Our team is part of the Digital Making Seminar Class at the University of Illinois Urbana-Champaign led by Professor Vishal Sachdev. This semester (Spring 2019) we worked on developing a C-Leg Prosthetic cover for our mentor Jenna. Our goal was to build a cover that safely protected her prosthetic, reduced the weight of her current cover, and had a less-buky attachment mechanism at the back of the cover to increase the leg's range of motion. Here is our DIY step-by-step guide on how to make your own prototype!
Step 1: Step 1: Gather Your Materials and Resource
- Super Glue
- Tough Nylon - 1 square yard
- Large Hinge - 15 inches
- Acrylic Sheet - 15 inches by 15 inches
- Velcro - 30 inches
- Inner padding (we used styrofoam, but you can use Silipos Relief Padding)
- Volleyball Knee Pad (Optional)
- Sewing Machine
- 3D Printer OR Laser Cutter, Acrylic Heater, and Heat Gun
Step 2: Step 2: Scan the Leg
We found it very helpful to make a 3D scan of the individual C-Leg. We used a scanner app to convert the image to a .stl file. Our mentor was out of town during our prototyping session so we 3D printer her scanned leg to use for her prototype. Even if you plan to prototype on your own leg, it still will be helpful to scan your leg if you plan on 3D printing because you can build your model design on the actual contours of the scan.
Step 3: Step 3: Choose and Print Outer Design
For our prototype, we created our design in Inkscape and then used a laser cutter to print out the design from the acrylic. You can customize your design however you want, but make sure to have two holes on the bottom edge of the design that will be big enough for velcro straps to hook through. Once we cut out the acrylic we wrapped the 3D printed prosthetic with about an inch of paper to simulate the foam we will add to the prosthetic later. We then used that acrylic heater and heat gun to heat the acrylic and then mold it around the paper cover.
If you don't have access to a laser cutter, acrylic heater, and heat gun, another option is to 3D print the outer cover. It is possible to use import a scan of the prosthetic to a 3D modeling software and then design a cover based on the contours of the design. Two good 3D modeling softwares are Fusion 360 and Solid Works.
After you have shaped the acrylic cover around the leg you will have to cut it in half from top to bottom. This allows us to insert a hinge that makes it easier for the user to take it on and off.
Step 4: Step 4: Build Inner Protection
The next step to building the prosthetic cover is to build the inner padding. We got tape and taped it along the outline of the leg. We then removed the tape, keeping the outline attached, and taped it to paper. We cut out the paper to have an outline of the pad we wanted to create and used the outline to cut out the foam and the tough nylon covering. For the foam padding, we used Silipose pressure relief padding. We sewed the tough nylon to make the cover and then put the padding inside. We used velcro to close the padding so that you can easily switch out the padding if you need to change it.
Like the last step, we need two separate halves for the padding and covering, so that they can be attached together with the hinge later on.
Step 5: Step 5: Make Straps
To attach the cover to the prosthetic we used velcro straps. We made straps of black nylon and sewed on velcro straps. We attached the velcro strap to two holes in the cover design and used them to wrap around the leg. The strap function similar to a watch loop, where one side is fully attached and sewn together and the other side is adjustable.
Step 6: Step 6: Add Everything Together
The final step is assembling all of your parts together. At this point, you should have two halves of an acrylic design laser cut or a 3D-printed cover molded in the shape of the prosthetic, two sewn nylon compartments filled with foam padding, a hinge, and two velcro straps. An optional addition is an upper knee protection pad. This is not necessary for the cover to work, but may add some extra protection. We used high-density foam, which can be taken from any volleyball kneepad, and cut two small segments to attach at the top of the acrylic.
We used super glue to first attach the acrylic cover to the hinge. Then we used super glue to attach the cover to the foam-filled nylon cushion. Finally, we attached the straps by sewing one side together through the loop on the hole in the design. Once you have completed these steps you should have a functioning cover for the prosthetic C-leg so feel free to try it out!