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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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Fabrication processes and results. (a) 2D Au MEA; (b) 3D Au MEA.
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sensors-15-14345-f001: Fabrication processes and results. (a) 2D Au MEA; (b) 3D Au MEA.

Mentions: Two types of MEAs were fabricated. The first type of MEA consists of 2D circular microelectrodes with an electrode diameter of 75 μm and an effective surface area of 4418 μm2. The second type of MEA consists of 3D arrowhead-shaped microelectrodes, which have a base electrode diameter of 25 μm and an effective surface area of 4802 μm2. The effective surface area of a 3D microelectrode can vary due to the electrode height of the cylindrical part. For the fabrication of 2D and 3D microelectrodes, we utilized the methods presented in [11,13,15], which use electroplating to fabricate the Au microelectrode structures. In this paper, the height of the cylindrical part is defined as 50 μm by the silicon deep-reactive-ion-etching (DRIE) process used. The fabrication processes and results of each MEAs are shown in Figure 1. The fabricated MEAs are wire-bonded to a printed-circuit board (PCB) to measure the electrical characteristics, such as the electrode-electrolyte interface impedance and the current injection limit.


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

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

Fabrication processes and results. (a) 2D Au MEA; (b) 3D Au MEA.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-14345-f001: Fabrication processes and results. (a) 2D Au MEA; (b) 3D Au MEA.
Mentions: Two types of MEAs were fabricated. The first type of MEA consists of 2D circular microelectrodes with an electrode diameter of 75 μm and an effective surface area of 4418 μm2. The second type of MEA consists of 3D arrowhead-shaped microelectrodes, which have a base electrode diameter of 25 μm and an effective surface area of 4802 μm2. The effective surface area of a 3D microelectrode can vary due to the electrode height of the cylindrical part. For the fabrication of 2D and 3D microelectrodes, we utilized the methods presented in [11,13,15], which use electroplating to fabricate the Au microelectrode structures. In this paper, the height of the cylindrical part is defined as 50 μm by the silicon deep-reactive-ion-etching (DRIE) process used. The fabrication processes and results of each MEAs are shown in Figure 1. The fabricated MEAs are wire-bonded to a printed-circuit board (PCB) to measure the electrical characteristics, such as the electrode-electrolyte interface impedance and the current injection limit.

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