Monodisperse w/w/w Double
Emulsion Induced by Phase
Separation
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Abstract
We develop an approach to fabricate monodisperse water-in-water-in-water
(w/w/w) double emulsion in microfluidic devices. A jet of aqueous
solution containing two incompatible solutes, dextran and polyethylene
glycol (PEG), is periodically perturbed into water-in-water (w/w)
droplets. By extracting water out of the w/w droplet, the solute concentrations
in the droplet phase increase; when the concentrations exceed the
miscibility limit, the droplet phase separates into two immiscible
phases. Consequently, PEG-rich droplets are formed within the single
emulsion templates. These PEG-rich droplets subsequently coalesce
with each other, resulting in transiently stable w/w/w double emulsions
with a high degree of size uniformity. These double emulsions are
free of organic solvents and thus are ideal for use as droplet-vessels
in protein purification, as microreactors for biochemical reactions,
and as templates for fabrication of biomaterials