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 µm 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.