Ionic liquids (ILs), characterized by high electrical conductivity, negligible vapor pressure, and wide physicochemical tunability, hold promise for applications in cooling, coating, and energy systems where droplet impact is critical. We experimentally investigate the effect of an external electric field, $\mathbf{E}$ (0–10 kV/cm), oriented parallel to the impact velocity, on the deformation and impact dynamics of high-conductivity IL droplets across a broad range of Weber $(31\le \mathrm{We}\le 629)$ and Ohnesorge $(0.11\le \mathrm{Oh}\le 1.19)$ numbers. The results show that IL droplets undergo pronounced prolate deformation driven by field-induced Maxwell stresses, with the deformation magnitude increasing with electric field strength and travel time but decreasing with surface tension and viscosity. Despite substantial preimpact deformation $(0\le \mathcal{D}\le 0.62)$, the impact outcomes—spreading and splashing—remain largely unchanged. The maximum spreading factor $\left({\beta }_{\text{max}}\right)$ and splashing threshold exhibit negligible changes compared with spherical droplets. No field-induced jetting or breakup is observed, in contrast to previous findings for water droplets under $\mathbf{E}$. The data for ${\beta }_{\text{max}}$ collapse onto the semiempirical scaling ${\beta }_{\text{max}}=0.61{(23.3+\mathrm{We}/\mathrm{Oh})}^{1/6}$, derived from a simplified energy conservation model in which the initial kinetic energy is dissipated by viscous losses. These findings demonstrate that while electric fields strongly alter droplet morphology in flight, the high viscosity of ionic liquids suppresses electrostatic coupling during impact.

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• Drop & bubble phenomena
• Drop interactions
• Electrohydrodynamic effects
• Multiphase flows
• Drops & bubbles