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X. Sui, Y. Shao, T. Liang, F. Tan, Z. Han, X. Chai, Q. Ren; In-vitro and in-vivo Evaluation of Penetrating Microelectrode Array for Optic-Nerve Visual Prosthesis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4586.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the in-vitro electrochemical characteristics and in-vivo experiment of multi-channel Pt/Ir microelectrode array for optic nerve visual prosthesis.
A five-channel Platinum/Iridium (Pt/Ir: 70%/30%) microelectrode array was custom-designed (Micro Probe Inc) for intraorbital optic nerve stimulation. The metal shafts were 125µm in diameter, spaced 400µm apart from the center part and mounted step-wisely on a base plate with 1.75mm in length and 0.5mm in width. Height of five different shafts ranged from 0.9mm to 1.5mm with 0.15mm increased step. Each shaft was insulated by Parylene-C with penetrating tip exposed. The impedance of the microelectrode array was measured by the Agilent E4980A Precision LCR Meter in physiological saline solution at room temperature with three electrodes: the working electrode, a flat platinum counter electrode, and an Ag/AgCl reference electrode with the amplitude of 50 mVpp. Charge injection capacity of the microelectrode array was measured by current pulse stimulation with the three-electrode system. Symmetric cathodal-first, charge- balanced biphasic pulses of different amplitudes with time duration from 72 µs to 504 µs were applied without bias potential applied. Besides, the proper implantation surgery was applied for in-vivo experiment with stimuli of different parameters.
It was shown that five shafts of the microelectrode had uniform impedance-frequency and phase-frequency characteristics and the typical impedance value was about 10±0.5kΩ at 1 kHz. The voltage response of current pulse stimulation of the array indicated the charge-injection capacity was 200±20µC/cm2. The in-vivo acute animal experiment showed that the electrical evoked potentials (EEPs) can be recorded from primary visual cortex.
The in-vitro electrochemical measurement indicated the uniform impedance and desirable charge injection capacity of the microelectrode array. The in-vivo animal experiment was applied and relevant EEPs were recorded. Study results suggested that the microelectrode array satisfied the experiment requirements.
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