Washable, Sewable, All-Carbon Electrodes And Signal Wires For Electronic Clothing

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Researchers demonstrate sewable carbon-nanotube-based fibers for fabric that can gather accurate EKG and heart rate.

Smart clothing has been an interesting research topic with development of sewable carbon-based fibers. According to Rice University Lab’s smart clothing idea, there is no need to wear uncomfortable smartwatches or chest straps to monitor your heart if a comfy shirt can do a better job. 

The Brown School of Engineering lab of chemical and biomolecular engineer Matteo Pasquali, in the journal Nano Letters, reported sewable nanotube fibers into athletic wear to monitor the heart rate and take a continual electrocardiogram (EKG) of the wearer. 

The shirt they made by sewing nanotube fibers was better at gathering data than a standard chest-strap monitor. Moreover, the carbon nanotubes provide better EKG results as compared to commercial medical electrode monitors.

“The shirt has to be snug against the chest,” said Rice graduate student Lauren Taylor, lead author of the study. “In future studies, we will focus on using denser patches of carbon nanotube threads so there’s more surface area to contact the skin.”

The clothing developed is washable, and carbon nanotube fibers can be machine-sewn into fabric just like standard thread.

“The fibers provided not only steady electrical contact with the wearer’s skin but also served as electrodes to connect electronics like Bluetooth transmitters to relay data to a smartphone or connect to a Holter monitor that can be stowed in a user’s pocket,” Taylor said. 

The original carbon nanotubes were very thin to be machine-sewn. Taylor and her team used rope-maker to create a sewable thread, essentially three bundles of seven filaments each, woven into a size roughly equivalent to regular thread.

“We worked with somebody who sells little machines designed to make ropes for model ships,” said Taylor, who at first tried to weave the thread by hand, with limited success. “He was able to make us a medium-scale device that does the same.”

The fibers woven on clothes can embed antennas or LEDs. According to the researchers, minor modifications to the fibers’ geometry and associated electronics could eventually allow clothing to monitor vital signs, force exertion or respiratory rate. 

According to Taylor, other potential uses could include human-machine interfaces for automobiles or soft robotics, or as antennas, health monitors and ballistic protection in military uniforms. 

“We demonstrated with a collaborator a few years ago that carbon nanotube fibers are better at dissipating energy on a per-weight basis than Kevlar, and that was without some of the gains that we’ve had since in tensile strength,” she said. 

“We see that, after two decades of development in labs worldwide, this material works in more and more applications,” Pasquali said. “Because of the combination of conductivity, good contact with the skin, biocompatibility and softness, carbon nanotube threads are a natural component for wearables.”  

“We’re in the same situation as solar cells were a few decades ago,” Pasquali said. “We need application leaders that can provide a pull for scaling up production and increasing efficiency.”


 

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