June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
A monolithic diamond microelectrode array fabricated for a high acuity retinal prosthesis
Author Affiliations & Notes
  • Kumaravelu Ganesan
    Physics, The University of Melbourne, Parkville, VIC, Australia
    Bionic Vision Australia, Melbourne, VIC, Australia
  • David Garrett
    Physics, The University of Melbourne, Parkville, VIC, Australia
    Bionic Vision Australia, Melbourne, VIC, Australia
  • Mohit Shivdasani
    The Bionics Institute, East Melbourne, VIC, Australia
  • David Nayagam
    The Bionics Institute, East Melbourne, VIC, Australia
    Department of Pathology, The University of Melbourne, Fitzroy, VIC, Australia
  • Joel Villalobos
    The Bionics Institute, East Melbourne, VIC, Australia
  • Hamish Meffin
    NICTA, Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC, Australia
  • Kate Fox
    Physics, The University of Melbourne, Parkville, VIC, Australia
    Bionic Vision Australia, Melbourne, VIC, Australia
  • Samantha Lichter
    Physics, The University of Melbourne, Parkville, VIC, Australia
    Bionic Vision Australia, Melbourne, VIC, Australia
  • Robert Shepherd
    The Bionics Institute, East Melbourne, VIC, Australia
  • Footnotes
    Commercial Relationships Kumaravelu Ganesan, None; David Garrett, None; Mohit Shivdasani, None; David Nayagam, None; Joel Villalobos, The Bionics Institute of Australia (P); Hamish Meffin, NICTA (P); Kate Fox, University of Melbourne (P); Samantha Lichter, National Information and Communication Technology Australia (NICTA) (F), Bionic Vision Australia (E), Bionic Vision Australia (P); Robert Shepherd, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 1047. doi:
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      Kumaravelu Ganesan, David Garrett, Mohit Shivdasani, David Nayagam, Joel Villalobos, Hamish Meffin, Kate Fox, Samantha Lichter, Robert Shepherd; A monolithic diamond microelectrode array fabricated for a high acuity retinal prosthesis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1047.

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

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Abstract
 
Purpose
 

To fabricate and test a biocompatible, chemically inert, hermetically sealed, near-conformable microelectrode array comprised of two kinds of diamond materials

 
Methods
 

Feedthroughs were made on insulating polycrystalline diamond (PCD) substrate using laser milling and electrically conducting nitrogen incorporated ultrananocrystalline diamond (N-UNCD) was grown on top of it using chemical vapour deposition. Finally, the N-UNCD electrodes were electrically isolated by laser milling. An optical 3D profile image of the flat part of a 16x16 electrode array is shown in Fig.1. The electrode array was tapered in order to reduce the space between the electrode and the retina with approximate radius of 12 mm as shown in the Fig. 2. In order to test the stimulation efficacy, diamond electrodes were tested using acute in vivo preclinical models. The hermeticity of the array was tested using a helium leak tester by attaching the electrode array by a Viton® O-ring.

 
Results
 

A high density hermetic diamond microelectrode array was fabricated and implanted in vivo with a PDMS carrier and the average minimum charge density required to produce cortical activity was 151 µC cm-2. The in vivo electrode impedances were between 2.5-76kΩ and stable over the course of the acute testing phase. The helium leak rate was found lower than the detection limit of the helium mass spectrometer (10-11 mbar L s-1) for approximately 30s and thereafter helium is found to leak through the O-ring.

 
Conclusions
 

The average threshold charge density exhibited by the diamond arrays presented here is well within the safe charge injection limit. The hermeticity of the high density electrode array means that the array can also function as encapsulation for implantable microelectronics. The use of a single material for construction of the array eliminates any potential materials mismatches that could lead to device failure. The results are evidence that diamond shows potential for both active and passive components of an implantable neural prosthesis.

 
 
Fig. 1: A 3-D optical profile image of the 16x16 diamond micro electrode array.
 
Fig. 1: A 3-D optical profile image of the 16x16 diamond micro electrode array.
 
 
Fig.2: A schematic of the near-conformable diamond electrode array and the high acuity implant. (Not to scale). 1. Retina, 2. N-UNCD electrode. 3. Electrical feedthrough. 4. Indium contact bump. 5.Diamond Encapsulation. 6. PCD substrate. 7. microprocessor chip.
 
Fig.2: A schematic of the near-conformable diamond electrode array and the high acuity implant. (Not to scale). 1. Retina, 2. N-UNCD electrode. 3. Electrical feedthrough. 4. Indium contact bump. 5.Diamond Encapsulation. 6. PCD substrate. 7. microprocessor chip.
 
Keywords: 688 retina • 507 electrophysiology: clinical  
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