Effect of electrode structure on pumping performance of electrohydrodynamic pumps based on the dissociation-injection mechanism

Electrohydrodynamic (EHD) pumps are promising for microfluidic actuation because of the absence of mechanical moving parts and their ease of integration. In this study, a multiphysics numerical model of an EHD pump considering the coupled dissociation–injection mechanism is developed based on the finite volume method. The effects of electrode polarity connection, injection intensity C, conduction number C0, electric Rayleigh number T, and electrode configuration on pumping performance are systematically investigated. For the mirror-symmetric arrangement of asymmetric electrode pairs, the steady-state outlet velocity is 36.7% higher when the narrow electrode is connected to the positive potential than when the wide electrode is connected to the positive potential. This enhancement arises from the synergistic effect between injected-charge migration and the net Coulomb force generated by charge dissociation. With the other parameters fixed, increasing C from 0.1 to 10 increases the steady-state velocity by 48%, indicating the dominant contribution of charge injection under strong-injection conditions. The conduction number exhibits a non-monotonic effect on pumping performance: a moderate increase enhances the flow, whereas an excessively large C0 weakens the effective driving force. Among the electrode configurations examined, the mirror-symmetric arrangement of asymmetric electrode pairs provides the strongest pumping performance, whereas staggered arrangements with larger spacing induce more pronounced secondary flows and flow disturbances, indicating greater mixing potential. These results clarify the synergistic and inhibitory interactions between dissociation and injection under different operating conditions and electrode configurations, providing guidance for the structural optimization of EHD pumps.