Lauren Taylor, a Rice University graduate shows off a shirt made with carbon nanotube thread. This thread allows for constant monitoring of the wearer's heart rate. Credit: Jeff Fitlow/Rice University
If your shirt does a better job, you don't have to wear an uncomfortable smartwatch or chest strap to monitor your heart rate.
This is the concept behind smart clothing, developed at Rice University. Rice's conductive nanotube thread was used to create functionality in regular clothing.
Matteo Pasquali, a Brown School of Engineering chemical and biomolecular engineering engineer, reported in Nano Letters of the American Chemical Society that the lab sews nanotube fibers into athletic wear to monitor heart rate and take an electrocardiogram (EKG).
According to researchers, the fibers are as conductive as wires but they can be washed and made to be more comfortable. They also have a lower chance of breaking when in motion.
Overall, the shirt that they enhanced was more effective at collecting data than the standard chest-strap monitor which takes live measurements during experiments. The carbon nanotube shirt produced slightly better EKGs when matched with commercial medical electrode monitoring devices.
Lauren Taylor, a Rice graduate student and lead author of this study, said that the shirt must fit snugly against the chest. "In future studies we will concentrate on using denser carbon nanotube threads to provide more contact with the skin."
Researchers discovered that nanotube fibers can be machine washed, as they are flexible and soft. These fibers can be machine-sewn to fabric in the same way as regular thread. Fabric can stretch easily with the zigzag stitching technique.
Taylor stated that the fibers not only provided steady electrical contact with the skin of the wearer but also functioned as electrodes to connect electronic devices such as Bluetooth transmitters to transmit data to a smartphone or to a Holter monitor that can then be stored in a user’s pocket.
Pasquali's lab created carbon nanotube fiber in 2013. The fibers, which contain tens or billions of nanotubes each, were first introduced by Pasquali's lab in 2013. Rice-based Carbon Hub is a multiuniversity research project that began in 2019 and includes their development.
Rice University's athletic shirt was woven with carbon nanotube threads. It was able to collect electrocardiogram and heart beat data. These data were comparable to standard monitors and beat chest strap monitors. Credit: Jeff Fitlow/Rice University
At 22 microns in width, the original nanotube filaments were too thin to be used by a sewing machine. Taylor stated that a rope-maker was used for creating a sewable thread. This consisted of three bundles made up seven filaments each and woven into a size approximately equivalent to regular thread.
Taylor said that he worked with a person who sells small machines to make ropes for model ship models. Taylor had initially tried weaving the thread by hand but with only limited success. He was able make us a small-scale device that does the exact same thing.
She explained that the zigzag pattern can adjust to accommodate how much fabric, such as shirts, will stretch. Taylor stated that Taylor and Dr. Mehdi Rasavi, from the Texas Heart Institute, are working together to optimize contact with the skin.
Lauren Taylor, a Rice University graduate student, sews carbon nanotube yarns into a shirt. Smart clothing can monitor the wearer's heart rate using conductive fibers. Credit: Jeff Fitlow/Rice University
Researchers claim that fibers embedded in fabric can be used to embed LEDs or antennas. The researchers suggest minor modifications to the fibers' structure and electronics to enable clothing to monitor vital signs, force exertion, or respiratory rate.
Taylor pointed out that there are other uses for carbon nanotube fibers. These could be used as human-machine interfaces in automobiles or soft robots. They can also be used as antennas, sensors, and protection against ballistic damage in military uniforms. She said that she and a colleague demonstrated that carbon nanotube fibers dissipate energy more efficiently per-weight than Kevlar a few years back, but without some of our recent improvements in tensile strengths.
Rice University has developed a device that weaves carbon nanotube fibres into larger threads to sew. These threads were used to create smart clothing that can monitor the wearer's heart rate. Credit: Jeff Fitlow/Rice University
Pasquali stated that the material has been proven to work in more applications after being developed in laboratories around the world for over two decades. Carbon nanotube threads make a great component in wearables because of their conductivity, good skin contact, biocompatibility, softness, and conductivity.
Although the wearable market is small, he said it could be an entry point to a new generation sustainable materials. These materials can be made from hydrocarbons via direct split, which also produces clean hydrogen. The Carbon Hub is focused on the development of such materials.
Pasquali stated that we are in the same position as solar cells a few decades back. "We need leaders who can pull off scaling up production and increasing efficiency."
Learn more Woven nanotube fibers transform heat into power
Lauren W. Taylor and colleagues, Washable. Sewable. All-Carbon Electrodes. Signal Wires. Electronic Clothing. Nano Letters (2021). Information from Nano Letters Lauren W. Taylor and colleagues, Washable. Sewable. All-Carbon Electrodes. Signal Wires. Electronic Clothing. (2021). DOI: 10.1021/acs.nanolett.1c01039
