Evaluation of polyimide as substrate material for electrodes to interface the peripheral nervous system

The introduction of micromachining technologies into design and development of interfaces to the peripheral nervous systems more than 20 years ago led to novel silicon and polymer based microimplants. Polyimide has been chosen as candidate for flexible implants. In this work, the investigations on different designs, the material stability and different aspects of biocompatibility as well as the functional outcome of different electrode designs will be presented. Sieve electrodes to interface regenerating nerves, multichannel cuff electrodes but also newer concepts like longitudinal and transverse intrafascicular multichannel electrodes (LIFE, TIME) have been developed with polyimide as substrate and insulation material. Evaluation in vitro as well as in vivo of the material itself but also of the different electrode designs and concepts showed good material stability, no material toxicity, only little foreign body reaction after implantation and good spatial selectivity of the electrodes depending on the chosen concept to interface the peripheral nerve.