More dreaming

My mind is still wandering as I'm looking out into the garden and I've just realised that nature already sussed has the problem of how to maximise exposure to the sun. Those clever little plants just bend and twist to face it. So now I'm thinking about how great it would be to have a PV cell on a stalk that tracks the sun. Is there some kind of semi-organic material out there that does this without the need for lots of clunky tracking machinary?

It even has a cool name - heliotropism. It seems such a simple idea and one that must exist somewhere. I'll have to do a little bit of research when I find a little spare time.