Smart Textiles Use Nanomagnets to Feel and Measure Body Movement

Using a composite of nanomagnets and conductive threads, scientists have invented a smart textile that can sense and measure body movements —from stretched muscles to throbbing veins. The device, presented June 27 in the journal AffairsIt’s self-powered, stretchy, durable, water-resistant, and can be made on a sewing machine for a few dollars. It may one day assist doctors in assessing muscle injuries and supporting patient recovery.

Smart textiles are technically not made of cloth but have a cloth-like texture. It’s made of a rubber patch filled with nanomagnets that’s about the size of two postage stamps. Using a sewing machine, the researchers sewed silver-coated conductive threads onto the patches in a spool design. Mechanical forces, such as finger tapping, can disrupt the magnetic field patterns within the rubber, creating an electric current through the threads. The two phenomena whereby a force changes the magnetic field and a variation in magnetic flux generates electricity are known as the magnetoelastic effect and electromagnetic induction.

“Our device is very sensitive to biomechanical stress,” said senior author Jun Chen (@JunChenLab) of the Department of Engineering, University of California, Los Angeles. “The device converts muscle activity into computable high-fidelity electrical signals that are sent wirelessly to a phone application. This demonstrates the potential for personalized physical therapy and enhancing muscle injury rehabilitation.”

The device is not only sensitive, but also precise, detailing body movements down to every muscle group. Attaching the devices to different parts of the body, the researchers clearly measured throat movements when drinking water, ankle movements when walking, and even monitored a person’s pulse from their wrist. When attached to a person’s biceps, the device can show whether they are bending their arm or gripping a fist and the extent of the force. Based on this type of information, doctors can locate the Goldilocks zone to prevent overexcursion and encourage moderate activity, tailoring recovery goals for their patients.

Chen and his team also tested the device’s functionality. To mimic real-world conditions like excessive sweating and heavy rain, the team wet the device with a spray of water and tested its signal output. Signal remains strong. As well as being water-resistant, the device is also elastic and durable, with 3.5 times the length and withstanding 100,000 cycles of deformation. From a production standpoint, Chen notes that the kit is easy to build and highly scalable, and each patch is estimated to cost less than $3.

“Another highlight of this device is its self-powering nature,” he said. “The ability to convert biomechanical forces into electricity means this device is also a generator. This eliminates the need for bulky, heavy, and rigid battery packs typically required in wearable electronics designs.”

Next, the team wanted to make smart textiles thinner and lighter to optimize the wearer experience. Chen and his team, who discovered magnetoelastic effects in soft systems in 2021, also plan to explore new ways to incorporate their findings into wearable or implantable bioelectronics.

“We have tested the device for cardiovascular monitoring as well as respiratory monitoring,” he said. “One day, we may be able to reinvent or replace current systems, such as EKGs, that require an external power source, and make them less bulky and easier to use.”

This work was supported by the University of California, Los Angeles; Hellman Fellows Research Grants; the Brain & Behavior Research Foundation Young Investigator Grant; and Los Angeles Children’s Hospital.

Affairs, Xu et al. “A textile magnetoelastic patch for customized, personalized muscle physiotherapy” https://cell.com/matter/fulltext/S2590-2385(23)00294-1.

Source: https://www.cell.com/