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The Leveraged Freedom Chair

The Leveraged Freedom Chair, shown here in prototype, lets riders travel 80 percent faster or with 50 percent more torque.

Walk into Amos Winter’s lab on any given day and you might find the assistant professor of mechanical engineering working on a water purification system, a high-efficiency diesel tractor engine, prosthetic feet, or a prosthetic knee that enables users to walk with a natural gait, all of which he’s designing to help people in the developing world. But Winter didn’t set out to be a do-gooder. It happened by accident, a twist of fate—happier but no less unexpected than a fall from a tree, a motorcycle crash, or a tropical fever, any of which might leave someone in need of the invention for which he’s become best known.

In 2005, Winter had just earned his master’s degree in mechanical engineering at MIT and wanted to spend the summer with his then girlfriend, who was in Tanzania. MIT’s Public Service Center helped him get there by hooking him up with two organizations that assist people with disabilities; they needed someone to assess the state of wheelchair technology in that country. Winter talked to manufacturers and asked users how well existing products fit their needs—and saw a lot of room for improvement.

Conventional wheelchairs worked fine indoors, but they were hard to use in rural areas because they wouldn’t let users traverse uneven ground. Hand-pedaled tricycles were useful in those conditions, but they were too large to work indoors. The missing product was a chair that worked well on both flat and rough terrain and was small enough to use inside. It would also need to be simple and easily repairable—and cost approximately $200, since other wheelchairs being distributed by aid organizations cost between $150 and $300. Some high-end off-road wheelchairs have a multi-gear system like the kind you’d find on a mountain bike, allowing users to adapt easily to different terrain. But that wasn’t an option here: 10-speed gear trains are expensive, hard to find in many developing countries, and not rugged enough.

Winter returned to MIT for his PhD and toyed with the problem for a year and a half before hitting on the idea of using two handheld levers. Each of the chair’s two wheels would have a single gear connected to a vertical lever that the user could push forward for propulsion. Grip the levers close to the pivot points for fast movement on smooth surfaces, and grip them higher for greater torque on tougher terrain. The person becomes the gear-change system.

While still a grad student, Winter created the undergraduate course Wheelchair Design in Developing Countries and assembled a group of students who worked with him on a prototype and took it to Tanzania, Kenya, and Vietnam to test. “It was a great lesson for us,” he says. “We had created this prototype, we were all gung ho about it, we had actually won an award for it already, but you bring it to the users and they’re like, ‘No, this isn’t gonna fly.’” It was too heavy, too hard to get in or out of, and too unstable on hills. The experience emphasized the importance of working with end users every step of the way. Winter kept at it, redesigning with the feedback in mind and going back into the field repeatedly. The Leveraged Freedom Chair (LFC), as he calls it, became his main focus as a postdoc at the Singapore University of Technology and Design–MIT International Design Centre.

Now, five years after the first prototype was built, the chair is ready for mass production and distribution. It is light and cheap, contains readily available bike parts, and uses a form of steel that can be easily repaired, as I saw before piloting the chair around a snowy parking lot behind Building E34: a wheel rim had gotten bent while being transported on an airplane, but Winter banged it back into place in a matter of seconds. And in addition to directing the Global Engineering and Research (GEAR) lab, which he started at MIT in the fall of 2012 after joining the faculty, Winter serves as the chief scientific advisor for Global Research Innovation & Technology (GRIT), a company he cofounded to manage the distribution of the LFC in developing areas.

It’s too early to know how many people might choose this chair when presented with a variety of options, says Matt McCambridge, an engineer at Whirlwind Wheelchair, one of the disability assistance groups Winter first worked with in Tanzania. “But the World Health Organization estimates there are 65 million people who need a wheelchair,” he says, “so if this new technology met the needs of even 2 percent of the population, that’s more than a million people.”

Winter, 33, started making stuff at a young age. As a kid in New Hampshire, he played with Legos, sewed stuffed animals, and took part in Odyssey of the Mind, a problem-solving competition that often involved building vehicles or load-bearing structures. He filled his time in high school with trumpet and sports but spent a formative summer building a pipe organ powered by a vacuum cleaner for a course on the physics of sound and music at St. Paul’s, a prep school in New Hampshire. For his senior thesis at Tufts, he constructed a robot that could be driven upside down and had a pneumatic arm that could lift more than 100 pounds. He would have competed with it on the TV show BattleBots, had it not been canceled that spring.

When Winter returned to MIT after his time in Tanzania, he went back to robotics for his PhD project, inventing RoboClam, an under water digging device that mimics the action of a razor clam. He discovered that by opening and closing its shell at just the right speed, a clam creates a pocket of quicksand that allows it to move efficiently through soil. Winter replicated that effect with machinery. He’s now refining the RoboClam for possible industry applications—setting anchors, blowing up mines, or installing oil-drilling equipment. “With people like Amos, we’ll work with him on whatever he wants, really,” says Jeffrey ­Wadsworth, CEO of Battelle, the nonprofit institute that funded the bulk of the project. “I don’t know how you print people like this. If the world was full of Amoses, we would be in wonderful shape.”

Winter admits that even outside the lab, he remains “a total gearhead.” (He enjoys tinkering with his 1987 Porsche and 1987 Land Rover and jokes that his recently purchased carriage house is a garage with a house on top.) He also has a thing for what he calls “dorky engineering-related museums”—and shared that love with his students last fall when he led a trip to the Larz Anderson Museum in Brookline, an old carriage house full of cars from around 1900. “What’s cool about it is that none of the car designs were standardized at that time,” he says. “They have all these wonky solutions for transmissions and suspension and cooling.” He had his students think through how those designs would have worked: “We spent, like, two hours there and got yelled at by the curator because we were lying on the floor underneath a car.” They’d bypassed the velvet ropes and were inching beneath the car’s undercarriage, gawking at its unusual torsion spring suspension. “That’s what I love,” he says. “That mechanicalness of mechanical engineering, seeing machines work and understanding why they work the way they do.”

But as students in Winter’s GEAR lab quickly learn, there’s a lot more to mechanical engineering than mechanicalness. “Amos demands that everything we do in our research be a deliberate decision,” says Katy Olesnavage 12, a grad student in the GEAR lab. “I’m designing a low-cost prosthetic foot. It’s not enough for me to tell him that I want to use a certain geometry because it will be flexible; I need to show him the literature that says specifically how flexible it should be and prove that the proposed geometry will be exactly that flexible using engineering principles.” The rigor that Winter insists on, she says, helps ensure that his students both contribute to the science of their field and develop products that perform as well as similar ones or better.

Winter also pushes students designing for emerging markets to travel at least twice a year to meet face to face with the people who will use or make the products they’re designing. “Amos stresses that each of us spend time with the people who will ultimately be using our products to fully understand their needs in the early stages, and later to get feedback on ideas and prototypes,” Olesnavage says. Such feedback proved critical in developing a drip irrigation system for off-grid subsistence farmers in India. Winter is designing a nozzle to reduce the system’s water pressure requirements so that it needs less power, and he had planned to configure it for use with thin, cheap tubing. But when Indian farmers weighed in, he learned that the Indian government subsidizes thicker tubing, which farmers also prefer because it won’t burst when an ox steps on it. You wouldn’t learn those things from a data sheet.

“There are many technologies—and I’m afraid we’ve invented some of them—that sit on the shelf because we haven’t done the A-to-Z thinking about whether it’s affordable, whether it’s socially acceptable, whether there are competitors,” Battelle’s Wadsworth says. In the fall, Winter will teach a graduate course on global engineering to emphasize the importance of such socioeconomic factors in engineering for emerging markets and unfamiliar cultures.

Classes like that are important because not much deep thought has been given to the process of designing products for people in poor, rural settings, says J. Kim Vandiver, SM 69, PhD 75, dean for undergraduate research and the director of the Edgerton Center, which helps students with engineering and service projects. “We’ve seen lots of stuff designed for the developing world,” he says. “Some of it’s junk. Some of it, the design itself is great, but they can’t figure out how to scale it up, how to distribute it, how to get the supply chain working, and how to do it at low cost.”

Winter’s five-to-10-year plan is to generalize from case studies in his lab and other technology organizations to define design principles for use in the developing world. “In all the complexity we deal with,” Wadsworth says, “to the extent you can write down the fundamental principles of what works, that’s a huge help.”

Winter was initially lured into the field by the sheer difficulty of the wheelchair problem. “When I started [the LFC] I was like, ‘Man, this is a crazy hard engineering challenge,’” he says. “There’s just no device that works like this, and we’re trying to innovate technology that’s been relatively unchanged for about 140 years.” But today, he’s equally driven by the desire to help people. “Giving somebody a tool that drastically changes their life is really, really compelling,” he says.

“There are technical challenges in the development space that affect billions of people in a life-or-death way, and no one knows how to solve them,” he adds. “I think that’s a really fertile area for research.”

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Credits: Continuum, Transitions Foundation of Guatemala, and GRIT, Amos Winter

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