High density micromachined electrode arrays useable for auditory nerve implants and related methods

A system for treating a hearing disorder in a human or animal subject, said system comprising:

• (a) an electrode assembly comprising i) a chip;
• ii) a silicon wafer bonded to the chip;
• iii) electrodes of varying length extending from the chip, said electrodes comprising columns of silicon of varying length formed on and extending from one side of the silicon wafer, each column having a sharp distal tip, an electrically conductive iridium layer on each of said columns of silicon and an insulating Parylene C layer on top of the electrically conductive iridium layer, the insulating Parylene C layer being absent from a distal portion of each column thereby exposing the electrically conductive iridium layer on a distal portion of each electrode, said electrodes of varying length being insertable into an auditory nerve of the subject such that the electrodes of varying length penetrate to varying depths within the auditory nerve;
• and iv) circuitry on the chip in communication with the exposed iridium layer on the distal portion of each electrode, said circuitry being configured to perform both neural recording and stimulation functions;
• and
• (b) a signal processor is communicably coupled with the circuitry on the chip, said signal processor configured to perform neural recording and to deliver stimulation through the electrodes to nerve fibers at varying depths within the auditory nerve.