Nanoemulsions
Just as colloidal dispersions of solid nanoscale particulates have received considerable attention, colloidal dispersions of deformable nanodroplets — nanoemulsions — are beginning to receive significant attention.
Although many basic principles of emulsification are already known for isolated droplets in relatively mild shear flows, the new principles of emulsification that govern nanodroplet rupturing and coalescence in extreme shear at high ø are still being discovered.
Quantitative theoretical predictions of droplet size distributions that include the combination of these two effects are sorely needed. Once formed, nanoemulsions can be manipulated and controlled in very precise ways.
Ultracentrifugal fractionation provides model monodisperse dispersions of nanoscale droplets in the size range from roughly a = 10 to 100 nm.
These monodisperse nanoemulsions have proven to be very useful in combination with neutron scattering methods to reveal the average bulk positional structures as droplet interactions range from repulsive to strongly attractive.
Through rapid osmotic compression, dilute nanoemulsions of repulsive droplets can be transformed into transparent soft elastic solids that can have surprisingly strong shear elasticity. Such materials have many potential scientific applications, such as exploring size-dependent droplet uptake through the membranes of living cells.
Moreover, the development of high-throughput production makes the potential for widespread commercial use of nanoemulsions in consumer products and medical applications highly likely. In the future, it may be predicted that nanoemulsions will become as ubiquitous as many polymer solutions and solid particulate dispersions are today.
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