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11th September 2014

Walk this way with your own bionic exoskeleton

What was once only the stuff of sci-fi movies and blue sky dreaming is now making more people more mobile. Exoskeletons and artificial muscles are tearing down obstacles and helping people move forward.

It took Claire Lomas seventeen days to complete the 2012 London marathon, but taking even one step was for her a miracle. Lomas is paralyzed from the chest down. She walked the course with the help of a robotic exoskeleton. Robotic exoskeletons are wearable devices which augment the physical capabilities of the human body to make it stronger, faster or otherwise more capable. The powered suit of armour used by the superhero Iron Man is an exoskeleton.

 Agnes (US) stands up from her wheelchair (Photo: ARGO ReWalk)

Around 200 people in Europe and Israel now use a ReWalk, which costs 52,500 EUR, for personal use. A considerably larger number have access to the suits via twenty rehabilitation centres all over the U.S. The CEO of Argo Medical Technologies (which makes the ReWalk), Larry Jasinski, expects the FDA to approve the suit for home use in the U.S. in Q2, 2014 (editor’s note: since this interview, the ReWalk has been approved by the FDA).

The ReWalk suit was designed by Israeli electrical engineer Dr Remit Gopher, who became a quadriplegic following an accident in 1997. Gopher devoted ten years of his life to developing a robotic exoskeleton which attaches to the user’s legs and waist and can bear the weight of both the user and the device itself.

The suit is controlled via shifts in the user’s centre of gravity, somewhat like riding a Segway. The suit’s motion sensor can detect a very small movement of say four degrees and send a signal to the bionic legs to begin to move. A backpack carries the suit’s battery and software. It takes around 15 sessions for a walker to become completely competent in the use of the suit. The company is now working on a new version for quadriplegics.

Exoskeletons in medicine

The ReWalk is not the only game in town if you want an exoskeletons for medical use, although many models are still in the research lab rather than walking around in the wild. Ekso Bionics started out developing exoskeletons to let soldiers carry heavy loads and now sells a gait training exoskeleton intended for use in rehabilitation of patients with various levels of paralysis or hemiparesis due to neurological conditions such as stroke, spinal cord injury or traumatic brain injuries.

ekso bionic exoskeleton

(Photo: The EksoBionics exosuit)

Ekso Bionics’s founder Professor Homayoon Kazerooni is now back in his lab at University of California at Berkeley tackling what he sees as one of the biggest obstacles to the use of exoskeletons for medical use: cost. Kazerooni wants to build a $10,000 version to put the technology within the reach of many more patients. Because the technology is new, patients who want an exoskeleton for personal use generally need to pay for it themselves. Argo Medical Technologies recently received the first approvals for reimbursements by medical insurance companies in Germany and Austria.

Other researchers are working on improving various other aspects of current models. Michael Goldfarb at the Vanderbilt School of Engineering is building smaller, lighter exoskeletons which don’t require a backpack since the battery is built into the “limbs” of the suit. Sunil Argawal at Delaware University has developed a completely passive exoskeleton (no battery required) to help stroke victims.

The exoskeleton helps in rehabilitation by making the repetitive physical movements required for stroke patients to relearn motor control in the affected parts of the body. Passive suits would cost much less to manufacture, although they offer less precise control.

Soft robotics

All the above suits are rigid. Yong-Lae Park, an assistant professor of robotics at Carnegie Mellon University, developed a prototype soft robotics device to help rehabilitate patients with ankle-foot disorders such as drop foot, a common problem in patients with cerebral palsy, amyotrophic lateral sclerosis, multiple sclerosis or stroke. The most common current treatment is a passive, plastic brace.

“Before doing any design I started to look at anatomy first so that I can have a better understanding of how our ankles move and how I can help people to echo movement,” says Park.  “For one type of motion there are multiple muscles involved. I wanted to give those kinds of muscle functions outside of the leg so we can have some corresponding artificial muscles outside of the leg.”

Park developed several pneumatic artificial muscles which attach to the outside of the leg and ankle joint. These “muscles” give the ankle a much wider range of movement than a plastic brace or most rigid exoskeletons. The sensors which detect and amplify the user’s movements are made from artificial skin.

Yong Lae-Park’s Artificial Muscle

“We attach this material on the ankle area and then when you move your ankles it stretches and contracts a little bit,” says Park. “That strain information is converted into the joint angle. Using the joint angle information we do trajectory control. There are already a lot of artificial skin sensors which can be used for robotic applications but most of them are flexible but not really stretchable.  My sensor is really stretchable in any direction. Imagine you wear this elastic material made into a suit. If it is not stretchable your skin will rub the material.”

Park’s device is still a prototype. He is working on improving wearability by reducing the number of pieces in the device and the size of the artificial muscles from 2-3 cm to 3-5 mm in diameter. After that it would need to go through clinical trials and achieve approval from bodies like the FDA before patients can use it.

Clinical data

The lack of clinical data has been one of the main obstacles to more widespread use of exoskeletons in medical applications. Argo Medical Technologies just completed a three year study with thirty patients to see if they could successfully walk on multiple surfaces like concrete, carpet and grass and whether there were any falls or injuries.

Another issue for  is establishing inclusion and exclusion criteria:  whether patients have sufficient bone densities, whether their blood pressure is such that they can stand up without getting light-headed, etc.

“Regular use of exoskeletons by patients with spinal injuries can not only be life-changing but have a dramatic effect on their overall health. “The metabolic benefits of the product which have been done in some independent studies are better than we had anticipated,” says Larry Jasinski, CEO of ReWalk Robotics. “The VA center in the Bronx, New York (James J. Peters Veteran Affairs Medical Center), made a great deal of effort to measure outcomes — your metabolism, your gastrointestinal tract, your urinary tract, bone density, fat loss — things of that nature. The results have turned out to be better than we anticipated. Your doctor tells you to get off the couch and walk more. He was right. And when you are in a paralysed state he is even more right.”

Jasinski expects to see a huge increase in investment in the sector over the next 5-10 years. Several competitors have recently received large investments or have been acquired. “It’s not hard to see when you see the number of patients,” he says.

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Photo credit: Ekso BionicsARGO