Weekend Nanotech – Virus Tech at MIT

By Elf Eldridge 11/06/2011

Anyone that has met me probably knows that I have a great love of Viral Technology – not the ‘Evolution of Dance‘ or ‘Old Spice‘ kind, but the kind that uses viruses to improve or generate totally new technology. In that regard, I though i’d start off my ‘Weekend Nanotech’ series with a paper published in Nature Nanotechnology from the Viral Tech group at MIT.

Standard Solar Cell
Standard Solar Cell

This is some seriously gorgeous science with HUGE implications. First off, they attempt to fix one of the fundamental problems of solar cells, which in itself is a big enough ask, but beyond that they use and fledgling technology to do it and come away with simply spectacular results. The problem is that solar cells are quite good at creating energy from light, but then getting it out into a circuit before it decays is the tricky bit. Previously groups have shown that including carbon nanotubes into these cells makes sometimes makes them better – because the tubes provide an easy ‘route’ for energy to be extracted – kinda like a highway onramp from the centre of a city making it much easier to drive out than if you had to thread through heaps of tiny side-streets. If you’re interested, this energy is in the form of electrons and holes which, after extraction, can be used to directly power things.

Ebola Virus - similar shape to M13 Bacteriophage
Ebola Virus - similar shape to M13 Bacteriophage

So what have the viruses got to do with things? Well, this group bound the nanotubes to a bacterial virus, M13 Bacteriophage (it’s well known and we’ve been using it for ages to do all sorts of cool things), and used it to line them up and prevent then tangling together. I know this sounds laughable, but the tangling of nanotubes can cause huge problems, because the electrons trying to escape down them can get ‘lost’ along the way, this is identical to ‘short circuit‘ that you might find in normal-sized electronics. Long story short – that’s not good for the solar cell, and so the use of a virus ‘template’ prevents it.

From there, the group used biomineralization (yes, nanotechnology has the sexiest terms for the most mundane processes!) to grow nanocystals of Titanium Dioxide (a typical solar cell material) on the edges of the nanotubes. If you want to compare this to photosynthesis by plants, these tiny crystals would be the leaves and chloroplasts, absorbing energy from light and converting it – then the nanotubes would be the stems, branches and trunks, funneling this energy to where it is needed. (N.B. Sorry plant biologists – the analogy isn’t perfect i know!)

Virus,Nanotube and TiO2 patterning process (ref.1)
Virus, Nanotube and TiO2 patterning process (Ref 1)

So what was the result? Instant 10% increase in the efficiency of the solar cells when the viruses were used. There’s your result right there. So, with a little more research and commercialization, simple patterning techniques with viruses will help the solar cell industry expand!. But this misses my favourite bit of the research – they controlled Carbon nanotubes using a virus! Carbon nanotubes are the ‘microchips’ of modern research – huge potential and everyone wants a piece of them – and being able to control how they move is a gigantic step forward in all sorts of areas. And this group did it. Just casually, as a side project. Awesome!

Reference: [1] X.Dang et al “Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic device” Nature Nanotechnology 6, 377—384(2011) doi:10.1038/nnano.2011.50