This shouldn’t be an idea that bites the dust. Rafts made from dust-like particles have carried water droplets across a sea of oil, without the water dribbling out. The idea could be useful for shunting drops around, giving greater control over chemical reactions.
Small particles are often added to mixes of oil and water – emulsions – to stabilise them, because the particles stick to the boundary between the two liquids, keeping them well mixed up.
of the Pierre and Marie Curie University in Paris, France and his colleagues found that when they placed a large number of 250-micrometre particles made from zirconium oxide blended with amorphous silica on top of a pool of oil, they stuck together and acted as if they were a solid surface.
Placing a drop of water on top of the raft makes part of it sink just beneath the surface, but it stays in shape and holds the water aloft.
“This phenomenon surprised us a lot so we decided to look at it more carefully,” says Jambon-Puillet. Adding or removing water through a syringe changed the shape of the raft, but didn’t sink it. The team presented the work at thein Boston last month.
Jambon-Puillet says the team doesn’t have any firm applications in mind and is still exploring the fundamental science behind the rafts. But he thinks they could be useful in microreactors, which are used to carry out chemical reactions in small volumes.
“A chemical reaction would occur within the droplet, then it can be moved anywhere on the surface and its contents released just by piercing the interface below the drop with a needle,” says Jambon-Puillet.
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