Development of an Infrared Nerve Stimulator

Greg Wigger, Chris Tedder, and Melanie Gault

Advised by:Dr. Duco Jansen, Ph.D.

The Problem

This requires a reliable stimulation modality to gain better control over neural signals.

There is a need for an implantable device that will reliably stimulate individual nerve fascicles

Our Solution: Infrared Stimulation

Infrared StimulationSame advantages as electrical

stimulation, but: Less damaging to nerve Artifact free Spatially selective

Electrical StimulationHas fundamental shortcomings that

create a need for an alternative Contact can cause permanent damage

to nerve Stimulation artifact Hard to selectively stimulate

Rat Sciatic Nerve

Electrical Stimulator

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CM

AP

(V)

Rat Sciatic Nerve

Electrical Stimulator

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AP

(V)

Fiber Coupled Laser

Rat Sciatic Nerve-0.1

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AP

(V)

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Fiber Coupled Laser

Optical Fiber

Group ObjectiveDevelop an infrared

nerve stimulator containing optical fibers running parallel to the nerve fibers Create a single fiber

prototype that sends infrared signal at 90° angle

Three models will be tested

Fiber with flat angled mirror

Fiber polished at 45 degree angle

Fiber with concave angled mirror

The Three Prototypes Biocompatibility –

PEGylation Minimal Power Loss Small Beam Size

Energy Density Low Cost Durability

Flat Mirror Prototype

Curved Mirror Prototype

Possible Future Uses

Implantable devices for use in victims of paralysis

Incorporation of sensors to provide brain with feedback from the external environment

Past Work

Completed Solidworks

Tested nylon tube for infrared break down

Determined beam size, energy density, and power loss of 45°-polished fiber and curved mirror prototype with “Knife-Edge Technique”

Before

After

Past Work cont.

Past Work cont. (Data collected)

Energy Density and Beam Area

10-fold difference in energy density and order of magnitude difference in spot area of the beam

Side-Firing Prototypes0.0005.000

10.00015.00020.00025.00030.00035.00040.00045.00050.00055.000

5.012

50.505

0

Energy Density of Pro-totypes

45-Degree Polish Curved Mirror Flat Mirror

Ener

gy D

ensi

ty (

J/cm

²)

Side-Firing Prototypes0.0000.0200.0400.0600.0800.1000.1200.1400.1600.1800.200

0.183

0.028

0

Spot Area of Prototypes

45-Degree Polish Curved Mirror Flat Mirror

Spot

Are

a (c

m²)

Past Work cont. (Data collected)

Power Loss Coupling loss

measured from the laser to the fiber▪ Faulty lens?

Nylon is either scattering or absorbing infrared light as seen in large loss from fiber to nylon▪ Future direction From fiber From nylon Overall

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

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100.00

76.3

4

79.2

4

95.0

9

67.8

3

84.1

0

94.8

8

0 0 0

Percent Energy Loss of Pro-totypes

45-Degree Polish Curved Mirror Flat Mirror

Perc

ent

Loss

Current Work

Determine if nylon scatters or absorbs light by flattening a piece of nylon and measure loss and spot size

Find absorption spectra of nylon Calculations

Find theoretical spot size of concave mirror and compare it to actual measured spot size

Find maximum distance that the fiber can be from the concave mirror without any light being lost

Future Work

Obtain capillary tube (600 µm ID)to determine if glass is more transparent to infrared light than the nylon tubing We will conduct an energy-loss test

using the angle-polished fiber Determine the actual distance at

which the curved mirror focuses Place 100 µm pinholes over power meter

Future Work cont.

Still waiting on our flat mirrors to arrive…

Optimistic about about its feasibility and effectiveness: Unnecessary to polish the fiber, as with

angle-polished model Convergence/divergence are non-issues,

as with concave model