Thoracic vertebrae

How a Robotic Exoskeleton Is Helping a Paralyzed Acrobat Walk Again

Silke Pan usually swung 22 feet above the ground on the trapeze, but on that day in September 2007, she was just 13 feet up. Pan, a performer with Switzerland’s Nock Circus, had just finished a seven-month gig at the Fiabilandia Amusement Park in northern Italy, where her troupe performed seven days a week, six shows a day. Now they were on a two-week break. But Pan, a contortionist and acrobat, didn’t take the break. She and her long-time partner, Didier Dvorak—a juggler, unicyclist, and her husband—wanted to fine-tune their act before the next gig began. So back up on the trapeze they went.

Pan remembers that Dvorak was hanging by his feet from his trapeze, his hands outstretched to her, as she swung from her own trapeze, hands reaching toward him. She knows she was meant to catch his hands in hers, as she had countless times during the 15 years she had been performing professionally.

But she doesn’t know what happened next, because she can’t remember. Others have had to fill in the blanks for her (but not her husband; it’s too painful for him to talk about, she says). They say that as she and Dvorak swung toward each other and she let go of the trapeze, they missed each other’s grip.

Pan plummeted to the ground. She landed on her head at the feet of the spotter, whose job it was to catch her if something went wrong. He, too, had missed.

“At first they thought I was dead because I didn’t move or respond,” she says.

She awoke in an Italian hospital to learn she was paralyzed from the waist down due to an injury to her T10 and T11, or 10th and 11th thoracic vertebrae, located in the lower mid-back.

For someone who had devoted her entire life to pushing the boundaries of what her body could do in the service of entertaining people, it was devastating to be unable to move. “I felt as if I was born again,” she recalls. “I lost everything from my identity. People who knew me, knew me as a circus artist and an acrobat. I was like a baby in an adult body. I didn’t know what to do with my life. All the things I had thought before about what I could do were things that weren’t anymore possible.”

Yet last year—nearly a decade after she became paraplegic—Pan began to do something she never thought would be possible again: walk. It became possible thanks to Twiice, a powered lower-limb exoskeleton developed by engineers and scientists at the Laboratoire de Systèmes Robotiques (LSRO) at the Ecole Polytechnique Federale de Lausanne (EPFL) in Lausanne, Switzerland. Pan has taken so thoroughly to the exoskeleton that not only does she walk in it—she competes in it.

The augmentation of the human body with technology isn’t new; prosthetics can be found as far back as ancient Egypt. Nor is the idea of enveloping the body in a functional shell revolutionary; armor is essentially an exoskeleton. But taking the concept of the exoskeleton from protection to mobility is more recent. As robotics specialist José Pons and his colleagues from Spain’s Instituto de Automatica Industrial recount in Wearable Robots: Biomechatronic Exoskeletons, in 1883 one H. Wangenstein proposed a “Pneumatic Bodyframe” for paraplegic scientists that would be controlled by “Neuro-Impulse Recognition Electrodes” attached to the wearer’s temples. He enthused, “Even running and jumping are not beyond its capabilities, all controlled by the power of the user’s mind.” It’s unclear whether Wangenstein ever attempted to build his bodyframe.

Decades later, in the early 1960s, the U.S. military began investigating designs for a powered “suit of armor,” Pons writes, as did the Cornell Aeronautical Laboratory and General Electric. This interest has continued to the present day; in 2000, the Defense Advanced Research Projects Agency (DARPA) funded the development of the Bleex exoskeleton, built by a team at the Berkeley Robotics & Human Engineering Laboratory; later iterations were called the ExoHiker and HULC. In 2015, DARPA beta tested an exoskeleton created by Harvard’s Wyss Institute on enlisted soldiers; the goal is to lighten the load of their heavy packs and reduce their metabolic cost during long missions.

But while the military has been at the forefront of developing the tech, wearable robotics for industry, prosthetics, and orthotics are catching up. In the past decade or so, the number of teams developing wearable robots has grown tremendously. Today, many companies are making them. They serve a variety of purposes, from load bearing (military and industry) to helping people move (prosthetics and orthotics).

It’s with orthotics that LSRO comes into the picture. The Rehabilitation and Assistive Robotics lab, a division of LSRO, is headed by robotics engineer Mohamed Bouri, and it was his idea to build the exoskeleton that restored Pan’s ability to walk. Bouri’s initial goal was to create one for people less than 5 feet tall—mainly children. While there are several commercially available adult-size exoskeletons, including the Phoenix, ReWalk, REX P, and Ekso, there are none for kids, says Tristan Vouga, a Ph.D. student in microengineering at LSRO. (One child exoskeleton is in preclinical trial.)

Bouri tasked Vouga with creating a design for the exoskeleton. Microengineering is key to the production of Switzerland’s most famous export—watches—but it’s also highly useful in robotics, Vouga says. In early 2015, he came up with the initial design for an exoskeleton that was lightweight, easy to operate, relatively low cost, modular, and adjustable. The latter was especially important because every spinal injury is different, and kids grow. Ideally, every exoskeleton would be customized for its user.

The LSRO engineers and scientists built the exoskeleton in 18 months, using mostly carbon-fiber parts that Vouga fabricated in the lab with new manufacturing techniques developed specifically for the exoskeleton (details of which Vouga won’t disclose because they’re proprietary). Weighing about 30 pounds, it’s one of the lightest exoskeletons in the world. The lab can manufacture a personalized exoskeleton in a few days.

The engineers named the device Twiice. “The idea is that they’re two people walking—actually, two pairs of legs: the human and the robot, and they have to walk together,” Vouga says. “It’s a collaboration. It’s like a dance: You have coordinate, to be aware of each other, and there’s this real symbiosis between the two actors.”

But there was a snag: a pressing deadline. The team had learned about the first-ever Cybathlon, a competition for disabled athletes to be held in Kloten, Switzerland, on October 8, 2016. The goal was to showcase the latest developments in assistive technology—devices aimed at making daily life easier for people with disabilities.

Bringing a child in to “pilot” or beta test the very first trial of this new technology was going to be problematic. “It’s hard to bring children in for ethical reasons,” Vouga says. It would require a complex approval process involving not only a child but their parents and doctors. By that point, October was just months away. They needed to train someone to use the exoskeleton if they wanted to field an entry in the Cybathlon.

The team decided that what they needed was a very small—but adult—competitor. That meant they also needed a new, slightly larger, exoskeleton. Switching gears, the team constructed another one in just two weeks.

Now they needed the competitor to pilot it. They approached a local wheelchair club looking for the ideal recruit: small and slim, with superior upper body strength.

But that wasn’t all. They aimed not only to enter the Cybathlon, but to win it. “We wanted to find someone who is competitive and who was already an athlete,” Vouga says. “That’s hard to find.”

Shortly after her accident, doctors in the Italian hospital implanted a metal spine stabilizer in Pan’s back. As she recovered, they told her they were impressed with her positive outlook and that her sunny smile was an example to other patients.

“I hadn’t realized I was smiling,” she recalls. It was sheer habit. “As a circus artist, I had learned to keep smiling. When I was on stage, I always had to smile, and the smile had to come from my heart, because if I would smile only with my face, I always thought it wouldn’t look real.”

The truth was, she told her doctors, “‘I‘m really sad. It’s terrible for me.’ But I didn’t show it.”

After leaving Italy, Pan spent nearly seven months recovering in a Swiss hospital. When she left the facility, she tried to return to her old life. She and Dvorak developed a show in which she performed in a wheelchair. It was successful enough that the pair was contracted by Fiabilandia to bring the show to the amusement park.

That’s how, in 2009—two years after the fall that took her mobility—she found herself back at the scene of the accident. “I thought it would be good because I didn’t want to close my eyes to what had happened,” she said. “I thought I needed to see the reality.”

She badly miscalculated how it would affect her. The experience was devastating. “It was a most difficult time, because every day, I heard the music I had heard two years before. I met some of the same artists I had worked with, and every day I couldn’t stop comparing myself to what I had been,” she says. “That was very hard, because I felt really handicapped. I saw myself in the wheelchair. I could only move my arms and speak, and before I was … standing on one hand, and hanging from my trapeze. Compared to what I was before, I felt as though I was nothing.”

She decided she had…