# Recent Advances in Fiber-Shaped Electronic Devices for Wearable Applications
## 3 Device Applications
### Sensing Devices  
Wearable 1D sensors have been developed to accurately monitor the environment and health, which can be characterized using various optical, mechanical, and chemical signals [1]. The flexible and compact sensor devices can conform to dynamic and irregularly shaped surfaces to collect high-quality data. This section briefly describes the most widely realized fiber-shaped sensor systems. Detecting human motion is necessary for medical care, sports science, and rehabilitation [46]. Wearable motion sensors can contribute to the quick diagnosis of characteristic movement disorders, including sudden paralysis and tremors in the body, and to quality care of physical diseases, such as Alzheimer's disease, Parkinson's disease, and diabetes [46]. To track human motion in real time, wearable mechanical sensors that can detect continuous deformation have been developed. [PERSON] et al. reported a sensing textile system for biomonitoring and interacting over the Internet (Figure 5a,b) [47]. A 3-ply-twisted polyester-silver fiber was made by entwining polyester fibers around a silver wire to form a triboelectric layer and an electrode on a silver-coated polyester fabric (Figure 5c) [47]. The hybrid fibers were stitched onto the silver-coated fabric, where they detected a continuous pulse wave induced by a combination of triboelectrification and electrostatic induction that originated from the fiber when it was mechanically deformed by human skin (Figure 5c) [47]. The textile-based sensor exhibited a high sensitivity of 3.88 V kPa\({}^{-1}\) in sensing tiny ambient pressure signals, and continuous operation across 80,000 cycles [47]. Based on the sensors, a wireless biomonitoring system (WBS) was developed to collect patients' health data, wirelessly transmit those data, and display the data through an APP interface on a mobile phone (Figure 5d) [47]. The WBS was able to diagnose obstructive sleep apnea and hypopnea syndromes, even with body movements [47]. The textile-based WBS highlights the great potential of smart textiles for personalized health care [47]. The triboelectric fiber device could have applications in a fiber rescue sensor [47]. A 3D honeycomb-structured triboelectric nanogenerator (TENG) based on a flame-retardant wrapping yarn was developed by [PERSON] and coworkers [48]. The sustainable and durable single-electrode triboelectric yarn was fabricated through a continuous, hollow-spinning, fancy twister process [48]. The conductive core yarn was wrapped with polyimide yarn for a core-sheath structure [48]. The TENG fibers offer flame retardancy and reduce vibration and noise [48]. Because the fibers can perform both energy harvesting and emergency signal transmission, the woven TENG fabric could be applied to locate a survivor's position in a fire and thereby enable the timely search and rescue of victims [48]. Flexible actuators can convert external energy (heat, light, electricity, humidity, etc.) into mechanical deformation. [PERSON] et al. reported a soft electroactive textile actuator [49]. A fabric electrolyte was coated with PEDOT:PSS conductive ink, doped with SWCNTs, and wired into a zeolite imidazolate framework-8 [49]. The intermediate electrolyte fabric was prepared by immersion in poly (vinylidene fluoride-co-hexafluoropropylene) to increase the ionic conductivity (6.7 mS cm\({}^{-1}\)) [49]. The resulting textile actuator operated under 3 V at frequencies from 0.1 to 10 Hz and showed a large strain difference of 0.28% s\({}^{-1}\) at 10 Hz and a good blocking force of 0.62 mN at 0.1 Hz, thanks to the high ionic conductivity, large specific surface area, and good mechanical features of the conducting electrodes based on metal-organic framework derivatives [49]. [PERSON] et al. applied SWCNT/PVA thermoelectric (TE) materials to wearable electronics [50]. The TE materials can convert temperature into an electrical voltage for use as touch sensors, health monitoring, and heat energy harvesting [50].