Multilayer structured AgNW/WPU-MXene fiber strain sensors with ultrahigh sensitivity and a wide operating range for wearable monitoring and healthcare

The development of wearable healthcare electronics has created higher demands on both the sensitivity and stretchability of flexible sensors. As it is generally difficult to obtain a trade-off between sensitivity and stretchability, the fabrication of strain sensors with both a wide operating range (>= 100%) and high sensitivity (GF >= 100) remains a great challenge. Here, we propose for the first time a strategy based on the consolidation of two basic but seemingly paradoxical sensing mechanisms, i.e., slippage and crack propagation mechanisms, to greatly enhance the sensitivity of stretchable strain sensors. Based on stretchable polyurethane (PU) fibers, which can be easily woven into conventional fabrics to produce wearable devices, we present a multilayer sensing structured fiber sensor fabricated by layer-by-layer self-assembly of sliver nanowire (AgNW)/waterborne polyurethane (WPU) layers and MXene layers. The sensor simultaneously exhibits an ultrahigh sensitivity (GF = 1.6 x 10(7)) and a wide operating range (up to 100%), as well as great reliability and stability (1000 cycles) and fast response (344 ms) and relaxation (344 ms). Moreover, smart fabrics were fabricated by integrating fiber strain sensors into different clothes and a prototype body posture monitoring, analysis, and correction system was presented for healthcare applications. Our work not only breaks down the technological wall between high sensitivity and high stretchability of strain sensors, but also shows the great potential applications of wearable, comfortable, and non-intrusive electronics for real-time health monitoring.