Project Overview

Problem Overview

Prosthetic devices aim to alleviate the frustrations associated with loss of limb; however, the service of this primary goal leads to collateral problems. One such problem is skin irritation that exists at the interface between the skin and prosthesis. This is not merely an inconvenience, which alone should warrant a solution, but a tangible threat to the health of the prosthetic user. It is known that the skin coming in contact with the prosthetic device is at a higher risk of irritation, skin deterioration, and infection. Skin breakdown can cause blood vessel disorders and even the emergence of diabetes. In other cases, the individual may lose the ability to feel pain, which can turn an infection into a potentially life-threatening dilemma (The Merck Medical Manual, 2011). It is clear that perspiration at the prosthesis-skin interface is a concern, which is caused by inadequate permeability of current prosthetic devices and stagnant air flow in the prostheses.

Figure 1: Sores caused by a lower limb prosthetic

Design Constraints

Prosthetics are unique in the fact that they are an integral part of someone’s life on a daily basis. They are not a luxury but a means to functioning at an effective level. This generates several constraints: durability, reliability, weight of the design, and cost to manufacturer. The design must be durable to the user, otherwise the product will need to be continually replaced and prove to be useless over the long haul. Along the same lines, the product must have a replicable result. Reliability of product is a critical aspect of the design, and will grant users peace of mind. Another factor to consider is the overall weight of the finished product. The human arm can only withstand substantial weight for so long, before the muscles tire and give way. Due to this physical restraint, the prosthetic byproduct has to be as lightweight as possible. Finally, the idea of budget comes into play. Although the design has lofty goals, the designing process was limited by how affordable materials were.

Pre-Existing Solutions

When given a prosthetic it is recommended to put baby powder in the device to help ease it on. However, if worn for long periods of time, the baby powder soaks up the moisture and sweat in the device and then there is no other way to keep the moisture from building up.  Additionally numerous professionals in the field of prosthetics have designs on the market. Majority of these products consist of silicone gel, and those that do not are usually comprised of the substance urethane (Joan E. Sander, 2004). These substances demonstrate enhanced breath-ability, and there is already an existing U.S. Patent for a liner that boasts protection from moisture retention from prolonged wear (Jean Norvell, 1996). While pre-existing solutions to the problem are available, they all focus on the avenue of biomaterials rather than a mechanical approach to circulating air through the prosthetic in question.

Figure 2: Lining material for use with prosthetics and similar devices.  US Patent, 5,480,455

Design Goal

The design goal of the engineering group is to retrofit an existing prosthetic device with a small-scale ventilation system that can facilitate the evaporation of sweat and moisture from the skin-device interface and alleviate skin irritation.

Project Deliverables

The air circulation system design will target a wide range of prosthetic devices that cause uncomfortably and irritation at the contact area between the skin and prosthetic. By aiming to subdue the irritation that arises from wearing the prosthetic on a daily basis, other more severe issues that can arise will be resolved. Foremost, perspiration at the contact site of the skin and the prosthetic will be lessened by providing a means of air circulation. From this, irritation at the contact point will be less likely since sweat is not building up. By providing a constant flow of air, the skin will still be able to breathe despite the impermeable material of the prosthetic resting on the skin. With less irritation occurring, the skin will less likely be rubbed raw, which in turn could cause infections at the contact area. By lessening the chance of skin irritation and deterioration to occur, the risk of other severe medical problems, such as diabetes, will be decreased greatly as well. Overall, providing ventilation in prosthetic devices will not only improve the everyday comfortableness of wearers but it will also minimize the likelihood of long term issues that could arise if irritation becomes a persistent problem.

Project Schedule

Week 3: Experiment and research different ways in which air can be circulated in tight spaces, sketch ideas
Week 4: Begin working with materials to create an air circulation system that is small enough to not irritate the way a prosthetic fits
Week 5: Start creating a prototype - build/install a small fan/pump into a prosthetic
Week 6: Continue work on the prototype
Week 7: Make finalization to the prototype
Week 8: Test the prototype
Week 9: Make alterations to the prototype after having the results of the test
Week 10: Finalize the design and present

Project Budget

For the design there are two major areas that need to be budgeted, the prosthetic that the system will work in conjunction with and the actual circulation system that will be built into it. The former will be provided by the Shriner's hospital, a hospital that specializes in prosthetics based in Philadelphia. The air circulation system will be made from scratch after analyzing an existing model. The following are the prices  for the respective pieces of the circulation system:

Air pumps: Roughly $10-25
-Pumps range from battery powered to mechanical to plug-in versions. For the purposes of this design, the pump will need to be smaller than what can be purchased and may not be of the plug-in version.  the pump will merely serve as a template on which to base our version.
-Source: amazon.com

Medical Miniature Tubing: $7-35
-Tubing comes in a variety of sizes, all of which can be fit to the pump in the design process. For the purposes of the design the smaller sizes will be utilized,
-Source: http://www.amazon.com/dp/B003TJ9YGU/ref=biss_dp_sa2