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

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 Product Molecular FormulaMWCompanyProduct DescriptionPriceProduct # Kevlar C14H10N 2O2 238 g Edmund Scientific 600 yard spool 1mm dia$ Nylon C12H22O 2N2 226 gDuPont200 yards, 0.5mm dia$ T729 FiberglassSiO260 g Fiberglass Supply Style 1522, 3.7 oz./yd.² X 27", E Glass, Plain Weave, Roll $2.21 per yardC

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

Gantt Chart