What it does
A functional prosthesis developed to aid trans-tibial amputees when swimming. It is digitally customisable and helps the amputee walk to the pool, dive in, and swim with recreated anthropometric symmetry that is lost due to an amputees imbalance in water.
The need for a swimming prosthesis was identified by the New Zealand Artificial Limb Service. A prosthesis that also allowed the user to get to, and into the water was identified by the researcher after observing the difficulties of an amputee getting to a pool. This project is a great example of a student working with real world partners to fulfil their needs whilst also innovating and developing the project beyond the initial brief.
How it works
A digital system to and prosthesis prototype that uses a suction socket and flexible interior fin to help amputees swim, and a rigid sleeve that clips over the socket for walking to and from the pool. First the amputee's limb is scanned using a handheld 3D scanner. Some manipulations are made for a good socket fit. This scan is then imported into a parametric CAD file that has custom built processes to take the geometry of the scan and construct the prosthesis around the amputee's limb for the perfect fit. The first parameter the user/prosthetist decides is the thickness of the socket, with a 5mm default. Then the size, thickness, length and asymmetry of the fin can be adjusted to meet the users needs. Finally the exterior sleeve can be adjusted to the right height and to correct alignment. The file outputs a flexible fin and rigid socket for the interior fin and a rigid sleeve and soft grip for the exterior sleeve to be FDM 3D printed.
The design process was heavily human and user centred. Initially interviews and observation were undertaken to help me really understand what made swimming difficult as an amputee. This uncovered many details of the difficulty of not just swimming, but getting to, from and into a swimming pool. User testing was the most important tool for understanding the benefits and limitations of prototypes. As few examples of FDM printing of flexible materials exist large amounts of iterative testing were undertaken to refine this as a technique for fabrication. The amputee's limb was 3D scanned by researchers and a prosthetist from the NZALS. This measurement was also compared using alginate casting and scanning the amputee's walking socket. Prototyping relied heavily on sketches, card and clay modelling followed by CAD modelling and 3D printing. Hundreds of maquette models and test models were printed with 5 major prototypes being developed during the research. Prototypes helped resolve techniques used for measuring the limb, hydrodynamics, structure and walking and lastly the visual communication of the form and aesthetic details.
How it is different
Unlike previous swimming limb concepts, this is a fully functional prototype. It is rare that a master student concept overcomes all of the nuances and details of development and is ready to be tested by professional entities. This prosthesis has invigorated the user's interest in swimming by giving back his independence and making time in the water a far more enjoyable experience. It uses anatomical referencing not to replace or "fix", but to enhance his experience, imbue pride and confidence in his body whilst helping those viewing the limb to understand the form and it's purpose. It helps encourage him to keep fit by swimming which reduces the risk of cardiovascular disease, a major issue among amputees.
The prototype is ready to undergo prosthetist testing and further user testing with a larger group of amputee swimmers to help finalise default measurements, parametric ranges and fin customisation. With investment into a large format 3D printer the concept would be a viable, economical and sustainable product that can easily be customised to allow for confident and independent swimming by trans-tibial amputees.