A Parylene-Silicon Cochlear Electrode Array with Integrated Position Sensors

Abstract

A thin-film cochlear electrode array has been developed for a cochlear prosthesis to achieve improved sound perception and position accuracy. The array is fabricated using a bulk-silicon micromachining process that allows parylene deposition and patterning at wafer level, followed by a wet silicon release etch that is compatible with the use of boron etch-stops. The process is capable of realizing arrays with substrates stressed to hug the modiolar wall in the rest state and whose stiffness can be adjusted over a wide range. Built-in tip and curvature sensors respond to tip contact and bending-induced shank stress, respectively during in-vitro and in-vivo implants. The process is also compatible with the integration of parylene ribbon cables for lead transfer to an implanted electronics package.

High-density cochlear implants with position sensing and control

“…The field dielectrics around the intended array substrate are next removed. A 3 lm-thick layer of parylene is now deposited using physical vapor deposition (PVD) at room temperature and is patterned using an oxygen plasma to remove it from the sites and the field portions of the wafer (Wang et al, 2006). The field etch is used to form undercut anchor holes for the parylene in the substrate, mechanically locking it in place and providing additional protection against delamination.…”

A Thin-Film Cochlear Electrode Array With Integrated Position Sensing

“…After patterning the field dielectrics, a deep reactive-ion etch is used to undercut the silicon along the probe edge and create holes (anchors) along important features such as gold pads. The 3-μm-thick conformal parylene coating then wraps the probe and fills the anchor holes, mechanically locking parylene in place [18], [19].…”

“…These performance limitations are imposed by the difficulties in achieving deep insertion in the scala tympani of the cochlea (Fig. 1), by the small number (16)(17)(18)(19)(20)(21)(22) of wires that can be accommodated in the scala tympani, and by the current spreading that occurs due to the physical separation between the sites and the receptors in the modiolus. Ultimately, frequency resolution will likely be determined by this separation and by the effectiveness of multiple sites in shaping the stimulus currents.…”

Algorithms and design considerations for robot assisted insertion of Perimodiolar Electrode Arrays

“…We subsequently designed and constructed models of steerable electrode arrays that bend by pulling on a strand embedded in them [15], [16]. Wang [11] designed MEMS electrode arrays with embedded sensors for sensing the bending angle during insertion. More recently, [6], [9] designed a two DoF tool for perimodiolar electrode array insertion and with integrated force sensing.…”