A laboratory testing and driving system for AIROF microelectrodes.
ABSTRACT The charge-injection currents of AIROF (activated iridium oxide film) microelectrodes, which are subjected to charge-balanced biphasic pulsing or monophasic current pulsing, have to be limited such that the anodic and cathodic voltage excursions are kept within safe limits of operation. In earlier studies it has been shown that when using anodic bias asymmetry in the magnitude of the balanced biphasic waveform can be used to increase the charge injection capacity of AIROF electrodes. We present the design of a single-channel testing and driving system for laboratory testing and driving of AIROF microelectrodes within safe charge-injection limits.
- SourceAvailable from: Luke S. Theogarajan[show abstract] [hide abstract]
ABSTRACT: A miniaturized, hermetically encased, wirelessly operated retinal prosthesis has been developed for preclinical studies in the Yucatan minipig, and includes several design improvements over our previously reported device. The prosthesis attaches conformally to the outside of the eye and electrically drives a microfabricated thin-film polyimide array of sputtered iridium oxide film electrodes. This array is implanted into the subretinal space using a customized ab externo surgical technique. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete circuit components. Feedthroughs in the case connect the stimulator chip to secondary power and data receiving coils on the eye and to the electrode array under the retina. Long-term in vitro pulse testing of the electrodes projected a lifetime consistent with typical devices in industry. The final assembly was tested in vitro to verify wireless operation of the system in physiological saline using a custom RF transmitter and primary coils. Stimulation pulse strength, duration, and frequency were programmed wirelessly from a Peripheral Component Interconnect eXtensions for Instrumentation (PXI) computer. Operation of the retinal implant has been verified in two pigs for up to five and a half months by detecting stimulus artifacts generated by the implanted device.IEEE Transactions on Biomedical Engineering 12/2011; · 2.35 Impact Factor