This article was taken from the November 2012 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by <span class="s1">subscribing online.

Hugh Herr<span class="s3">keeps six <span class="s4">pairs of legs in his cupboard. Most days, he wears a set of bionic ankle-and-foot devices which are motorised, making them ideal for walking long distances. When trail-running, he swaps them for large C-shaped carbon legs ("Just like the ones Olympic sprinter Oscar Pistorius wears," he says). And for climbing he's got at least four different types.

Some are designed for rocky cliffs and others for specific tasks: rubber feet for vertical walls, tapered blades to penetrate rock fissures and crampon-claws for icy surfaces. "I am made of aluminium, silicon, carbon composites and titanium," the 48-year-old says. "Depending on my activity, I can adapt."


Herr's love of physical exercise is purely recreational. At his day job as director of the Biomechatronics Group at MIT he researches the mechanics of movement and builds high-performance robot legs. His goal: to blur the lines between human disability and human augmentation, using technology.

Herr's desire to design leg prostheses began in 1982 when a climbing accident left the then-17-year-old a double amputee. Although he was walking within months of his accident, the prostheses available in the early 80s were limited and inflexible. "Because I was desperate to climb again, I was pushed into fashioning my own limbs and testing them on myself," he says. Herr, who now has 14 patents related to prosthetic limbs, including a computerised knee and the BiOM ankle and foot, arrived at MIT in 1993 as a graduate student in mechanical engineering. His favourite phrase, he says, is: "There is no such thing as a disabled person, only disabled technologies."

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The Biomechatronics lab addresses physical interfaces between humans and machines, and how these might be enhanced. Herr's team studies how best mechanically to attach prosthetics and braces to bodies, builds smart limbs that can adjust to a person's individual gait, and connects prosthetics back to the nervous system so that mechanical limbs can detect motor intent in the wearer.

Currently, Herr is working on the first problem: how to build a socket that attaches a robot limb to a person without inflicting pain. "If you ask a hundred leg amputees about the number-one problem they want solved, a hundred will say the socket," Herr says. "Millions of people are in pain, all because an advanced socket should exist and it doesn't." Modern sockets are simple carbon composites that are moulded into the shape of an amputee's stump using sculpting techniques. "We are dynamic creatures, so our interfaces can't be fixed," Herr says. He is currently working with Media Lab colleague and assistant professor of media arts and sciences Neri Oxman to build a flexible socket embedded with pressure sensors that can change shape when the stump swells or shrinks. In tests conducted on walking amputees, a prototype has reduced pressure from the socket by 20 percent, according to Herr.


Oxman, who is an architect and designer, is Herr's climbing partner and has worked closely with him since 2008. "He is a rare kind of thinker, because he can translate big visions into a set of detailed protocols," she says. The two are also working together on designing an exoskeleton with a spiderweb structure, to enhance climbers' athleticism. "The suit would be made of many springs -- as you stretch your muscles, the suit will also expand, turning your body into a giant, moving spring," says Oxman.

Herr also runs a company called iWalk, based in Bedford, Massachusetts, that commercialises and sells the BiOM ankle-and-foot prosthesis. Priced at about £45,000, the BiOM contains three microprocessors and 12 sensors that measure force, pressure and motion. With each step, a motor powered by a 25V battery and a set of springs provide the wearer with an extra push, replicating the work of human calf muscles and the Achilles tendon.

Sensors adjust the position of the foot, reducing the amount of energy required to walk and giving the wearer a natural-looking gait. "We've managed to dynamically capture how a real foot and ankle behave, at least on level surfaces," Herr says.

Will Borden can relate. The 40-year-old high-school history teacher from Cambridge, Massachusetts, lost his right leg in a car accident in 1993. He was fitted with a J-shaped carbon-fibre foot that proved adequate: held fixed at a 90 degree angle, it allowed him to walk, run and even play tennis. In 2008, he was the one of the first people to test an early prototype of the BiOM. "I could immediately feel its power," he says. "I started walking faster and faster, it felt like a race between my human and my bionic side." The flexible ankle joint means Borden can now walk to and from work without tiring, and the socket is far less painful. "It's exhilarating," he says.


Next, Herr wants to design a bionic brace for people with damaged knees. He says a wraparound knee brace will allow users to walk and run without injuring their joints. The brace's functionality can be programmed to individual specifications -- ideal tightness, pressure or force -- using a mobile phone. "In a decade, one will commonly see people jogging with a robot strapped on -- either to prevent injury, or to heal it," Herr says.

In Herr's view of the future, prosthetics will soon be superior to, and more coveted than, biological limbs. "He doesn't see disability, just beauty," Borden says. Playing out Herr's prophecy is athlete and double amputee Oscar Pistorius, who ran at the London 2012 Olympic and Paralympic Games in the summer. In 2008, Herr was the biomechanics expert testifying for Pistorius's case at the Court of Arbitration for Sport in Switzerland, causing the court to overturn an International Association of Athletics Federations ban imposed on Pistorius competing against able-bodied athletes. Herr continued to be the South African athlete's supporter and scientific adviser throughout the 2012 Games. "I was in London in August to watch Oscar compete," he says. "The atmosphere was electric." Pistorius came second in his 400m Olympic heat, reaching the event's semi-final, but didn't qualify for the main event. Herr's prediction of athletes' prosthetics becoming superior to biological limbs doesn't look like coming

true just yet, but it only may be a matter of time.