Swiss team designs robotic exoskeleton that mimics human knee stability

A rendering of the VariLeg II device--Courtesy of ETH Zurich

While a robotic exoskeleton to help paraplegics walk is hardly a new concept, mechanical engineers from ETH Zurich have designed one with a knee that mimics the variable stiffness and therefore the stability of the human knee so that it can adapt to uneven terrain.

The device, dubbed VariLeg, implements mechanical variable impedance, which allows the knee stiffness to change when encountering irregular terrain or unexpected obstacles, said Patrick Pfreundschuh, a mechanical engineer at ETH Zurich, in a Reuters video. No other exoskeleton has this function, he said.

The proof-of-concept prototype is pretty unwieldy, but the team is already working on the VariLeg II, a more streamlined and lightweight version, Reuters reported. They are also developing "smart crutches," that, will allow the user to toggle between "straight-walking mode," "stair mode" and "sit-down mode," Pfreundschuh said.

Patrick Pfreundschuh, mechanical engineer, ETH Zurich

In June 2014, ReWalk Robotics' ($RWLK) exoskeleton became the first FDA-cleared robotic exoskeleton for spinal injury patients. Though it was the first of its kind and had a potential market of 200,000 people in the U.S. with spinal cord injuries to capitalize on, the Israeli company has lost momentum. The Berlin-based company just squeaked through with a $36 million IPO in September 2014, and 6 months later struggled with net losses and investor skepticism about the market for the device. And just this month, the FDA sent over a warning letter regarding concerns that the device could lead to falls and serious injuries or death, concerns that could be addressed in a device like VariLeg.

Other competitors include Parker Hannifin's ($PH) recently approved Indego and Ekso Bionics' self-contained, full-body robotic walking suit with mechanical braces and crutches, which it supplies to rehabilitation centers in the U.S., Europe and South Africa. While the Department of Veterans Affairs has signed on to pay for the ReWalk device for paralyzed veterans, robotic exoskeletons don't come cheap. ReWalk's sells for $70,000, while Parker Hannifin's goes for $80,000 and Ekso's launched with a price tag $140,000 with a $10,000 service contract.

- here's the Reuters video