At any given time, 1 in 20 hospital patients is battling an infection that they got on site, according to the Centers for Disease Control. Hospitals now pay greater attention to hand hygiene—Purell dispensers have become ubiquitous—but their main infection control methods haven't changed much for decades. Most rooms are still disinfected by housekeepers armed with chemical cleaners. Enter the Xenex, a mobile, robotic device that combats germs with blasts of light.