How I Made My $250 Robotic Arm

Force does not come from muscles but from mutual assistance. Unity makes us stronger. I appreciate this because I am not shaped like Sylvester Stallone.

Since an accident with a hydraulic press 12 years ago, I wear a myoprosthesis — an electrical hand that I can control by muscle sensors. There are new models that are much better, but they are very expensive. I tried them all — from RSLSteeper’s bebionic to Ottobock’s Michelangelo — but even $50,000 models were lacking. It was a moot point; my favorite was not covered by health care.

At first, I thought this was unfair, that I would not benefit from the articulated, carbon-fiber fingers, the variable speed, 14 grip patterns, and myoelectric sensors on the bebionic. But then I remembered how lucky I was to have the version I had, thanks to decades of research and access to first-world health care. What about people without that access?

There are a few options. Alternative prosthetics — many 3D-printed, articulated, and open-source — built at universities, fab labs, and even companies, are beginning to fill the gaps. California-based Not Impossible Labs built a lightweight 3D-printed hand based on the open-source Robohand, which itself has been downloaded more than 9,000 times from Thingiverse. A loose coalition of volunteers called e-NABLE includes Robohand creators Ivan Owen and Richard van As, and boasts eight different designs as well as video tutorials for making them. Others are based on the hands of InMoov, the open-source, 3D-printable robot from France. It’s the basis for a design by Ananya Cleetus, a 17-year-old girl from Pennsylvania, for Help is at Hand, a robotic prototype she brought to the White House Science Fair. The Open BioMedical Initiative is working on several open-source hands of its own, and the Open Prosthetics Project shares dozens of designs, how-tos, and advice.

The list goes on. But I didn’t know about any of them. I didn’t even know about 3D printing.

In October 2012, while walking through Rennes, France, where I live, I passed an exhibition where strange machines, like something from science fiction, were depositing layers of material onto platforms. They were 3D printers.

I entered, asking “Excuse me, is it possible to make a robotic hand with this? Because I have a prosthetic hand.” Usually when people see my disability they try not to look at it or ask what happened, but their reaction was different. They were excited. They wanted to know how it worked. “We can download a robotic hand on Thingiverse and make the pieces with this 3D printer,” one said. “Here is one called InMoov, the guy is using Arduino and it’s open source.”

I didn’t understand a word they were saying. But I knew what they meant: It’s possible to design an inexpensive bionic hand that you can make yourself, then share your work so other people can improve it and share it further. I had discovered a world where we share knowledge much differently from this crazy world we are used to. I was looking at things differently; it was my revolution, my change.

We launched the project a few months later, in February 2013, with the LabFab in Rennes. But it was a truly international effort: printed digits from Rennes; muscle sensors from the U.S.; and design input from Brazil.
The foundation is a 3D-printed hand, equipped with actuators to move the digits and joints, fishing line to connect the actuators to those joints, muscle sensors and a socket where they rest, batteries, and an Arduino brain. It’s all built for a 
price around $250.

That’s a vastly lower sum than typical hands, which run from $8,000 to $80,000. For decades, a German company called Ottobock dominated the relatively small market. Touch Bionics appeared in 2003, and it built i-limb, the first prosthetic hand with articulated digits. Then RSLSteeper released the first of three versions of bebionic. DARPA pushed for advancements as well, due in part to a growing number of injuries from Iraq and Afghanistan. These devices have a few things in common, not least their articulation and multiple degrees of freedom.

For a low-cost hand to challenge medical-grade prosthetics, there are a few non-negotiable capabilities it must have. It has to be durable and reasonably lightweight, with an opposable thumb. It should reach a maximum open size at least large enough to grab a coffee cup or a water bottle, yet close precisely enough to hold a coin, a pen, or the cable to your headphones. It must grasp laterally — in a neutral position, like holding a key — and palm-down, as if to carry a suitcase. And it helps to design something fun to build and with an attractive aesthetic.

But first, we needed a prototype. Along with my collaborators from LabFab Rennes, I presented the first prototype, with 3D-printed plastic, some fishing line, and an old Nesquik box, at the Tu Imagines? Construits! festival in Rennes in June, 2013, with Gael Langevin, the creator of InMoov.

From there, things took off. We got invited to the first European Maker Faire in Rome. I learned how to use a 3D printer and we made a second slightly improved prototype. We got invited to Geek Picnic, a science and technology festival in St. Petersburg, Russia, and brought a third prototype to World Maker Faire New York.

Again and again, we were asked the same question: What’s that?

It’s a device for which there is great need. In the United States, insurance may pay for a prosthesis. In Colombia, they give you a hook; and in Russia, not much else. Spain is really suffering — kids have access to prosthetics, but often, adults won’t because of the price. And that’s not even mentioning emerging countries.

Bionico is not yet robust enough to be a prosthesis. It’s a prototype, but with it we’ve traveled the world as self-financed volunteers. So what do we do now? We may organize a crowdfunding campaign. We may look for sponsors who share our philosophy of a utopia of health for everyone. Above all, we want to create an international network and database devoted to improving low-cost prosthetics. This is an open-source project, which means you can participate or make it yourself. The prosthetic-hand field is very small, but if we build a bridge between countries and people, we can make it better and stronger, and go further, faster. As the American philosopher Sylvester Stallone said, “Big arms can move rocks, but big words can move mountains.”