Purchase this article with an account.
L.J. Johnson, D.A. Scribner, P. Skeath, F.K. Perkins, R. Klein, L. Wasserman, J. Peele, W. Bassett, D. Panigrahi, M. Helfgott; Study of Curved Microwire Glass Electrodes for Use With a High Resolution Retinal Stimulation Array . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1498.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The NRL retinal stimulator with 80 x 40 individual electrode areas (pixels) has three components; the curved microwire glass electrode, the microelectronic multiplexer, and the drive electronics. The device is designed to be placed against the retina during acute 1–hour tests –the device is connected to the drive electronics by a microcable the passes through a small slit in the sclera. Our recent efforts have focused on the integration of the device components, characterizing the electrical current delivery capabilities of the multiplexer, and performing mechanical and electrical pre–clinical trials. Methods: The novel design of the NRL stimulator required a number of new device integration methods. Here we report the first successful hybridization of microwire electrodes to a microelectronic chip using bump bonds. The microelectronic chip was directly connected to a polyimide microcable via a novel ribbon bonding method. The device was encapsulated with a biocompatible epoxy, EpotekTM ND353. The integration was tested with saline immersion. The biphasic pulse can be programmed to be of arbitrary shape, duration, and intensity. Electrical current as a function of both image intensity and biphasic pulse amplitude was characterized during saline immersion. Plasma etching removed any epoxy that inadvertently wicked onto the electrode area. Pre–clinical trials were performed by a surgical team at the WNEC to evaluate the device design, drive electronics, and possible tissue effects. Results: The signal–to–noise ratio of individual pixels is estimated to be on the order of 100:1. We found that the device is capable of producing currents of more than 1 µA per electrode with no electrode damage in saline testing. The device survived many hours of saline testing indicating that the device will withstand the planned 1–hour clinical tests. The device structure and the stimulation sequences used in pre–clinical trials were shown to have no effect on the target tissue. Conclusions: The fully integrated device , i.e. microwire glass, microelectronic multiplexer, and microcable connector assembled using indium bump bonding, ribbon bonding, and epoxy encapsulation makes this a unique system. The microelectronic multiplexer current delivery performance matched electronic design predictions closely. Pre–clinical trials indicated that the NRL stimulator could be safely used for 1–hour, acute experiments.
This PDF is available to Subscribers Only