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Want an extra arm? A third thumb? Check out these awesome robotic appendages

3D printing and robotics technology are responsible for some amazing work creating artificial limbs for people who have lost theirs. But what if you’re the greedy sort who wants, say, an extra arm, instead of just two? What if the idea of going through the rest of your life without a third leg is simply unimaginable? Don’t worry: technologists are ready to cater for you, too.

Here are five of the most fascinating extra appendages that exist in research labs right now:

Supernumerary Robotic Limbs
standing in doc oc suit

Perhaps inspired by the additional mechanical arms worn by Spider-Man villain Doctor Octopus, researchers at MIT have created a set of wearable devices called Supernumerary Robotic Limbs (SRL). Whether you’ve dreamed of having additional arms or extra legs, this could be the project for you.

“These robotic limbs can move independently from the natural arms and legs of the user, and therefore enable the execution of entirely new, complex tasks that would be impossible with only the four natural limbs,” researcher Federico Parietti told Digital Trends. “The SRL can also coordinate with the user in order to improve the performance or the safety of normal tasks.”

Possible use-cases include everything from handing workers tools or securing them to scaffolding, to helping elderly people to walk and avoid falls.

MetaLimbs: Multiple Arms Interaction Metamorphism (2017)

It’s a familiar situation: You’re tapping away with both hands at your laptop, when suddenly your phone rings. Do you momentarily stop what you’re doing, and reach over to pick up the handset lying directly next to you on the desk? Of course not: You get your robotic arms to scoop it up and hold it by your ear so you can type and talk at the same time.

Or, at least, that’s what you’ll do if the MetaLimbs created by University of Tokyo’s Inami Laboratory ever catch on. Controlled by a user’s feet and knees, the MetaLimbs allow users to move a pair of artificial robo-limbs around and even grasp objects — such as phones — with them.

Of course, you could just use the loudspeaker function your phone comes with, but where’s the high-tech fun in that?


We live in an age of global competition and 24/7 capitalism, in which the big winners are the ones who can carry out astounding feats of round-the-clock productivity. In such a world, having one hand on each arm simply isn’t enough. Fortunately, Italian “augmented human” startup YouBionic has stepped up to the plate with the introduction of (you guessed it!) its Double Hand prosthesis.

Powered by Arduino, the 3D-printed hands are attached to a gauntlet that’s worn by the operator. By moving individual fingers at different speeds, the user is able to control each robotic hand separately. There’s a bit of a learning curve involved to figure out all the movements the hands are capable of — but your boss will certainly appreciate the 100 percent increase in productivity that (presumably) results.

Brain-controlled limbs
BMI control of a third arm for multitasking

For supernumerary limbs to really find widespread usage, one thing they’ll need is an intuitive control system. That’s something researchers from the Advanced Telecommunications Research Institute in Kyoto, Japan have been working on. Their idea? A way to allow the control of a robotic third arm using mind control.

This is achieved by using electrodes attached to the user’s head to capture their brain activity, and turn it into movement commands. Using this technique, it’s possible for the user to do one thing with their biological arms, while carrying out a second, robo-assisted activity simultaneously.

“In our experiments, we used a human-like robot arm for participants to grasp a bottle, while they did a different task [of] balancing a ball,” Christian Penaloza, a researcher on the project, told Digital Trends. “[In terms of real-world applications] we could think of future use cases for this particular system, such as future construction or manufacturing workers who can use a third arm to increase their productivity, or even astronauts in space. However, the applications do not have to be limited to a robotic arm. Perhaps in the future, we could use the system to control other devices — household devices, cell phones, or machinery — while we do another task.”

Third Thumb
Controllable Third Thumb lets wearers extend their natural abilities

Want to get an extra appendage, but not quite ready to make the leap to an arm, or even an extra hand? No problem: a graduate student at London’s Royal College of Art (RCA) has created a functioning prosthetic third thumb you can control with your feet.

The prosthesis’ motors are controlled via two pressure sensors retrofitted into the wearer’s shoes, which then send instructions via Bluetooth. With one sensor controlling flexion and extension, and the other controlling the thumb’s adduction and abduction, you can mimic… well, just about anything a thumb can ordinarily good. Perfect for those movies so good that a simple “two thumbs up” just won’t suffice.

“The Third Thumb investigates the relationship between the body and prosthetic technology in new ways,” creator Dani Clode told Digital Trends. “It is part tool, part experience, and part self-expression; a model by which we better understand human response to artificial extensions.”

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