A fully flexible stimulator using 65 nm CMOS process for 1024-electrode epi-retinal prosthesis

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Materials Science

Background:

• Visual prostheses aim to restore sight for individuals with retinal degenerative diseases.
• Existing retinal stimulators face challenges in flexibility, power consumption, and electrode control.
• Advancements in microelectronics are crucial for developing sophisticated neural interfaces.

Purpose of the Study:

• To present a fully flexible, high-electrode-count stimulator for epi-retinal prostheses.
• To demonstrate a novel electrode driver design for improved performance and simplified circuitry.
• To evaluate the electrical characteristics, including current crosstalk, of the developed stimulator.

Main Methods:

• Fabrication of a 1024-electrode epi-retinal stimulator using a 65 nm CMOS process.
• Implementation of an alternately pull-push electrode driver for efficient voltage and charge management.
• Support for flexible electrode selection (any number, any time) and stimulation modes (mono-polar, multi-polar).
• Investigation of current distribution and crosstalk between adjacent electrode groups.

Main Results:

• The stimulator is fully flexible and integrates 1024 electrodes.
• The novel driver design reduces headroom voltage and ensures electrode charge balance.
• Simplified CMOS circuit design is achieved using positive supplies only.
• Measured maximum current crosstalk between nearby electrode groups is 8%.

Conclusions:

• The developed flexible retinal stimulator offers advanced electrode control and simplified design.
• The novel driver architecture is effective in managing voltage and charge balance.
• The low current crosstalk indicates suitability for high-density retinal stimulation applications.
• This technology holds promise for improving the efficacy of visual prostheses.