Microfluidic production of monodisperse functional o/w droplets and study of their reversible pH dependent aggregation behavior

Wolfgang-Andreas C. Bauer, Jurij Kotar, Pietro Cicuta, Robert T. Woodward, Jonathan V. M. Weaver and Wilhelm T. S. Huck

We report the use of microfluidics for the production of monodisperse oil-in-water droplets functionalized by a pH responsive branched co-polymer surfactant. The droplet functionality facilitates the reversible aggregation of the micron-sized droplets into macroscopic engineered emulsions in response to solution pH changes. Co-injection of dye-loaded and non-dyed droplets into acidic water yields bi-colored dumbbell-shaped aggregates that disassemble into their constituent droplet building blocks upon an increase in pH. Optical tweezers are used to study and quantify the pH dependent interactions of individual droplets.

DOI