I ran into her company's PR person at the Foresight Institute gathering a few months ago, and I asked her just that question. What she does is wonderfully innovative, but what makes it "nanotechnology?" She answered that it really isn't.
I'll call it nanotech, though, so I can write a little bit more about it here. I'm a big fan.
Belcher's ultimate goal is to grow replacement organs, but meanwhile, she's come up with some cool uses for biomaterial. She helped found a company called Cambrios -- the name borrowed from the Cambrian explosion, when all sorts of creepy-crawly things decided to cover the earth almost all at once, in evolutionary time frames. The "low-hanging fruit," BusinessSpeak for a first market opportunity, is in mixing organic and inorganic materials onto semiconductors.
Organic materials normally just don't want to cooperate with inorganic electronics, much to the annoyance of the semiconductor industry, which would prefer organic materials because they can be more easily manipulated and modified at the molecular level, giving scientists the ability to tailor their properties to do nearly anything they want.
Most of the time you throw metal and protein from a living organism together and they want nothing to do with each other. But the organic material can do something the metal cannot -- it can act just a little bit differently and unpredictably every once in a while. So, by some fluke of nature, a protein might grab hold, move some atoms around and form interesting bonds and crystals. Then you take that generation, toss it into another pile and see what evolves from there. Over time, you use controlled evolution to "grow" components that stick to electronics, do a little dance for you or whatever you want.
Think of it as the first blob in our primordial soup that happened to develop a shape that allowed it to propel itself forward and stand out from the other blobs. Before you know it, you have fish, lizards, dinosaurs and NASCAR dads.