Bionic Limb Research Breakthroughs of the 21st Century

Disabled athletes competing as equals with regular athletes. High-tech prostheses that don’t need (too much) money to be worn by kids. These are innovations in bionic limbs that, to someone in the late 90s, would seem like ideas of the distant future.

Yet, we are here, witnessing the very fruits of the toil and labour of researchers around the world to make these achievements a reality. Indeed, the first two decades of the 21st century have been a rollercoaster of different medical and technological milestones for bionic limb research. The most notable ones bridge the gap between science fiction and science fact in the most revolutionary ways.

1. Bionic limb research contributes to the world’s first bionic woman (2006)

The pioneering bionic limb research at the Rehability Institute of Chicago (RIC) eventually led to a former marine, Claudia Mitchell, being the first woman to be successfully fitted with what we can now technically call a bionic arm. In 2004, she was in a motorcycle accident that resulted in the loss of her left arm.

A year later, she was successfully evaluated as a prime candidate to test out a new robotic arm, the technologies of which were initially developed by Todd Kuiken et. al.

The neuro-controlled bionic arm was capable of following simple instructions via registered muscle movements sensed at the very edge of her shoulders. As you can see from the video above, it was significantly more primitive than what we have today, and can only exhibit limited motion with delayed responses. However, this became one of the many pioneering research projects that proved the feasibility of bionic limbs at a more practical, possibly more economically-available level.

As for Claudia Mitchell herself, she has since moved on to a slightly more advanced version of her original bionic limb and is still reaping the benefits initially given by the restoration of her lost upper limb.

2. Making commercial bionic limbs three times cheaper (2014)

Advanced bionic limb technology combined with cheap 3D printing technology is the basic operating principle of Open Bionics. Although founded in 2014, it was not until at least 2015 that the company took significant steps to put its principles into action.

Its most popular Hero Arm product currently costs (approximately) $13,000, which is technically one-half to a third of the cost of regular high-tech prosthetic devices. Well… still a very hefty amount to be paying for something 3D-printed unlike the Hackberry actually.

But, it is intended as a use-and-forget commercial product, built to compete with the likes of Ossur and Fillauer within the same market tier, of which it is still significantly less expensive.

There are quite a number of ‘open’ demonstration videos online, uploaded by Open Bionics, that showcase the Hero Arm’s features. But for the younger customers, its biggest feature is perhaps its visual customizability. Yes, you can request specific designs! Be it from a bionic superhero or movie robot to tech-clad warriors such as Iron Man.

Additionally, Open Bionics open sources some of its bionic arm designs (available for download), so that people could 3D print their robotic arms themselves. With all the relevant agreements and restrictions, of course.

3. Emulating more accurate limb movement via novel surgical procedure (2015)

Hugh Herr’s history with bionic limb research and development may have started in the 2000s. But the inspiration goes all the way back to his accident in 1982. During this time, both his legs had to be amputated due to severe frostbite.

After gaining most of his academic credentials at MIT, he started achieving milestone after milestone in refining and developing a true bionic limb that would be functionally indistinguishable from natural human legs.

But perhaps one of the most complex and astonishing breakthroughs his research team at MIT made was the Agonist-Antagonist Myoneural Interface (AMI). The procedure required two groups of muscles, which are surgically connected to each other so that when one contracts, the other gets stretched, and vice versa.

First, this allowed another layer of interfacing to the bionic leg that perfectly preserves the muscle dynamics of the damaged body part. Second, after the procedure, the proprioceptive signals can be communicated to the central nervous system from both sources as it was prior to the accident (albeit in a completely new way).

The result? Not only did it improve intuitive use of the leg by sheer dexterous enhancement, but it also allowed better force feedback, as the sensation of resistance to the bionic leg allowed users to gauge their even more accurately their steps.

4. Restoring the sensory information to artificial limbs (2018)

On the subject of providing external information to the prosthetic limbs, Luke Osborn, and yet another dedicated team of researchers at Johns Hopkins University, have conducted bionic limb research to solve the lingering “phantom limb” issue for many amputees by directly providing the bionic limbs a sense of touch.

We have already discussed the benefits of additional sensory information at length in a previous article. But in a nutshell, restoring the sense of touch frees the users from always relying on visual information to gauge the movements of their bionic body parts.

To this end, Luke Osborn and his team have developed what they call the E-Dermis. It’s a layer of fabric and rubber laced with sensors that mimic nerve endings. When something comes in contact with the material, the system emulates skin reacting to stimuli, allowing the user to experience a full-ish range of touch information, including pain if the stimulus is deemed harmful to the bionic limb.

Of course, being that the project is in its initial stages, the implementation is far from perfect. For one thing, the E-Dermis is not designed to sense temperature (yet). But, even at its current stage of development, the concept has already proven itself worthy enough to be pursued further for the foreseeable future.

5. Probably the most dexterous bionic fingers to date (2020)

Lastly, for a more recent technological development, University of Michigan researchers recently unveiled a new system that can tap into the faintest of electric nerve signals to use as motion data for a bionic set of fingers.

Even today, bionic hands tend to be slow, never functioning similarly to the lost hand. But with the new system, the fingers can dynamically change function literally at the user’s robotic fingertips.

The first step is to wrap tiny muscle grafts around the nerve endings of the user. These new biological interfaces would then receive the signals of the severed nerves, a bit like targeted muscle reinnervation.

The second step is to then connect the team’s super-sensitive nerve signal detection system that is connected to an integrated robotic hand to translate into more accurate motion.

To be fair, the bionic hands shown in the video do still tend to have the same general slowness as regular modern prostheses. But the way it shifts between different uses and positions at the flick of thought is still something that is rarely witnessed with typical myoelectric sensory systems.

You often have to wait a whole second for the hand to “shift modes”, or even have to manually move the finger with another hand. Instead, we see the test subjects simply moving the finger that is required for that moment, without any visible mode switching.

Other Directions, Unknown Frontiers

It is remarkable to think that, in just the last twenty years, bionic limb research has advanced to the point that it actually catches up to the sci-fi counterparts we used to associate with the elusive “21st century.”

Of course, there is still huge room for improvement from our current generation’s perspective. But if you are privileged enough to enjoy these function-restorative technologies, then you’re already experiencing the future we previously imagined.

As such, it is even more exciting today to imagine the road ahead. We have yet to navigate its other directions, and unknown frontiers, such as further integration of brain-machine interfaces, could perhaps highlight even more concepts that could revolutionize bionic limb research as early as the next five years.

Featured image credit by Open Bionics.