Our favorite ultra-skinny molecules have performed a lot of useful functions over the years, but keeping fruit flies away was never one of them. Now MIT scientists, with US Army funding, have discovered a way to give these nanotubes the canine-like sense of smell needed to stop produce spoilage and waste. Doping sheets of them with copper and polystyrene introduces a speed-trap for electrons, slowing them and allowing the detection of ethylene gas vented during ripening. A sensor produced from such a substance could be combined with an RFID chip, giving grocers a
