Graeme Clark Collection

Permanent URI for this collection

http://hdl.handle.net/11343/375

Filters

1985 - 1989 1 2000 - 2001 1
Reset filters

Settings
Statistics
Citations
Author: Clark, Graeme × Type: Conference Paper × Subject: electrode array ×

Search Results

Now showing 1 - 2 of 2
  • Item
    Thumbnail Image
    A prototype micro-machined thin-film electrode array for cochlear implants
    Parker, J. R. ; Duan, Y. Y. ; Patrick, J. ; Harrison, H. B. ; Reinhold, O. ; Clark, Graeme M. ( 2001)
    Development of a micromachined electrode array for cochlear implant application is presented. The device is constructed from a silicon substrate with sputtered platinum electrodes and connection tracks. Electrochemical impedance spectroscopy (EIS) is used to study the properties of the electrode, and to identify potential problems caused by the micromachining process and materials. A variety of insulators are studied and a two-part epoxy is identified as an adequate insulator for operation under harsh electrochemical testing conditions. The semiconducting silicon substrate is found to contribute to the total impedance of the device at high frequencies due to the thin insulating oxide between the substrate and conducting tracks. This is a potential problem for micromachined electrodes operating under high frequencies or using square stimulating pulses. The charge-delivery properties are studied using electrochemical impedance spectroscopy. It is found that platinum sputtered under particular conditions results in excellent surface conditions for optimum charge-delivery.
  • Item
    Thumbnail Image
    Histopathology following electrode insertion and chronic electrical stimulation
    Shepherd, R. K. ; Clark, Graeme M. ; Pyman, B. C. ; Webb, R. L. ; Murray, M. T. ; Houghton, M. E. (Raven Press, 1985)
    We have examined a number of safety issues associated with cochlear implants. This work has been primarily designed to evaluate the histopathological effects of intracochlear electrode implantation and chronic electrical stimulation. The results of these studies may be summarized as follows: 1) The insertion of the banded free-fit scala tympani array into human cadaver temporal bones produces minimal damage, occurring primarily to a localized region of the spiral ligament. This damage would not result in significant neural degeneration and thus, would not compromise the efficacy of the multiple channel device; 2) chronic intracochlear electrical stimulation for continuous periods of 500 to 2000 hours, using charge balanced biphasic current pulses developing charge densities of 18-32 }?C/cm2. geom./phase, does not adversely affect the spiral ganglion cell population; 3) labyrinthine infection severely reduces the viable spiral ganglion cell population; 4) the formation of new bone present in approximately half of the animals we have implanted --is not associated with electrical stimulation per se; 5) scanning electron microscope studies of electrodes subjected to long periods of intracochlear electrical stimulation reveals minimal platinum dissolution when compared with unstimulated control electrodes, and electrodes that have been stimulated for similar periods in inorganic saline.