Electrical impedance-based characterization of electrostatic suppression of the Leidenfrost state

Abstract

A drop of liquid will levitate on its own vapor on a sufficiently hot surface (the Leidenfrost effect). Application of an electric field across the vapor gap suppresses the Leidenfrost state by electrostatically attracting liquid towards the surface. This study highlights and quantifies the statistical nature of wetting during electrostatic suppression via electrical impedance characterization of Leidenfrost pools under electrostatic suppression. The influence of the electric field, surface superheat, and size of the Leidenfrost pool on the wetted area is studied. High-speed measurements (0.01 s resolution) indicate that the wetted area is not constant during electrostatic suppression, but instead fluctuates. This technique can also be used to study the onset of suppression. Interestingly, we identify two distinct threshold voltages required to initiate periodic and continuous electrostatic suppression, respectively. The dependence of these voltages on surface superheat and the frequency of the applied AC waveform is studied. Together, these results enable an in-depth understanding of electrostatic suppression and highlight the benefits of impedance-based characterization towards understanding the Leidenfrost effect.