May 2021


Bending the coated threads creates strain, which changes their electrical conductivity (normal thread left, bent thread right; scale bar 200 microns).

Engineers at Tufts University have created and demonstrated flexible thread-based sensors that can measure movement of the neck, providing data on the direction, angle of rotation, and degree of displacement of the head. The discovery raises the potential for thin, inconspicuous tattoo-like patches that could measure athletic performance, assist with physical therapy, and more.

In their experiments, the researchers placed 2 threads in an “X” pattern on the back of a subject’s neck. Coated with an electric conducting carbon-based ink, the sensors detect motion when the threads bend, creating strain that changes the way they conduct electricity. When the subject performed a series of head movements, the wires sent signals to a small Bluetooth module, which then transmitted data wirelessly to a computer or smartphone for analysis. The data analysis involved sophisticated machine learning approaches to interpret the signals and translate them to quantitate head movements in real time, with 93% accuracy. In this way, the sensors and processor track motion without interference from wires, bulky devices, or limiting conditions such as the use of cameras, or confinement to a room or lab space.

While algorithms will need to be specialized for each location on the body, the proof of principle demonstrates that thread sensors could be used to measure movement in other limbs, according to the researchers. The skin patches or even form-fitting clothing containing the threads could be used to track movement in settings where the measurements are most relevant.

For situations such as on the athletic field, by placing thin tattoo-like patches on different joints, an athlete could carry motion sensors to detect their physical movement and form.

“[T]here could be a wide range of applications in healthcare as well,” said Yiwen Jiang, an undergraduate student at Tufts University School of Engineering, and a member of the research team. “For example, those researching Parkinson’s disease and other neuromuscular diseases could also track movements of subjects in their normal settings and daily lives to gather data on their condition and the effectiveness of treatments.”

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