Traveling wave dielectrophoresis micropump based on the dispersion of a capacitive electrode layer

A traveling wave dielectrophoresis microfluid pump based on structural dispersion is demonstrated. The phase shift between medium polarization and applied propagating field, necessary to generate asynchronous propagative forces in dielectrophoresis, is generated by an RC circuit consisting of the electrode insulator and the liquid conductivity. Since the device characteristics involve only bulk properties, the micropump does not require conductivity gradient or double layers, unlike existing micropumps using electro-osmosis and electrohydrodynamic shear forces. Its frequency of maximum pumping force can be made considerably lower than the dielectric relaxation frequency of the liquid. By decomposing the traveling wave electrode array into a rudimentary RC model, coincidence is found between optimized pumping conditions and crossover of the impedance measured between electrode combs. By using impedance spectroscopy alternately with pumping, the frequency of the applied signal can be matched in real-time to the complex dielectric constant of the liquid to keep the pumping force maximized. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3152787]