Dynamic Interactions of Retinal Prosthesis Electrodes with Neural Tissue and Materials Science in Electrode Design - Artificial Sight: Basic Research, Biomedical Engineering, and Clinical Advances - page 216

Figure 11.3. Electrolytic hydrogen evolution, 0.1 and 1.0msec monophasic pulses.

threshold electrolysis in both cases was approximately 200C/cm 2 . Monophasic
pulses applied at charge densities below 200C/cm 2 fall safely within the water
window for electrolysis and fit the criterion for safe stimulation of neural tissue.
The same tests were performed on 76m Pt wire electrodes under the same
conditions but with repetitive biphasic pulses. In these experiments, the charge
density ceiling was also 1mC/cm 2 . Pulse amplitudes were

1-50A and the
positive and negative phases of the pulse were symmetrical and balanced. Steady-
state hydrogen production was recorded again as a function of charge density
(Figure 11.4). With biphasic pulsing, hydrogen was not detected in the air stream
at charge densities less than 1mC/cm 2 . These results demonstrate proof of

±

Figure 11.4. Hydrogen evolution from Pt electrode with biphasic pulsing, charge density
≤ 1mC/cm 2 .