The robotic schnozz can sniff for bombs and air pollution, along with other simple chemicals, but it still can't tell a smushed banana from a sprig of peppermint. Now researchers at the University of Warwick in England have hit upon a way to dramatically improve a robot's sense of smell: synthetic snot.

Just as in the human nose, man-made mucus catches molecules and ferries them to scent receptors, which identify individual scent molecules based partially on how long it takes for each molecule to dissolve in the mucus. Molecules of paint thinner,