Humidity sensors have been widely used for humidity monitoring in industrial fields. However, the application of conventional sensors is limited due to the structural rigidity, high cost, and time-consuming integration process. Owing to the good hydrophilicity, biodegradability, and low cost of cellulose, the sensors built on cellulose bulk materials are considered a feasible method to overcome these drawbacks while providing reasonable performance. Herein, we design a flexible paper-based humidity sensor based on conductive 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose fibers/carbon nanotubes (TOCFs/CNTs) conformal fibers network. The CNTs are dispersed by cationic cetyl trimethyl ammonium bromide (CTAB), which introduces positive charges on the CNTs surface. The conductive fibers are achieved by an electrostatic self-assembly process that positively charged CNTs are adsorbed to the surface of negatively charged TOCFs. The vast number of hydrophilic hydroxyl groups on the surface of TOCFs provide more water molecules adsorption sites and facilitate the electron transfer from water molecules to CNTs, endowing the sensor with an excellent humidity responsive property. Besides, the swelling of the TOCFs greatly damages the conductive CNTs network and further promotes the humidity sensitive performance of the sensor. Benefiting from the unique structure, the obtained sensor exhibits a maximum response value of 87.0% (ΔI/I₀, and the response limit is 100%), outstanding linearity (R² = 0.995) between 11 to 95% relative humidity (RH), superior bending (with a curvature of 2.1 cm⁻¹) and folding (up to 50 times) durability, and good long-time stability (more than 3 months). Finally, as a proof of concept, the sensor demonstrates an excellent responsive property to human breath, fingertip humidity, and the change of air humidity, indicating a great potential towards practical applications.

湿度传感器已广泛用于工业领域的湿度监测。然而，由于结构刚性、成本高、集成过程耗时，传统传感器的应用受到限制。由于纤维素具有良好的亲水性、生物降解性和低成本，构建在纤维素散装材料上的传感器被认为是克服这些缺点同时提供合理性能的可行方法。在此，我们设计了一种基于导电 2,2,6,6-四甲基哌啶-1-氧基 (TEMPO)-氧化纤维素纤维/碳纳米管 (TOCFs/CNTs) 保形纤维网络的柔性纸基湿度传感器。碳纳米管通过阳离子十六烷基三甲基溴化铵（CTAB）分散，在碳纳米管表面引入正电荷。导电纤维是通过静电自组装过程实现的，带正电的 CNT 被吸附到带负电的 TOCF 表面。TOCFs表面大量的亲水性羟基提供了更多的水分子吸附位点，促进了水分子向碳纳米管的电子转移，赋予了传感器优异的湿度响应性能。此外，TOCFs的膨胀极大地破坏了导电的CNTs网络，进一步提高了传感器的湿敏性能。得益于独特的结构，所获得的传感器的最大响应值为 87.0% ( TOCFs表面大量的亲水性羟基提供了更多的水分子吸附位点，促进了水分子向碳纳米管的电子转移，赋予了传感器优异的湿度响应性能。此外，TOCFs的膨胀极大地破坏了导电的CNTs网络，进一步提高了传感器的湿敏性能。得益于独特的结构，所获得的传感器的最大响应值为 87.0% ( TOCFs表面大量的亲水性羟基提供了更多的水分子吸附位点，促进了水分子向碳纳米管的电子转移，赋予了传感器优异的湿度响应性能。此外，TOCFs的膨胀极大地破坏了导电的CNTs网络，进一步提高了传感器的湿敏性能。得益于独特的结构，所获得的传感器的最大响应值为 87.0% (ΔI/I ₀，响应极限为 100%），在 11 至 95% 相对湿度（RH）之间具有出色的线性度（R ² = 0.995），出色的弯曲（曲率为 2.1 cm ^-1）和折叠（高达50 次）耐久性，长期稳定性好（3 个月以上）。最后，作为概念验证，该传感器对人体呼吸、指尖湿度和空气湿度变化表现出出色的响应特性，表明在实际应用中具有巨大潜力。