Steven D. Hudson1, Jai A. Pathak2, Joao T. Cabral3, and Samuel P. Forry1. (1) Polymers Division, NIST, 100 Bureau Dr., STOP 8542, Gaithersburg, MD 20899, (2) Polymer Physics Section, Materials Chemistry Branch, U. S. Naval Research Lab, 4555 Overlook Avenue SW, Bldg. 207, Washington, DC 20375-5342, (3) Chemical Engineering, Imperial College London, South Kensington Campus, London, United Kingdom
A microfluidic instrument to measure liquid-liquid interfacial tension during flow has been developed and tested. The measurement principle rests on the deformation and retraction dynamics of drops (in the small deformation limit) under extensional flow. Fluid flow is tracked by drop motion and matches creeping flow predictions. Surfactant dynamics were also modeled to explore the validity of the small deformation limit. Experimental conditions (such as residence time, flow rate, and geometrical factors) were adjusted to probe the dynamic response of mixtures containing surfactant.