Stretchable optical fiber strain sensor comprising zinc oxide and PDMS for human motion monitoring

Wearable sensors are extensively used in various healthcare applications, including human motion monitoring. Stretchable, soft, and flexible strain sensors are essential for the fabrication of smart wearable devices for human motion monitoring. In this study, we propose a zinc oxide (ZnO) nanoparticle-composited polydimethylsiloxane (PDMS) polymer fiber with good mechanical properties. This polymer optical fiber was successfully measured for human joints and had a reliability of 99 %. To obtain a calibration curve, the polymer fiber sensor obtained data on the change in optical loss with angle at a resolution of 15° within the 0–90° range. The calibration curve was used in the joint motion monitoring to measure the unknown strain and angle values in real-time. The strain measurement of the ZnO-PDMS optical fiber (ZPOF) sensor is evaluated in various conditions, including human joints, wet conditions, and hand tremors. The results demonstrate that the ZPOF sensor can be used in wearable devices for various healthcare applications, such as rehabilitation, sports, and physical therapy.