Abstract Despite the wide applications of strain sensor in wearable devices and electronic skins, the poor flexibility, low sensitivity and repeatability, as well as the utilization of noxious agents dramatically restrict its large-scale application. Herein, a simple and efficient strategy is demonstrated to fabricate flexible, ultrahigh sensitive and reproducible strain-sensing platforms via an eco-friendly water-based layer-by-layer assembly method. Specifically, renewable and biocompatible cellulose nanocrystals with electronegativity were used as the stabilizer to disperse multiwall carbon nanotubes (MWCNTs), meanwhile chitosan solution with rich positive charges was used as the effective “gluing” to enhance the interaction force between the monolayer MWCNTs. The resulting multilayer cracking-structured nanocomposites exhibited ultrahigh sensitivity with a gauge factor ∼359 and detection limit of e = 0.5%. The samples maintained similar sensitivity even after 200 cycles of stretching/releasing. The high sensitivity is attributed to the disconnection-reconnection of the bioinspired spider-like microcrack junctions in MWCNTs layer. Moreover, the obtained strain sensor showed the abilities to detect not only large-scale body motions (finger bending) but also small-scale physiological strains induced by minute movements of muscles upon swallowing and smiling. It is promising to integrate this kind of strain sensors with human beings in future wearable devices and electronic skins.

中文翻译：

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用于高灵敏度应变传感的仿生多层组装微裂纹结构纳米复合材料

摘要 尽管应变传感器在可穿戴设备和电子皮肤中有着广泛的应用，但其灵活性差、灵敏度和重复性低以及有毒物质的使用严重限制了其大规模应用。在此，展示了一种简单有效的策略，通过环保的水基逐层组装方法制造灵活、超高灵敏度和可重复的应变传感平台。具体而言，具有电负性的可再生和生物相容性纤维素纳米晶体被用作分散多壁碳纳米管（MWCNT）的稳定剂，同时具有丰富正电荷的壳聚糖溶液被用作有效“粘合”以增强单层MWCNT之间的相互作用力。所得的多层裂纹结构纳米复合材料表现出超高的灵敏度，应变系数约为 359，检测限为 e = 0.5%。即使经过 200 次拉伸/释放循环后，样品仍保持相似的灵敏度。高灵敏度归因于 MWCNTs 层中仿生蜘蛛状微裂纹连接的断开-重新连接。此外，获得的应变传感器不仅能够检测大规模的身体运动（手指弯曲），还能够检测由吞咽和微笑时肌肉的微小运动引起的小规模生理应变。有望在未来的可穿戴设备和电子皮肤中将这种应变传感器与人类集成。即使经过 200 次拉伸/释放循环后，样品仍保持相似的灵敏度。高灵敏度归因于 MWCNTs 层中仿生蜘蛛状微裂纹连接的断开-重新连接。此外，获得的应变传感器不仅能够检测大规模的身体运动（手指弯曲），还能够检测由吞咽和微笑时肌肉的微小运动引起的小规模生理应变。有望在未来的可穿戴设备和电子皮肤中将这种应变传感器与人类集成。即使经过 200 次拉伸/释放循环后，样品仍保持相似的灵敏度。高灵敏度归因于 MWCNTs 层中仿生蜘蛛状微裂纹连接的断开-重新连接。此外，获得的应变传感器不仅能够检测大规模的身体运动（手指弯曲），还能够检测由吞咽和微笑时肌肉的微小运动引起的小规模生理应变。有望在未来的可穿戴设备和电子皮肤中将这种应变传感器与人类集成。获得的应变传感器不仅能够检测大规模的身体运动（手指弯曲），还能够检测由吞咽和微笑时肌肉的微小运动引起的小规模生理应变。有望在未来的可穿戴设备和电子皮肤中将这种应变传感器与人类集成。获得的应变传感器不仅能够检测大规模的身体运动（手指弯曲），还能够检测由吞咽和微笑时肌肉的微小运动引起的小规模生理应变。有望在未来的可穿戴设备和电子皮肤中将这种应变传感器与人类集成。