高强度耐低温纳米纤维素/聚乙烯醇导电复合水凝胶制备及其在柔性传感中的应用

纳米纤维素具有大长径比、较高的弹性模量与比表面积及丰富的表面官能团，是一种优良的纳米增强材料。首先以纳米纤维素(CNFs)为分散介质辅助分散MXene纳米片层，制备CNF-MXene纳米复合物，并通过FTIR与XPS分析CNFs与MXene的相互作用。以此复合物为增强填料，聚乙烯醇(PVA)为基底，制备CNF-MXene/PVA复合水凝胶，进一步通过KOH溶液处理，提高复合水凝胶的力学性能，并赋予复合水凝胶优异的离子导电性。该复合水凝胶表现出优异的力学性能，其拉伸强度与断裂伸长率分别达到255.9 kPa与1098.2%，还具有高电导率(2.38 S/m)、一定的抗冻性能与灵敏的应变/压力响应性。基于该复合水凝胶组装的应变/压力柔性传感器，由于具有极低的检测极限质量(100 mg)与极快的响应时间(225 ms)，可以监控脉搏跳动与喉咙发声微小震动引起的压力变化。因此，该复合水凝胶基柔性传感器非常有希望应用于未来新一代可穿戴电子、人机交互等领域。 

Preparation of high-strength and low-temperature-resistant nanocellulose/polyvinyl alcohol conductive composite hydrogel and its application in flexible sensing

Nanocellulose is an excellent nano-reinforcing material with large aspect ratio, high elastic modulus and specific surface area, and abundant surface functional groups. Nanocellulose (cellulose nanofibers, CNFs) was first used as the dispersion medium to disperse the MXene nanosheets for preparing the nanocellulose/MXene nanocomposites, and the interaction between nanocellulose and MXene was characterized and analyzed by FTIR and XPS. Then the CNF-MXene/PVA composite hydrogel was prepared by using the CNF-MXene nanocomposites as the reinforcing filler and polyvinyl alcohol (PVA) as the matrix, which was further treated with KOH solution to improve the mechanical properties of the composite hydrogel and endow the composite hydrogel with excellent ionic conductivity. The composite hydrogel exhibites excellent mechanical properties, the tensile strength and elongation at break were 22.5 kPa and 1098.2%, respectively. The hydrogel also possesses high conductivity (2.38 S/m), anti-freezing, and excellent strain/pressure responsive properties. Thanks to the extremely low detection limit (100 mg) and extremely fast response time (225 ms), the hydrogel-based strain/pressure sensor could monitor the pressure changes causes by pulse beating and small vibration of throat. Therefore, the composite hydrogel-based flexible sensor showes great promising applications in the next-generation wearable electronics and human-machine interaction.