Long term LFP measurements with ultra-fine neural electrodes embedded in porous resorbable carrier

We have developed a novel type of neural electrode array for future brain-machine interfaces (BMIs) or neural prosthesis requiring high resolution recording and stimulation on the cortex. The microelectrode arrays developed comprise of a down to 5 μm thin stack of platinum and polyimide or Parylene C insulation, which is finely microstructured for increased flexibility. The electrode stack is temporarily reinforced with a matrix of porous chitosan, which resorbs after implantation. This design ensures low invasiveness and mechanical irritation during prolonged use, while the chitosan matrix ensures the implant is stiff enough for practical handling during the implantation procedure and is resorbed afterwards. Furthermore, it adds haemostatic and antiseptic properties to the implant. The design and fabrication process are presented. In vitro and long-term in vivo test results are illustrate the ability to measure an evoked physiological response in a period of up to 12 months. Finally, the concept of using porous, scaffold-like materials as main constituent of neural implants is discussed.