Effect of soluble surfactant on regime transitions at drop formation

Abstract Formation of surfactant-laden aqueous drops by liquid flow through a capillary is studied and compared with two reference pure liquids, water and low viscosity poly(dimethylsiloxane). Attention is paid to two transitions: (i) between regimes with and without satellite droplet formation and (ii) from dripping to jetting. It is shown that transition from dripping to jetting occurs at critical Weber number We J  = 1.2 ± 0.1 based on dynamic surface tension on the flow timescale. Critical Weber number for transition to the regime without satellite droplets depends noticeably on the liquid surface tension and therefore cannot be used as a single parameter characterising this transition. Flow rate at transition decreases with decrease of surface tension for pure liquids and solutions of surfactants with critical micelle concentration, CMC > 10 mM. For solutions of surfactants with CMC