SANTA CLARA, CALIFORNIA — Hitting the track with a bulky fitness tracker on your wrist or hip may soon be a thing of the past. Tiny sensors that can be embedded into a shirt, sports bra or even a pair of glasses are now able to continuously track your heart rate, log miles walked and calculate calories burned.
These sensors are possible because scientists have developed new technologies that allow tiny, stretchable electrical circuits to be printed onto fabric. These new technologies — from printable ink to yarn that can conduct an electrical impulse — are being paired with rugged sensors, to create new types of wearable fitness trackers.
And unlike some of the best fitness trackers for your wrist, these can simply be tossed in the wash after a sweaty workout.
Traditional electronic devices can contain a labyrinthine electrical circuit made of metal wire and silicon chips. But typical electronic components aren't stretchy or waterproof, and so they must be placed on a rigid backing, like a computer motherboard.
For several years, researchers have been trying to develop stretchy, conductive materials that could be used to power the next generation of sci-fi devices, from stretchy batteries for bionic eyes to electronic skins. Some technologies have even worked fairly well, but they couldn't be scaled up to the existing manufacturing processes for textiles. But in the last few years, technologies for stretchy conductive materials have taken off.
One way of making such devices uses stretchable ink that serves as the wires between different sensors, such as global positioning systems (GPS), accelerometers, heart rate monitors or temperature sensors. The ink is made of conductive-silver nanoparticles that are embedded in a stretchy polymer resin, said Michael Burrows, the segment manager at DuPont Microcircuit Materials, which developed the ink.
Unlike past efforts, newer conductive inks can be screen-printed or laminated onto a shirt or a bra using technology that's available in almost any textile factory, from Bangladesh to the United States, said Steven Willoughby, the marketing manager for DuPont Microcircuit Materials. The new printable ink will be unveiled here at the IDTechEx Conference tomorrow (Nov. 20).
"The backbone to the entire system will be this stretchy ink system that allows the entire technology to be worn on a shirt, on a sleeve, on a watch or even on glasses," Burrows told Live Science.
And while an accidental trip through the washing machine spells doom for the average smart phone, the new ink can withstand at least 100 wash cycles, Burrows said.
Another technology already in use is a type of conductive yarn, made of metal strung through the fibers of the clothing. Conductive yarns tend to be stretchier and more comfortable than printable inks, whereas the inks provide a more ready-made platform for inserting silicon-based processors into clothing, said Akseli Reho, the CEO of Clothing+, a company that designs wearable technology.
Despite changing fashion trends, clothing is a very old technology whose main functions — keeping people cool or warm, covering the body, and helping people to look attractive — haven't changed much since early humans draped fur pelts over their bodies.
"I would claim that the pocket is the last big invention in clothing," Reho told Live Science.
But that is set to change, with several smart shirts, bras, bicycle pants and socks on or about to hit the market. These smart clothes are only a little more expensive than their "dumb" counterparts.
And new smart sensing technology could bring a whole new set of uses to clothing, such as highly accurate, continuous heart-rate monitoring — which could be key for getting real measures of calories burnt, recovery time and workout impact for a wearer, Reho said.
Clothing could also one day be used in clinical applications to monitor patients' health more closely and could even predict or avert health crises, he added.
And unlike existing fitness trackers, the new electronics could be embedded into something the person would wear anyway, Burrows said.
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Tia is the managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.