Highly Stretchable and Fluorescent Visualizable Thermoplastic Polyurethane/Tetraphenylethylene Plied Yarn Strain Sensor with Heterogeneous and Cracked Structure for Human Health Monitoring

Abstract

Smart wearable technology has been more and more widely used in monitoring and prewarning of human health and safety, while flexible yarn-based strain sensors have attracted extensive research interest due to their ability to withstand greater external strain and their significant application potential in realtime monitoring of human motion and health signals. Although several strain sensors based on yarn structures have been reported, it remains challenging to strike a balance between high sensitivity and wide strain ranges. At the same time, visual signal sensing is expected to be used in strain sensors thanks to its intuitiveness. In this work, thermoplastic polyurethane (TPU) and tetraphenylethylene (TPE) were wet-spun to fabricate flexible fluorescent fibers used as the substrate of the sensor, followed by the drop addition of polydimethylsiloxane (PDMS) beads and curing to produce a heterogeneous structure, which were further twisted into a plied yarn. Finally, a visualizable flexible yarn strain sensor based on solidified liquid beads and crack structure was obtained by loading polydopamine (PDA) and polypyrrole (PPy) in situ. The sensor exhibited high sensitivity (the GF value was 58.9 at the strain range of 143−184%), a wide working strain range (0−184%), a low monitoring limit (<0.1%), a fast response (58.82 ms), reliable responses at different frequencies, and excellent cycle durability (over 2000 cycles). At the same time, the yarn strain sensor also had excellent photothermal characteristics and a fluorescence crack visualization effect. These attractive advantages enabled yarn strain sensors to accurately monitor various human activities, showing great application potential in health monitoring, personalized medical diagnosis, and other aspects.

Polydopamine/Carbon Black/Carbon Nanofiber/Thermoplastic Polyurethane Composite Nanofiber Strain Sensor with Ultrahigh Loading Rate for Human Activity Monitoring

“…Therefore, it can be linked to a low-voltage driver or low-precision signal collector, and has lower signal processing accuracy requirements and larger error tolerance space, which proves the excellent applicability and reliability of PCCT. Comparing the PCCT with other schemes in the articles, the two parameters that GF in the common strain response interval of 0–100% and the approximate cost of the active filler were used as the judging indexes, respectively, and the obtained results are shown in Figure b, which shows that the PCCT achieves an excellent performance over most of the schemes based on a lower cost, proving the validity and significance of our work. ,,,,− Importantly, optimizing the encapsulation process or materials to reduce the interference of the encapsulation layer with the conductivity of the sensitive element can further improve the sensing performance of the device and extend the benefits of the polarity-induced mechanism.…”

“…(a) Relative change of resistance of PCCT with effect of tensile strain. (b) Comparison of data for PCCT with schemes from other articles. ,,,,− (c) Response time and recovery times of PCCT. (d) Effect of tensile velocity on the response stability of PCCT.…”