Microvalve using electrokinetic motion of electrically induced Janus droplet.

A novel microvalve using the electrokinetic motion of electrically induced Janus droplet (EIJD) is presented in this paper. The device is fabricated by injecting an EIJD with the diameter of approximately 80 μm into a microchamber connecting several microchannel branches. The EIJD is developed from an oil droplet covered by Al2 O3 -nanoparticles under electric field. The microvalve is controllable by electric field. Under an electric field, the Janus droplet undergoes electrokinetic motion in the microchamber, moves to one branch channel and blocks its entrance. By switching the electric field direction, the Janus droplet detaches from this entrance and moves to block another branch channel. In this way, the flow direction in the microvalve changes. In this research, the electrokinetic motion of the EIJD in a circular microchamber under the switching electric field was studied first. The result indicates that the Janus droplet always rotates to get aligned with the electric field. Then, the performance of the microvalve was investigated systematically. The results confirm the capability of such a microvalve in sealing, switching time and flow rate control. Furthermore, by comparing with the case of using a plain oil droplet in such a microvalve, it is proven that the EIJD is essential in realization of a non-leakage microvalve. The EIJD-based microvalve shown in this paper offers great potential in fabricating integrated microfluidic devices.