Article
Flexible Multi-Electrode Array for Retinal Implants
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Authors
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Nadine Winkin
- RWTH Aachen University, Germany
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C. Etzkorn
- Department of Ophthalmology, RWTH Aachen, University Hospital Aachen, Germany, Germany
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S. Johnen
- Department of Ophthalmology, RWTH Aachen, University Hospital Aachen, Germany, Germany
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W. Mokwa
- RWTH Aachen University, Germany
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P. Walter
- Department of Ophthalmology, RWTH Aachen, University Hospital Aachen, Germany, Germany
| Published: | March 7, 2016 |
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Outline
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Objective: The objective was to develop a flexible multi-electrode array with an integrated silicon chip for stimulation of neurons.
Materials and Methods: Micro-electrodes and micro-electrode arrays (MEAs) are widely used in medical applications and biological research. For many medical implants, like retinal implants, flexible MEAs with a large area and a large number of stimulation electrodes are needed. Due to the high number of electrodes, it is no longer possible to connect each of them with conductor lines. A connection via a bus system will be necessary. In this work, a flexible MEA with an integrated CMOS-chip facing these challenges was designed and manufactured. Mechanical stress tests, biocompatibility assays and in vitro functionality experiments were carried out. In order to ensure the flexibility of the MEA, the chip was thinned to a thickness of 20 µm before it was integrated into a polyimide foil. The used polyimide is known to have an excellent biostability and biocompatibility. Furthermore, it can easily be structured with standard photolithographic techniques. For electrical isolation of the integrated conductor lines and to obtain well-defined electrode openings, parylene C was used, which can easily be structured by reactive dry etching.
Results: A novel MEA with an integrated silicon chip was successfully manufactured. Measurements of the electrical resistances of the integrated conductor lines were carried out during bending tests. The results showed that the integrated metallization was not influenced by deflections, which are typical for retinal implants. The used materials exhibited a very good, non-toxic biocompatibility profile. The MEA was coupled to the corresponding stimulation and recording hardware and taken in operation analogous to commercial systems to analyze its functionality.
Discussion: This approach now makes it possible to increase the density and the number of electrodes significantly by connecting and addressing several of these “intelligent” MEAs via a bus system.
Acknowledgement: This work was supported by BMBF under grant No. 16SV5322K.
