researchers have devised a way to "print" devices directly onto the skin so people can wear them for an extended period while performing normal daily activities. Such systems could be used to track health and monitor healing near the skin's surface, as in the case of surgical wounds.
At a music festival, Heineken set up a booth to print QR codes with a personal message to encourage meeting new people using the U-code as an icebreaker. They printed over 5,000 in 4 days.