Development of an Infrared Nerve Stimulator

1. Greg Wigger, Chris Tedder, and Melanie Gault Advised by: Dr. Duco Jansen, Ph.D. Development of an Infrared Nerve Stimulator

2. The Problem Current prosthetic limbs do not fully replace function of native limbs • Current prosthetic limbs cannot mimic the fine tuned movements of human limbs. • Creates a need for a reliable stimulation modality to gain better control over neural signals.

3. Overview of Neural Stimulation • The nervous system controls our bodily functions, decision making, emotions, and more • Neural information is transmitted via action potentials (APs) • APs travel down the nerve until reaches its target • APs propagate due to the opening and closing of gated sodium-ion and potassium-ion channels • Electrical stimulation opens voltage gated channels to cause neural activation • Infrared neural stimulation induces neural activity through an unknown mechanism

4. Current Solution: Electrical Stimulation • Gold standard for neural stimulation • Easily controllable parameters (current, voltage, repetition rate) • Spatially specific in contrast to other forms of stimulation including chemical and mechanical stimulation. Cardiac Pacemaker Vagus Nerve Stimulation Cochlear Implant Spinal Implant

5. 10 5 0 -5 0 2 4 6 8 10 12 14 16 Our Solution: Infrared Stimulation 10 5 Electrical Electrical CMAP (V) 0 Stimulator Stimulator -5 0 2 4 6 8 10 12 14 16 Infrared Stimulation Same advantages as electrical stimulation, but: • Less damaging to nerve • Artifact free • Spatially selective CMAP (V) Rat Sciatic Nerve Rat Sciatic Nerve 0.2 Fiber Coupled Fiber Coupled 0.1 Laser Laser CMAP (V) 0 Optical Fiber -0.1 0 2 4 6 8 10 12 14 16 0.2 0.1 CMAP (V) 0 Rat Sciatic Nerve -0.1 0 2 4 6 8 10 12 14 16 Electrical Stimulation Has fundamental shortcomings that create a need for an alternative Contact can cause permanent damage to nerve Stimulation artifact Hard to selectively stimulate

6. Group Objective Develop an infrared nerve stimulator containing optical fibers running parallel to the nerve fibers • Create a single fiber prototype • Create a four fiber prototype embedded in a cuff to be wrapped around entire nerve bundle • Two models will be tested: Fiber with angled mirror Fiber polished at 45 degree angle

7. Past Work • Research of nerve stimulation techniques • Electrical stimulation • Infrared stimulation • Ordered supplies for prototype • Steep tubing, mirrors, optical fibers, plastic tubing • Testing of Ho:YAG laser • 80 to 100mJ with 960V power supply

8. Current Work • Further testing of laser output • Attaining an optic fiber polisher • Training for animal studies through IACUC • Begin building side-firing prototypes

9. Future Work • Polishing fibers (flat and 45˚) • Biomaterial of the nerve cuff • Research • Biocompatibility and optical testing of PDMS • Proof-of-concept experimentation of side-firing with animal studies • Nerve cuff design • Adjustable circumference • Locking device • Positioning of optic fibers