When a droplet moves in air, its interface also moves. Surfactants are molecules that possess one segment that prefers to be in water and another that does not. This reduces the surface tension. If the density of surfactant at the interface increases, the surface tension decreases still further. As a result, the motion of the interface depends on the amount of surfactant on it.
Surface tension causes interfaces to resist stretching.
Reducing the surface tension by adding surfactants can improve the ability of droplets to deform and mix with other fluids. Understanding this process can improve our ability to control immiscible fluid systems. That can produce benefits in space and on Earth. They are interested in the fundamental issues behind fluid flow in order to use it effectively in microgravity. Surfactants play a key role in a wide array of applications that require the mixing of two immiscible fluids.