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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Fabricating high-density microarrays for retinal recording

Mathieson, K and Cunningham, W and Marchal, J and Melone, J and Horn, M and O'Shea, V and Smith, KM and Litke, A and Chichilnisky, EJ and Rahman, M (2003) Fabricating high-density microarrays for retinal recording. Microelectronic Engineering, 67-8. pp. 520-527. ISSN 0167-9317

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Abstract

Understanding how the retina encodes the visual scene is a problem, which requires large area, high-density microelectrode arrays to solve. The correlated signals that emerge from the output (ganglion) cells of the retina form a code, which is not well understood. We use a combination of electron beam lithography, photolithography and dry-etch pattern transfer to realise a 519-electrode array in the transparent conductor indium tin oxide (ITO). The electrodes are spaced at 60 μm in a hexagonal close-packed geometry. A mix and match lithography procedure is utilised, whereby the high-density inner region is fabricated using electron beam lithography whilst the outer sections are realised by photolithography. Reactive ion etching (RIE), using CH4/H2, of the ITO forms the array structure and SF6 RIE allows resist removal and patterning of vias through a plasma deposited Si3N4 protective layer. The electrical properties of the ITO layer are unaffected by the etching procedures. A reliable method for achieving low-impedance electroplated platinum electrodes has been employed to yield electrode impedances of ∼20 kΩ. An array fabricated using these dry-etch techniques is shown to record action potentials from live retinal tissue in neurophysiological experiments.