Parylene-coated metal tracks for neural electrode arrays - fabrication approaches and improvements utilizing different laser systems

Design of Experiment Evaluation of a 2.5D Printing Process for Implantable PDMS-based Neural Interfaces

Current laser fabrication processes for PDMS-based neural interfaces are associated with excessive costs, due to time-consuming manual handling and expensive machinery. The products of this process, specifically embedded metallic electrical tracks, are prone to breakage under mechanical loading, as well as delamination from their surrounding PDMS substrates. In this work, we develop an alternative 2.5D printing process, using electrically conductive PDMS material for the tracks. The entire electrode was fabricated in a custom-made printing setup, which features the possibility of rapid prototyping. The printing performance of the selected materials was evaluated with the aid of statistical methods for experimental design. We found optimal printing parameters for conductive and non-conductive PDMS which allows the fabrication of flexible and stretchable neural interfaces, while simultaneously minimizing the track resistivity.Clinical Relevance- 2.5D printing processes pave the way for individualized neural interfaces to suit the specific needs of every single patient.

Development of a multichannel implantable connector

Further development of active implantable medical devices (AIMDs) coming along with higher channel counts and improved maintainability raises the requirements for implantable connectors in such systems. We developed a concept for an implantable multichannel connector. Contact pads manufactured by laser-structuring that are embedded into a silicone substrate serve as contact partners. Processing features specific to two laser technologies were exploited not only to cut the materials but also to 3D-shape the surfaces of the contact pads. First tests for the long-term behavior show stable contact and isolation properties during 6 weeks of soaking at elevated temperature.

Morphological and electrochemical properties of an explanted PtIr electrode array after 15 months in vivo

We investigated the morphological and electrochemical properties of an explanted laser-machined 32 channel electrocorticogram (ECoG) electrode array made of platinum-iridium and silicone rubber. It was connected to a wireless brain-computer interface (BCI) and implanted in a sheep for more than 15 months. Recordings and stimulations of cortical activity were conducted over the whole period on a regularly basis. Currently, this is the longest in vivo study for this type of ECoG electrode array. Results were compared with an unused electrode array of same dimensions, material and production method. Visual inspections revealed no significant material alterations, despite organic residuals which could be easily removed though. Electrochemical impedance measurements also attested proper long-term stability of magnitude and phase, the difference between explanted electrode contacts and those of the unused array were found negligible.