Tech Takes


When I was in seventh grade I tried to make a prosthetic arm using Lego, I succeeded in creating a very primitive device which could pick up stuff, and I would control it by using switches or touch. I had this idea that you could put the stub of the arm in a frame and make it move around inside it activating pressure pads causing the arm to move. I really wanted to use nervous stimulus for it but I didn’t know how to go about it.

Anyway the point my design was and is common to majority of the prosthetic arms out there today, it had a claw, and an elbow. That’s it. It’s pretty primitive isn’t it? Also there was another thing which bugged me; it was heavy, way too heavy for day to day use. I tried to place the load of the forearm near the elbow but it didn’t quite work out, it was simply too heavy. So the motor took quite a beating each time it went up or down.

Then today I saw this;

“Prosthetic legs are in the 21st century. With prosthetic arms, we’re in the Flintstones.”

Dean Kamen has done it again, this arm is so insanely great that I can’t overestimate it! I mean, this will go down in history as a turning point. He has somehow managed to reduce the weight (it’s about 3.6 kg and made out of aluminium), made it modular and then to trump it all he has made an agile hand. No claw but a really, really compact and agile mechanical hand. Normal prosthetics have about 3 degrees of freedom* they could open/close, move up/down, and rotate left/right. However the normal human arm has 22. So this was a major shortcoming, Kamen has managed to pack in 18 into his arm, 18!! This is a quantum leap, no one has done something like this at this level before. It’s something truly amazing. They’re using 6 micro-processors to handle all the data and to control the thing. I loved the stacked radial PCB assembly they’ve created to save space.

What’s even more amazing is how they’re controlling it;

Deka worked closely with the Rehabilitation Institute of Chicago, where neuroscientist Todd Kuiken has had recent successes in surgically rerouting amputees’ residual nerves—which connect the upper spinal cord to the 70 000 nerve fibers in the arm—to impart the ability to “feel” the stimulation of a phantom limb. Normally, the nerves travel from the upper spinal cord across the shoulder, down into the armpit, and into the arm. Kuiken pulled them away from the armpit and under the clavicle to connect to the pectoral muscles. The patient thinks about moving the arm, and signals travel down nerves that were formerly connected to the native arm but are now connected to the chest. The chest muscles then contract in response to the nerve signals. The contractions are sensed by electrodes on the chest, the electrodes send signals to the motors of the prosthetic arm—and the arm moves. With Kuiken’s surgery, a user can control the Luke arm with his or her own muscles, as if the arm were an extension of the person’s flesh.

Guess what, they also can provide feedback with a tiny vibrator, called a tactor, so that a patient can ‘feel’ without surgery. The harder the grip the more it vibrates and vice versa. Now that’s ingenious.

This is revolutionary stuff, seriously I can’t over-estimate it. Watch this video and you’ll know what I mean.

*Degrees Of Freedom (D.O.F.): We basically count the number of movements a joint can do around the 3 axes of reality; x, y, z. If it can rotate around the x axis then it counts as one degree of freedom, if it can move backward and forward then it counts as another one. We get the figure of total D.O.F. of a body by summing up the D.O.F.s of it’s respective parts

5 replies on “Wow”

You “tried” to create a prosthetic arm, when you were in the 8th grade?

pfffffffffff…… in your DREAMS.

Making a prosthetic hand out of lego doesn’t require much effort just 5 days of work and a good imagination. I guess you do need to create it in your dreams before hand.

@Ram: I really find it amusing and irritating at the same time, how people find it odd – ‘kids doing stuff beyond what they are normally supposed to at their age’ – and I don’t mean the three-letter S-word. :P Grow up. Students these days know and do a lot more technical stuff than earlier.

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