Fraunhofer and BTU Cottbus-Senftenberg introduce membrane-free MEMS loudspeakers in Nature Microsystems and Nanoengineering scientific journal

In the coming years, demand and market penetration for internet of voice services are expected to grow. Services are already available via Hearables, intelligent wireless headphones equipped with mini-speakers combined with numerous additional features that are inserted directly into the human ear. When the required hardware is sufficiently miniaturized to fit comfortably and permanently in the ear canal, these micro-headphones will have the potential to take over the entire Internet communication.

Together with the Brandenburg Technical Universtiy Cottbus-Senftenberg (BTU), scientists at the Fraunhofer Institutes for Photonic Microsystems (IPMS) located in Dresden and Cottbus have developed a new, power-efficient acoustic transducer principle for in-ear loudspeakers. This central core component has now been presented in detail for the first time in the Nature Microsystems and Nanoengineering scientific journal.

No longer using a conventional membrane, the new acoustic transducer principle takes form in a variety of bending actuators similar to the strings of a harp placed within the volume of a silicon chip. New types of electrostatic bending Nano-e-Drive (NED) actuators have been integrated into the only 20 μm thin transducers. The voltage of the audio signal causes the actuator to oscillate. To prevent any acoustic short circuit on either side, a team of scientists led by Bert Kaiser, Holger Conrad and Prof. Harald Schenk bonded two silicon wafer layers with input and output slots on both – the top and bottom of the bending NED actuators. The work presented results in a micro speaker completely manufactured via pure silicon technologies.

The first battery-operated demo system for in-ear playback was developed. For the first time, sound pressures greater than 100 dB and promising linearity has been presented. An amplifier drive circuit making it easier for commercial customers to access benefits in terms of both shape and energy efficiency is currently being developed.

From 2016-2018, the acoustic transducer technology based on MEMS processes was founded by the German Federal Ministry of Education and Research (BMBF) in the VIP+ “MEMSound” project as well as further developed and patented for the Hearables, Hearing Aid, and Smartphone markets.


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