis micro-array using a permittivity gradient

Microparticles, e.g. biological cells, can be selectively trapped or released from a dielectrophoretic (DEP) electrode array by manipulation of the relative permittivity of the suspending medium. Frequency windows are predicted in which the DEP force decreases, increases or even reverses polarity as a function of medium permittivity, depending on the type of organism. Experimental validation is presented for yeast cells which showed progressive release as the relative permittivity was reduced from 130 to 78. Quantification of DEP collection used a combination of dark-field microscopy with image processing.