StiMote: An Ultrasmall, Modular Neurophotonic Stimulator

Vision loss remains a significant societal problem, decreasing independence and quality of life for millions world-wide. Though electrical stimulation of visual pathway neurons creates the sensation of light in people with severe blindness, inadequate brain machine interface (BMI) technology represents a barrier to clinical implementation of this potentially impactful technology.

Current systems use large bundles of wires connecting the visual cortex (the part of the brain that processes visual information) to the skull, which leads to movement, scarring, and eventual device failure. This research project will create and test StiMote, a modular brain stimulator that uses light (rather than wires) to power and program individual modules and electrical stimulation to activate nerves in the brain to recreate sensory perception or modulate brain activity.

StiMote is only 0.3 mm on a side and is being designed for sight restoration to help people with severe visual impairment participate more fully in society. The StiMote architecture can also be used to treat other medical conditions, including diseases affecting the brain or nervous system. To promote diversity, equity, and inclusion (DEI) in research and society, the investigators will reach but to campus groups including the local chapters of Society of Women Engineers, the National Society of Black Engineers, and the Society of Hispanic Professional Engineers to make them aware of the project and involve them in research through internships.

This project is focused on solving significant technical challenges that will enable impactful parallel brain interfaces through the development of StiMote. StiMote is designed to overcome three limitations in current approaches for Visual Cortex Prostheses (VCPs): (1) Surface stimulation that is low resolution, (2) Penetrating electrode arrays that can meet requirements for density and channel count, but will evoke significant foreign body reaction and require stiff multi-wire tethers to large percutaneous connectors and (3) Modular stimulators with inductive power/data schemes that do not meet the density needed to restore high acuity vision due to inductive coil size requirements.

The initial estimates suggest that StiMote can improve the spatial resolution of stimulation by more than 60X compared to VCPs currently in clinical trials. Eight micron carbon fiber electrodes will be combined with electrodeposited platinum iridium to create a highly efficient neural interface. Carbon fibers are minimally scarring in long term implants, resulting in a large number of healthy neurons within 20 microns of the electrode.

This close proximity improves the efficiency of stimulation. Electrodeposited platinum iridium minimizes electrode polarization during stimulation, through efficient charge transfer. The investigators will develop new photovoltaic and ultra-low power circuit chips to form a wireless stimulation mote with the lowest power consumption to date.

The project will integrate technical advances into StiMote and demonstrate the safety and efficacy of StiMote for vision restoration in an animal model of blindness.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.