(168z) Surfactant Effects On Drop Formation in Co-Flowing Fluids

The desire to produce droplets of controlled size in applications such as ink-jet printing and microcapsule fabrication makes the study of drop formation in co-flowing fluids important. Surfactants are present or added intentionally to such applications to influence the sizes of detaching primary drops and satellite drops. We will present our experimental results for the formation of a drop at the tip of a needle with a co-flowing fluid in the presence of soluble surfactants. Experiments are conducted using glycerol water and carboxymethyl cellulose solutions as the bulk phase and silicone oil as the drop phase. The effects of flow rate ratio and viscosity ratio of the fluids on the drop volume are investigated. As outer flow increases, drop volume decreases due to increased drag. Slug flow occurs at small flow rate. As drop viscosity increases, drop volume increases as the drop fluid resists the breakup. The effect of a non-circular outer wall on the drop breakup is also determined. Surfactants such as Triton X-100, SDS, and Tween-80 with different kinetics are added to the system and their effect on the drop breakup dynamics at different concentrations is explored.