Swedish researchers have created billboard displays that talk back by using conductive inks connected to touch sensors and speakers 'printed' onto the paper.

The technology has been used in a prototype for a 'music display board', on which a number of music albums were printed directly onto the paper.

Users can sample the music by touching the front of the board, at which point the sound is streamed right out of the paper.

Other applications for the Paper Four technology could include advertising campaigns, marketing and events, as well as in-store product displays.

Research teams at Mid Sweden University's Fiber Science and Communication Network are now working on the fourth generation of products that integrate paper with the digital world. 

"We combine paper with printed graphic codes and electronically conductive ink that is engineered to be sensitive to pressure," said Mikael Gulliksson, coordinator for media technology at Mid Sweden University.

"The digital information is embedded in the paper, and comes out via printed speakers when it is touched."

Gulliksson added that his team has used "roll-to-roll methods" used by industry to process paper materials, allowing the two-metre high billboards to be made almost entirely from materials which are cheap to assemble and easy to recycle.

The posters are made in three layers. The base is made from a 3cm layer of cardboard called Wellboard. The middle layer consists of a sheet of paper printed with conductive ink containing silver particles. 

This layer is connected to a power source and the microelectronics required to interpret the interactions with the paper.

The speakers are made by printing electromagnets from conductive ink and stretching the paper over cavities in the Wellboard. When a current is passed through, the electromagnets vibrate to create sound.

A video of the technology in action can be viewed at the Project Paper Four website.