Open Source Prosthetic Hands Focus on Function and Personality

3D Printing & Imaging Arduino Biohacking
Open Source Prosthetic Hands Focus on Function and Personality
Exiii's Tetsuya Konishi, Genta Kondo, and Hiroshi Yamaura
Exiii’s Tetsuya Konishi, Genta Kondo, and Hiroshi Yamaura

A month or so back, a Japanese company called exiii publicized its HACKberry 3D printed myoelectric prosthetic arm. With the help of Wevolver, an online platform for project documentation and sharing, exiii shared the plans as open hardware, encouraging Makers and hackers to build their own versions. Last week, upon reading a request by a Reddit user for workout regimes for his recent-amputee brother, Wevolver’s Cameron Norris responded by offering the poster’s brother a custom printed aluminum version of HACKberry.

It wasn’t even a technology subreddit; Norris was in r/fitness. “I’m sitting here with six 3D printers in the room, thinking, I should do something about this. I’ve got the means, why not?” he says.

The arena of prosthetic limbs is one of many examples of the way 3D printing and other increasingly accessible DIY technologies are helping drive innovation. From fashionable wear on the runway at Maker Faire Bay Area to Nicolas Huchet’s adaptation of the InMoov arm for his own hand, printed prosthetics are beginning to flood what was once a highly expensive medical device market with DIY options that are not only affordable, but customizable and even fun.

Exiii’s version focuses on precision, as well as open hardware — Wevolver maintains a repository of the project plans and code. “I get pretty furious when I think about how patents are preventing people from accessing technology that will change their lives,” says Norris, whose grandmother had a paralyzed right arm. “She used to joke all the time about getting a robot arm,” he says. “It just kind of stuck with me, it’s been something I’ve always dreamed about.”


In addition to 3D printing, building a HACKberry involves some wiring, myoelectric sensors, an Arduino, and detailed information about the limb to which it will fit. For this particular build, Norris plans to use RepRapper Tech’s new aluminum-filled PLA (about 30% aluminum), which should make it stronger and more durable, but also add to the “wow” factor (says Norris) that’s already strong with the HACKberry and 3D printed prosthetics in general.

“We are focusing on appearance,” says exiii CTO Hiroshi Yamaura. “We make it look stylish instead of imitating a natural hand. We would rather express one’s personality than conceal disability.”

Their functionality is impressive, too, though for Norris, the practical is far more powerful than the stuff you might show off. “There’s a lot of flashy tricks, I mean, you could have the wrist spinning around and glowing different colors, but that doesn’t really make a difference to someone’s everyday life,” he says. His most powerful impression of the device is of a guy simply tying his shoe. “I think it’s things like that that help people remain independent. They’re the things that really matter.”


These tools are not only becoming more available, they’re becoming more complex and more functional — Huchet’s arm and Joel Gibbard’s Open Bionics project also use myoelectric sensors to pick up electrical signals on the muscles of the limb. At the same time, they’re becoming more accepted, highlighting individuality and style over blending in.

And while the Maker community is leapfrogging medical devices in price point and functionality — compare these to extremely expensive medical prosthetics, or non-functional rubber appendages, or metal hooks — scientists are still working to develop new means of control. Facial expressions, galvanic skin response, and brain waves combined — as has been explored in VR — exceed the control available via EEG alone. According to a study published Monday in Nature Nanotechnology, scientists are also studying a flexible electronic mesh that is injected directly into the brains of mice as another possible way to aid in brain control of electronics.

Exiii does have a more agile, more expensive version that is not open source, a device called Handiii that incorporates a smartphone to process the EMG (electromyographic) data. “The purpose of disclosing HACKberry is to accelerate the development,” says Yamaura. “We have to improve its quality (particularly its durability) with the developers around the world.”

You can read DoctorSpacemann’s full story on Reddit. Also, Norris says that Makers who are interested in learning more or making their own should go to Wevolver and download the files: “If you’re interested in getting involved with prosthetics, with 3D printed robots, you just do it. A lot of people seem to be looking for permission to get involved, and it’s not like that, it’s always completely open.”


Photos: exiii

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Nathan Hurst is an editor at Make. He loves anything having to do with science or bicycling. He tweets as @nathanbhurst.

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