Discerning the world undiscovered: The incredible breakthroughs in smartprosthetics.

Every year, thousands of veterans return home from service, losing arms and legs to new lives that will forever be changed, unable to do the most menial tasks that they could once do without thinking. These honorable people fall to a point where they have lost a large part of their independence and their lives become incredibly difficult. To such people, prosthetics are typically given. While it's the best solution that they have, they lose the ability to do the simplest things like comfortably shake hands and even hold an egg due to the lack of control and sensitivity. But this is quickly changing with developments in sensitive prosthetics.

Going in, it is important to understand how we feel the world around us and how pain is felt. Receptors on our skin detect the environment and send electrical impulses up to the brain where it is processed. From there on, the brain determines what kind of surface it is and we feel the respective sensation. People who have typical commercial prosthetics, don't have a way of detecting these surfaces and so cannot feel any sensations from the limb that the prosthetic has replaced.

Researchers at the University of Utah have seen success in developing a new sensitive prosthetic. This was done on a man that had lost his hand 17 years ago. The procedure was done using a brain-controlled robot prosthetic. This device, known as the LUKE arm, can tap into the wearer’s nerves and send signals back to the brain where it can mimic a sense of human touch. The test subject, Keven Walgamott has been able to differentiate between 118 different touch sensations. The prosthetic uses a microelectrode that sends back signals to the brain, which they have tried to make as biologically realistic as possible. Though currently, it only works by being connected to a computer, they are working on releasing a model that can work completely portably.1

Furthering our progress in sensitive prosthetics, engineers at Johns Hopkins University have created an electronic skin. This allows people to engage in real sensation at their fingertips. With prosthetic arms that are already very well established in the market, there are major opportunities that arise when we merge the two, we get even closer to a complete restoration of the lost part of the body. The Human skin is a complex collage of receptors, and the researchers are using this as a template to recreate it in the e-dermis.2

Although very unpleasant, simulating pain is essential. This is because it protects us from harm by making us associate certain harmful actions with the sensation of pain3 .This very essential feeling of pain is something that the prosthetic wearers don't have and so this can deprive them of this very essential sensation. And because of this, they may engage in activities that damage the prosthetic - like touching hot surfaces and exerting large amounts of pressure on it. The E dermis that is used in many of these sensitive prosthetics can detect pain because it imitates the natural mechanoreceptors. Pressure sensors used can differentiate between blunt and sharp objects nowadays. When the prosthesis bends over a curved object it differentiates it as blunt from a sharper object where it will almost fold. This is done by sensing the distribution of pressure. The signals are then sent through the peripheral nervous system. Currently, it doesn’t feel like a typical pain sensation - it’s more of a discomfort. Biomedical engineer Luke Osborn is hoping that as the technology develops, the pain sensation will become more accurate.

Obviously, with such kinds of technology, there is an ethical question that comes to play. As doctors, they aim to cause no pain. But with sensitive prosthetics like this, we are actively trying to make the patient feel pain. Luke Osborn has made it very clear that they do not intend to damage the volunteer in any way. Then the other issue is tolerance. People have varying degrees to tolerate pain. Pain is very personal - the same thing can make a person feel a very large amount of pain and for someone else, it could go completely unnoticed. The researchers at Johns Hopkins are therefore trying to tailor the prosthetic to the wearer. For another group of individuals, who have never had a limb in the first place, suddenly experiencing different pain sensations can be overwhelming and so for these kinds of people, the researchers propose a light of sort to indicate that the wearer is damaging the prosthesis. Overall, the sensation of pain is hugely complex and even more so when artificially created with prosthetics, and it is important to tread with caution with such technologies that come very close to human function.4

In addition to the E-dermis developed by Johns Hopkins, another approach is that of the one taken by RMIT University, published in Advanced intelligent systems5. This variety is made of silicone rubber with integrated electronics. This is built up by their group's previous breakthroughs in stretchable electronics, temperature-sensitive materials, and brain-mimicking electronics. The material used here is vanadium oxide that can change its properties in temperatures above 65 degrees. This is also able to generate the signals from those like our nerve endings to send the information. About the environment to the brain. This almost completely recreates the pain response. The main key takeaway from RMIT’s work is that they have been able to recreate the threshold - pain is only detected above a certain threshold. Holding something of a comfortable temperature does not make us feel pain, but holding something of a higher temperature makes us feel it -this is all managed by the threshold. The potential for this technology is immense - from surgeons feeling palpating tissue to athletes in sport6.

The general conversation about prosthetics usually is negative - that is reasonable because we are talking about people who have lost their limbs here. But interestingly, a new line of designer prosthetics has emerged that helps the patients reflect on themselves through a little creativity on their prosthetic. While the option for realistic prosthetics is available, this isn't very favorable because they don't have nearly as much functionality as the more ‘robot’ like one has. This is simultaneously helping change society’s opinions on prosthetics. It is important in science to make sure that our technologies not only help people on a physical level but also on a human level and that is what these designer prosthetics are doing7.

Psyonic, a startup out of the University of Illinois, is working on a commercial prosthesis with pressure sensitivity. What is unique about their work is using machine learning to give the person a sense of intuitive control. This, along with the work by Johns Hopkins, may come about to allow amputees to perform the tasks that most of us take for granted. Very similar to Psyonic, a German company ‘Ottobock’ uses a pattern recognition algorithm. They have been able to accurately translate intention into movement.

The future of prosthetics mainly involves unlocking involuntary control - to allow the amputees to carry out daily activities with their prosthetic without intention. We are looking at using pill-sized implants that can surgically be inserted into the nerve ending to carry this out. Whatever the new approach might be, we have come very far with improving the lives of thousands of individuals who might otherwise be subject to a life without sensation.

Ahmedh Aaqil Rifky

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Citations

1 https://www.medicaldevice-network.com/news/prosthetic-arm-gives-wearers-a-sense-of-touch/

2 https://www.sciencedaily.com/releases/2018/06/180620171004.htm

3 https://www.news24.com/health24/medical/pain-management/about-pain/the-importance of-feeling-p

ain-20140604

4 https://www.wired.com/story/pain-is-weird-making-bionic-arms-feel-pain-is-even-weirder/

5 https://onlinelibrary.wiley.com/doi/full/10.1002/aisy.202000094

6 https://theconversation.com/pain-sensing-electronic-silicone-skin-paves-the-way-for-smart prosthetics-and-skin-grafts-145386

7 https://theconversation.com/prosthetic-limbs-affect-our-attitudes-to-disability-expressive-design-might -change-things-for-the-better-140796