Formal Design Review

Team 4Limb-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 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

Clear Liner

Clear Liner- Library Match

White Liner

White Liner- Library Match

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