Over the years, we’ve seen many examples of smart clothing equipped with technology to monitor various aspects of a wearer’s physical well-being, but lately, we’ve seen how very thin conductive fibers can make work more comfortable.
Researchers at Rice University have applied this approach to a smart shirt that uses interwoven carbon nanotube fibers to monitor the heart rate and take a continual electrocardiogram (EKG) of the wearer. According to the researchers, the fibers are as conductive as metal wires but washable, comfortable, and far less likely to break when a body is in motion.
The technology is based on carbon nanotube fibers, first introduced by researchers back in 2013. The original nanotube filaments, at about 22 microns wide, each containing tens of billions of nanotubes. The scientists have since explored their potential in repairing damaged hearts, electrical interfaces with the brain, cochlear implants, flexible antennas, and automotive and aerospace applications.
Because the original nanofibers were too thin for a sewing machine to handle, the team used a rope-maker to create a sewable thread, essentially three bundles of seven filaments each, woven into a size roughly equivalent to regular thread. Then the fibers could be machine-sewn into the fabric just like standard thread, and the researchers used a zigzag stitching pattern that allows the fabric to stretch without breaking them.
The engineers sewed nanotube fibers into athletic wear and compared the smart shirt’s ability to record real-time heart rate data with a standard chest-strap monitor taking live measurements during experiments. They found that the shirt performed better. Also, when matched with commercial medical electrode monitors, the carbon nanotube shirt gave slightly better EKGs.
“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.”
According to the researchers, fibers woven into fabric can also be used to embed antennas or LEDs. Minor modifications to the fibers’ geometry and associated electronics could eventually allow clothing to monitor vital signs, force exertion, or respiratory rate.
“We see that, after two decades of development in labs worldwide, this material works in more and more applications,” said biomolecular engineer and the study author Matteo Pasquali. “Because of the combination of conductivity, good contact with the skin, biocompatibility and softness, carbon nanotube threads are a natural component for wearables.“