Electrospun Fiber-Based Hydrophobic Nanocomposite Sensors with Rapid Humidity Response for Sustainable Respiratory Monitoring

Slow humidity response and poor tolerance to high-humidity environments have limited the use of flexible humidity sensors in continuous respiratory monitoring. Herein, we report a flexible multifunctional sensor composed of a multilayered three-dimensional (3D) thermoplastic polyurethane (TPU) fiber network with firmly attached carbon nanotubes (CNTs) and silica (SiO2) nanoparticles fabricated via electrospinning, followed by a swelling-assisted self-assembly process. Benefiting from the weak interaction bond between CNTs and water molecules, the sensor achieves an ultrafast humidity response (0.82 s) and a broad humidity detection range, enabling real-time monitoring of human respiration. The hierarchical 3D fiber network of the sensor surface increases the contact area with airflow, accelerating moisture exchange and thus improving the sensitivity to humidity. The superhydrophobic surface (water contact angle = 167.8°) allows the sensor to detect human respiration stably for extended periods of time in high humidity environments. The strong 3D fiber skeleton and firmly anchored CNTs endow the device with excellent stability and robustness under repeated use. In addition, the sensor is breathable and lightweight, enhancing the wearer comfort. Owing to these advantages, the sensor enables accurate, long-term respiratory monitoring in real time and shows great promise for human–machine interfaces and early warning systems for sleep-related breathing disorders.