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Formal Design Review . Team 4 Limb-itless Chris Bruce, Anna Chen, Grant Hofmeister. Brief Update. Went to Dr. Miller’s prosthetist in NH Obtained plaster molds of Dr. Miller’s socket Obtained chemical composition of Liner. Problem Statement.
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Formal Design Review Team 4 Limb-itless Chris Bruce, Anna Chen, Grant Hofmeister
Brief Update • Went to Dr. Miller’s prosthetist in NH • Obtained plaster molds of Dr. Miller’s socket • Obtained chemical composition of Liner
Problem Statement • Redesign the transtibial prosthesis liner so that it is more comfortable. • Improve the load distribution of prosthesis to lower pain. • Allow for athletic use and volume changes during the day. • Decrease the “play” between the stump and the liner– make prosthesis easier to control.
Design Focus • Focus on liner design • Socket redesign is not within our scope and timeframe. • Liner has more interesting material issues. • Great potential for advances in liner design. • Within liner, focus on suspension. • Less focus on accommodating volume change and other issues.
Evolution of Design Initial Ideas • Magnets • Negative Poisson Ratio Material • Graded Elastic Modulus We will focus on the graded elastic modulus solution to improve the load distribution and “play.”
Design Plan • Elastomer liner • Anisotropic Fiber support matrix • Pin attachment for connection with socket. Cross-section
Elastomer Liner Materials Choices • Silicone • Polyurethanes • Spandex fabric for interface between socket and liner Design Issues • Variable Thickness • Shape • Choosing Material- Use ATR FTIR to determine chemical composition of current liners
Materials Choices Kevlar Nylon Carbon Fiber Fiberglass Design Issues Density Orientation Adhesion to elastomer Fiber Length Fiber Matrix
Pin Attachment Materials Choices • Steel • Aluminum Design Issues • Compatibility with existing socket • Integration with liner
Production of Liner Techniques • Mold with offset center • Include fibers and pin in mold design • Sew sheets together • Dipping Other Issues • Fabric Adhesion
Risks • Liner-fiber adhesion • Delamination • Puncture of liner by fiber • Fabric adhesion • Variable thickness of liner • Controlling orientation of the fibers • Incorporating pin into liner
Testing and Analysis • Tensile testing in multiple directions • Fatigue testing • Qualitative field testing with Dr. Miller • Comfort • Load distribution • Control of prosthesis http://www.instron.us/wa/products/universal_material/3360.aspx