The Harvard technology consists of a thin sheet of silicone sandwiched between two layers of conductive fabric, creating what's known as a capacitive sensor. This kind of sensor can track even the slightest movement by constantly monitoring tiny electrical charges as they travel through the material.
"When we apply strain by pulling on the sensor from the ends, the silicone layer gets thinner and the conductive fabric layers get closer together, which changes the capacitance of the sensor in a way that's proportional to the amount of strain applied,” said co-author Daniel Vogt, in a statement announcing the new research. “We can measure how much the sensor is changing shape."
The material is sensitive enough to register physical strain of less than half a millimeter. According to testing on a pair of gloves made from the material, that level of sensitivity is good enough to measure fine motor movements like slightly moving one finger side-to-side. But the material is so light and flexible that such movements are entirely unimpeded.
The new process is also easy to set up and duplicate, making it immediately useful for manufacturers of smart apparel and other wearables.
“We have designed a unique batch-manufacturing process that allows us to create custom-shaped sensors that share uniform properties, making it possible to quickly fabricate them for a given application,” said researcher Asli Atalay in an email.
The National Science Foundation, the Scientific and Technological Research Council of Turkey, and the US Department of Defense provided research support.
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The paper, published in the journal Advanced Materials Technologies, is only a preliminary proof-of-concept study, but the research team is optimistic that the textile technology could be used for motion capture applications — athletic clothing that tracks physical performance or soft clinical devices to monitor patients in a medical setting.
“This work shows promising results for human motion monitoring in sports, for performance optimization, or training purposes,” Atalay said. “For example, a golfer who wears sensor integrated clothing can train himself on correct posture, or an athlete can optimize his performance by learning from sensor feedback.”
Another possibility: By combining the sensor material with fabric-based soft actuators, engineers could develop robotic systems that truly mimic apparel. In other words, instead of simply tracking movement, the material itself could assist or even initiate specific movements, leading to soft exoskeleton systems for physical labor or disabled patients.
“There is a growing interest in utilizing textile technology in soft robotic systems,” Atalay said. “For example, the Wyss Institute develops fabric-based assistive robots to help people with physical impairments such as spinal cord injury or ALS. Another example is monitoring breath rate with sensors integrated into garments to prevent sleep apnea.”