Exoskeletons and the Blurry Line Between Science Fiction and Reality
Two of the most exciting scenes in science fiction movies in the last 40 years happened at the conclusion of Aliens (1986) and Avatar (2009). In Aliens, the hero, Ellen Ripley played by Sigourney Weaver, fights against a terrifying alien monster that kills everyone in its path. In Avatar, the hero, Jake Sully played by Sam Worthington, fights against a ruthless military commander who wants to plunder a planet’s resources at the expense of its indigenous people. In both scenes, an exoskeleton is used to enhance human ability in combat against a physically more powerful opponent.
What’s an exoskeleton?
In nature, notably among insects and crustaceans, an exoskeleton is an external skeleton that supports body shape and protects the internal organs of an animal. In that sense, both Ellen Ripley and the alien had exoskeletons — one synthetic and one natural, respectively. Natural exoskeletons have the advantage of being hard and strong but the disadvantage of being heavy. Picture a snail’s shell as an example.
In technology, an exoskeleton is a mechanical device worn by a person and designed to enhance their physical capabilities. The Exoskeleton Report categorizes devices into Consumer, Industrial, Medical, and Military uses. Devices can also be categorized according to the body area they support, for example the lower body (e.g., ankle, knee, hip), the upper body (e.g., waist, shoulder, elbow, hand), and various combinations of these.
In a recent report, the global exoskeleton market was estimated to have generated $700 million in revenue in 2023. It is expected to grow to $3.7 billion by 2028. This rising adoption is expected to be led by healthcare demand as well as industrial and military growth. Growth drivers include advances in robotic technology and insurance coverage for medical applications. Challenges will include regulatory scrutiny for medical applications and high equipment costs. Significant development is occurring in Asia, where large electronics companies are contributing to growth.
Clearly, exoskeletons are no longer science fiction. They are being developed and used in the real world today. But how are they being used? Are they really neurotechnologies? And where are they going next?
Applications
Military applications
As implied in Avatar, there has long been interest in using exoskeletons for military applications. In fact, military-grade robotic exoskeleton suits have been in development for nearly 60 years. In the early 1960s, Neil Mizen, a researcher at Cornell University, attempted to develop a Man Amplifier. The Amplifier was intended to have military uses but was never completed. Another early exoskeleton was General Electric’s Hardiman Suit, co-developed with the U.S. military in 1965. Research was focused on one arm of the suit, which ultimately managed to lift 750 pounds — but as it weighed three quarters of a ton itself, the project was never completed.
Fast-forwarding several decades, the Berkeley Lower Extremity Exoskeleton (BLEEX) entered development in 2000 with a $50 million grant from the U.S. Defense Advanced Research Projects Agency (DARPA). The prototype allowed wearers to carry up to 200 lbs while feeling no additional weight. Also in 2000, a technology company called Sarcos began designing the XOS Exoskeleton after receiving a grant from DARPA. In 2007, the defense giant Raytheon acquired Sarcos, and subsequently in 2010 Raytheon-Sarcos released the XOS version 2 suit. DARPA also began its Warrior Web program, aimed at creating a lightweight under-suit that protects wearers’ joints and helps increase the weight a soldier can carry.
Exoskeletons have not been broadly adopted for operational use in the military since they do not yet demonstrate significant augmentation to individual and team capabilities. There is a need for the human and the exoskeleton to readily adapt to different movements in different contexts, and current exoskeletons are unable to concurrently adapt to the user, task, and environment. For example, the Australian Defense Force recently studied how exoskeletons could assist personnel to avoid musculoskeletal injuries. They reviewed 67 unique exoskeletons studied from 1990 to 2019 and found that exoskeleton support of manual tasks occurs largely through deadlift lower limb systems to be used for load carrying, with reported reductions in back muscle activation of up to 50%. However, the authors concluded that the “unique considerations for military applications … suggest that a significant adaptation to current technology or customized military-specific devices would be required”.
Industrial applications
As implied in Aliens, there is also great interest in using exoskeletons for industrial applications. For example, automotive giant Hyundai developed exoskeletons for assembly line workers to aid them with their overhead work. The Vest Exoskeleton (VEX) can reduce the strain for industrial workers and imitates the way a shoulder joint operates to offer load support and adapt to the way a worker operates when handling overhead tasks. The Fortis exoskeleton developed by Lockheed Martin has a robotic arm that extends from the waist to hold heavy tools that weigh up to 36 pounds as the operator uses the tool. The Fortis design aims to make the tool feel weightless, so an operator can work longer without fatigue and use their hands freely.
A recent review of 35 studies of 18 different industrial exoskeletons found that the majority supported the shoulder joint and were used to assist individuals with overhead work. Overall, 16 studies showed a reduced activity in shoulder muscles with exoskeleton use, and participants reported a reduction in exertion and discomfort. However, benefits in the working environment may be less pronounced than in the laboratory setting, since so-called secondary tasks also have to be performed in the real world. For example, one study showed that an exoskeleton hindered work performance up to 22% in multiple tasks. The need to extend the benefits and reduce the hinderance of exoskeletons across a broader range of tasks is a recurring theme in industrial and military settings. Although there is potential to benefit workers, limitations in hindrance and comfort need to be addressed.
Medical applications
Besides their potential military and industrial applications, there is significant interest in exoskeletons for medical applications. In fact, the U.S. Food and Drug Administration has defined an official product category for powered lower extremity exoskeletons.
There are now a growing number of reports of exoskeletons in the medical literature. As an example of a fully external exoskeleton (i.e., no brain-computer interface), a hip-assistive robotic exoskeleton has been shown to improve clinical outcomes in persons with chronic stroke. Fifty participants completed a randomized, single-blind study of gait training with the Honda Stride Management Assist (SMA) exoskeleton delivered in 18 sessions over eight weeks. Gait training with the SMA improved walking speed and may promote greater walking endurance and balance than functional gait training. As an example of an exoskeleton that acts more like a traditional neurotechnology, another group tested the feasibility of a system that uses brain signals to drive an exoskeleton in a 28-year-old man paralyzed by spinal cord injury. Two wireless recorders were implanted over the sensorimotor areas of the brain. Signals derived from those recorders were processed by an algorithm to send commands to an exoskeleton. Throughout the 24 months of the study, the patient completed various cognitive tasks to progressively increase the degrees of freedom that simulated walking and made upper-limb movements during various reach-and-touch tasks. These results exemplify a neuroprosthetic exoskeleton driven by a brain-machine interface system.
Other medical exoskeletons have moved past the research stage. The FDA-approved EksoNR manufactured by Esko Bionics, which is an exoskeleton that is used for patients in neurological rehabilitation centers — and may ring some bells for those of us are old enough to remember the Six-Million Dollar Man and The Bionic Woman from 1970s television. The suit is designed to help traumatic brain injury, spinal cord injury, and stroke patients to regain their natural gait by re-teaching the brain and muscles how to walk.
In addition, a company called Cyberdyne (unrelated to the Cyberdyne Systems from The Terminator) has developed a device called the Hybrid Assistive Limb (HAL) (no relation to the artificial intelligence system from 2001: A Space Odyssey). HAL is also intended for use by neurology patients. With HAL, brain signals intended for the muscles are captured by sensors placed on the legs, which feed this motor activation information to a device that helps the user move and walk with their legs by simply thinking of moving their legs. The South Korean and U.S. militaries offered to fund the program, but the company wanted to avoid military applications for its technology. In 2013, the fifth-generation HAL prototype, HAL 5, received a global safety certificate for worldwide medical use. It was the first powered exoskeleton to receive this certification.
What’s next?
We don’t yet need exoskeletons to explore other planets, as in Aliens and Avatar. However, it’s striking that the types of exoskeletons depicted in these two movies, now nearly 40 and 20 years old respectively, are no longer science fiction.
In general, public opinion in the United States is still mixed about the use of robotic exoskeletons. In a recent survey by Pew Research, two-thirds of respondents aligned with the view that “as humans we are always trying to better ourselves and this idea is no different”, while one-third took the opposing view that “this idea is meddling with nature and crosses a line we should not cross.” Public awareness of robotic exoskeletons is still limited, and those who are more familiar with exoskeletons are more positive about their use. Some worry that employers will need fewer workers if exoskeletons become widely used, but others also see the potential for exoskeletons to benefit workers by reducing the risk of injury and allowing a wider range of people to do manual labor jobs. At this early stage, a large majority of Americans stress the importance of a rigorous review of safety and effectiveness, saying robotic exoskeletons should be tested using a higher standard than what is used for other workplace equipment.
While practical details will need to be worked out, research groups are still reaching for the stars. NASA’s X1 robotic exoskeleton may someday help astronauts stay healthier in space. The 57-pound device could be worn to assist or inhibit movement in leg joints. In the inhibit mode, the device would serve as an in-space exercise device to supply resistance. As the technology matures, X1 could also provide support to astronauts as they work, improving the ability to operate in a reduced gravity environment. Other innovators at NASA’s Johnson Space Center have developed a soft, wearable, robotic upper limb exoskeleton garment designed to actively control the shoulder and elbow. In the future, the technology may find applications in human performance augmentation, including spacesuit designs.
Science and science fiction will continue to inspire each other. In 2001, U.S. Army Rangers veteran Monty Reed set up North Seattle Robotics Group which opened the They Shall Walk non-profit, dedicated to developing exoskeletons for the disabled. Reed became fascinated with the exoskeletons in Robert Heinlein’s novel Starship Troopers. At various times, the U.S. military has also considered options for developing a Tactical Assault Light Operator Suit (TALOS), nicknamed the Iron Man suit, after the comic book hero. In the movie The Martian, set just a few years from now in 2035, Matt Damon’s character references an Iron Man-like suit that is not yet available to him. The world of RoboCop however, where the main character becomes more machine than man, seems much further away.
It’s likely that military, industrial and medical exoskeletons will be available before everyday, consumer-grade devices. It’s also likely that externally worn devices will be available before neurotech exoskeletons with implanted brain sensors. However, as true science continues to reference science fiction, we can only speculate as to how and when exoskeletons, space flights to Mars, and other technologies will become commonplace.
Written by Marco Sorani, edited by Dilara Parry, Lars Olsen, and Sankalp Sharma, with AI-generated artwork prompt-engineered by Sophie Valentine.
Marco Sorani works in biopharma and has a PhD in Bioinformatics. He sustained a spinal cord injury in 1994 and advocates for innovative research approaches.
Dilara Parry is a data scientist at a global consultancy. She has a neuroscience (MSc) academic background with BCI research experience and the curiosity to explore the overlap of her two disciplines.
Lars Olsen is a regulatory medical writer. He works in the pharmaceutical industry writing submission documents, and has additional experience with medical devices. He has a biology background and is interested in AI, AGI/ASI, and BCI/HCI.
Sankalp Sharma, B.Tech (Converging Technologies) M.Tech (Cognitive Neurosciences) is currently working as a Research Data Analyst at Nims University Rajasthan, working on Avian Genomics (House Sparrow), Artificial Intelligence, Oral cancer and Neuroblstoma. He is associated with Agronomy and Nano-Biotechnology groups.
Sophie Valentine has a background in experimental psychology and cognitive neuropsychology research, with degrees from Bristol University. Her work is focussed at the intersection of tech-for-good, product, digital health, and neurotechnology.
