GUBING WANG
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Endura 2.0
Problem Breifing
The conventional prosthetic sockets cannot meet the needs of lower-limb amputee athletes in two aspects; Their high activity level leads to residual limb expansion and sweat accumulation in the socket, which greatly influences their performance.
Endura, a novel trans-femoral prosthetic socket, was designed to tackle these two problems previously, however the design is not strong enough to withstand the body weight. The object of this project was to further develop Endura, which would allow for radial adjustability of the socket and also incorporate a sweat management system.
Interviews and Insights
We gained representative insights from our two main user groups from interviewing Andrew Lewis (Paralympic triathlete) and Gillian Conway (Prosthetist).
Andrew showed the amount of sweat he can spill out after one hour of cycling, which is about 70ml. The current liner he is using costs £253 and he is willing to pay £500 for the new liner with sweat dissipation ability. [The liner is a protective cover worn over the residual limb]. Gillian pointed out another cause of residual limb volume fluctuation is postoperative edema and the following muscle atrophy, so another big user group would be new amputees.
Later on, we brought our finalized sketches to UK's first-ever Para-Triathlon to ask feedback from more amputee athletes and discuss the design with Prosthetic Specialists from Ottobock. The amount of sweat produced and muscle expansion varies a lot from person to person, and the locations of muscle expansion vary. Some athletes are satisfied by their current prosthesis so far. We observed some athletes removed their prosthesis after races, and their replies are that they will feel more relaxed by doing so.
My task involves: literature research, preparing interview questions, communicate with interviewees, record and interpret their replies and behaviours.
Ideas Exploration
We think of a variety of concepts initially and check each concept against the design requirements (functional, comfort, durability, manufacturing)and selected the most suitable design.
My task involves: brainstorming and written up design requirements.
Final Design
The final design consists of a specially-shaped CFRP shell, a channeled silicon liner, a magnet attachment system, one air expulsion valve, one sweat expulsion valve, and Boa Closure System.
The open design of the socket shell improves ventilation around the silicon liner, and the flexion of its two sides accommodates muscle expansion. The shape of the shell is optimised with the help of finite element (FE) analysis, and it is designed to be manufactured via a wet layup or prepreg lamination.
The shallow longitudinal channels on the inner surface of the liner facilitates movement of the sweat to the bottom of the liner and get outside of the liner through the hole at the bottom. Considering a liner is changed every 4 months, the sweat expulsion valve is attached to the shell to lower the manufacturing cost of the liner.
A pair of ring magnets are attached to the edge of the hole on the liner and the sweat expulsion valve cap respectively, which guides the correct alignment of the liner in the shell and forms the path for sweat expulsion, and partly provides suspension.
The suction suspension has been used in the current prosthesis and is created by expelling the air in the socket through the air expulsion valve when the amputee is donning the socket.
The valve used for sweat expulsion is a reed valve, and it is attached via adhesives to the inner shell. While the athlete is active, the pistoning action of the residual limb pushes the valve to open to expel the sweat.
Boa Closure System, a rotary ratchet cable tensioner, was selected for its validated design, robustness and usability. It can be replaced easily by the user and its tightness can be adjusted on-the-go. The three tensioners can be adjusted independently so that it accommodate the variation in locations for muscle expansion. The Boa Closure System combining with suction and magnet locking will provide sufficient suspension for the athletes.
My task: FE analysis
Prototyping
The socket (1/3 of its original size) and the sweat expulsion system (cross section) was prototyped using 3D printing. The Ultimaker 2 was used for its low costs and reliability. PLA was chosen as the printing material instead of ABS for its higher geometric accuracy and better sandability.
My task: 3D printing machine troubleshooting