Finding a leak in a pipe is labor-intensive work –
especially if the leak is small, or the pipe is underwater and leaking invisible chemicals. Some approaches include running colored liquid the Detecting contamination can also be a tall order — taking water samples from one location may not reveal the plume of pollution just a few yards away.
Researchers are working on a novel a solution: remotely controlled water droplets. At a lab at King Abdulla University of Science and Technology in
Saudi Arabia, Peng Wang, an assistant professor of environmental science and
engineering, and his team have found a way to coat single droplets of water in a nanometer-sized sphere made of iron oxide coated in silicon and a polymer. Once coated the spheres behave liquid marbles that — because the coating contains iron oxide — can be remotely controlled and moved around using a magnetic field.
Another important characteristic of these liquid marbles is that exposing them to ultraviolet light or hydrogen ions weakens the bonds between the tiny nanoparticles and the water. When the bonds weaken, the coating falls apart, releasing the water inside. And it's not just water that can be contained. Other liquids could be coated and sealed within a marble that can have a volume as small as about two millionths of a liter of fluid.
So what does one do with a liquid marble that can be moved with a magnetic field and then released using UV light or hydrogen ions? If you said, "Find a chemical leak," then you probably read the headline.
Here's how it would work: contain dyed droplets of water in nano-spheres and then release them into a pipe that may be leaking some kind of pollutant underwater. Use an underwater robot to direct the particles through the pipe using a magnetic field. The moment the nanoparticles hit the polluted water, the coating would dissolve, releasing the dyed water droplets, spreading the color and revealing the location of the leak.
To locate a contamination in a body of water, drop the marbles near the relevant area, direct them with a magnetic field and as soon as they make contact with the pollutant, the nanospheres break down, releasing the dyed water. The marbles could also carry dispersers to the exact location of an oil spill.
Moving the marbles with a magnet would also be useful when one wants to coat something evenly: arrange the marbles on a surface, held in place by a magnetic field, and shine an ultraviolet light to make them release a paint or solvent. (Something useful in etching).
Wang said that while this could be used for drug delivery,
it will be some time before the "marbles" can be made small enough to
reliably fit into a capsule.
The work was reported online on July 26 in Advanced
Materials and will appear in the Sept. 11 print edition. Videos of the droplets
in action are here.
Image: Peng Wang