The Bongo King writes "There have been several stories about digital paper discussed here on the site recently, but an offering from Swedish research scientists has a new twist. They have made a prototype billboard of interactive paper with built-in flat loudspeakers apparently also made of paper. 'Touch sensors are made using a fine pattern of conductive lines in which the current flow is altered when a hand touches it. Laptop computer touchpads use the same principle. Speakers are made by printing electromagnets out of conductive ink and stretching the paper over a cavity like a speaker cone behind the billboard. The electromagnets vibrate in response to a current, creating a sound.'"