Flexible strain sensors have attracted tremendous interest due to their potential application as intelligent wearable sensing devices. Among them, crack-based flexible strain sensors have been studied extensively owing to their ultrahigh sensitivity. Nevertheless, the detection range of a crack-based sensor is quite narrow, limiting its application. In this work, a stretchable strain sensor based on a designed crack structure was fabricated by spray-coating carbon nanotube (CNT) ink onto an electrospun thermoplastic polyurethane (TPU) fibrous mat and prestretching treatment to overcome the trade-off relationship. Our sensor exhibited combined features of high sensitivity in a greatly widened workable sensing range [a gauge factor of 428.5 within 100% strain, 9268.8 for a strain of 100–220%, and larger than 83982.8 for a strain of 220–300%], a fast response time (about 70 ms), superior durability (>10 000 stretching–releasing cycles), and excellent response toward bending. The microstructural evolution of CNT branches extending from two edges of the cracks and the excellent stretchability of TPU fibrous mats are mainly related to the remarkable sensing properties. Our sensor is then assembled to detect various human motions and physical vibrational signals, demonstrating its potential applications in intelligent devices, electronic skins, and wearable healthcare monitors.

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With the booming development of flexible electronics, the need for a multifunctional and high-performance strain sensor has become increasingly important. Although significant progress has been made in designing new microstructures with sensing capabilities, the tradeoff between sensitivity and workable strain range has prevented the development of a strain sensor that is both highly sensitive and also stretchable. Here, a wrinkle-assisted crack microstructure is designed and fabricated via prestretching the multiwalled carbon nanotubes ink (CNTs ink)/polyurethane yarn (PU yarn). This designed structure originates from the mismatch in Young’s modulus and elasticity between the CNTs ink and PU yarn during the stretching process. The structure endows the sensor with combined characteristics of a high sensitivity toward stretching strain (gauge factor of 1344.1 at 200% strain), an ultralow limit of detection (<0.1% strain), excellent durability (>10 000 cycles), a wide workable strain range (0–200%), and outstanding response and stability toward bending deformation. This high-performance strain sensor will see widespread improved performance across applications such as intelligent fabrics, electrical skins, and fatigue detection for full-range human motion monitoring.

A polydopamine (PDA)/carbon nanotube (CNT)/elastic band (EB) flexible strain sensor has desirable integration of an ultra-high strain range (920% strain), large sensitivity and superior durability (10 000 cycles).

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