Higher order multiple emulsions
Multiple emulsions with an “onion” topology are useful vehicles for drug delivery, biochemical assays, and templating materials. They can be assembled by ternary liquid phase separation using microfluidics, but the control over their design is limited because the mechanism of their creation is unknown. Here it is shown that phase separation occurs via self-similar cycles of mass transfer, spinodal decomposition or nucleation, and coalescence into multiple layers. Mapping out the phase diagram demonstrates a linear relation between concentric layer diameters, whose slope depends on the initial ternary composition and the molecular weight of the surfactant. These general rules quantitatively predict the number of droplet layers (multiplicity). Further, self-assembly routes for polymer capsules and liposomes are provided with techniques to assemble lipid-stabilized droplets with ordered internal structures.
1. A method of creating an emulsion comprising:
passing a single phase mixture, comprising an oil, a polar solvent, and water, through a square, tapered microcapillary disposed within a round microcapillary;
passing a continuous phase stream containing water and a surfactant between the square, tapered, microcapillary and the round capillary;
dripping the single phase mixture from the square, tapered microcapillary into the continuous phase; and
phase separating the single phase mixture to form an emulsion having an order greater than 1, wherein the emulsion has at least an outermost droplet and an innermost droplet.
2. The method of claim 1 wherein the outermost droplet has a diameter of 5.6 μm and at least a doublet is formed.
3. The method of claim 1 wherein at least a triplet is formed.
4. The method of claim 1 wherein at least a quadruplet is formed.
5. The method of claim 1 wherein the outermost droplet has a diameter of 60 μm and at least a quintuplet is formed.
6. The method of claim 1 wherein phase separating includes a process selected from the group consisting of 1) spinodal decomposition and 2) nucleation and growth.
7. The method of claim 1 , further comprising altering osmotic pressure.
8. The method of claim 7 , wherein altering the osmotic pressure comprises adding a salt to the continuous phase.
9. The method of claim 7 , wherein altering the osmotic pressure comprises adding salt to the water dripped through the microcapillary.
10. The method of claim 1 comprising draining away a portion of the continuous phase stream.
11. The method of claim 1 , further comprising a second draining wherein a second round capillary is disposed within the square capillary and a second portion of continuous phase is drained between the square capillary and the second round capillary.