Emulsion production by pulsed spark discharges at the interface of two immiscible liquids: Effects of the discharge energy and power of the discharge*

Discharge at the interface between two immiscible liquids is a recent subject of study in plasma physics research [1,2]. In spark mode, the mechanical energy dissipated by the plasma in the liquids produces a cavitation bubble at the interface [3]. A few hundred microseconds later, the bubble violently implodes, projecting part of the organic phase into the aqueous phase. This process produces an emulsion of heptane in water [4]. The aim of this study is to vary the properties of the discharge (width and duration of the electrical pulse) to control the properties of the emulsion. To achieve this, the cavitation bubbles from the discharges were observed with a high-speed camera to analyze their dynamics, and images of the produced emulsions were taken using an optical microscope for each set of conditions.

Initially, it was observed that discharge energy was not the most suitable parameter to describe the cavitation bubble and the emulsion. Instead, the maximum discharge power at the moment of breakdown better described the bubble dynamics. Secondly, it was noted that the size distribution of the emulsion did not vary significantly, even though the conditions and power levels were different. However, the density of the emulsion was affected by the discharge power, with higher power leading to a denser emulsion.

[1] Hamdan & Cha (2016). AIP Adv., 6(10)

[2] Hamdan & Diamond (2021). PSST, 30(5), 055021

[3] Hamdan et al. (2013). JASA, 134(2), 991-1000

[4] Dorval et al. (2023). JPhysD, 57(1), 015201