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A Bionic Man: Hugh Herr Strides Forward on Next-Generation Robotic Legs

Hugh Herr, charismatic leader of MIT’s biomechatronics research group

You’ll likely hear Hugh Herr before you see him.

The charismatic leader of MIT’s biomechatronics research group wears two next-generation prosthetic legs, each barely visible under the cuff of his gray slacks, which produce a faint percussive buzz with each footfall, like the sound of a tiny electric drill. The sound serves almost as a leitmotif—you hear it, faintly, as he ascends the stairs to his office in the glass-and-metal MIT Media Lab or as he ambles across the stage during a lecture.

Among futurists, Herr’s story is the stuff of legend. In the early 1980s, after he lost both legs below the knees to frostbite in a climbing accident in New Hampshire’s White Mountains, a doctor told him he would never climb again. Defiant, Herr used a local machine shop to hack together custom prostheses from rubber, metal, and wood. He designed a set of small feet that could find a foothold where his old pair would have slipped and a spiked set he could use to ascend the steepest walls of ice. He went on to become as confident a climber after his accident as he’d ever been before.

Hugh Herr with robotic legs
Hugh Herr with his robotic legs. Courtesy Matthew Septimus.

That process of redesigning elements of his own body became an epiphany for Herr. “I viewed the missing biological part of my body as an opportunity, a blank palette for which to create,” he told an audience at the 2015 Autodesk University conference.

That ethos has paved the way for an exceptional academic and public career that defies easy categorization. He earned degrees at MIT and Harvard and eventually became the head of MIT’s biomechatronics group, which has become a research titan under his leadership. In 2011, the same year he launched prosthetic maker BionX Medical Technologies—which created the BiOM prosthesis he wears daily—Time dubbed him the “leader of the bionic age.”

In a sunny room overlooking the airy biomechatronics gait-testing laboratory, Herr doesn’t mention those accolades. Instead, he frames his research as a moral imperative to fight against the pain and frustration caused by underwhelming interfaces between humans and machines—a path, he believes, that will lead to a world in which artificial limbs no longer chafe and bruise and where quadriplegics might walk again.

“My personal experience underscored for me how poorly designed the world is,” he says, “and the profound human suffering that’s caused by bad design.”

In a certain light, the central theme of that work could be framed as the notion that effective assistive technology needs to respond intelligently to human activity. However advanced a traditional prosthetic might be, its gross morphology is that of a pirate’s peg leg; to adequately bridge a human body and a prosthetic limb, the limb must sense its wearer’s intention and respond accordingly.

The BiOM ankle, a key component of Hugh Herr’s robotic legs
A BiOM ankle depends on microprocessors, motors, and sensors that determine how the prosthetic is positioned so it can figure out its next step. Courtesy Bruce Peterson for Boston Magazine.

That’s the reasoning that informs the design of the BiOM ankle. Housed in a sleek casing of carbon fiber and chrome is a dense nest of sensors and circuitry that controls an artificial calf muscle, actuated by a spring and a small electric motor. When the wearer steps down, the spring captures the potential energy; when he or she steps up, the motor gives a little boost. The device also measures things like walking speed and the angle of the heel strike; the onboard computer calculates what the ankle needs to do for each step.

The result is an elegant hybrid of the biological and mechanical that emulates the function of a flesh-and-bone calf. It is unprecedented in the field of prosthetics: With each step, the BiOM propels the user forward with a natural gait that an old-fashioned, nonautomated prosthetic could never reproduce.

BiOM users speak about the technology in rapturous terms. Former Marine William Gadsby, who lost his right leg in an ambush in Iraq in 2007, started wearing one after prolonged difficulties adapting to a traditional prosthetic. “To me, this guy, Dr. Herr, was an inspiration,” Gadsby told Smithsonian magazine. “He wasn’t sitting around, thinking, ‘Gee, I wish they could come up with a better gadget.’ He got those degrees so he could fix himself—and fix everyone else.”

In Herr’s vision, though, prosthetics like the BiOM are only a stepping stone to a broad meshing of man and machine. Though each unit is a sophisticated biomechanical apparatus—“I’m basically a bunch of nuts and bolts from the knees down,” Herr says—its intelligence is essentially circumstantial. The BiOM uses sensors to detect a user’s stride and react accordingly, but it is still fundamentally disconnected from its wearer’s nervous system.

To design a hand that’s more dexterous than any artisan’s or a foot stronger and more nimble than any ballerina’s, that gap will need to be bridged, Herr says. New types of sensors will need to connect the human nervous system with the digital.

His team at MIT is looking into a number of strategies to accomplish that. One promising avenue, for example, involves growing nerves through synthetic tubes that use electrodes to pick up impulses directly from the nervous system.

Regardless of the specific tech that brings that bridge about, Herr is bullish on the concept’s long-term feasibility. “Basically, if you know how to input and output information to peripheral nerves, you solve a whole long list of disabilities,” he says.

The FitSocket, a key tool for fitting better robotic prosthetic legs
One of Hugh Herr’s MIT research projects is the FitSocket. It uses an array of actuators to sense stiffness and softness in a limb in order to create more comfortable, better-fitting prosthetics. Courtesy Matthew Septimus.

Philosophically, it’s part of a future Herr imagines in which extremely detailed data about the human body, nervous system, and environment will enable design of objects customized for each individual. “Better design is going to be informed by a deep, deep understanding of the human being,” Herr says. “In the future, every human will have a digital representation of themselves, and there will be quantitative design frameworks that use a digital body to design all kinds of things that humans use.”

That’s a formidable technical goal, but also an ethical one, because it would free people with nontypical bodies of all types from the irritation and discomfort of using things designed for the average body.

Herr leans back, absentmindedly tipping his chair onto its two rear legs. One day, he says, he envisions, “a seamless integration between the built world and our bodies—a world in which stuff actually works, stuff doesn’t cause pain, stuff doesn’t cause profound frustration.”

This article is an excerpt from The Future of Making by editor/author Tom Wujec and Autodesk. The book explores how emerging technologies and new ways of designing are transforming what and how people make things.


About the Author

The Future of Making, a book by editor/author Tom Wujec and Autodesk, explores how emerging technologies and new ways of designing are transforming what and how people make things.

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