Scientists at Harvard University have nestled droplets inside droplets by squeezing three concentrically arranged streams of fluids into a glass tube. The double droplets could be useful for encapsulating food additives and components of cosmetics. The innermost (1) and outermost (3) fluids shown here are silicon oil, and the middle fluid (2) is a water-glycerol mixture. The two inner fluids, flowing right to left, pinch off (at arrow) to form uniform, two-layer microscopic droplets within the outermost oil.
These double emulsions, described in the April 22 Science, are more stable than single emulsions, which are commonly used for encapsulating flavors and other types of food additives, says lead investigator David Weitz. With this technique, researchers can also create droplets harboring multiple droplets, each capable of storing a different flavor or fragrance.