Fluid pumping and cells separation by DC-biased traveling wave electroosmosis and dielectrophoresis

Fluid pumping in microchips using electrokinetic methods has been a hot area of research. This paper mainly investigates effects of DC offset imposed on traveling wave (TW) signal on electroosmotic flow above a spiral electrode array with 800 mu m wavelength. The traveling wave voltage with different DC offsets was applied, and four cases were analyzed by superimposing consecutive images. Experiment results indicate that symmetric electrode array energized with DC-biased TW signal can not only generate a prominent improvement in flow rates, but also be capable of altering the flow direction by changing the polarity of electrical signal. Furthermore, such a device can also be used as an effective means to manipulate and separate PS microbeads and cells on their own for very small and non-flowing sample volumes in terms of the combination of the conventional dielectrophoresis (cDEP) forces and traveling wave DEP (twDEP) forces by properly choosing the parameters associated with the Clausius-Mossotti factor (K(w)). Through adjusting the applied frequencies, we successfully separated yeast cells from a mix containing PS microspheres based on the combination of cDEP and twDEP, providing new opportunities for integration with a charge-coupled device for various biomedical diagnostic devices.