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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 LinerMaterials Choices Silicone Polyurethanes Spandex fabric for interface between socket
and linerDesign Issues Variable Thickness Shape Choosing Material- Use ATR FTIR to determine
chemical composition of current liners
Fiber Matrix
Materials Choices Kevlar Nylon Carbon Fiber Fiberglass
Design Issues Density Orientation Adhesion to
elastomer Fiber Length
Fiber Purchasing Information
ProductMolecularFormula MW Company Product Description Price Product #
Kevlar C14H10N
2O2238
gEdmundScientific
600 yard spool 1mm dia $49.95 3034863
NylonC12H22O
2N2226
g DuPont 200 yards, 0.5mm dia $19.95 350-96-T729
Fiberglass SiO2 60 gFiberglass Supply
Style 1522, 3.7 oz./yd.² X 27", E Glass, Plain Weave, Roll
$2.21 per yard C03-1039
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 DippingOther 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 prosthesishttp://www.instron.us/wa/products/universal_material/3360.aspx
Gantt Chart8-Feb 15-Feb 22-Feb 1-Mar 8-Mar 15-Mar 22-Mar 29-Mar 5-Apr 12-Apr 19-Apr 26-Apr 3-May 10-May 17-May
Researchmeet/call Brucevisit NOPCOVisit Prosthetist
Liner designinvestigate designsdesign modelMaterial purchasesprototyping
TestingTensile testingField testingFatigue testing
DeliverablesGroup Formal Design Group PrototypeMid-term Group Final