Synchronously coupled magnetic field weakening the dynamic deformation response of salt-containing droplet to an electric field

Combining a magnetic field with an electric field offers a promising approach for enhancing oil–water separation, yet its underlying mechanisms are not fully understood. We systematically investigated the dynamic deformation of salt-containing water droplet suspended in oil under an electric–magnetic coupling field. Integrating high-speed camera experiments with molecular dynamics simulations, we found that the dynamic response amplitude of droplet is reduced compared to a single electric field. Our analysis suggests that ions deflect under electric–magnetic coupling, affecting ion enrichment and water molecule polarization, thereby weakening droplet tip charge and induced electric forces, which suppresses droplet deformation. Increasing the electric capillary number and ion concentration enhances suppression, whereas improving the electric field frequency to 500 Hz almost eliminates this suppression effect. Notably, the degree of droplet deformation inhibition remains consistent across different viscosity ratios. These research findings offer insights for designing dehydrators to intensify oil–water separation.