Sample Flow Switching Technique Based on Combined Effect of Hydrodynamic and Electroosmosis

This paper presents theoretical and experimental investigations on valveless microfluidic switch using the coupled effect of hydrodynamics and electroosmosis. In the experiment, two sheath streams (aqueous NaCl and glycerol) and the sample stream (silicon oil) are introduced by syringe pumps to flow side by side in a straight rectangular microchannel. External electric fields are applied on the two sheath streams. Under the constant inlet volumetric flowrates, the sample stream is delivered to the desired outlet ports using electroosmotic effect. The liquid fractions of sheath streams are measured using fluorescence imaging technique. The results indicate that under suitable cooperation of electric fields, the sample stream can be delivered to the desired outlet ports.