Professor Dr Thomas Stieglitz has held the position of a full professor for Biomedical Microtechnology in the Institute for Microsystems Technology (IMTEK) at the University of Freiburg (Germany) since October 2004, prior to which he was with the Fraunhofer-Institute for Biomedical Engineering (IBMT).

Abstract

Neural prostheses are technical systems that interface nerves to treat the symptoms of neurological diseases and to restore ‐at least partially‐ sensory of motor functions of the body. Success stories have been written with the cochlear implant to restore hearing, with spinal cord stimulators to treat chronic pain as well as urge incontinence, and with deep brain stimulators in patients suffering from Parkinson’s
disease.

How can neural implants be miniaturized if higher complexity is required for novel medical applications? One can either further miniaturize systems with means of precision mechanics technologies using known and established materials for electrodes, cables, and hermetic packages or develop devices with promising materials and technologies from microsystems engineering to obtain higher
integration densities. In the latter case, toxicity, material‐issue interaction and long‐term stability have to be carefully assessed according to the requirements of an approval procedure for active implantable medical devices.

Examples for both approaches will be introduced and discussed that have been developed in the Laboratory for Biomedical Microtechnology. Electrode arrays for recording of electrocorticograms (ECoG) during pre‐surgical epilepsy diagnosis have been manufactured out of silicone rubber and metal sheets using a marking laser for structuring. Cables and connectors are similar to commercially available solutions in
clinical practice but the technology allows the integration of small electrodes with high spatial resolution for applications in the context of brain machine interfaces, e.g. on the motor cortex.

If further miniaturization is needed, photolithography, sputter deposition of thin film metals and reactive ion etching of polymers have been used to develop flexible and light‐ weight electrode arrays to interface the peripheral and central nervous system. The material properties of polyimide as substrate and insulation material will be discussed as well as several application examples for nerve interfaces like cuffs, filament‐like electrodes and large arrays for subdural implantation.

The overview will be concluded with latest results that show possibilities to integrate additional sensor and actuator modalities into neural implants. These multimodal probes are novel tools for neuroscientific research in the emerging field of optogenetics to investigate brain functions via light sensitive ion channels.

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