Flow Structures and Charge Behaviors of Electroconvective Silicone Flows Induced by a Surface Dielectric Barrier Injection Actuator Subjected to Bipolar Pulsed DC Signals

Surface dielectric barrier injection (SDBI) actuators have received increasing interest due to the presence of dielectric barriers, which can greatly improve the applied voltage. The success of SDBI actuators in driving silicone oil makes silicone flow a very promising application in the field of microfluidics. However, polarity-dependent flows that are different from conventional cases are observed experimentally under bipolar pulsed DC signals. To interpret this specific phenomenon, a new model of electrohydrodynamic (EHD) wall jet considering both electrochemical injection and the initial presence of an electrical double layer (EDL) at the dielectric solid/liquid interface is developed for the first time based on the finite element method. The results show that the flow field in the simulation is consistent with the experimental bidirectional flow field. The silicone vortex movement is accompanied by charge injection, migration, and accumulation in the near-wall region. Through studies of the effect of signal parameters on flow behavior, including voltage amplitude, duty cycle, frequency, and waveform, a square wave signal with a frequency of 0.2 Hz proves to be the most efficient in generating a high-velocity silicone flow.