A Sub-mm³ Wireless Neural Stimulator IC for Visual Cortical Prosthesis With Optical Power Harvesting and 7.5-kb/s...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Vision restoration is a critical challenge in neuroscience.
• Current visual prosthetics often face limitations in wireless operation and precise stimulation.
• Untethered, addressable stimulation motes are needed for advanced visual cortex interfaces.

Purpose of the Study:

• To develop and validate StiMote, an untethered, free-floating, and individually addressable stimulator mote for visual cortex stimulation.
• To enable wireless power and data transmission for vision restoration applications.
• To implement and assess an automatic charge balance technique for safe and effective stimulation.

Main Methods:

• Optical powering using a custom photovoltaic (PV) layer and photodiode (PD) receiver.
• Time-division multiple access (TDMA) framework for addressing up to 1024 motes.
• Automatic charge balance (CB) technique for bi-phasic switched-capacitor stimulation (SCS).
• In vitro electrode testing and in vivo experiments in rats.

Main Results:

• StiMote confirmed fully functional wirelessly using harvested light.
• Low power consumption (4.48 μW) with a 7.5-kb/s optical downlink data rate.
• DC-DC converter achieved 4.3-V output with 67.4% maximum efficiency.
• CB circuit demonstrated linear charge control (<0.2 nC imbalance) up to 16 nC.
• In vivo experiments verified effective stimulation in rats.

Conclusions:

• StiMote offers a promising untethered solution for visual cortex stimulation.
• The optical powering and TDMA framework enable precise, wireless control of multiple stimulation motes.
• The automatic charge balance technique ensures safe and effective bi-phasic stimulation.
• Successful in vivo validation paves the way for future vision restoration therapies.