But the solution offered by these devices also illuminates a problem they’ve helped to create. In thinking about the limits of exoskeletons, it’s perhaps most important to think about why many people seem more interested in hoisting someone out of their wheelchair than they are in making spaces accessible to that chair.

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Powered exoskeletons did not start as assistive devices. The first patent for a powered exoskeleton, filed by a Russian inventor named Nicholas Yagn, was approved on January 28, 1890. Yagn’s “apparatus for facilitating walking” involved long springs attached to each leg, designed to give soldiers in the Russian Army an advantage when running. There is no documented evidence that Yagn’s device was ever actually built or operated.

In the 1960s, inventors began to create elaborate powered exoskeletons, a rise fueled once again by the military. In 1965, with funding from the U.S. military, General Electric started developing something called the Hardiman, whose name was a mashup of “Human Augmentation Research and Development Investigation” and “MANipulator.” The machine was huge—once built, it would weigh 1,500 pounds, and was meant to amplify the strength and endurance of human arms and legs. “Man and machine can be combined into an intimate, symbiotic unit that will perform essentially as one wedded system,” the G.E. engineer Ralph S. Mosher wrote in a report on the Hardiman.

But the Hardiman never quite lived up to the hopes and dreams of its creators. In 1970, engineers finished building the leg and girdle systems, but they weren’t able to walk or stand up without support, and the project was abandoned the following year.

At the same time that G.E. engineers were working on the Hardiman, scientists in Belgrade were also experimenting with powered exoskeletons, this time for use on patients with various forms of paralysis. In 1970, the researcher Miomir Vukabratovic designed what he called a “partial active exoskeleton.” Unlike the Hardiman, this exoskeleton was far lighter (just 26 pounds) and was successfully built and tested on humans in over 100 clinical trials. But Vulabrotavic’s exoskeleton had no power source integrated into the device, and the limitations of the motor and battery technology of the time made the exoskeleton unusable.

It wasn’t until around 2000 that powered exoskeletons really passed from dream into working reality. That was the year that the Defense Advanced Research Projects Agency funded a project called the Berkeley Lower-Extremity Skeleton, or BLEEX. The BLEEX system, developed by engineers at the University of California, Berkeley, only includes legs, and the wearer has to carry the power supply and computer for the device in a large backpack. The premise of this system isn’t to help disabled people towalk again, but rather to make carrying large loads over long distances less exhausting. “While wearing the exoskeleton, the wearer can carry significant loads over considerable distances without reducing his/her agility, thus significantly increasing his/her physical effectiveness,” the researchers write.

Since then, a whole battery of exoskeletons for different purposes have been developed specifically with disability in mind. In addition to ReWalk, there’s the eLEGS system, HAL, and MindWalker, to name a few. In 2009, a group at MIT built an elastic exoskeleton based in large part on Yagn’s springy drawings.