3D Parylene sheath probes for reliable, long-term neuroprosthetic recordings

Parylene C neural probes with a 3D sheath structure are introduced as a novel interface for long-term intracortical neural recording. 3D sheath structures were assembled from surface micromachined Parylene microchannels by thermoforming the thermoplastic around a solid microwire mold. Multiple Pt electrodes lined the interior and exterior of the sheath. Electrochemical characterization of the electrodes confirmed impedance values (50-250 KΩ at 1 kHz) suitable for neural recordings. A novel insertion approach was developed that temporarily stiffens the neural probes for surgical implantation and optimized in agarose brain tissue model. Sheath probes implanted into rat cortex recorded neural signals for four weeks. To achieve long-term, reliable recordings, the sheath structures will be coated with eluting neurotrophic factors to promote and attract neural ingrowth towards electrode sites.