Printing hearing aids with customized hardness zones

Multi-material printing allows for individually shaped hearing aids with customized hardness zones. (Photo: LZH)

LZH | Individually shaped earmolds are already commercially available, but do not take into account the varying tissue hardness in the ear canal. In a joint project on multi-material printing, the Laser Zentrum Hannover e.V. works on hearing aids with customized hardness zones.

Besides its individual geometry, the ear canal has hard and soft tissue regions. To improve the wearing comfort of mold fittings for hearing aids, so-called earmolds, the hardness of the material must be locally adjustable.

To print earmolds with hard and soft regions, the Production and Systems Technology Department at the LZH is developing a new 3D printing process that is based on a layer-by-layer spraying of the material. If two nozzles are used with polymers of different hardness degrees, a hardness of between 55 and 75 ShoreD can be achieved.

The research works are part of the project "3D-PolySPRINT - Additive Manufacturing of Customized Hearing Acoustic Transducers Made of Multi-Material Systems", which is funded by the Federal Ministry of Education and Research. Project partner are: Sennheiser electronic GmbH Co. KG, KIND Hörgeräte GmbH Co. KG, OptoMedical Technologies GmbH, Materialize GmbH, Dreve ProDiMed GmbH, LPKF Laser & Electronics AG, microTEC Gesellschaft für Mikrotechnologie mbH and the Laser Zentrum Hannover e.V. (LZH).

by Arndt Hohnholz and Silke Kramprich

Image gallery for this article

  • Multi-material printing allows for individually shaped hearing aids with customized hardness zones. (Photo: LZH)
  • The aerosol jet applies the material, a laser hardens the layer locally. (Photo: LZH)
  • Setup of an aerosol jet system with two nozzles for the 3D printing of plastic components. (Scheme: LZH)
  • Figure 4: The laser-based hardening of the layer allows a lateral resolution of up to 10 μm. (Photo: LZH)
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