Ideation Process
Project Initiation
Project name: Design of an Infrared Nerve Stimulator
Project timeline: October 2010 - May 2011
Project team: Melanie Gault, Greg Wigger, Chris Tedder
Primary Objectives
1. Develop three infrared nerve stimulator prototypes containing optical fibers running parallel to
the nerve for eventual implantation in a nerve cuff stimulator
2. Compare the efficacy and infrared light output of each of the three designs
Importance of the Situation
Design of the side-firing prototypes will provide the means for an implantable nerve stimulator. This
implantable device will have the capabilities to be included in the next generation of prosthetic
devices and for treatment of those suffering from paralysis.
Innovation Situation Questionnaire
Brief description of the situation
Researchers have determined that infrared light can stimulate nerve fascicles with greater precision,
specificity, and less damage than electrical nerve stimulation. For future use and implantation of
infrared nerve stimulators, a design must be created that can direct an infrared beam at a 90° angle,
or “side-fire” the signal. Using mirrors and/or optical properties of an optical fiber, the side-firing
of the beam is possible.
Detailed description of the situation
In order for a nerve stimulator to be feasible for implantation, it must lay in parallel with the nerve
fascicle of the patient. To lie in parallel and still stimulate the nerve, the infrared light must be
directed at a 90° angle. By polishing an optical fiber at a 45° angle, the infrared light experiences
total internal reflection so that it goes in the 90° direction. The other two strategies involve using a
flat mirror or a concave mirror laid at a 45° angle so that the infrared light is reflected in a 90°
direction.
Supersystem - System - Subsystems
System name
Infrared Nerve Stimulator
System structure
The infrared nerve stimulator must always contain an optical fiber that transmits the infrared light
from the laser source. Ideally, this optical fiber has maximum flexibility and minimum size. All
nerve stimulators must also include a casing, made of glass, nylon, or some other transparent
material, to protect the air-fiber interface of the polished fiber or to contain the mirrors for the
mirrored stimulators. The mirrored stimulators must contain either a concave or flat first-surface
mirror with a minimum size.
Supersystems and environment
The infrared nerve stimulator must be attached to an infrared light source. This light source must
emit an infrared laser with a high energy output and will therefore be connected to an external power
source. In order for the nerve stimulator to be as precise and efficient as possible, the stimulator
must lie, in parallel, on top of the nerve fascicle and aligned with pre-determined, particular axons.
This conditions requires that the patient be alive, healthy, and with a viable nerve system.
Systems with similar problems
No other system experiences a similar problem since electric stimulation does not rely on “sidefiring” methods. Electric stimulation simply attaches to the nerve fascicle for direct delivery of
stimulation while infrared light must be delivered in less direct fashion. However in optical research,
mirrors have been precisely fabricated and are used throughout to reflect light in any desired
direction. Using this previous mirror usage, along with the known optical properties of an optical
fiber, the three side-firing methods can utilize the solutions.
Input - Process - Output
Functioning of the system
Infrared light will be passed through the different side-firing prototypes and the various properties of
infrared beam directed in the 90° angle will be measured.
System inputs
The input of our system is the infrared light and its energy.
System outputs
The output of our system is an infrared beam that has been directed in a 90°angle or “side-fired.”
The output of this beam includes its beam size, radiant exposure, and energy loss in each stage of
the infrared light’s movement.
Cause - Problem - Effect
Problem to be resolved
Infrared light must be directed at a 90° angle while maintaining a minimum beam size, a high
energy throughput, and a sufficient radiant exposure for nerve stimulation.
Mechanism causing the problem
The human body anatomy requires that the infrared nerve stimulator lie in parallel with nerve
fascicles in order for a patient to maintain functionality and a high quality of life.
Undesirable consequences if the problem is not resolved
Patient using an infrared nerve stimulator without side-firing abilities will lose original mobility and
functionality of affected body areas.
Other problems to be solved
Reflection and transmission of the infrared light changes the beam’s characteristics and its energy
output.
Past - Present - Future
History of the problem
Electric stimulation of nerve fascicles have existed for over 150 years. Infrared stimulation of nerve
fascicles has existed for less than 50 years however. Until now, infrared stimulation has only
occurred by directing infrared light on the nerve fascicle in a perpendicular manner. With the future
of implantation ensuing, side-firing techniques must be developed.
Pre-process time
Research into previous methods of nerve stimulation. Determining top prototype candidates through
proof-of-concept modeling.
Post-process time
Research into afferent stimulation and a portable, infrared laser source are future directions.
Resources, constraints and limitations
Available resources
The substance resources that we have are optical fibers from Ocean Optics, transparent nylon
tubing, glass tubing, and first-surface flat and concave mirrors from Edmund Optics. Our primary
resources for space are Vanderbilt Optics lab facilities. We have two semesters to complete the
project which is our time resource. Dr. Duco Jansen, Dr. Kurt Schoener, and Dr. Paul King are our
information resources.
Allowable changes to the system
Small changes are allowed regarding the tubing/encasement of the side-firing prototypes. The fiber
optic system must be encased in a material that is biocompatible and transparent to infrared light
with maximum throughput.
Constraints and limitations
The system is constrained to emit an infrared beam with a minimum radiant exposure of 0.4 J/cm^2
to result in nerve stimulation. The air-fiber interface must remain on the 45° polished fiber prototype
so that is optical properties retain its ability for side-firing.
Criteria for selecting solution concepts
Primary characteristics include radiant exposure and energy throughput. The ideal model will have
the highest values in both of these categories. Other considerations include durability, cost, and
design complexity.
Problem Formulation and Brainstorming
Infrared Nerve Stimulator
Infrared Nerve Stimulator produces Side-Firing Capabilities, Spatially selective
1. stimulation and Need for nerve cuff produces Narrow energy window for effective
stimulation.
Side-Firing Capabilities produces Ability to lie fiber in parallel with nerve and Ability
to fire infrared beam at 90 degree angle produces Difficulty in producing desired
2.
beam profile, Energy lost in reflection and Polished fiber requires air-fiber interface
is produced by Infrared Nerve Stimulator.
Ability to lie fiber in parallel with nerve produces Ideal for implantation produces
3. More contact with nerve that could induce damage to nerve is produced by SideFiring Capabilities.
4.
Ideal for implantation is produced by Ability to lie fiber in parallel with nerve and
Ability to fire infrared beam at 90 degree angle.
5.
Difficulty in producing desired beam profile produces Energy lost in reflection is
produced by Side-Firing Capabilities.
6.
Energy lost in reflection is produced by Side-Firing Capabilities and Difficulty in
producing desired beam profile.
7.
Spatially selective stimulation produces Ability to stimulate individual fascicle is
produced by Infrared Nerve Stimulator and Need for nerve cuff.
8.
More contact with nerve that could induce damage to nerve is produced by Ability to
lie fiber in parallel with nerve.
9. Ability to stimulate individual fascicle is produced by Spatially selective stimulation.
10.
Polished fiber requires air-fiber interface produces Need for material is produced by
Side-Firing Capabilities.
11.
Need for material produces Larger risk for immune response is produced by Polished
fiber requires air-fiber interface.
12. Larger risk for immune response is produced by Need for material.
Narrow energy window for effective stimulation produces Below stimulation
13. threshold results in no effect and Above safety range can cause tissue ablation is
produced by Infrared Nerve Stimulator.
14.
Below stimulation threshold results in no effect is produced by Narrow energy
window for effective stimulation.
15.
Above safety range can cause tissue ablation is produced by Narrow energy window
for effective stimulation.
16.
Ability to fire infrared beam at 90 degree angle produces Ideal for implantation is
produced by Side-Firing Capabilities.
Need for nerve cuff produces Spatially selective stimulation, Stimulate multiple
17. fascicles at once and Need for biocompatibility produces Must anchor cuff to nerve is
produced by Infrared Nerve Stimulator.
18. Stimulate multiple fascicles at once is produced by Need for nerve cuff.
19.
Must anchor cuff to nerve produces Potential damage to nerve is produced by Need
for nerve cuff.
20. Potential damage to nerve is produced by Must anchor cuff to nerve.
21.
Need for biocompatibility produces Limits use of materials is produced by Need for
nerve cuff.
22. Limits use of materials is produced by Need for biocompatibility.