Norwegian University of Science and Technology researchers have found they can use electricity to control droplets, from the July 5, 2013 news release on EurekAlert,
You’ve seen Hollandaise sauce or mayonnaise that has separated, or that shiny layer of oil that forms on top of skin cream. This mixture of water and oil is called an emulsion, but it can be difficult to keep emulsions from separating. A special substance called an emulsifier is used to keep the mixture stable and prevent separation.
This is an ongoing problem for the food and medical industries, as well as for oil recovery. In fact, the petroleum industry also has to deal with the opposite problem, which is to separate oil that is pumped up from a well in a mix of water and gas.
Now, researchers from the Norwegian University of Science and Technology (NTNU) have found a new method to control how drops of oil behave, using electricity. The results were published in late June  in Nature Communications.
Here’s how the researchers produced the emulsion effect (from the news release),
The researchers used micrometer-sized particles of clay and silicone oil droplets for their experiment. First, the clay particles coated the droplet, but when the voltage was turned on, the clay particles made a ring around the drop. By controlling the strength of the electrical voltage, researchers can control how the particles accumulate in the ring, much like the way your eye controls how much the pupil opens in response to light.
The method could also be used to control the emulsion’s properties with electricity. Its features could thus be turned on and off quickly, without adding new chemicals.
Naturally, there’s talk of patents (from the news release),
Fossum [Jon Otto Fossum, a professor in the Department of Physics at the university] says the experiment is basic research in physics, and offers a number of possibilities across disciplines. The research group has thought of several different applications for their finding that they may consider filing patents for, but they do not want to discuss specifics.
“The physical or chemical control of emulsions is very important for many areas of technology and for many different applications,” said Fossum.
Fossum says next step is to expand their understanding of what the experiment illustrates, and to perform more laboratory experiments with particles other than clay, and with other types of fluids. At the same time, the researchers are exploring some of the ideas they have about how their technique can be applied.
You can find the paper here,
Active structuring of colloidal armour on liquid drops by Paul Dommersnes, Zbigniew Rozynek, Alexander Mikkelsen, Rene Castberg, Knut Kjerstad, Kjetil Hersvik, & Jon Otto Fossum. Nature Communications 4, Article number: 2066 doi:10.1038/ncomms3066 Published 28 June 2013.
This article is open access.