| We study extremely fine metastable emulsions known as nanoemulsions because the droplets are typically less than 100 nm. Nanoemulsions are not equilibrium mesophases (i.e. lyotropic liquid crystalline phases known as "microemulsions") that can exhibit swollen spherical micellar phases over a relatively narrow range of droplet volume fractions. Instead, once formed by extreme emulsification, metastable nanoemulsions have droplet volume fractions that can be controlled over an extremely wide range through osmotic concentration and dilution. |
 A highly concentrated
nanoemulsion is a strongly
elastic biliquid foam. Due to the extremely small size of the droplets, concentrated nanoemulsions are nearly transparent. |
| This schematic illustrates the structure of emulsions as a function of the droplet volume fraction. As the volume fraction is increased well beyond the dilute regime through the application of an osmotic pressure, the diffusion of the droplets becomes restricted due to their proximity to neighboring droplets. This results in jamming of the droplets and a colloidal glass of spheres that exhibits an entropic elasticity. As the volume fraction is increased even further, the droplets pack and then deform. Such compressed emulsions have an elasticity that arises from the resistance of droplets to additional deformation by surface tension. At the highest volume fractions approaching unity, the droplets become highly compressed and facetted due as they press up against neighboring droplets, forming a biliquid foam. |  |