Image courtesy of SUTD.
Singapore University of Technology and Design (SUTD) researchers have developed a fully knitted, circuit-embedded knee wearable for wireless sensing of joint motion in real time. Compared to other knitted electronics, this model has fewer externally integrated components and a more sensitive sensor. The innovation is a collaboration between Associate Professor Low Hong Yee, PhD, and her colleagues from SUTD, along with Tan Ngiap Chuan, MBBS, MMed (Family Med), FCFP(S), MCI (NUS), FAMS, of SingHealth Polyclinics.
Their key considerations when designing the wearable were sensor data accuracy and reliability and for the sensor to rely on as few external components as possible. The result was a highly stretchable, fully functional sensing circuit made from a single fabric. Because the knee joint is important for lower limb mobility, the wearable was designed for the knee.
To develop this single-fabric circuit, the team mechanically coupled an electrically conductive yarn with a dielectric yarn of high elasticity in various stitch patterns. Dimensions were customized according to the subject’s leg. The functional components—sensors, interconnects, and resistors—formed a stretchable circuit on the fully knitted wearable that allowed real-time data to be obtained.
The team assessed the wearable through extension-flexion, walking, jogging, and staircase activities. Subjects wore the knee wearable together with reflective markers that were detected by a motion capture system, which allowed the comparison between sensor data and actual joint movement. The sensor response time was less than 90 milliseconds for a step input. Additionally, the smallest change in joint angle that the sensors could detect was 0.12 degrees. The sensor data showed strong correlation with joint movement data acquired from the motion capture system, demonstrating reliability of the sensor data.
