Champaign-Urbana Community Fab Lab
Champaign-Urbana Community Fab Lab

Iteration Project: Make-a-thon Participation

During the week of the Iteration assignment, I opted participating in the Make-a-Thon.

My team was named “MOVI” and the goal was to design a protective guard for a prosthetic leg. Prosthetic legs are very sophisticated and are extremely valuable. Yet those products are worn at the part of our body with the most movement and thus are exposed to scratches, impact, and lots more other threats in daily life. The reference model, C-leg, cost more than $100K. It has been a pain point among users, especially the active ones. To make the matter worse, people wearing only one of these are told to fell on the prosthetic side when imbalanced. Because, falling to the other side will make it rather difficult, if not impossible, to get up by themselves.

There are some prosthetic leg covers in the market. But most of them are like the same model: a dull thick bulky black cushion covers every section of the prosthetic leg. This leads to a problem, apart from the aesthetics, the back of the prosthetic knee is an area filled with delicate moving parts. The bulky protective sleeve covers that area and makes it very difficult to bend the knee.  

 

Thus we got the needs of users:

  1. easy for putting it on-and-off
  2. protection against scratches
  3. cushioning of physical impact (mostly in case of a fell)
  4. not blocking knee flex
  5. good looking

 

Our team started the design with a 3D scanning of the prosthetic leg. The model was then printed using three 3D printers and glued together. 

For the prototype, the team proposed a solution combining a hinge in the front and straps in the back for the top need. The user reported that the phase 1 prototype lacks coverage of the leg. So we created the phase 2 prototype, just to specify the max area of protection that is necessary, considering need 2, 3 and 4. Therefore, we’ve combined the two prototype together and came up with the final design. 

The final design adopted the hinge-straps design and used a two-layer solution for protection and aesthetic needs. A hard shell with patterns is put on the outside. In the future, users should be able to customize and switch the shell for their taste or even the mood at the moment. Two pieces of cushions are fixed inside of the shell. Each cushion used a heavy fabric cover with foam pads inside. To help further protect the user, we’ve inserted a layer of sheet metal between two layers of foam pads inside the cushion. Two extra cushion pads are added to the top for knee protection. Two straps go through holes on the shell. We fixed velcro strips onto the straps. 

 

Our team was well-paced during the make-a-thon, and each step was well executed throughout the event. After rounds of presentations and expert review, our team got the championship of the competition. 

 

During the event, I helped in the 3D printing post-process, and led the efforts in the fabric department. Cleaning and gluing the PLA parts were rather easy with the training in class. But I’ve got quite some challenge in the sewing part. I was quite confident before going into it. It was not long before I recognized the challenge. The cushion pad was of an irregular shape, with five corners of varied angles. And there was a significant thickness. For solving this problem, I design the two piece of fabric of different sizes, with all the side panels included in the front piece. While sewing the corners, Duncan gave me some useful tips. Cutting off some fabric inside the corner is key to a smooth outside. I’ve got some of them right, some of them not so. 

Just when I felt a relief finished sewing the cushions, there came the straps. “It’s just an extended square, not so different from the little pouch we’ve done in class!” That thought was so wrong. The fact that we’ve chosen a waterproof rubber coated fabric and a very thin strap width made the task very challenging. Flipping the strap inside out was not far from a mission impossible. It was a combination of stick and brutal force and dedication that helped me finished those two straps.

 

I am very happy about the results, and the fact that our team has developed something useful in real life. 

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