Made of silicone and fabric, the highly sensitive sensor is, say its creators, “inherently suitable for integration with fabric to make ‘smart’ robotic apparel.” By leveraging textile technology with robotic systems, the researchers see potential applications such as performance-tracking athletic clothing or soft clinical devices that monitor patients at home, as well as even new robotic systems that mimic apparel.
The sensor consists of a thin sheet of silicone sandwiched between two layers of silver-plated, conductive fabric electrodes. This forms a capacitive sensor that senses movement by measuring the change in capacitance (electrical charge) between the two electrodes.
“When we apply strain by pulling on the sensor from the ends,” says Daniel Vogt, Research Engineer at the Wyss Institute, and co-author of a paper on the technology, “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, so we can measure how much the sensor is changing shape.”
The key to the sensor’s performance is based on its manufacturing process, which allows the quick creation of custom-shaped sensors that share uniform properties. The sensor is fabricated by attaching conductive fabric to both sides of the silicone core with an additional layer of liquid silicone that fills some of the air gaps in the fabric and mechanically locks it to the silicone, increasing the surface area available for distributing strain and storing electrical charge.
The silicone/fabric hybrid approach leverages the strength of the fabric fibers, which limit how much the silicone deforms, while the rubbery nature of the silicone helps the fabric return to its original shape after being stretched. According to the researchers, the sensor detected increases in capacitance within 30 milliseconds of strain application and physical changes of less than half a millimeter, which, they say, confirms that it is capable of capturing movement on the scale of the human body.
In a real-world test of their sensor, the researchers integrated several of them into a glove in order to measure fine-motor hand and finger movements in real time. According to the researchers, the sensors were successful in detecting changes on individual fingers as they moved, indicating their relative positions over time.
“This technology opens up entirely new approaches to wearable diagnostics and coupled therapeutics that undoubtedly will pay a central role in the future of home healthcare.” says Wyss Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at SEAS. “It also reflects the power inherent in our focus on collaboration here at the Wyss Institute, as it draws insight and inspiration from both Conor Walsh’s Biodesign Lab and Rob Wood’s Microrobotics Lab, which are central to our Bioinspired Robotics platform.”
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