Smart fabrics are often outfitted with strain sensors to monitor the wearer’s movements, and while they can provide accurate data, they are often fragile, meaning most textiles with these sensors couldn’t survive a washing machine. Now engineers from Harvard’s John A. Paulson School of Engineering and Applied Sciences have developed an ultra-sensitive train sensor for smart textiles that can withstand nearly any punishment, including being hit with a hammer, run over by vehicles, and repeated washes.
The new sensor looks and acts like a toy Slinky; only instead of being cylindrical, it features a flat shape arranged in a serpentine pattern. The strain sensor was designed using an array of conductive carbon fibers sandwiched between a pair of elastic polymers. When the flat carbon fibers are stretched apart, the electric conductivity diminishes correspondingly by how far apart the fibers are. That lessened conductivity can then be used to determine how much strain the sensor is experiencing.
Even the slightest amount of separation between the conductive fibers can be measured, making the sensor ultra-sensitive. According to the researchers, they tested the sensors resiliency by stabbing it with a scalpel, hitting it with a hammer, running it over in a car, and washed it ten-times over in a washing machine, and it emerged unscathed and functional each time it was subject to abuse. The team then incorporated the sensor into a fabric arm sleeve, which was worn by a volunteer and found that when the subject flexed their forearm muscle, it could detect hand gestures, including fist, open palm, and a pinching motion.