For those who doubt that 3D printing has the possibility to change lives, perhaps 9-year-old Raimi’s story will convince you. The young girl was born without her right hand and part of her right forearm and for years her family struggled to find an affordable and functional prosthesis for her, especially as she required one that did not rely on a wrist for function. In a continued effort to help his 9-year-old daughter, Raimi’s father posted a request on Facebook, asking any developers or engineers for help in finding a solution. Fortunately, maker Patrick Joyce saw the request and decided to help Raimi by creating a 3D printed bionic arm designed just for her.
Of course, a number of open-source 3D printed prosthetics for children already exist through organizations like e-NABLE and OpenBionics, but as Joyce points out, many of them are designed to be operated through a functioning wrist, which Raimi does not have. Nevertheless, Joyce researched these existing models, and drew inspiration from two open hardware below the elbow prostheses, which he found useful but a bit too basic. Finally, the maker decided to create his very own design for Raimi.
As he explains on his page, Joyce had a number of criteria he wanted to fill in designing the functional bionic arm. The basic concept was “to create an open source, low cost, high functioning, bionic arm and hand for children with foreshortened forearms” and this involved having an arm design that was completely open-source, that was capable of four different grip styles, that had a rotating wrist joint, could be controlled by myoelectric sensors, and could be made for less than £300 ($433) at home. Additionally, because it was designed for a child, the prosthetic hand would have to be lightweight, and ideally could be adapted for a growing child.
Joyce started the design process in December 2015 by making several iterations of a single finger, operated with servo-actuated tendons. Within a month, and on the 14th prototype of the finger, Joyce had found a functioning design and went forward with designing the rest of the hand. In order to fit his system into a child-sized hand, the maker decided to use only three actuators (one for the fingers, and two for the thumb), and a whiffletree system for the finger tendons which was inspired by an OpenBionics design. Joyce explains that he included two actuators for the thumb to allow for increased function, saying, “Having independent control of both thumb joints, will enable the hand to do a number of different grip styles.”
The key elements of Joyce’s children’s bionic arm design are the following: a 3D printed articulated hand, controlled by tendons attached to the wrist, a 3D printed forearm equipped with three actuators, a 3D printed socket to fit onto Raimi’s arm with a rotating wrist section, a belt mounted control pack, and a cable connecting the control pack to the arm. The control pack itself is equipped with a Lipo battery, a power supply module, Arduino, a Myoelectric control module, and an Oled display system for Raimi to see the controls and system status.
Joyce also decided to equip the Oled display with a clock, saying “I believe that a bionic arm shouldn’t try to be a biological arm, but rather try and emulate the functionality of a biological arm, whilst adding any features that technology offers that biology can not. My bionic arm is never going to be as good as a human arm – but how many other kids will have arms with built in clocks!”
Joyce’s dedication to the project and to improving young Raimi’s life is inspiring, but what is particularly touching about their story is that Joyce is actually a quadriplegic, who has been suffering from MND/ALS for the past eight years. Despite his own limited movements, Joyce has been able to accomplish something many people with full functionality could not, using an eye-gaze system and a joystick. Joyce’s design for Raimi’s 3D printed bionic arm was recently recognized as one of the winners of the first round of HackadayPrize2016. The entry was awarded $1,000.