Water and oily liquids do not mix, but with modern oil production technologies, often barbarously dirty, fine-cellular foam is often formed from different substances. There is no effective and inexpensive way to separate them and purify water from impurities. However, the Massachusetts Institute of Technology has had some success using sunblock.
The cream is made from refined petroleum products, so it will work as a test sample. It contains titanium dioxide, an active element that reacts aggressively to light. In the dark, this substance repels water, and when illuminated with ultraviolet light, it begins to attract and becomes wettable. A phenomenon called photoreactivity - scientists have come up with the idea that they can point to highlight the liquid in order to change its properties. And form droplets where they need to.
And then everything is simple: we give the computer an ultraviolet flashlight and make it shine on the oil-water foam according to a special algorithm until all the water collects into drops and separates from the oil. Not the most efficient process, given the size of the oil spills in the tens of square kilometers. So the scientists added organic dyes and polymer films to make titanium dioxide sensitive to visible light as well. Now the muddy puddle separates itself into oil and water just under the sun.
Most of all, scientists are pleased not by the prospects for cleaning up oil production sites, but by the newfound control over photoreactive compounds. The technology makes it possible to change the wettability coefficient of a substance under a beam of light and to move droplets with great accuracy and speed. And this, no less, a sensation. Imagine a self-cleaning liquid that stops being "wet" on command and therefore no longer adheres to dirt particles?
Alas, a wonderful future is still far away, so far there is only a concept for the design of such systems and a few successful laboratory experiments. However, scientists are confident that as new, inexpensive dyes become available, they will be able to develop a "wet / not wet" formulation for applied use.