Electrokinetic Flow and Micromixer



The manipulation of bio-particles like cells, DNA, and proteins is important for biological and medical research. The term AC electrokinetics refers to the movement of either particles or fluid by using AC electric fields, such as dielectrophoresis (DEP) and AC electro-osmosis (AC EOF). We have been developing a variety of novel designs and applications for manipulating bio-particles in microfluidics for years, for example, trapping, sorting, pumping, micromixer, cell patterning, and tissue engineering.

A novel ac electrokinetic microfluidic driver based on alternating current electro-osmosis flow induced by asymmetrically capacitance/chemistry-modulated microelectrode arrays has been successfully developed and demonstrated. Asymmetric capacitance modulation (ACM) is made of comb electrode arrays and parts of individual electrode surfaces are modulated/deposited with a SiO2 dielectric layer. This proposed design can be utilized to shift the optimal operation frequency of maximum velocity to a higher frequency to minimize electrolytic bubble generation and enhance micropumping performance. The maximum pumping velocity at the applied potential of 10 Vpp in 5 mM buffer solution can reach 290 μm s-1, and the estimated flow rate is up to 26.1 μl h-1.


We successfully demonstrated a microfluidic mixer that takes advantage of field-effect control to dynamically manipulate local flow field to highly enhance mixing effect in microchannel. The influences of buffer pH, electrolyte concentration, and radial voltage on the ζ-potential, and the flow field analysis with nonuniform ζ-potential have been studied and characterized. The work reported in our group is considered as the first time temporal/spatial ζ-potential modulation for microfluidic mixer applications.


Selected Publication


[1] Ching-Te Kuo and Cheng-Hsien Liu, “A Bubble-Free AC Electrokinetic Micropump Using The Asymmetric Capacitance-Modulated Microelectrode Array for Microfluidic Flow Control,” Journal of MicroElectroMechanical Systems 18 (1), pp. 38-51, 2009

[2] Hsin-Yu Wu, and Cheng-Hsien Liu, “A Novel Micromixer,” Sensors and Actuators A: Physical, Volume 118, Issue 1 , 31 January 2005, pp. 107-115  (Research Highlighted by Lab on a Chip, 2005, 5(5) , 370 – 373)