Batch fabricated thin-film electrodes for stimulation of the central auditory system

Abstract

Silicon micromachining and thin-film technology have been employed to fabricate iridium stimulating arrays which can be used to excite discrete volumes of the central nervous system. Silicon multichannel probes with thicknesses ranging from 1 to 40 microns and arbitrary two-dimensional shapes can be fabricated using a high-yield, circuit-compatible process. Iridium stimulating sites are shown to have similar characteristics to iridium wire electrodes. Accelerated pulse testing with over 8 million 100 microA biphasic current pulses on 8000 microns 2 sites has demonstrated the long-term stability of iridium and activated iridium sites. In vivo tests have been performed in the central auditory pathways to demonstrate neural activation using the devices. These tests show a selective activation both as a function of site separation and site size.

Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

“…Each site had an area of about 400 m 2 and an activated impedance of Ͻ100 k⍀ (at 1 kHz). Activating the ICC sites from iridium to iridium oxide (by cyclic voltammetry) enabled us to use them for both recording and stimulation (Anderson et al 1989). However, based on the electrochemical charge injection limit for iridium oxide (about 3 mC/cm 2 ) (Beebe and Rose 1988;Weiland and Anderson 2000), we limited stimulation to a maximum current level of 56.2 A (200 s/phase pulses).…”

“…Using hydraulic manipulators, silicon-substrate Michigan probes with 16 sputter-deposited iridium sites (Center for Neural Communication Technology, University of Michigan, Ann Arbor, MI) (Anderson et al 1989;Drake et al 1988;Najafi et al 1985) were inserted into the ICC and A1 (Fig. 1).…”

Spatial sensitivity of neurons in the anterior, posterior, and primary fields of cat auditory cortex

“…Extracellular neural activity was recorded using multi-site, silicon-substrate probes provided by the University of Michigan Center from Neural Communication Technology (Anderson et al 1989). The probes used here had a linear array of 16 sites, spaced 150 µm apart, with surface areas of 177 µm 2 and impedances between 1 and 4 MΩ.…”

Nanoporous Platforms for Cellular Sensing and Delivery

“…While the majority of research has focused on the development of miniaturized diagnostic tools such as electrophoretic, chromatographic, and cell micromanipulation systems [1][2][3][4][5], researchers have more recently concentrated on the development of microdevices and constructs for therapeutic applications. Micro-and nanofabrication techniques are currently being used to develop implants that can record from, sense, stimulate, and deliver to biological systems.…”