Scientists build world's tiniest robot

Can you imagine a robot that's one hundred thousand times smaller than the width of a human hair? Devices this small called nanobots sound like something out of science fiction, but researchers at the University of Cambridge have this week moved us one step closer to them being a reality with the hope that one day, they'll be use them in the body for drug delivery. Professor Jeremy Baumberg spoke to Emma Sackville about this exciting development...

Jeremy - We've had this idea that you could make tiny machines - what people call nanobots that could actually go inside the body or they could do something useful for us and the problem has been we can't make them.

Emma - Why is it that we have problems making them?

Jeremy - When we try to make things move in water and they're very small, it's a bit like us trying to swim in treacle. It's very, very difficult so we need to actually swim in a different way. We can't do front crawl in treacle, we have to do something which is bit more like a bull terrier which flicks things backwards and forwards, and that's actually difficult to do and needs a lot of force, and we haven't found a way of actually making things that produce large force on this really small scale before.

Emma - But the research you've just done is actually looking at making something that moves on a really small scale and produce that kind of force.

Jeremy - Yes, we call them activating nano transducers, or ANTS for short, because they're strong things and they can move more than their body weight.  So what we've done is we've made some tiny particles which have got a coating on them and what these particles do, under the right circumstances, is they can actually produce a really large kick.

And the way it works is we take tiny little particles, in this case we make them of gold, and we've learned to coat them with a thin polymer, a bit like the polymers in our plastic bags, but this ones and gel and most of the time, at room temperature, it likes to have little fibrils of the polymer which spread spread out into water. But, if you just heated a tiny amount, a few degrees, what happens is it starts to hate water - it becomes hydrophobic, unlike many of us with swimming pools, and this gel will collapse.  So we have these metal nanoparticles and they want to stick together because they're trying to get away from the water, so they stick together really close. It's like a spring, they'll compress this polymer in between them. If they cool down very, very slightly, all of this reverses and now the polymer wants to spread out into the water but it's got to push apart the metal nanoparticles to be able to do that, so everything explodes. The nice thing is that we can do this heating and cooling with very weak beams of light and so we can actually make a little engine which is powered by a very small beam of light.

Emma - Great. Well, can I go and see some of them in action?

As Jeremy took me over the lab, I tried to mentally recap exactly how these ANTS worked. So we have tiny bits of gold, coated with a gel and below 30 degrees they like water and they really spread out. If we heat them up or shine a light on them, then they stop liking water and they all scrunch together just like a spring, as Jeremy said. PhD researcher Sean Cormier joined my in the lab to show me this change in action.

Sean - Some of the ANTS - a nice red colour and you just have to heat it up above 32 degrees.

Emma - Okay, so we've got like a little tiny capsule with a red liquid in and it's just in an oil bath at the moment so we're just heating it up, and what exactly are we looking for?

Sean - So what will happen is all the particles will actually change the way they interact with the water, and they'll change colour because they'll stop liking the water, and they'll collapse on top of each other, and now they're very purple.

Emma - Yes, okay.  So the liquids actually changed from red to purple.  It changed pretty quick! How fast have you been able to measure it changing?

Jeremy - In fact, it's too fast for us to measure at the moment and that's why it gives such a big force and, in fact, it's gone back to red. So what happens is all the ANTS cluster together - it goes purple, and as soon as it cools they explode. So that's how we keep track of it by looking at the colour.

Emma - It feels very weird to be in a lab without wearing lab specs, I must say!

Jeremy - It's very safe at the moment but you're right.

Emma - Despite the name, the gel Sean and Jeremy showed me really looked nothing like an ant. I asked Jeremy whether he had any specific ideas about how they could use the ANTS or whether there are any future applications.

Jeremy - So there's this area of science called microfluidics where you try and make little chemical refineries in some ways but shrunk down to the size of a chip, so that's the idea for one of the earliest applications. For applications where we put them in our body yes, indeed, we really don't know how to do that yet. One of the good things is we don't just have to use light to make these things open and close so it's actually a rather generic technology. Yes, we have to find out what's the killer application or maybe the non-killer application for the body!

Emma - And if we did want to use them for these kinds of applications, how easy is it to make them?  Is the large scale synthesis of them feasible?

Jeremy - Yes, that's the amazing thing.  All the components, as it turns out are completely commodity; we can buy them on a very large scale. So, in fact, already there's nothing stopping us scaling these up and making a kilogramme of these ANTS. We can replace the gold nanoparticles that we use at the moment with silver nanoparticles, which is cheaper, and we can use nickel or copper as well, that should be fine so making them is not the problem. The question is how to turn them into something useful and that's going to take us the next year.  We want to make some of these demonstrators in the next but, of course, what we really want is  a lot of other scientists to join us in this quest.