April 2009
Volume 50, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2009
Micro-Electrode Array with 171 Arrowhead-Shaped Three-dimensional Tips for Retinal Prosthesis
Author Affiliations & Notes
  • K.-I. Koo
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • D.-I. Cho
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • H. Chung
    Department of Ophthalmology,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • J.-M. Seo
    School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • S. Lee
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • J.-W. Ban
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • H.-Y. Jeong
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • H. Park
    ASRI / ISRC, School of Electrical Engineering & Computer Science,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • S. Ha
    Department of Ophthalmology,
    Seoul National University, Seoul, Republic of Korea
    Nano Artificial Vision Research Center, Seoul, Republic of Korea
  • Footnotes
    Commercial Relationships  K.-I. Koo, None; D.-I. Cho, None; H. Chung, None; J.-M. Seo, None; S. Lee, None; J.-W. Ban, None; H.-Y. Jeong, None; H. Park, None; S. Ha, None.
  • Footnotes
    Support  Nano Artificial Vision Research Center (NBS-ERC supported by KOSEF & Korea Health 21 R&D Project MOHW A050251)
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 4233. doi:
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      K.-I. Koo, D.-I. Cho, H. Chung, J.-M. Seo, S. Lee, J.-W. Ban, H.-Y. Jeong, H. Park, S. Ha; Micro-Electrode Array with 171 Arrowhead-Shaped Three-dimensional Tips for Retinal Prosthesis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4233.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : In this paper, a micro-electrode array (MEA), that has 171 stimulation electrodes with 3D arrowhead-shaped tips, for retinal prosthesis is fabricated and evaluated. This micro-electrode array has the following features that improve previous MEAs: firstly attributed to 50 ~ 150 µm height and arrowhead shape, the proposed MEA can be brought close to the stimulation target cells, and secondly, the array is concave shaped and fabricated on a flexible substrate for a close conformal contact with the eye ball.

Methods: : The proposed MEA is fabricated using MEMS (MicroElectroMechanical Systems) technology, which can make electrical and mechanical systems in the range from micrometers to millimeters. The base of each electrode is defined by silicon-oxide patterning on a (100) single crystalline Si wafer. The height of post structure part in each electrode is determined by subsequent deep RIE process. Alkaline wet etch reveals 8 {111} planes to result in uncompleted octahedron structure. The entire structure of Si mold is an octahedron positioned upon post, which is an arrowhead shape. The wet etched depth of Si mold is controlled by the pattern width on Si mold. Using this Si wet etch property, the individual electrode mold pattern width is designed differently and fabricated to be a concave-shaped array. After the Si mold fabrication, all films are removed, and then Au is electroplated to fill the fabricated mold. The exterior layer of electroplated metal serves as an interface with target cells. After electroplating, the polyimide body layer and the conductive metal layer are patterned. Finally, the whole Si substrate is etched away using SF6 from the opposite side. After fabrication, electrically evoked potential (EECP) is recorded in a white rabbit. Biphasic current pulse (5 ~ 200 µA) is injected and the visual cortex response is recorded.

Results: : The fabricated concave array has 171 arrowhead-shaped electrodes with a 200 µm pitch. The base plane of each electrode is a 15 ~ 125 µm diameter circle. The total height of each electrode is approximately 50 ~ 125 µm. The interface impedance shows a magnitude of 10 ~ 100 kOhms. The N1 peak and P1 peak amplitude of visual cortex response increases as the stimulation current amplitude increases. However, the N1 peak and P1 peak evoked time is consistent almost regardless of stimulation current amplitude.

Conclusions: : A new type MEA was fabricated using MEMS technology and evaluated at in vivo environment. These evaluation data shows the feasibility of clinical applications.

Keywords: retina • retinal development • retinal degenerations: hereditary 
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