A novel implantable ultra-flexible brain machine interface. Manufacturing and initial characterisations

Sammanfattning: This thesis describes for the very first time the development of a miniaturized neural interface which is flexible in three dimensions (3D) to enable it to follow the brain movements with minimal dislocation. Both the design rationale and the material choice for the electrodes aim to develop interfaces that minimize the damage and/or the irritation of the tissue during and after the implantation. The electrodes are made of 23 ¾ karat gold and insulated with parylene C. After their design in AutoCAD, the electrodes are milled from a 4 μm-thick gold foil in a Nd:YAG laser system and are subsequently insulated with a 4 μm layer of parylene C in a Compact Bench Top Coating System. The recording tips are deinsulated with laser photoablation and the electrodes are then embedded in a special gelatin matrix and finally coated with Shellac before implantation. The implanted part of the electrodes is equipped with protruding branches that function as anchoring as well as recording points at the tips. Between the electrode chip and the implantable part of the electrode, an ultra-flexible, Z-shaped, transitory zone can flex with the motions between the brain and the skull. By embedding the probe in a hard biocompatible material that dissolves after implantation, it has been successfully implanted into the cerebral cortex. The implications of this novel type of Brain-Machine Interface for the field of Neuroscience are potentially huge, not only in understanding fundamental brain functions such as the processing of sensory information and mechanisms of learning, but also in deciphering the mechanisms of altered network processing in pathological conditions such as neuropathic pain, neurodegenerative disorders and psychiatric conditions. However, the long term performance of our probes in vivo still remains to be evaluated.