This Flexible Knitted Wearable Sensor Wants to Track Your Knee Health in Comfort

A team of researchers from the Singapore University of Technology and Design (SUTD), working with SingHealth Polyclinics, has developed a knitted wearable designed for continual monitoring of the knee joint — combining data acquisition with user comfort.

"Most existing approaches require the CF [Conductive Fabric] to be externally attached to users' clothing or other non-conductive substrates through manual techniques like sewing or thermal welding," the researchers explain of the issues they worked to solve "These CF sensors' sensitivity and working range are restricted by the properties of the underlying substrate and the limited selection of commercially available CF. Moreover, CF based sensors are prone to error if misplaced from their intended location during fabrication."

To solve that, the team stopped trying to add conductive fabric to existing garments and instead knitted the device from scratch as a single fabric — using an industrial knitting machine with computer numeric control (CNC) to vary the geometric and material properties as it's produced. "CNC knitting machines are analogous to multi-material 3D printers as they can seamlessly integrate multiple yarns in various stitch patterns and stitch densities into a single textile of arbitrary 3D geometry," the team explains. "This can produce a bespoke textile in a single manufacturing step that minimizes the need for post-processing methods, such as cutting or sewing."

The material the researchers created was designed as a sensor to be worn on the knee, and in testing an Arduino Nano 33 BLE Sense-powered prototype proved capable of accurately tracking movements through leg extension and flexion, walking, jogging, and stair-climbing — responding to step activities in under 90 milliseconds and measuring joint angles changes as low as 0.12 degrees. This, its creators say, could prove the device's worth for the tracking of mobility-related health conditions in everyone from athletes to the elderly — and without discomfort.

"We have started working on extending the wearable to special user groups and to monitor other body joints, such as the shoulder," says co-corresponding author Low Hong Yee, associate professor at SUTD, of the team's future focus. "We're also looking at securing an incubation fund to explore the commercialization potential of the wearable."

The team's work is available under closed-access terms in the journal Advanced Healthcare Materials.