Micromachined, Polyimide-Based Devices for Flexible Neural Interfaces

Micromachining technologies were established to fabricate microelectrode arrays and devices for interfacing parts of the central or peripheral nervous system in case of neuronal disorders. The devices were part of a neural prosthesis that allows simultaneous multichannel recording and multisite stimulation of neurons. Overcoming the brittle mechanics of silicon, we established a process technology to fabricate light-weighted and highly flexible polyimide based devices. Concerning the challenging housing demands close to the nerve to prevent mechanical induced nerve traumatization, we integrated interconnects to decouple the nerve interface from plugs and signal processing electronics. Hybrid integration with a new assembling technique—the MicroFlex interconnection (MFI)—has been applied for the connection of the flexible microsystems to silicon microelectronics. In this paper, we present different shapes and applications of the flexible electrodes: sieve electrodes for regeneration studies, cuff electrodes for interfacing peripheral nerves, and a retina implant for ganglion cell stimulation. The discussion is focused on electrode and material properties and the hybrid assembly of a fully implantable neural prosthesis.