T-Ring: surround sound from loudspeakers as light as paper.  © 2021 Technische Universität Chemnitz. Photo: Jacob Müller

Music and sound everywhere and no clunky speakers in box-like cases? If researchers at the TU Chemnitz Institute for Print and Media Technology have their way, the loudspeakers of the future will not only be as thin as paper, they will also bring sound to that paper in a very impressive way. It is already a reality in the institute’s laboratories, where back in 2015 researchers developed the multiple-award-winning “T-Book”, a large-sized picture book featuring printed electronics. If the reader turned a page, sound began to come out of an invisible speaker located inside the paper. Its disadvantage was that the paper loudspeakers had to be made through a semi-automatic sheet-fed process, where normal paper or film was coated with two layers of a conductive, organic polymer to act as electrodes. In between them was a piezoelectric layer that worked as an active element to induce vibrations from the paper or film. This was only possible with certain sheets in a limited range of formats, so the scientists looked for new solutions. That is why the goal for their most recent project, “Web-Printed Loudspeaker Paper”, or “T-Paper” for short, was to transfer the sheet production to web-fed printing. Roll-to-roll printing methods combined with other in-line technologies, like laminating functional layers, now make it possible to produce metres of loudspeaker installations in a web or circular (“T-Ring”) shape.

“Our T-Ring prototype connected an almost four-metre-long paper web with 56 individual loudspeakers to seven segments and shaped it as a circle, making a 360-degree surround-sound installation possible,” says Georg C. Schmidt, the project leader. The loudspeaker web consists 90% of conventional paper printable on both sides. It weighs just 150 grams, including with wiring. “This now enables cost-effective infotainment solutions at places such as museums and trade fairs or in advertising. In public buildings, for example, it allows highly homogeneous public-address systems in long stretches such as corridors. The process technology itself could become interesting for other domains, too, like for manufacturing in-line measurement systems for Industry 4.0,” says the project leader, describing its future uses. The project received EUR 1.37 million in funding from Germany’s Federal Ministry of Education and Research between 2017 and 2020.

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