ETH spinoff IDUN Technologies is developing soft, dry electrodes for long-term brainwave measurement. Torson Injex has accompanied the development of this sophisticated 2K injection molded component. Within a very short time, five iterations and a wide variety of material pairings were successfully implemented.
Initial Situation
IDUN Technologies, a spinoff of ETH Zurich, develops portable EEG systems for long-term brain wave measurement. The key advantage is that soft, dry electrodes are used which measure directly through human hair or in the auditory canal. This allows these electrodes to be integrated directly into existing devices, such as headphones. The electrode for application through hair is designed as a two-component injection molded component. The hard component serves as a button that clips into the EEG system and must be conductive. The soft component must provide the necessary flexibility to conform to the shape of the head. At the same time, the soft component must accommodate the "Dryode™ Ink" coating developed by IDUN. This coating provides the electrical contact to the body.
Implementation
The design came with several challenges. The first step was to focus on the soft component. The most suitable shore hardness had to be determined so that the feet would make reliable contact with the body while not compromising comfort. In addition, the special coating of Dryode™ Ink also had to adhere to it. Once the appropriate material for the soft components was identified, the hard-soft bond could be addressed. Adhesion of the two components was a particular challenge, as a folding process was used at the prototype stage. To enable clean adhesion, the hard component was thermally activated before overmolding. Furthermore, the geometry was iteratively improved and adapted.
Results
Thanks to the rapid tooling process from Torson Injex, four different soft components and five hard components were tested and evaluated in a very short time. A total of five different geometries were produced with the corresponding injection molds. The lead time for one variant including both hard and soft components, was approximately one week. The costs for all five iterations were significantly lower than the price for a single conventional 2K injection mold.
