EWOD-driven stirring in lab-on-a-chips: Dependence on the electrodes’ geometry

Electrowetting on dielectrics (EWOD) with coplanar electrodes is increasingly used in microsystems. This paper enlightens the physical mechanisms of stirring flows in sessile droplets actuated by oscillating EWOD with potential applications to biochemical reaction enhancement or cells handling. Depending on electrodes design (circular vs. square electrodes), EWOD-induced convective flow can be observed to switch from toroidal to quadripolar flows. Due to the coplanar geometry of the electrodes, a model can be proposed which helps to interpret EWOD-induced flow as a result of capillary streaming. Numerical calculations are compared with imaging of drops and demonstrate clearly the essential role of oscillating EWOD as a flow actuator.

Figure optionsDownload as PowerPoint slideHighlights
► Electrowetting on dielectrics (EWOD) with coplanar electrodes is increasingly used.
► Oscillating EWOD generates drop streaming flows.
► Electrode geometry and voltage frequency monitor flow patterns in actuated drop.
► Flow patterns can be selected depending on applications (focusing, functionalization, mixing, separation).