Technology Father prints arm for amputee son

Editor: Rosemarie Stahl

3D Printing – To avoid the wait for a state-developed version, a father decided to design and produce his own 3D printed hydraulic arm prosthesis for his two-year old son. In the end, his version was cheaper and more time-efficient compared to traditional methods.

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Two-year-old Sol with his fully-functioning Stratasys 3D printed hydraulic prosthetic arm, which enables him to move his thumb on his own.
Two-year-old Sol with his fully-functioning Stratasys 3D printed hydraulic prosthetic arm, which enables him to move his thumb on his own.
(Source: Ambionics)

The 3D printing and additive manufacturing company Stratasys has announced that its multi-material, multi-color Poly-Jet 3D printing technology has enabled Ben Ryan, founder of Ambionics, to create a fully-functioning 3D printed hydraulic prosthetic for his two year old son, Sol.

Researching infant development with prosthetics, Ben Ryan has developed a unique prosthetic for infants to wear, enabling a more natural acceptance of prosthetic arms for young children. The customised design and production of the 3D printed hydraulic prosthetic has delivered cost savings of up to 76%, as well as time savings in design and production of 90%, compared to traditional methods of manufacture. This crucially permits prosthetics to be used at an earlier developmental stage, the company says.


When Ben’s son, Sol, was born in March 2015, complications resulted in the amputation of his lower left arm. Although able to keep approximately one inch of his lower arm, Sol would have to wait three years for a myoelectric prosthetic from the NHS (UK National Health Service), and one year before a cosmetic, non-functional prosthesis would be fitted. Ben saw his son losing responsiveness and acceptance of his left arm, and decided to act.

Having undertaken extensive research into infant development, Ben saw that higher rejection rates occur when children are fit after the age of two years and that early fitting of functional devices correlates with continued prosthetic use throughout childhood. Another study also found that children fitted before two years of age tend to accept their powered prosthesis more than those fitted after two years. With this in mind, Ben first designed a foam arm for his son, and later a hydraulic prosthetic, enabling Sol to move his thumb on his own.

Ben designed and created his 3D printed hydraulic prosthetic arm on the Stratasys Connex 3D Printer. First practicing with prototypes of his design, Ben 3D printed flexible actuators and a power-splitting unit (double acting helical bellow or DAHB) for the prosthetic. According to Ben, the DAHB unit enables the wearer to open and close the thumb in manual mode or with assistive power (using compressed air or a hydraulic pump and reservoir), but the grip continues to operate manually in the event of power interruption.

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