Funky nanofilm separates oil from water

A mirror that cannot get dirty and a meshwork capable of instantly separating oilfrom water have been developed by scientists in the US. Both technologies are based on a special surface treatment based loosely on the famed self-cleaning physics of a lotus leaf. Chris Smith reports...

Chris - There's a very interesting story which has come out from researchers at Ohio State University who've made this oil water separating sieve which I read with great intrigue. I thought well, that come in useful when you're cooking Sunday dinner because instead of pouring your gravy, which has got oil and fat mixed together, into one of those separating funnels, actually, you could just pour it through a sieve made of this material that they've come up with and it would just separate it for you.

Kat - How does this work then?

Chris - Well, what they were doing was first of all, looking at how they could make self-cleaning mirrors in fact. They were trying to make a surface that would just shed water or shed oil. Then they discovered that you could actually apply this to a thin stainless steel mesh and it would do the same thing. The way it works is first of all they spray onto a stainless steel mesh some particles - effectively sand. It's silica nanoparticles and that makes the surface a bit bumpy. They then layer on top of that a polymer, which is called PDDA because it's got a horribly long, unpronounceable name, but embedded in that polymer are some surfactant molecules. Surfactants are chemicals that break the surface tension of water; they make water much less sticky. The effect of this is that the water will very happily spread out across the surface, but oil hates the surface so it forms little droplets. If you make a mesh of this material and hold it over a jug at a slight angle you can then pour a mixture of water and oil through the sieve. The water leeches straight through and goes into the pot underneath, but the oil runs off sideways. So, you get two pots - one full of oil and one full of water. It's absolutely stunning.

Kat - You're clearly making much classier gravy than I am because I just open the Bisto. Other gravies are available.

Chris - Don't you use the meat juices?

Kat - Well, we're vegetarians.

Chris - Okay, you could still use meat juices. How can you make gravy with no meat juices? It's fantastic!

Kat -我们素食者…