BACKGROUND:  Emulsions comprised of microscale droplets of a liquid in another immiscible liquid are common products and have been made for centuries. These emulsions can be simply made by applying viscous stresses using a mechanical mixer that break larger droplets into smaller droplets, consequently storing energy in the additional droplet interfacial area that is created. Traditional mechanical mixing devices can achieve droplet diameters to around 200 nm, but usually have difficulty creating droplets smaller than this limit. Existing methods for making elastic emulsions of small droplets typically alter the composition to raise the volume fraction of the dispersed (i.e. droplet) phase up to the point where the droplets begin to pack and deform. Due to the geometrical nature of the packing of disordered spheres, a significant elasticity appears at droplet volume fractions above sixty percent, and is reached by adding more of the dispersed phase while mixing. Obtaining elastic emulsions at droplet volume fractions much below sixty percent has never been achieved simply by the history of applied flow stresses.

INNOVATION:  By controlling the magnitude of the applied viscous stress without altering the composition of the emulsion, a novel high-throughput method has been developed to obtain large-scale volumes of elastic biliquid nanoemulsions. The droplet diameters and resulting elasticity can be controlled simply through the history of the maximum applied stresses. In contrast to more common microscale emulsions that appear white, the nanoemulsions created here exhibit optical transparency over a wide range of droplet volume fractions and can have strong elasticity even at low droplet volume fractions.

POTENTIAL APPLICATIONS:  Nanoemulsions with strong elasticity have applications in pharmaceuticals, personal care products, cosmetics, and food products, as well as paints and coatings.

ADVANTAGES:  The nanoemulsions described here are comprised of uniform droplets, have excellent transparency, enhanced shelf stability against gravitationally driven creaming, and can exhibit a high elastic modulus for creams or patch delivery applications.

DEVELOPMENT-TO-DATE:  The invention has been experimentally verified.

Reference: UCLA Case No. 2007-249