Fragmentation of emulsion-based liquid sheets: influence of the oil viscosity*

Agricultural spraying uses oil-in-water emulsions as additives to reduce drift and mitigate environmental contamination by increasing the mean size of spray droplets. Here, we investigate the effect of the oil phase viscosity on the dynamics of a liquid sheet of oil-in-water emulsion. We use T-junction microfluidic devices to produce emulsions of controlled composition and drop size. We then release a drop of emulsion on top of a small target. Upon impact, a transient free-liquid sheet expands radially. We use high-speed imaging to capture the expansion of the sheet and its fragmentation into droplets. Our study suggests that increasing the viscosity of the oil phase in oil-in-water emulsions results in suspension-like dynamics of the liquid sheet.