Large-scale Integration–Based Stimulus Electrodes for Retinal Prosthesis - Artificial Sight: Basic Research, Biomedical Engineering, and Clinical Advances - page 166

Figure 8.15. Photograph of the fabricated microchip-based stimulator device.

shows the packaged chip and the experimental result in saline solution of the
fabricated stimulator that is packaged as described. For each timing, only one
electrode is activated. This demonstrates that we can select an arbitrary electrode
to be activated.
We have developed a dedicated fabrication process for the distributed
microchip-based stimulator. The fabricated stimulator is shown in Figure 8.15.
The stimulator will be implanted and tested in the near future.
It should be noted that the number of microchips to be controlled is restricted
with the asynchronous counter design, and that this number could easily be
increased by designing the counter to have a greater number of bits. A stimulator
that consists of 4 4 microchips with 9 electrodes (total 144 electrodes) is

connected with another stimulator in a daisy chain, and thus a stimulator with
288 electrodes is realized.
The distributed microchip-based device we have fabricated has a broadcast
architecture. Only a single electrode can be activated. In order to activate multiple
electrodes as well as different pulse parameters in each electrode, we have
developed serial bus architecture and confirmed its fundamental functions [9].
In the future, we will develop a more sophisticated device in order to introduce
such serial architecture.

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Summary

We have demonstrated the PFM photosensor that is suitable for application
as a subretinal implantation device. The fabricated PFM-based image sensor
with 128

× 128 pixels demonstrated a wide dynamic range of 60 dB. In order