Photodiode Circuits for Retinal Prostheses
Photodiode Circuits for Retinal Prostheses
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DOI：
10.1109/tbcas.2011.2144980
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发表时间：
2011-10-01
影响因子：
5.1
通讯作者：
Palanker, Daniel V.
中科院分区：
文献类型：
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作者：
Loudin, James D.;Cogan, Stuart F.;Palanker, Daniel V.
光电二极管电路显示了高分辨率视网膜假体的发展前景。虽然已经构建了几个这样的系统，其中一些甚至被植入人体，但现有对光、光电二极管和电极/电解液负载之间复杂的光电相互作用的描述有限。这项研究通过理论计算和实验测量深入地研究了这种相互作用。研究了主动偏置光导电路和被动光伏电路，其中光伏电路由一个或多个二极管串联组成，光导电路由单个二极管串联在脉冲偏置电压下组成。铂电极和溅射氧化Ir膜(SIROF)电极的电路行为和电荷注入水平明显不同。光伏电路对于50微米铂电极的光电二极管能够提供0.038 mC/cm(2)(0.75nC/相)，对于以25赫兹的0.5ms脉冲驱动的50微米SIROF电极，每个光电二极管能够提供0.54 mC/cm(2)(11 nC/相)。同样的脉冲施加到具有相同电极的光导电路上，能够分别提供高达0.38和7.6mC/cm(2)(7.5和150nC/相)的电荷注入。我们演示了光伏刺激兔视网膜的体外，用0.5ms脉冲的905 nm的光，峰值辐射为1 mW/mm(2)。基于实验数据，我们得出了不同电路中像素密度和电荷注入的电化学和光学安全极限。虽然光导电路提供更小的像素，但光伏系统不需要外部偏置电压。这两类电路都显示出高分辨率光电视网膜假体的发展前景。
Photodiode circuits show promise for the development of high-resolution retinal prostheses. While several of these systems have been constructed and some even implanted in humans, existing descriptions of the complex optoelectronic interaction between light, photodiode, and the electrode/electrolyte load are limited. This study examines this interaction in depth with theoretical calculations and experimental measurements. Actively biased photoconductive and passive photovoltaic circuits are investigated, with the photovoltaic circuits consisting of one or more diodes connected in series, and the photoconductive circuits consisting of a single diode in series with a pulsed bias voltage. Circuit behavior and charge injection levels were markedly different for platinum and sputtered iridium-oxide film (SIROF) electrodes. Photovoltaic circuits were able to deliver 0.038 mC/cm(2) (0.75 nC/phase) per photodiode with 50-mu m platinum electrodes, and 0.54-mC/cm(2) (11 nC/phase) per photodiode with 50-mu m SIROF electrodes driven with 0.5-ms pulses of light at 25 Hz. The same pulses applied to photoconductive circuits with the same electrodes were able to deliver charge injections as high as 0.38 and 7.6 mC/cm(2) (7.5 and 150 nC/phase), respectively. We demonstrate photovoltaic stimulation of rabbit retina in-vitro, with 0.5-ms pulses of 905-nm light using peak irradiance of 1 mW/mm(2). Based on the experimental data, we derive electrochemical and optical safety limits for pixel density and charge injection in various circuits. While photoconductive circuits offer smaller pixels, photovoltaic systems do not require an external bias voltage. Both classes of circuits show promise for the development of high-resolution optoelectronic retinal prostheses.