An Active Thin-Film Cochlear Electrode Array With Monolithic Backing and Curl

This paper reports the development of a robust, 32-site, four-channel, flexible cochlear implant as a prototype for a 128-site, eight-channel human prosthesis. The electrode array is comprised of metal layers embedded in Parylene C and includes parylene rings and self-curling parylene layers that can achieve a minimum radius of curvature . Finite element analysis simulations predict that the substrate stiffness of the arrays can be tailored from 0.2 to 1.4 kN·μm
²
with parylene rings to increase the rigidity seven-fold over that of a flat parylene array. Guinea pig arrays have achieved insertion depths of up to 6.5 mm in the cochlea with no visible damage to the scala media. The application specific integrated circuit (ASIC) for the cochlear implant was realized in 0.5 μm technology to support a wide range of multisite multipolar stimulus configurations. The ASIC fits within the space of the otic bulla with a size of 2.2 mm by 2.5 mm and operates from a ±2.5 V supply at clock speeds up to 500 kHz. The maximum power consumption is 2.5 mW when outputting monopolar 500 μA biphasic pulses.