Stretchable and Strain-Decoupled Fluorescent Optical Fiber Sensor for Body Temperature and Movement Monitoring

A stretchable fluorescent optical fiber provides a flexible platform for wearable functional devices due to its stretchability and immunity to electromagnetic interference. However, for wearable applications, stretchable fiber sensors suffer from severe body movement-induced strain interference. Here, we report a stretchable optical sensor with strain-decoupling ability. The stretchable core-clad structured optical fiber is prepared with fluorescent nanoparticles and silicone-based elastomers that enable both efficient excitation light delivery and fluorescence collection. The excitation light loss and fluorescence intensity exhibit a linear response to the sensing variables and strain change, which have been utilized as the sensing parameters to decouple the strain from the sensing variables. Our strain-decoupled scheme is widely applicable to other stretchable fluorescent optical fiber sensors that are simultaneously subject to strain. In the experiment described here, the temperature-sensitive fluorescent nanoparticle-doped stretchable fluorescent optical fiber exhibits stable temperature-sensing in the range −10 to 60 °C, with an uncertainty as low as ±0.23 °C and a relative sensitivity of 1.3% °C–1, even when it is subjected to large strain up to 40%. We demonstrate sensor-integrated wearable masks and gloves, which can simultaneously measure physiological thermal changes and the movement of the wrist joint. Our sensor shows great promise as a technology for wearable health monitoring.