The exceptional properties of carbon nanotubes have tantalized researchers for years because of the possibility they could be used to make smaller, faster and cheaper electronic devices. A big barrier to building useful electronics with carbon nanotubes has always been the fact that when they're arrayed into films, a certain portion of them will act more like metals than semiconductors – an unforgiving flaw that fouls the film. Now Illinois professor John Rogers and a team of researchers have shown how to strip out the metallic carbon nanotubes from arrays using a relatively simple, scalable procedure that does not require expensive equipment.