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A soft, flexible sensor system created with electrically conductive yarns could help map problematic pressure points in the socket of an amputee\u2019s prosthetic limb, researchers from North Carolina State University report in a new study.<\/p>\n
In\u00a0IEEE Sensors Journal<\/a><\/em>, researchers from North Carolina State University reported on the lightweight, soft textile-based sensor prototype patch. The device incorporates a lattice of conductive yarns and is connected to a tiny computer. They tested the system on a prosthetic limb and in walking experiments with two human volunteers, finding the system could reliably track pressure changes in real-time.<\/p>\n \u201cWhat people commonly use to measure pressure within prosthetics are rigid sensors,\u201d said the study\u2019s first author\u00a0Jordan Tabor, a graduate student in the NC\u00a0State College of Textiles. \u201cThey\u2019re hard, they\u2019re bulky; they can be heavy. These are not things that amputees can use on a daily basis because rigid sensors negatively affect the fit of amputees\u2019 prosthetics. Rigid sensors can also cause discomfort. We designed sensors that can be integrated into textiles in a way that doesn\u2019t cause any additional discomfort for the user, and could be worn on a more regular basis.\u201d<\/p>\n In one experiment, the researchers tested whether the patch could detect changes in pressure when they placed it on an artificial limb, turned at different angles. Then they used it to test pressure changes when an able-bodied person wore the sensor patch while walking with a bent-knee adaptor and while shifting their weight between legs.<\/p>\n In their last experiment, a volunteer with an amputated lower leg wore the patch on the liner of their prosthetic limb in areas where the prosthetic limb typically applies higher pressure. They tested the sensor patch while the volunteer shifted weight and walked on a treadmill, finding the system was durable and could reliably monitor pressure changes in the socket.<\/p>\n \u201cThis approach that we thought of a few years ago does work, and it\u2019s a readily manufacturable technology,\u201d said\u00a0Tushar Ghosh, the study\u2019s co-corresponding author. \u201cYou cannot put materials next to the skin that are uncomfortable and may not be safe. So we are putting things that are used around us all the time, and are soft and flexible.\u201d Ghosh is the William A. Klopman Distinguished Professor of Textile Engineering, Chemistry & Science in NC\u00a0State\u2019s Wilson College of Textiles.<\/p>\n Part of the researchers\u2019 work involved designing the sensor system to be lightweight and small enough for human use. The work was a collaboration between researchers in textile, electrical, computer and biomedical engineering at NC\u00a0State. The human experiments were performed by rehabilitation engineering researchers led by\u00a0Helen Huang, the Jackson Family Distinguished Professor in the UNC\/NC\u00a0State Joint Department of Biomedical Engineering and a senior co-author of the paper.<\/p>\n They created the sensor patch by sewing the yarns together in such a way that they created an electromagnetic field. When the researchers sewed the yarns into a lattice, and applied a small amount of electrical power using a small battery, they found they could measure the amount of electrical charge drawing the yarns together at each lattice point. The charges changed depending on how close the yarns were together, which related to how much pressure was applied by the wearer. They connected yarns, insulated them, laid them on a textile fabric, and connected them to a small electronic device to capture the data. They also included a small radio in order to wirelessly track the measurements.<\/p>\n \u201cWe connected the textile fibers to an electrical circuit that is a little larger than a quarter, and that can scan as many as 10 by 10 fibers,\u201d said the study\u2019s co-corresponding author\u00a0Alper Bozkurt<\/a>, professor of electrical engineering at NC\u00a0State. \u201cThat gives us 100 points of measurement. Everything is connected to a tiny microcomputer, which has a radio for wireless data tracking.\u201d<\/p>\n While researchers used a yarn that was commercially available for the study, they are also working on developing their own textile fiber to detect more than just pressure changes in the socket of an amputee\u2019s prosthetic limb.<\/p>\n The next step in the project is to integrate the sensors into prosthetic sockets directly, or into a wearable item. They would also need to study the sensor\u2019s potential clinical value in a larger study.<\/p>\n \u201cOur broader vision is to design something like a sock, or to integrate the sensor system into the prosthetic socket, so when a person dons their prosthesis, they are able to monitor what\u2019s happening in terms of pressure distribution and other measurements,\u201d\u00a0Huang said.<\/p>\n