THE UNIVERSITY OF AKRON
The Department of Biomedical Engineering
Development of Prosthetic Liner with Air Channels:
Honors Research Project
Authors
Honors College
Adam Carver, Daniel McFarland & Sarah Richardson
College of Engineering
Tim Shary & Mauricio Uribe
Honors Faculty Advisor
Dr. Mary Verstraete, The University of Akron
In collaboration with
Dr. Brian Davis, The Austen BioInnovation Institute in Akron (ABIA)
April 22, 2011
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Abstract
Currently, thousands of people every year require a lower limb amputation. In order to
maintain locomotion, these patients require the use of a prosthetic limb. Many patients choose
not to wear their prosthetic device because regardless of all the current technology available,
their prosthetic device remains very uncomfortable. None of the current solutions available are
able to regulate the temperature at the residual limb/prosthetic interface, which leads to sweat
and tissue degradation. Therefore, a need currently exists for a new device that prevents tissue
degradation at the interface.
The energy generated by the leg during normal gait can be used to pump air onto the
residual limb during the ground-contact phase, and draw a vacuum during the swing phase of
the gait. Our design team has designed a liner which incorporates several air channels at the
liner-residual limb interface that allow pumped air to flow between the liner and the limb. This
design creates a cooling effect on the leg due to convection and evaporation of sweat, resulting
in a more comfortable prosthetic device that patients can wear for longer periods of time,
ultimately giving amputee patients a better quality of life. Prototypes were manufactured by 1.)
physically modifying existing liners, and 2.) printing the 3D CAD model with an Eden 3D printer.
A testing protocol has been developed to determine the ability of the device to dissipate heat,
but it has yet to be carried out.
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Background and Introduction
There are currently thousands of people every year that require a lower limb amputation. In
order to maintain locomotion, these patients require the use of a prosthetic limb. The price of
these devices range from $20 to tens of thousands of dollars. In addition to the actual
prosthetic device, there are other components that the patient may also choose to wear to
increase comfort and functionality. For example, many patients choose to incorporate a
custom-fit socket, specially made socks, and/or custom liners. However, many patients still
choose not to wear their prosthetic device for a number of reasons. Most of these patients
claim that regardless of all the current technology available, their prosthetic device remains very
uncomfortable.
Overall, none of the current solutions available are able to regulate the temperature at the
residual limb/prosthetic interface. This leads to a number of complications such as discomfort,
overheating, sweating, moisture buildup, chaffing of the skin, blister formation, infection, and
tissue degradation. Therefore, a need currently exists for a new device and/or technology that
prevents tissue degradation at the interface by addressing one/all of these issues. This would
result in a more comfortable prosthetic device that patients could wear for longer periods of
time, ultimately giving amputee patients a better quality of life.
Research Objective
In determining an effective system to address the problem statement above, our design team,
comprised of five individuals, has decided to use the energy generated by the leg during normal
gait to pump air onto the residual limb during the ground-contact phase, and draw a vacuum
during the swing phase of the gait. This idea can be developed with mechanical pneumatic
pumps like the one used in the Harmony® System (Otto Bock, Duderstadt, Germany) combined
with a series of one way valves. As a result, the liner would have to be redesigned in order to
allow air to flow between the liner and the limb. The efforts of our design team will, for the
most part, be focused on a new design for a liner which incorporates several air channels at the
liner-residual limb interface to help cool the limb. Our design team intends to develop a
prototype of our proposed device and use it to compare its heat dissipation effectiveness in
relation to a conventional liner without air channels. The results of our test experiment will lead
us to determine the rates of heat dissipation and will aid in determining how much air needs to
be generated to keep the limb cool. Future work (outside the scope of this project) may look
into air flow generation systems that can be compatible with our proposed liner and the
possible biological effects of this device on the residual limb due to novel geometry and varying
air pressures (i.e. window edema).
Research Methodology
Purpose:
The purpose of the experiment would be to determine the relative efficacy of including air
channels in a prosthetic liner to dissipate heat in a model residual limb.
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Materials:
1.
2.
3.
4.
5.
6.
7.
8.
One (1) custom liner with air channels
One (1) identical custom liner without air channels
Two (2) balloons or plastic bags which fit inside the liners
Water
Digital thermometer
Spatula
Stop watch
Air pump and associated connections (possible options: air compressor, output on a
vacuum cleaner, bike pump, etc.)
Method:
First, a crude model of a residual limb will be built. The crude model will not have the same
thermal properties as an actual limb. Most importantly, it will not have a feature for
perspiration. However, this experiment is a relative comparison between liners, so the results
from the crude model will be analyzed with this in mind. The internal surface of each of the
liners will be fitted with a plastic bag or balloon to create a water bladder. The water bladder
will be outfitted with a digital thermometer to measure water temperature and a spatula to mix
the water to maintain consistent water temperature. The water bladder will be filled with hot
water (ex. 120 F).
Next, the air flow model will be built, and it will be applied ONLY to the liner with channels. An
air flow that perfectly mimics what is to be expected in the final device is not necessary, because
this experiment is relative in nature. However, it should at least still be within an order of
magnitude. Furthermore, the final device may have pulsatile air flow, but this experiment will
not for simplicity. The air flow will be accomplished by attaching the air pump with the
appropriate connections to the air input on the liner with channels.
Once the model is fully assembled, the experiment can begin. For the liner with channels, the
spatula will stir the hot water, the air pump will be turned on, the stopwatch will begin, and the
water temperature will be recorded every one (1) minute. The experiment will be stopped once
the water reaches a certain temperature (ex. 100 F). The experiment will be repeated for the
liner without channels.
Consider perspiration model. Example: allowing water in the water bladder to enter convective
area and evaporate via pinhole or wick materials.
Intended Research Analysis
Using computer simulations, the group plans to determine how much heat was lost during each
experimental trial and use these results to determine the rate of heat dissipation. The
calculated rate from our proposed device will then be compared to that of a conventional liner
without air channels. The model does not accurately represent in-vivo conditions, and therefore
it would be arbitrary and meaningless to define pass/fail criteria at this time. It is more
appropriate for the design team to meet and discuss whether the results of the proposed design
change justify moving further into other research models and tests.
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Estimated Timeline
This project is an assignment for a senior design project to complete our undergraduate studies.
Therefore, our official involvement with it ends in May 2011. However, the project may be
carried on beyond that in three ways: either through voluntary involvement by our design team
after May 2011, or through the involvement of next year’s senior class. The third option was
created when our group submitted this project idea to the Austen BioInnovation Institute in
Akron (ABIA), via the “Ideas” portal on the Medical Device Development Center (MDDC)
homepage. Currently, our project is being reviewed by staff members at ABIA and is being
considered for additional funding.
At this time, the design for a new prosthetic limb liner allows for ventilation across the skin
surface. The design is represented and specified in drawings and a 3D CAD model. The current
design is just the first iteration of the device, and an analysis of prototype testing may result in
changes to the design.
The remainder of this report contains a detailed description of the progress made throughout
the year on this project.
Please see the attached Gantt chart in the Appendix of this report for a full timeline.
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History of Design (Fall Semester)
Selecting the Project/Team
The first meeting involved a group discussion about the possible project ideas. There were eight
ideas total, and each of the group members met to discuss the pros and cons of each.
Afterwards, the team chose to email Dr. Verstraete to request the project involving the
prosthetic limb sensor/device. The details and background of this project have already been
mentioned previously.
During the second week, the group discussed the many topics to consider in order to stay
organized and up to date throughout the semester. Everyone was assigned with the tasks to
formulate a list of strengths and weaknesses, along with times of availability. Also, everyone in
the group was instructed to begin brainstorming possible company names.
It was established that Dr. Brian Davis from the Austen BioInnovation Institute in Akron (ABIA)
would be the main contact (sponsor) for the company.
The strengths and weaknesses of each group member were also presented during a meeting in
the third week. Team strengths included experience working at Zimmer and Depuy, mitigation
of complaints, working with project teams, history files, and project design. In addition, paying
attention to detail, staying organized, delegating tasks, reading peoples’ emotions, being
patient, and explaining important information to non-technical people were included. Other
strengths involved researching techniques, literature reviews, experience with case studies and
retrieval of desired materials and information; consulting with customers, researchers and
medical professionals; staying organized and up to date with what is demanded to better the
group; constructing plots and organizing data; and resource connections with the Cleveland
Clinic and the prototype lab. Team individuals also mentioned experience with SolidWorks and
3-D prototype printers, a strong understanding of anatomy and physiology, organizational skills,
and a teachable demeanor. Additional strengths included design history file experience, CAD
software, looking at the bigger picture (customer requirements, design transfer, manufacturing),
thriving in a structured environment, a strong business sense, and developing leadership and
communication skills. Lastly, experience with computer programs/software (i.e. Origin, Excel,
MATLAB), reliability, and organization were also mentioned.
During week three, the design history file binder was officially started, which is meant to include
all of the actions that the company will take from initial concept to the marketing process,
design validation, and meeting minutes. Throughout the following week, each group member
was expected to research information on prosthetics to gain a better understanding of general
knowledge of the device, see what exists, and to locate companies working with the device. A
literature review was to be completed to combine all of the information found. Additionally,
group members were to brainstorm further company names and send ideas out in a thread of emails to be voted on during the next meeting.
StepOne Medical was chosen to be the official company name of our design team, and the
product name was chosen by the company members to be InvisiPro. Figure 1 shows our
company logo.
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Figure 1. Company logo for StepOne Medical
During the fourth week, team members also created a list of divisions needed to keep the
company notebook neat and organized. Further research was conducted using online databases
to gain a better understanding of general knowledge of the device, what currently exists, and
current companies that manufacture similar products.
A list of possible contacts from various organizations was created at this time. Also, the mission
statement was finalized. It reads as follows:
“At StepOne Medical our responsibility is to improve the quality of life of our
customers. Customer satisfaction will be achieved through collaboration with patients
and professionals. We will develop practical and innovative solutions by
understanding the problems that they face.”
Researching the Problem
StepOne Medical also began brainstorming customer needs and expectations along with
clinician expectations. Customer needs included comfort, regulations with the prosthetic stump
interface, temperature change, amount of sweat, a quiet cooling system, etc. Possible
questions for our customer were also mentioned and included:
How long should we expect patients to wear the prosthesis?
What is the current procedure for a patient with an amputation?
What is their alternative?
What do patients do to accommodate for this?
Values for heat control (At what saturation do pressure sores develop?)
Range for how much we should regulate at
What temperature/pressure leads to chaffing/sweating?
Should the development be used for a specific weight/sample population? Specific
differences among demographics (Is it different for gender, weight, height, etc?).
A literature review of prosthetic liners was presented at a general group meeting. It was
discovered that most are made of wool, cotton, nylon, and synthetic materials. There are socks
with a gel pad that press up against the stump. Also, there are sheaths with nylon type fabric to
provide a moisture barrier to control friction.
Another literature review was presented at the next meeting, which included thermal
conductivity. Increasing thermal conductivity decreases temperature related discomfort. If it is
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possible to start out with a lower temperature, patients don’t notice a change in temperature as
drastically. The limitations with convective and radiative cooling were also presented to the
group.
At this point, it was decided that it would be helpful to continue researching efficient liners and
brainstorming methods for initial cooling of the residual limb to aid in patient comfort. Silicon
liner sockets were also discussed. As a result of these, it was discovered that skin breakdown is
greatly reduced, it can fit/suction the female part of the socket, there will be low/no shear
forces acting on the limb, and the suspension system can therefore be improved.
With the socket, StepOne Medical initially looked into a porous interface that doesn’t
concentrate stress on the skin. Also, a more comfortable material was thought of that could
increase thermal conductivity for conducting heat.
Meeting with the Sponsor
Week eight involved the customer meeting. Dr. Mary Verstraete presented the general
expectations of the senior design project to Dr. Brian Davis, vice-president and director of the
Austen BioInnovation Institute’s (ABIA) Medical Device Development Center in Akron. He then
provided an overview of the problem to members of StepOne Medical. There are three
separate interfaces to the prosthesis in below-the-knee amputee patients (see Figure 2). First,
there is a cotton sock liner which covers the residual limb. Then, there is a gel-like sleeve which
adds durability and comfort. Finally, the residual limb is secured into a patient-specific plastic
socket.
The main problem, as identified by Dr. Davis, is chaffing and skin breakdown due to the plastic
socket-residual limb interface. It was identified that the plastic socket does not do a good job of
keeping the leg temperature regulated and moisture-free during normal patient use. Thus,
possible factors leading to tissue degradation arise due to elevated skin temperatures and sweat
at the interface.
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Residual limb
Sock liner
Gel
Plastic Socket
Figure 2. Diagram of the lower limb prosthesis.
In the discussion of alternative solutions Dr. Davis made mention that certain powders and
transcutaneous sweat stimulation have not been shown to be effective at stopping or
minimizing the sweat response. In addition, a heavy air conditioning unit would be an
impractical solution. The gel liners used by patients, which usually last for a couple months, also
tend to trap heat in the socket. One promising solution consisted of using
microelectromechanical systems, or MEMS, in order to drive heat away from the residual limbsocket interface, but modifications would be needed to increase the low efficiency of MEMS
devices (currently, approximately 25%). Passive-type systems were also considered which
would require research into new materials, gels and liner fabrics.
Lower limb amputee patient demographics include two groups. Elderly diabetic patients
constitute the most common group of limb amputation, while the more active and youthful war
veterans comprise a second important patient group. Due to the high level of activity of the war
veteran group, these patients are more prone to skin breakdown and would greatly benefit from
a new prosthesis design. A third group, namely victims of war landmines in third world
countries (some even children), could also be targeted with this new prosthesis.
Therefore, one major stipulation for the design team will entail deciding between two design
paths: developing a high cost and state-of-the-art prosthesis for war veterans and the U.S.
Department of Defense, or reaching out to the much larger third world population for which a
low cost solution is needed. As of now the very simple and affordable Jaipur Below Knee
Prosthesis ($20-40) exists on the market to attend to the needs of the third world population.
Dr. Davis and Dr. Verstraete also suggested several contacts that the design team could solicit
for ideas and help:
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Ohio Willow Wood - Company currently working on a new hybrid leg with hydraulics
and springs, used to store energy and release during gait cycle. Also, manufacturer of
the Alpha® Liner, a gel liner used by amputee patients (http://www.owwco.com/).
Mark Yankee - Founder/president and prosthetist from Yankee Bionics, Inc. in Akron,
OH.
Mike Haynes - A separate contact at Yankee Bionics, Inc.
Dean Frazier - Prosthetist.
Harold Shangali - President of the International Society for Prosthetics and Orthotics
(ISPO). Provided by Dr. Davis.
Longini Mtalo - Prosthetist/Orthotist in collaboration with ISPO. Provided by Dr. Davis.
Continued Research
A literature review was presented to the group on the causes of sweating. The types of sweat
glands were discussed along with the means of regulating temperature and heat production.
Another journal article informed the group that there cannot be holes drilled or punched into
the socket walls because it can’t retain the necessary strength. This was an extremely important
discovery in helping eliminate the prospect of drilling holes to create airflow. The reviews went
further into discussing other possibilities of materials used between the socket and stump to
decrease heat production and sweating, and the temperature ranges dealing with sweat
production and other ways to try to keep good hygiene with the stump and prosthetic device.
To be able to find other predicate devices and ideas that would be helpful to us throughout our
project, our group decided to investigate the intellectual property which is currently available.
In order to accomplish this task, our group did a preliminary patent search for devices similar to
our idea. One patent discussed how quickly one can cool the stump/socket area such as using a
heat sink to adjust the temperature. Another patent discussed using cryogenic fluid with an
infrared sensor by spraying cold fluid onto the surface. This would help in cooling the limb to a
specific temperature. MEMS technology was additionally discussed, regarding its cost-efficient
and effective properties. MEMS are used to cool down machines, act as micro-sensors, microactuators, pressure sensors, and temperature sensors. Ideas of how this technology can be
incorporated to help with cooling the device and be used as a sensor were discussed.
A literature review was discussed regarding the amount of heat that is dispersed at the interface
between the socket and stump. The article included the rate of heat production at rest (100
Watts) and upon completing heavy work (430 Watts). This occurs because heat is being brought
in from other parts of the body because of blood. The article helped with providing a range of
numbers for heat production when the average male is completing various activities.
The concept of heat flux when one is on the operating table (including wearing a surgical drape
vs. no clothes) was discussed. Values for heat flux were found along with the rate at which one
loses heat. Heat is lost in various areas of the body and can be broken down into body parts; for
example, one loses 9.5% of heat in the thigh. The group can utilize these findings and multiply
this with the values discussed when walking, running, sitting, and other various activities to
narrow down the upper and lower limits of heat loss at various occurrences. An example is that
approximately 15 Watts of heat is lost when walking for an average individual. These findings
will help in giving plausibility for further calculations throughout the building process.
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Useful Data
Out of 255 amputees, 74% had residual limb pain with a mean intensity of 5.4 on a scale
from 0 to 10;
The average cost of a below knee prosthesis is $8,000, and the average cost of an above
knee prosthesis is $15,000.
History of Design (Spring Semester)
Forming a Solution
The group met with our customer, Dr. Davis, on February 3, 2011. The purpose was to inform
him of all of the ideas that we had generated, and to ask for his advice as to which ideas to
develop. He liked the ice pack idea, but was concerned about the size and weight of an ice pack
that would last long enough for the patient. Ultimately, he thought that the focus should rely on
a device that both cools and dries the leg via air flow. The best idea was to use the energy in the
leg to pump air onto the leg during the ground-contact phase of the gait, and draw a vacuum
during the swing phase of the gait. This idea can be developed with mechanical pneumatic
pumps like the one used in the Harmony® System, combined with a series of one way valves.
The liner would have to be redesigned in order to allow air to flow between the liner and the
limb.
On February 9th, our group met with Dr. Tan, Associate Professor in the Department of
Biomedical Engineering at the University of Akron. In his previous work he had come across
ground-breaking research concerning patella-tendon loading for prostheses which would help
by changing where the residual limb is loaded. By reducing the load on the bottom of the limb it
would help to minimize the sores that normally develop. One area of concern, however, was
the patella tendon’s ability to effectively support body weight for long periods of time during
walking. In regards to a cheap and affordable solution that could be applied to the third-world
global market, Dr. Tan suggested investigating the International Committee of the Red Cross
(ICRC) who currently develops and distributes many low-cost and functional prostheses to
impoverished areas.
It was later identified that a helpful solution to the problem of tissue degradation could be one
which would give the patient comfort for even a couple hours, allowing them the freedom to
carry out their daily routine. As a result, the focus of the meeting with Dr. Tan shifted to the
design of a new liner. Neoprene skins used by scuba divers and gel materials that keep the limb
cool with an endothermic reaction were discussed. A new idea that was collaborated at the
meeting consisted of a socket interface which would address the poor fit of the prosthesis and
would function similar to an Aircast ankle brace. It was identified that sores come from ill-fitted
prostheses in conjunction with the heat and moisture at the interface. Thus, it was
hypothesized that by addressing the poor-fit of the prosthesis, sores and tissue degradation
would be minimized. The new liner would consist of several air chambers and would envelop
the residual limb, offering both a comfortable and strong fit while reducing pressure sores. The
air chambers would be fed from an inlet valve and pump that would force in air with each step.
An escape valve could allow excess air pressure to escape from the chambers while still
maintaining a predetermined and constant pressure throughout. The new proposed liner was
named “The Michelin Liner” because of its similarity to the Michelin company mascot.
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During impromptu conversations after the meeting with Dr. Tan, the group decided to pursue
two ideas until one was evidently better than the other. The first idea, which was the idea that
was discussed with Dr. Davis, would get 60-70% of our attention. The second idea would get the
remainder of our attention, which was the idea that was created during the meeting with Dr.
Tan.
Selecting an Idea
The group had a general meeting on February 14, 2011. The main purpose of the meeting was
to formalize the two ideas that were being pursued, and to discuss them at length.
1. Air flow idea
a. Noise during air movement between liner and skin
b. High pressure required to force air through liner
c. Liner must still create suction during one part of gait, and allow air to flow past
during another part of gait
d. Liner must not move with respect to skin, which causes sores
e. Where would the air flow in/out (location, number of locations)?
f. Do we have time/money to develop a pump system and a liner?
g. How will this system fit with the socket?
h. Yanke has ability to create custom liners, so they may be able to create a highquality prototype of our idea if we give them a 3-dimensional CAD model
Aircast idea/Michelin Liner
. How do we always keep the same pressure on the limb?
a. The system could be a regulated pump, or have a reserve pressure chamber
b. Constant pressure throughout the day could squeeze the limb too much,
resulting in loss of circulation
c. A crude, proof-of-concept prototype can be made from bike tire tubes.
Both ideas
. Customer must not be required to control it
a. Both ideas must work with existing prosthetic limbs
b. Both ideas could be used with an active cooling system
c. Device may need a fail switch to avoid high pressure
Modeling will demonstrate two things: mechanical integrity and heat transfer. The modeling
can therefore demonstrate the amount of pressure, air flow, and material strength required to
achieve the desired results.
The group requested liner material samples from Ohio Willow Wood (Dayton, Ohio) and Yanke
Bionics (Akron, Ohio). Six small samples were donated by Ohio Willow Wood and four urethane
liners were donated by Yanke Bionics. The smaller samples were used to identify the material
needed to make a prototype, while the liners were used to actually make the prototype.
Final Stages of Design Process
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The group chose one plausible and marketable idea.
Modeling
Attached are figures of our liner that were completed in Unigraphics NX5 to show the crosssectional area, the space for the residual limb, an intake/outlet air hole at the proximal end, and
vertical channels to allow air flow (Figures 1-5 in Appendix, section A).
A MATLAB code was attempted but not completed. The group had the desire to calculate the
heat flux and gradient with the air flow through the channels in the urethane liner and relate
the findings to a liner without such channels and sufficient heat regulation. The values could not
be confidently determined, therefore, heat analysis was decided to be completed through Algor
Simulation via the finite element analysis method. The completed CAD file was uplaoded into
Algor to determine results for thermal and mechanical regulation.
Intellectual Property and Tech Transfer
Prior to sending the completed CAD files to Yanke Bionics for manufacturing the urethane
prototype, the team met with the University of Akron Tech Transfer office to discuss filing for a
provisional patent in order to protect the idea.
StepOne Medical met with Cheryl Garcia and Ken Preston in the Technical Transfer Office at the
University of Akron. The meeting began by first describing the project and the current need,
and then explaining the origin of the design. Discussing the IP issues involved with this project
was an extremely important topic, which was needed in order to protect our idea prior to
manufacturing a prototype. As a result of this meeting, the group then completed and
submitted an Invention Disclosure Form (IDF), which is included in the Appendix (section B).
After submitting the IDF, the group filed for a provisional patent. The provisional patent
application is located in the Appendix (section C).
Prototyping
Our contact at Yanke Bionics has been Jerry Bernar. While Yanke Bionics does not directly
manufacture liners, Jerry said that they can send the CAD file to one of their partners, Otto
Bock, in order to manufacture a prototype of our current design.
However, due to some issues during transferring the stl. file into the software used by Yanke, it
was discovered that it was not possible for their company to produce a liner with channels on
the inner surface. Therefore, StepOne Medical decided to simply use the four liners that were
previously donated by Yanke to make the prototype. Prototyping of the device took place in the
Olson Research Lab at the University of Akron as well as in the ABIA Medical Device
Development Center prototyping lab.
In addition to these prototypes, project engineer Samantha Stucke from the MDDC agreed to
work with the team on another model. With her help and the 3D Eden Printer at ABIA, a scaleddown 3D prototype of the prostehtic liner with air channels was created.
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Conclusion
With the 3D model, the urethane prototypes, and the results from the Algor simulations,
StepOne Medical has successfully proved the concepts behind the initial project idea. The team
plans on presenting the project outcomes to the University of Akron Biomedical Engineering
Department on Wednesday, May 4 from 8:00 am until 12:00 pm in Olson Hall room 321. The
project sponsors from ABIA and contributing individuals from Yanke Bionics will be in
attendance.
In addition, this project could potentially become a commercial success if funded by the MDDC
committee. As discussed briefly, the group’s idea has been accepted by the MDDC and assigned
a project number. Currently, the project is being reviewed and considered for funding.
It has been the continued hope and desire of StepOne Medical that this project be used to
better the lives of the many individuals that require the use of a prosthetic limb.
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Appendix
A) Images
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B) Invention Disclosure Form
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C) UA #903 Provisional Patent Application, Prosthetic Liner with Air Channels: USPTO:
61/472,438
Description:
Prosthetic liner used for a lower limb amputation to provide comfort on the residual limb while
wearing a prosthetic device. This liner will be designed out of a silicon or urethane resin and
have several channels on the inside running vertically along the sides and converging to the
distal cusp. These channels will not run to the proximal edge, but will come within 1 inch of the
proximal edge of the liner to maintain suction of the liner onto the limb. There will also be
several evenly spaced circumferential rings around the inside to connect the vertical channels
for better air flow. At the distal cusp and on the circumferential rings, there will be several holes
to allow the intake and expulsion of air flow. The air flow may be generated by a pump, and air
flow direction will be controlled by one-way valves. Having these channels which allow airflow
to come through and contact the patient’s skin will result in a cooling effect of the patient’s limb
for a more comfortable fit, and will most likely result in fewer sores and blisters on the limb that
are caused by the heat and sweat generation that can occur with normal liners.
Claims:
Claim 1: Cooling of the skin will occur by utilizing air flow during the stance phase of gait.
Claim 2: Socket suspension through the use of negative pressure will be achieved during the
swing phase of gait.
Claim 3. Liner will have one way valves that permit air to flow during various phases of the gait
cycle, and prevent air flow during other phases.
Claim 4. Air intake will be located either distally or proximally.
Claim 5. Air outlet will be at a location on the liner/socket opposite to where air intake occurs.
Claim 6. This system will work in conjunction with a pneumatic pump, but not be limited to
external pumps.
Claim 7. The initial design is meant for air flow to be between the skin and the liner. However,
cooling can also be achieved by having air flow between the liner and the socket.
Claim 8. The material will either be silicone or urethane and its performance can be augmented
by including thermally conductive materials into the polymer.
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D) Gantt Chart
Tasks
Choose Project
Team Name
Strengths & Weaknesses
Mission Statement
Background Research
Team Expectations
Problem Statement
Team Logo
Customer Requirements
Functional Requirements
Constraints & Limitations
Brainstorm Solutions (Winter Break)
Share and Discuss Solutions within Group
Share and Discuss Solutions w/ Others
Choose Best Idea(s)
Finalize Characteristics of Design
3D CAD Design
MatLab Heat Transfer Model
Algor Simulation
Contact Yankee about manufacturing
Tech Transfer and Provisional Patent
First Prototype
Device Testing
Refine Device Design
Finalize Documentation
Complete DHF
Finalize Design
Start Date
Duration (days)
9/16/2010
7
9/23/2010
19
9/30/2010
5
9/30/2010
12
10/5/2010
30
10/19/2010
7
10/28/2010
7
11/4/2010
5
10/21/2010
19
11/9/2010
14
11/18/2010
5
11/24/2010
47
1/10/2011
28
1/23/2011
15
2/7/2011
7
2/14/2011
14
2/28/2011
14
2/28/2011
14
4/4/2011
14
3/14/2011
21
3/18/2011
20
4/4/2011
7
4/15/2011
14
4/15/2011
14
4/1/2011
21
4/14/2011
7
4/22/2011
7
End Date
9/23/2010
10/12/2010
10/5/2010
10/12/2010
11/4/2010
10/26/2010
11/4/2010
11/9/2010
11/9/2010
11/23/2010
11/23/2010
1/10/2011
2/7/2011
2/7/2011
2/14/2011
2/28/2011
3/14/2011
3/14/2011
4/18/2011
4/4/2011
4/7/2011
4/11/2011
4/29/2011
4/29/2011
4/22/2011
4/21/2011
4/29/2011
25 | P a g e
26 | P a g e