Roll-printed paper generates surround sound
Five years ago, the sonorous paper loudspeakers from the Institute of Print and Media Technology at Chemnitz University of Technology were still produced in a semi-automatic single-sheet production process. At that time, the researchers had developed the “T-Book”, a large-format illustrated book equipped with printed electronics. If you turn a page, it begins to sound through a loudspeaker invisibly located inside the sheet of paper. Normal paper or foils were printed with two layers of a conductive organic polymer as electrodes. In between, a piezoelectric layer was added as an active element, which causes the paper or foil to vibrate. The sound is produced by the displacement of air. The two sides of the loudspeaker paper can be printed in colour. Since this was only possible in single sheets in limited formats, the efficiency of this relatively slow manufacturing process is very low. Therefore, researchers at the Institute of Print and Media Technology have been looking for a new way – towards cost-effective mass production.
The goal of their latest project, “Roll Printed Speaker Paper” (T-Paper for short), was therefore to convert sheet production into roll production. Researchers from the fields of print media technology, chemistry, physics, acoustics, electrical engineering and economics developed a continuous, highly productive and safe roll production of loudspeaker webs. They not only used the roll-to-roll (R2R) printing process, but also developed inline technologies for other process steps, such as the lamination of functional layers. “In this way, electronics can be embedded in the paper – invisibly and protected,” says Prof. Dr. Arved C. Hübler, head of the corresponding technology department at TU Chemnitz. In addition, inline polarisation of the piezoelectric polymer layers has been achieved for the first time and complete inline process monitoring of the printed functional layers is possible.
The potential of the loudspeaker paper was extended to other areas of application in the T-Paper project. For example, metre-long loudspeaker installations can now be manufactured in web form or as a circle. “In our prototype, an almost four-metre-long web with 56 individual loudspeakers was connected into seven segments and formed into a circle, making a 360° surround sound installation possible,” says project manager Georg Schmidt. The loudspeaker track, including printed circuitry, weighs only 150 grams and consists of 90 per cent conventional paper that can be printed in colour on both sides. The technology could, for example, enable low-cost infotainment solutions for in museums, at trade fairs and in the advertising industry. In public buildings, for example, it could be used to provide very homogeneous sound for long distances such as corridors. But the process technology itself could also become interesting for other areas, for example for the production of inline measuring systems for Industry 4.0, according to Schmidt.
The “T-Paper” project was funded by the German Federal Ministry of Research with 1.37 million euros.
More information: https://www-user.tu-chemnitz.de/~schg/t-paper/wordpress/
Video (in German): https://www.youtube.com/watch?v=SojLNZB1-8g
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