A next-generation smart textile has been developed by a team of University of Delaware (UD) engineers using light, flexible, breathable carbon nanotube composite coatings on a range of natural and synthetic fibers, such as Kevlar, wool, nylon, Spandex, and polyester. Fabric coated with this sensing technology could be used in future smart garments where the sensors are stitched into clothing or slipped into the soles of shoes for detecting human motion. One potential application of the sensor-coated fabric is to measure forces on an individual’s foot while walking. This data could help clinicians assess imbalances after injury or help to prevent injury in athletes.
The discovery is reported in the journal ACS Sensors, wherein the engineers demonstrate the ability to measure pressure ranging from the light touch of a fingertip to being driven over by a forklift.
Nerve-like electrically conductive nanocomposite coatings are created on the fibers using electrophoretic deposition (EPD) of polyethyleneimine functionalized carbon nanotubes. “The films act much like a dye that adds electrical sensing functionality,” said Erik Thostenson, PhD, an associate professor in the UD Departments of Mechanical Engineering and Materials Science and Engineering. “The EPD process developed in my lab creates this very uniform nanocomposite coating that is strongly bonded to the surface of the fiber. The process is industrially scalable for future applications.”
The nanocomposite coating developed by Thostenson’s group is flexible and pleasant to the touch and is just 250–750 nanometers thick — about 0.25% to 0.75% as thick as a piece of paper. This would only add about a gram of weight to a typical shoe or garment. Furthermore, the materials used to make the sensor coating are inexpensive and relatively ecofriendly since they can be processed at room temperature with water as a solvent. Existing techniques, such as plating fibers with metal or knitting fiber and metal strands together, can decrease the comfort and durability of fabrics, said Thostenson, who directs UD’s Multifunctional Composites Laboratory.
Thostenson’s research group is collaborating with Jill Higginson, PhD, a professor of mechanical engineering and director of the UD Neuromuscular Biomechanics Lab, and her group as part of a pilot project with the goal of seeing how these sensors, when embedded in footwear, compare to biomechanical lab techniques such as instrumented treadmills and motion capture.
Sagar Doshi, a UD doctoral student in mechanical engineering, is the lead author on the paper. He worked on making the sensors, optimizing their sensitivity, testing their mechanical properties, and integrating them into sandals and shoes. He has worn the sensors in preliminary tests, and so far, the sensors collect data that compares with that collected by a force plate, a laboratory device that typically costs thousands of dollars.
This technology could also be promising for sports medicine applications, post-surgical recovery, and for assessing movement disorders in pediatric populations.