Note: This text is a work in progress. If you find any inaccuracies or material that needs to be included, please contact us.
Prototypes
Our first prototype of this idea was simply testing the mechanism with a commercially available product called FLEXO Expandable Sleeving from TechFlex, Inc. This material is basically biaxial braided sleeving in a variety of materials. We tried the 2.5” PET material and the 4” Heavy Wall material by sliding them over Jon’s stump and pulling on them. The 2.5” material gripped well, and would comfortably support loads without slipping. Here’s a picture of the sleeving on a simulated stump (rubber wrapped on a cylindrical carton) and a picture of Jon testing it.
The material needed at least 8-10 inches of engagement with the stump before it gripped properly. It would be more widely useful if it could grip a shorter residual limb, and it seems we might be able to do this by changing the material and/or geometry of the braid. Clearly this material is not as frictionate as it could be, since the monofiliments it is made of are very smooth and slick. Also, it would be desirable to be able to wick moisture away from the skin instead of retaining it on the surface of the fibers. The pitch of the braid may also be important, since it controls to some extent the proportion between pulling force and contracting force. A better fit would help as well, since the diameter of the stump at any given point affects the effective pitch of the braid at that point. An additional issue is dealing with the movement of the elbow or knee.
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