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.

Date Published: 21 March 2001
PDF: 8 pages
Proc. SPIE 4235, Smart Structures and Devices, (21 March 2001); doi: 10.1117/12.420853

Published in SPIE Proceedings Vol. 4235:
Smart Structures and Devices
Dinesh K. Sood; Ronald Albert Lawes; Vasundara V. Varadan, Editor(s)