Dynamic behaviors and stability limit of sessile droplet on dielectric surface under external electric field

Unlike droplets on conductive substrates, sessile droplets on dielectric surfaces exhibit constrained charge transportation under an external electric field, leading to distinct dynamic behaviors that remain insufficiently elucidated up to date. The present paper aims to address this issue by specifically investigating the stability limit and transient deformation response behavior of water droplets on a dielectric polyimide polymer surface through experiments. The results found that two deformation modes of droplets appeared successively with increasing electric field intensity, i.e., the tensile mode and ejection mode. For the tensile mode, the electric field, charge, and electrostatic force at droplet apex and tensile height of droplet are nonlinearly related to external electric field intensity. The tensile height is also affected by droplet volume, film thickness, and electrode-film distance. For ejection mode, the ejection frequency and length depend on droplet volume, electrode-film distance, and film thickness, but the ejection width is not affected by these parameters. The physical mechanism of ejection behavior is clarified through numerical simulation. The stability limit of droplets is elucidated through the energy minimization theory. This study provides a scientific basis and technical guidance for the manipulation and control of droplet behavior on dielectric surfaces.