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Electrical Characterization of 3D Au Microelectrodes for Use in Retinal Prostheses.

Lee S, Ahn JH, Seo JM, Chung H, Cho DI - Sensors (Basel) (2015)

Bottom Line: As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range.In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated.These results indicate that more electrodes can be implemented in the same area if 3D designs are used.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, ISRC/ASRI, Seoul National University, Seoul 151-742, Korea. sangmlee@snu.ac.kr.

ABSTRACT
In order to provide high-quality visual information to patients who have implanted retinal prosthetic devices, the number of microelectrodes should be large. As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range. In order to improve the trade-off envelope between the number of microelectrodes and the current injection characteristics, a 3D microelectrode structure can be used as an alternative. In this paper, the electrical characteristics of 2D and 3D Au microelectrodes were investigated. In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated. Interface impedances were measured and similar dynamic ranges were obtained for both 2D and 3D Au microelectrodes. These results indicate that more electrodes can be implemented in the same area if 3D designs are used. Furthermore, the 3D Au microelectrodes showed substantially enhanced electrical durability characteristics against over-injected stimulation currents, withstanding electrical currents that are much larger than the limit measured for 2D microelectrodes of similar area. This enhanced electrical durability property of 3D Au microelectrodes is a new finding in microelectrode research, and makes 3D microelectrodes very desirable devices.

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Related in: MedlinePlus

Time domain output of electrical durability evaluation. (a) 2D Au microelectrode; (b) 3D Au microelectrode.
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sensors-15-14345-f004: Time domain output of electrical durability evaluation. (a) 2D Au microelectrode; (b) 3D Au microelectrode.

Mentions: The current injection experiment results of both 2D and 3D Au microelectrodes are shown in Figure 4. The first part is the cathodic phase and the second part is the anodic phase. As the current flow passing through the microelectrode and the built-in 5 kΩ load increases, the measured voltage signal also increases. For the 2D Au microelectrodes, an injection current below a certain limit is delivered well (red line in Figure 4a). However, as the injection current is increased to approximately 51 μA (which is slightly over the calculated limit of 49.8 μA), the time domain output curve starts to distort (blue line in Figure 4a). As the injection current exceeds the limit, the time domain output curve becomes fully distorted (green line in Figure 4a), indicating a physical failure. In fact, the surface of the 2D Au microelectrode becomes damaged, as shown in Figure 5a. The same procedure is performed for the 3D Au microelectrode. For the 3D Au microelectrode, however, the time domain output curve is not distorted until the injection current is approximately 74 μA, which far exceeds the calculated theoretical limit of 56.5 μA. Even at a current level above 74 μA the output is not fully distorted. In fact, as shown in Figure 5b, the 3D Au microelectrode is not damaged even when it is exposed to a current level above the limit. Therefore, compared to the 2D microelectrodes, the 3D microelectrodes can handle approximately 30.9% more stimulating current without damaging the electrode surface.


Electrical Characterization of 3D Au Microelectrodes for Use in Retinal Prostheses.

Lee S, Ahn JH, Seo JM, Chung H, Cho DI - Sensors (Basel) (2015)

Time domain output of electrical durability evaluation. (a) 2D Au microelectrode; (b) 3D Au microelectrode.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507638&req=5

sensors-15-14345-f004: Time domain output of electrical durability evaluation. (a) 2D Au microelectrode; (b) 3D Au microelectrode.
Mentions: The current injection experiment results of both 2D and 3D Au microelectrodes are shown in Figure 4. The first part is the cathodic phase and the second part is the anodic phase. As the current flow passing through the microelectrode and the built-in 5 kΩ load increases, the measured voltage signal also increases. For the 2D Au microelectrodes, an injection current below a certain limit is delivered well (red line in Figure 4a). However, as the injection current is increased to approximately 51 μA (which is slightly over the calculated limit of 49.8 μA), the time domain output curve starts to distort (blue line in Figure 4a). As the injection current exceeds the limit, the time domain output curve becomes fully distorted (green line in Figure 4a), indicating a physical failure. In fact, the surface of the 2D Au microelectrode becomes damaged, as shown in Figure 5a. The same procedure is performed for the 3D Au microelectrode. For the 3D Au microelectrode, however, the time domain output curve is not distorted until the injection current is approximately 74 μA, which far exceeds the calculated theoretical limit of 56.5 μA. Even at a current level above 74 μA the output is not fully distorted. In fact, as shown in Figure 5b, the 3D Au microelectrode is not damaged even when it is exposed to a current level above the limit. Therefore, compared to the 2D microelectrodes, the 3D microelectrodes can handle approximately 30.9% more stimulating current without damaging the electrode surface.

Bottom Line: As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range.In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated.These results indicate that more electrodes can be implemented in the same area if 3D designs are used.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, ISRC/ASRI, Seoul National University, Seoul 151-742, Korea. sangmlee@snu.ac.kr.

ABSTRACT
In order to provide high-quality visual information to patients who have implanted retinal prosthetic devices, the number of microelectrodes should be large. As the number of microelectrodes is increased, the dimensions of each microelectrode must be decreased, which in turn results in an increased microelectrode interface impedance and decreased injection current dynamic range. In order to improve the trade-off envelope between the number of microelectrodes and the current injection characteristics, a 3D microelectrode structure can be used as an alternative. In this paper, the electrical characteristics of 2D and 3D Au microelectrodes were investigated. In order to examine the effects of the structural difference, 2D and 3D Au microelectrodes with different base areas but similar effective surface areas were fabricated and evaluated. Interface impedances were measured and similar dynamic ranges were obtained for both 2D and 3D Au microelectrodes. These results indicate that more electrodes can be implemented in the same area if 3D designs are used. Furthermore, the 3D Au microelectrodes showed substantially enhanced electrical durability characteristics against over-injected stimulation currents, withstanding electrical currents that are much larger than the limit measured for 2D microelectrodes of similar area. This enhanced electrical durability property of 3D Au microelectrodes is a new finding in microelectrode research, and makes 3D microelectrodes very desirable devices.

Show MeSH
Related in: MedlinePlus