A bioinspired MXene-based flexible humidity sensor with ultrahigh sensitivity for noncontact interaction and physiological monitoring.

Monitoring humidity accurately and reliably is critical for healthcare, human-machine interaction, and smart systems. However, existing humidity sensors struggle to simultaneously achieve ultrahigh sensitivity, fast response, environmental stability, and mechanical flexibility. Inspired by the cerebral cortex's folded structure and neural protection mechanisms, we develop a bioinspired flexible humidity sensor based on alkalized MXene (aMXene), oxygen vacancy-engineered TiO2 (Ov-TiO2), and sodium lignosulfonate (SL). The aMXene mimics cortical folds to provide abundant water-adsorption sites, SL acts as a protective "meningeal" layer to enhance hydrophilicity and oxidation resistance, and Ov-TiO2 nanoparticles function as "synaptic" sites to promote water dissociation and ion transport. This neuron-network-inspired synergy enables an outstanding response (26369) over a wide humidity range (11%-98% RH), a fast response time of 1 s, low hysteresis (2.24%), and robust flexibility (stable after 100 bending cycles). The sensor further demonstrates reliable non-contact interaction, real-time respiratory monitoring, and diaper wetness detection. This work offers a general biomimetic strategy to integrate structural and functional design for next-generation intelligent sensing systems.