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National Runner Up

Arcx

An innovative below knee prosthesis that mimics the human gait

  • The final design of Arcx - An innovative below knee prosthesis that mimics the human gait

  • User testing both the functional model (left) and the aesthetic model (right)

  • Key selling points – stability, walk & run, Personalized, ankle freedom

  • The different elements of Arcx

  • Process pictures

What it does

Arcx is an innovative prosthetic foot for below-knee amputees. The design allows users to experience daily life with minimal concessions by providing an adjustable ankle hinge, enabling both running and walking and giving extra comfortable sideways stability.


Your inspiration

A problem in the current segment of below knee prosthetics is that the available prosthetics in the lower price segment lack functionality, however prosthetics with advanced functionality, like bionic feet, are too expensive for most users and not covered by insurances.The aim of our project was to design an affordable modular below-knee prosthesis that allows users to experience their active daily life with minimal concessions.The design has been inspired by observing active users in their daily life, noticing that they are held back by their current prosthetics or carry around an extra prosthesis to be able maintain their active lifestyle.


How it works

Arcx has been provided with an adjustable ankle design. With one click the angle of the ankle can be adjusted to an optimal angle, which enables the user to walk, cycle, drive a car and run with the same prosthetic comfortably. In current prosthesis the foot is locked in one position, 90 degrees making most of these activities difficult or even impossible. Besides the hinge the carbon is also provided with an innovative crossing toe. This makes the sideways movement of the foot outward more flexible than the movement inwards. This function offers more stability and standing comfort and comes closer to the human foot. The carbon is also provided with an extra heel spring which gives a forward push when walking, ensuring more energy return when walking. Lastly current below knee prosthetics are provided with a rubber cover that looks like a human foot, which does not look very attractive. We redesigned the foot into customisable covers that have their own look.


Design process

We started our process by asking ourselves the question “how might we design an affordable modular below-knee prosthesis that allows users to experience their daily life with minimal concessions”. To find out what that meant we mapped out the daily journey of the prosthesis user, highlighting emotions, actions and difficulties. Using rapid prototypes basic principles were tested. These prototypes evolved from simple paper and cardboard models into 3D printed prosthetic feet that each were designed to test different innovations. The 3D printed prototypes have been tested to see how their energy is stored and relieved during gait and to test their stability using a pull-out couch. Also the ankle hinge was tested for ergonomics and safety. Meanwhile 3D models were developed to perform more advanced simulations. Simultaneously the aesthetics of the below knee prosthesis were analyzed and redesigned. Using the input of prosthesis users on different concepts. Using their insights we came to the solution of a customizable cover. To be able to validate our final concept the final prototype was split up in an aesthetic model and a custom made prototype for our end user to test. The first reaction: “This feels like a liberation, it has been 15 years since I was able to sit normally”.


How it is different

According to our research there is currently no product available in the lower price segment that covers all functionalities that Arcx has to offer. The ankle hinge in combination with the carbon design enables the user to both walk and run with the same prosthetic. Currently users have to carry an extra prosthetic with them in order to be able to do medium impact sports. Also the ankle hinge allows the user to sit, drive and move in small spaces comfortably. Currently adjustable ankles are only seen in bionic feet, which are very expensive and not designed to switch to faster activities, such as taking a sprint. Arcx is designed for a much lower cost price of around 1000 euros. Another important aspect in the design process was designing for the total product experience. As the prosthesis really becomes a part of the user’s body the aesthetics have a huge influence on how the product is experienced.


Future plans

The Arcx was designed for YES!Delft start-up Gyromotics. Based on our design Gyromotics further developed and patented the ankle hinge and overall design. Their goal is to bring the prosthetic to the market in the lower price segment as soon as possible.


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