Future Wear

If one MIT researcher has his way, our fabric could be the next great technological frontier.

RELATED TAGS: MATERIALS SCIENCE
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So-called functional fibers can have an array of capabilities, from acting as a speaker or a microphone to serving as a neural probe.
Kayana Szymczak

In a cluttered subterranean laboratory at MIT, Jung Tae Lee is attempting to make a battery as long and thin as a fishing line. With a focused gaze, the postgraduate researcher adjusts the knobs on an imposing blue machine that heats up and stretches out filament. “Must stabilize before making active fiber,” he mutters.

Benjamin Grena is more loquacious. The grad student explains that the blue machine, which stands nearly twice his height, is a draw tower, a custom version of an industrial appliance used to extrude glass rods into fiber-optic cable. Lee will make his device by elongating, or drawing, a fat polymer cylinder that has been embedded with electrodes and injected with battery fluids. The trick is to keep the metals and liquids aligned, as Lee heats and stretches the cylinder until its diameter is ideally a mere 1/200th its original size — a high-precision variation on pulling saltwater taffy. “And then,” Grena says, “you’ll have a power source that can be woven together with sensors and other functional fibers.”

These resulting electronic textiles could be worn as garments, implanted in a body or blanketed across a city. For Yoel Fink — Grena and Lee’s MIT adviser and supervisor, respectively, and the mastermind behind the high-tech threads — the textiles represent nothing less than a turning point in human civilization. “Fabrics have remained sort of immutable since the Late Stone Age,” Fink says. “That’s because they’re made of fibers that are made of a single material, and so long as you make fibers of a single material, they’re not going to be highly functional.”

With a method for crafting fibers that integrate everything from polymers to metals and fluids — and then controlling the internal arrangement of these materials — Fink envisions vast new possibilities for fabrics. And given the ubiquity of textiles in our world, he believes the fibers he’s working on will profoundly augment technology as a whole.

Fink’s vision is attracting a following well beyond the basements of MIT. In 2016, he founded an institute called Advanced Functional Fabrics of America (AFFOA), a public-private consortium comprising more than two dozen major research institutions, including Drexel University in Philadelphia and Carnegie Mellon University in Pittsburgh. The consortium also includes influential technology companies such as Tesla and Corning, as well as the U.S. Department of Defense.

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Yoel Fink, head of the Advanced Functional Fabrics of America (AFFOA) consortium, examines the two-story draw tower with colleague Chia-Chun Chung at the AFFOA offices in Cambridge, Massachusetts. The drawing process is key to shaping the functional fibers Fink has pioneered.
Sam Ogden
As CEO, Fink commands a total budget of $317 million, with which he intends to create a “distributed foundry” — an institutional network with expansive expertise that can efficiently push fiber innovations beyond zany lab experiments and into consumer products. He has already built a 20,000-square-foot prototyping facility, which began operating in the Boston area last June.

Far from resisting Fink’s assault on millennia of spinning and weaving, the traditional textile industry is a committed ally. “I’ve been around textile people my whole life, and I’ve never heard anybody talk about putting electronics into a textile,” says Norman Chapman, president of Inman Mills, a yarn-spinning and fabric-weaving company in South Carolina. Together with other industry mainstays such as Milliken and Warwick Mills, Inman has enthusiastically joined AFFOA.

In the frenzy of revolution, only Fink’s students seem unflappable. Fiber drawing cannot be hurried. As his battery takes form, Lee keeps a steady hand on the future.

The Perfect Mirror

Fink sits in his spacious MIT office, cradling an army helmet wrapped in camo-patterned fabric. “You see these golden fibers?” he asks, pointing at some barely visible metallic threads. “This was produced a few years ago at Natick.”

He’s referring to the U.S. Army’s Soldier Research, Development and Engineering Center, an early collaborator that helped him to demonstrate that functional fibers could be woven into standard gear. Ultimately, the Army is interested in preventing battlefield friendly fire by developing threads with special optical qualities that respond to laser sights. Fink and his collaborators have addressed this by weaving filaments with different reflective qualities into a kind of plaid pattern that’s instantly visible through a comrade’s laser sight. It’s a clear signal not to shoot.

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Fink displays chunky preforms that will become fibers once they’re processed in the draw tower. Behind the preforms sits a prototype military helmet covered in functional fabric. The fabric responds to a gun’s laser sight, signalling to a shooter whether or not the helmet-wearer is an enemy.
Sam Ogden

This project isn’t just a professional prospect for Fink. Saving lives in combat is a personal goal. When he was 2 years old, his deeply religious family emigrated from the United States to Israel. His parents signed him up for theological training, but he dropped out as a teenager to join the military. “This was 1984 to ’87,” he says, a period when Israel was building settlements in occupied territory and conflict was high. “It was very intense with a lot of people getting injured and killed,” he says. “You see how close you always are to making a mistake.” Fink not only witnessed fratricide in his own unit, but a similar incident took his cousin’s life.

His response, after completing three years of service, was to flee. He lived out of a backpack, visiting places like the Philippines, Nepal and the U.S. But his father had other ideas and enrolled him in the Technion-Israel Institute of Technology, signing him up for the chemical engineering program. “It seemed to me very mundane,” Fink recalls. So to keep himself entertained, he also took up physics.

The combination was fortuitous. “Chemical engineering has to do with processing fluids,” he explains. Today, he applies those principles to building physical systems using optics and electronics.

Not that this was obvious when Fink graduated and joined the Ph.D. program at MIT in 1995. Enrolled in materials science, he drifted in search of a research project, interviewing with dozens of professors across a broad spectrum of fields. One of them was Ned Thomas, a materials scientist who was involved in a secret multimillion-dollar program for the Defense Advanced Research Projects Agency (DARPA) to create a mechanism that would reflect light from any direction.

Thomas invited Fink to attend a meeting where MIT scientists would discuss a plan for tackling this problem. As Fink prepared, he started to look at dielectric materials — insulators and semiconductors that are layered to make high-precision mirrors — and a very simple question came into his head. “I knew from my optics studies that layered systems reflect, but the angle is limited,” he says. What he couldn’t find was a theoretical basis for this rule of thumb. So at the meeting, he naively asked if anybody knew a formula to determine the angle at which multilayered dielectrics stop reflecting. “I was sure one of them was going to say, ‘There’s this optics course I’m giving next term,’ ” Fink recalls. “But the room was silent.”

He immediately started to work on the problem, and several weeks and analyses later, he found there is no physical limit. By layering the right thicknesses of certain dielectric materials, he could make a mirror that reflected light from any angle — a perfect mirror. The physics community was agog. The New York Times called the discovery potentially “the most significant advance in mirror technology since Narcissus.”

But by then, DARPA had dropped the project for reasons as mysterious as its intended military application. Fink decided to keep working on the idea anyway, hoping to expand the use of his mirror into a high-efficiency alternative to fiber-optic cable for telecommunications. A conventional optical fiber is limited by the materials it’s made of, because they don’t perfectly reflect the light waves inside: The cord gradually absorbs the photons running through it, weakening the signal. Fink’s plan was to fabricate a hollow tube with multilayered dielectric walls that would perfectly reflect the light passing through.

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MIT materials scientist Polina Anikeeva examines fibers, each containing a single electrode, that will be drawn into super-thin neural probes. Anikeeva and her team can then insert them into the brain with very minimal disruption.
Justin Knight/McGovern Institute for Brain Research at MIT
“I actually needed to ask around how fibers were made,” he admits. But he’d successfully earned his doctorate and transitioned to MIT junior faculty in 2000, giving him the freedom to acquire a small draw tower and start experimenting, along with several grad students. He had no idea he was breaking the most basic industrywide rules. Until Fink came along, everyone assumed any materials you’d use to make a filament needed to have matching viscosities, thermal properties and other traits in order to extrude them together; you also needed to draw them at low tension and high temperature. Through trial and error, Fink figured out how to draw at high tension and low temperature. And the “OmniGuide,” as Fink calls his invention, became his first functional fiber.

However, the telecommunications field wasn’t prepared for a revolution. The industry was shrinking in the early 2000s, and cheap optical fiber was overabundant. Instead, Fink co-founded a company that put the OmniGuide to use in medicine. “We made a scalpel for minimally invasive surgery,” he says.

The bladeless tool uses the intense light of a carbon dioxide laser to cut through soft tissue. The CO2 wavelength is ideal for surgery because the water in fat and muscle absorbs it efficiently, making for easy cutting. And doctors have long favored CO2 lasers for procedures in tight spaces where metal tools would get in the way.

Before Fink got involved, CO2 laser procedures were arduous. Because glass won’t transmit light at the CO2 wavelength, surgeons couldn’t use conventional optical fiber to guide the laser beam; instead, they had to painstakingly and precisely aim the whole unwieldy laser unit at the patient to hit just the right spot, and they could only cut tissue in the laser’s line of sight. However, with a flexible omniguide putting the laser beam right at the doctor’s fingertips, surgeons can maneuver the light exactly where it’s needed. Fink’s invention has now been used in more than 200,000 procedures, many of them treating advanced stages of throat cancer.

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Above, a sample from Fink’s lab reveals functional fibers interwoven into a lightweight fabric.
AFFOA
It’s also served as a paradigm for Fink’s subsequent approach to engineering, which combines experimental openness with interdisciplinary reach, stretching fiber technology into every domain he encounters. “He is visionary, he’s rebellious, and he’s incredibly scientifically brave,” observes Polina Anikeeva, an MIT professor of materials science and engineering, and a frequent collaborator. “He goes after big questions without any fear.”

Fink’s relentless effort has vastly increased the uses of high-tech fibers. He’s also found that many of his techniques for fabricating these kinds of fibers could be used to make electronics. His optical devices already used semiconductors and insulators. With the addition of metal as a conductor, he realized he’d have the three basic elements of electronic circuits and computers.

Fink’s idea swiftly attracted interest at the academic journal Nature Materials. The publication commissioned him to write a review, published in 2007, about fibers that could “see, hear, sense and communicate.”

“There’s nothing to review,” Fink remarked.

His editor had a ready answer: “Let’s review the future.”

Beyond Wearables

In a subterranean laboratory several twists and turns away from Fink’s draw tower, Tural Khudiyev, another postdoctoral team member, is gently coaxing a fiber to sing. He has exposed metal conductors on one end of the strand and connected them to a high-voltage amplifier. Holding the tip of the filament in a vice, he switches on the amp and cups his ear. The cord softly hums.

“This,” Khudiyev says, “is the piezoelectric effect. It converts an electrical signal into a sound. The opposite is also possible. The fiber can be a microphone as well.”

Scientists have known about the piezoelectric effect since 1880 and have exploited the phenomenon in electronics for a century, not only for sound but also to exert and detect pressure. By introducing piezoelectricity into a thread that can be woven into a garment, Fink’s group is transplanting a hundred years of innovation into a new domain, endowing fabrics with capabilities that could be achieved previously only with devices that people strap on or carry. Those devices, such as health and fitness wearables, are limited by the fact that they’re accessories. “Stuff we wear is called clothes,” quips Fink.

He believes this is more than a trivial distinction. Our clothing has as much as 20 square feet of external surface area, touching nearly every part of the body. That means a piezoelectric textile could potentially hear our surroundings, sense our movements and monitor internal organs, such as our heart and lungs, with unprecedented fidelity. It could also generate energy as we walk.

And piezoelectricity is only one of many electronic capacities Fink’s lab is systematically mastering. Michael Rein, a former grad student of Fink’s and now a senior product engineer at AFFOA, has been drawing fibers that contain tiny diodes, semiconductors that can alternately emit or detect light. Woven into a fabric, they’ll be able to electronically change a garment’s appearance or allow for remote communication. In his thesis work, Rein demonstrated that these functional fibers are washable — an important milestone on the road from lab to marketplace.

As with any electronics, multiple components will be able to do far more collectively. For instance, by combining Rein’s diode fibers with Khudiyev’s piezoelectrics, “you could communicate at a distance,” observes Fink’s grad student Grena. The diodes could detect a voice-controlled laser beam and make the piezoelectric fabric vibrate so that troops could hear their commander’s orders on a chaotic battlefield. Conversely, vital signs measured by piezoelectric fibers could be relayed to a medic by light-emitting diodes (LEDs) on a wounded soldier’s uniform. Grena also foresees advantages in terms of scale, especially for sensor networks. Fibrous electronics can be stretched very thin to extend over vast distances. A piezoelectric mesh could take large-scale measurements, like bridge strain or ocean currents.

At the opposite extreme, Anikeeva is applying Fink’s fiber-drawing technique to neuroscience. Her flexible filaments take advantage of the miniaturization afforded by fiber drawing, combining optical waveguides with conductive electrodes and fluid channels to create a probe thinner than a human hair. A single probe can deliver drugs and measure neural activity in a brain or spinal cord without damaging tissue. It can even stimulate neurons that have had their DNA modified to respond to light, making it a powerful and versatile tool in the emerging field of optogenetics. “The fiber-drawing process,” says Anikeeva, “is the enabling capability.”

Closing the Gap

At MIT’s Computer Science and Artificial Intelligence Lab, Fink shows off some of the first products developed by AFFOA. He presents backpacks with unique barcode-like patterns woven into the fabric; an ordinary iPhone camera can scan the pack from across a room to bring up information, like a quote or a song, through a program the wearer can enable and use with a phone. He also shows off baseball caps woven with diodes that sense signals from overhead lights. The signals are sent by flickering the lighting more quickly than our eyes can perceive — a system that could help future wearers navigate disorienting buildings like hospitals and airports.

Toward the end of his presentation, Fink shows an organizational chart representing the design and production trajectory for his navigational baseball cap. Specialized threads, with technology from MIT, could be modeled and drawn at AFFOA. Textiles could be spun at Inman Mills in South Carolina. AmeriCap in North Carolina should be able to assemble those textiles into hats. And systems integration with the lighting could take place in the AFFOA prototyping facility, in collaboration with Massachusetts-based Analog Devices.

“Most university intellectual property is sitting on a shelf,” Fink explains. “And the reason is there’s a gap between where research ends and production begins.” With AFFOA and its approach to projects like these, the gap is eliminated.

“Functional fabric is one of the most transdisciplinary fields of our time,” says Genevieve Dion, director of the Shima Seiki Haute Technology Laboratory and an AFFOA leader at Drexel University. She and Fink crossed paths while attending a meeting that would lead to AFFOA, which benefits from her background in fashion. She, in turn, has brought her sociology colleagues on board. As groundbreaking as the materials coming out of Fink’s lab may be, Dion believes their adoption will depend on addressing real human needs in ways that people find appealing, issues that are more readily taken up by designers and sociologists than engineers. “We have to get beyond, ‘Let’s make Google Glass. It will be so cool that everyone will want it,’ ” she says.

For Dion, the obvious place to start using functional fibers and fabrics is in health care, especially for people with conditions that need constant monitoring and treatment. Functional fabrics might not only provide better support, but they could also eliminate the stigma of looking different. “We’ll be successful with wearable technology as medical devices when nobody can tell you’re wearing them,” she says.

Characteristically expansive, Fink carries Dion’s vision into all domains. His conversation spans from T-shirts to diapers. “People ask, how’s this fabric going to look?” he says. “Actually it’s not going to look any different. But it’s going to do a whole lot more.”

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