Prosthetic research has clearly helped the physically handicapped carry on with their daily lives. We have branched engineering and medical sciences in order to create prosthetics that can closely mimic actual limbs.
It is a revolutionary device to cure blindness, but to restore normal vision the device needs at least a million of these electrodes.
But we may be closer than we think, and once the bridge is built, the rapid expansion of roads leading to the possibilities of superhuman prosthetics will soon follow.
iTHINK examines advances in prosthetics and whether we’ll soon be cyborgs.
The Bionic Runners
Probably the first that comes to mind when thinking of prosthetics, we have come far from simple peg legs. Nowadays, Paralympic athletes have top-class running blades to help them soar through the finish line.
Interestingly, there is an argument that using high tech carbon fiber legs gives runners an unfair advantage over those who don’t.
Outside the competitive scene, running blades are an unreliable form of prostheses for everyday life. They are very springy and are unstable compared to normal prostheses.
This is as the running blade is engineered to impersonate the leg muscles and tendons at high impact. The blades store the impact force at touchdown and release at push-off, similar to how the calf muscle and Achilles tendon work.
The actual foot has a key advantage at the start as the calf can adjust his ankle and muscles as he/she goes from 0 to max speed.
However, at top speed the prosthetics are in their realm of expertise, they are very efficient are storing and releasing energy at top speed.
Moreover, they are lighter thus concentrates the weight of the leg at the thighs, allowing for a faster leg swing according to Newton’s Law of Rotation.
The Neural Link
An amazing prosthetic story to highlight would be about Hugh Herr, found in chapter 1 of The Body Builders: Inside the Science of the Engineered Human.
In his teen years Herr was a top-class rock-climbing athlete and was well known at his young age. Unfortunately, on an ice route, Herr was caught in a blizzard and lost his bearings. He had to travel 3 days in the extreme cold, and upon rescue, the doctors had to amputate both his legs below the knees.
After the incident, he focused on academics in order to create better prosthetic legs. He earned his Ph.D. at Harvard University and is currently working at the MIT Media Lab where he leads the biomechatronic research group.
Herr’s prostheses, which he uses personally, houses 24 microcomputers which have artificial electrodes which can sense signals from the central nervous system, the computers decode the signal and initiate mechanical movement in his metal limbs.
Essentially, when he thinks of moving his legs, his mechanical legs can read that and initiate movement. This marks the first prosthetics which is connected to the nervous system and allows a natural gait.
Herr’s prosthetics is revolutionary, but according to himself, it is still far from cyborg. In order to truly compete with the biological foot, the prosthetic must also be able to send signals back to the central nervous system to give feedback on the foot’s reaction to the movement.
Creating a bi-directional neural link between human and machine would possibly be one of the most astounding collaborations between engineering and biology. To study that, Herr’s team invented the Agonist-antagonist myoneural interface (AMI).
To create an AMI opposing muscles are surgically created so that when one contracts, the other stretches. When the agonist contracts and the antagonist stretches, the antagonist muscle sends feedback signals to the brain on proprioceptive sensations.
It took another rock-climbing accident for this to take place on a human, Herr’s friend, Jim, had lost his left foot above his ankle and reached out to Herr on whether he can help him get backed to climbing.
Herr’s team connected the agonist-antagonist muscle to his tibia bone and to the bionic leg as well. When the AMI muscle moves, they send signals to the brain regarding the position of the foot.
Even when blindfolded Jim was successful in knowing which position his bionic foot was in. He was quickly able to create distinct foot movements as if he had a normal limb.
What baffled the scientists the most was when Jim was told to stand up and walk up and down a flight of stairs.
In an instant, Jim was able to execute unconscious walking actions, without him even trying to move his limb.
In an interview, Jim was asked how his newly enhanced bionic leg felt.
“It feels natural, like I had my old foot back.” Jim said, “It doesn’t feel like its 2 separate entities, I don’t feel like a cyborg at all, it feels like it’s a part of me.”
Outside mechanical moving limbs, our individual organs are a separate aspect of prosthetics which recruit multiple fields of science as each organ has gone through millions of years of evolution to provide a specific action.
The Bionic Eye
Bionic eyes differ greatly from prosthetic eyes, as prosthetic eyes have no function and are only used to cover for aesthetics.
Currently the USA leads bionic eye studies, as they have started using photosensors to relay pictures into the brain.
The Argus II Retinal System uses 60 electrodes and can help blind people see light, movement and shapes. It is a revolutionary device to cure blindness, but to restore normal vision the device needs at least a million of these electrodes.
The Mechanical Heart
With the increasing need for heart transplants providing a prosthetic heart for patients will greatly benefit hospitals.
In 2012 doctors created a heart using 2 balloons like how ventricles and atrium works. Unfortunately, this required a noisy air compressor to be connected to the patient for life.
The first patient, Barney Clark, repeatedly asked the doctors to let him die within his 112 days using the device. Even if this was not the case, the doctors said he would not have lived long as the balloons have a durability issue due to the continuous pumping.
Recently, researchers from the Texas Heart Institute found an interesting way to fix this issue, a continuous flow heart where the patient would have no pulse.
After 6 years of animal testing they finally found a candidate patient. A 55-year-old man severe end heart failure. The patient survived for 5 weeks until he suffered multisystem organ failure, due to amyloidosis.
For the moment research is geared more towards the benefit of amputees. However, as science behind the neural network between bionics and nervous system continuous to increase.
The ability to combine humans and machine will closely follow behind.
Hello! I am Yudhis, an Indonesian studying Medical Sciences at the University of Exeter. I am a science writer for iTHINK Magazine. In my free time, I do a lot of sports including rock climbing and boxing. I also enjoy reading fictions when I’m having my rest days.
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