The Material-Tissue Interface is Key to Bioelectronic Implant Performance

19th October 2022

Timing : 1 pm EST

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Neural interfaces form the material-tissue interface between electronic and biological circuits and systems. They must provide stable and reliable functional interfaces to the target structure in chronic implantations both in neuroscience experiments and especially in human clinical applications. Proper selection of substrate, insulation, and electrode materials is of paramount importance. In addition, aspects such as size, thickness, and shape contribute significantly to structural biocompatibility. To establish intimate contact with neural targets, minimize post-implantation foreign body reaction, and maintain functionality throughout the implantation period, a comprehensive set of design parameters must be considered. Our work focused on polyimide as the substrate and insulating material with integrated thin film metallization as the conductor in our flexible neural interface approach. Iridium oxide, carbon, and PEDOT serve as electrode coatings, depending on the intended electrode size and application. The scientific goal is not to compete for the smallest neural probes, but to balance size, stability, and usability for each individual animal model and neural target area. This trade-off increases robustness in handling and improves translation of developments to daily use in neuroscience laboratories and implementation in first-in- human studies to investigate new research hypotheses. Data from long-term aging studies and chronic experiments demonstrate the applicability and reliability of thin-film implants for stimulation and recording studies. Assembling systems and connecting microsystems with robust cables and connectors remains a major challenge in both chronic preclinical and clinical studies. Results are shared on reliability, cross-talk and failure modes. Results are encouraging to continue the translational research path from basic studies to the first human clinical trials, which are necessary to prove that new materials, technologies and devices are applicable in clinical applications and can eventually be translated into an approved medical device.

Thomas Stieglitz
Laboratory for Biomedical Microsystems, Dept. of Microsystems Eng.IMTEK,
BrainLinks-BrainTools // IMBIT
Bernstein Center Freiburg
Albert-Ludwig-University of Freiburg, Germany

Thomas Stieglitz was born in Goslar in 1965. He received a Diploma degree in electrical Engineering from Technische Hochschule Karlsruhe, Germany, in 1993, and a PhD and habilitation degree in 1998 and 2002 from the University of Saarland, Germany, respectively. In 1993, he joined the Fraunhofer Institute for Biomedical Engineering in St. Ingbert, Germany, where he established the Neural Prosthetics Group. Since 2004, he is a full professor for Biomedical Microtechnology at the Albert- Ludwig-University Freiburg, Germany, in the Department of Microsystems Engineering (IMTEK) at the Faculty of Engineering and currently serves the IMTEK as managing director, is deputy spokesperson of the Cluster BrainLinks-BrainTools, board member of the Intelligent Machine Brain Interfacing Technology (IMBIT) Center and spokesperson of the profile neuroscience / neurotechnology of the university. He is further serving the university as member of the senate and as co-spokesperson of the commission for responsibility in research. His research interests include neural interfaces and implants, biocompatible assembling and packaging and brain machine interfaces.
Dr. Stieglitz has co-authored about 170 peer reviewed journal publications, 330 conference proceedings and holds about 30 patents. He is co-founder and scientific consultant of CorTec GmbH and neuroloop GmbH, two spin-off companies which focus on neural implant technology and neuromodulation, respectively. Dr. Stieglitz is Fellow of the IEEE and serves the EMBS in the neuroethics group as well as the technical committee of neural engineering, the German Biomedical Engineering Society (DGBMT im VDE) where he is chair of the Neural Prostheses and Intelligent Implants section, the Materials Research Society. He is also founding member of the International Functional Electrical Stimulation Society (IFESS).