2D Ti3C2Tx-MXene-patterned electrode enables highly sensitive humidity sensing

Flexible, metal-free humidity sensors with high sensitivity, linear impedance response, and fast response/recovery times are vital for next-generation wearable electronics and environmental monitoring, whereas poor linearity limits the rapid and precise detection of humidity. Here, we report a metal-free humidity sensor that integrates lithographically patterned two-dimensional (2D) Ti 3 C 2 T x -MXene nanosheets (2DMS) interdigital electrodes (IDEs) with an engineered ultrathin network of 2D anatase TiO 2 nanosheets (2DTS) as the active humidity-responsive layer on a cyclic olefin copolymer (COC) substrate. The solution-processed 2DMS IDEs provide high electrical conductivity, mechanical robustness, and scalable patterning, while the 2DTS film forms a continuous, hydroxyl-rich, chemically robust surface network for reversible water adsorption and rapid proton-mediated transport. The resulting 2DMS@2DTS sensor exhibits highly linear and reversible impedance and capacitance modulation across a broad humidity range (6–86% RH), with low hysteresis, minimal change over 24 h, and a sensitivity of 4.41 × 10 5 Ω/%RH at 1 kHz. COMSOL-assisted finite element method (FEM) simulations reveal humidity-induced dielectric redistribution in the IDE’s electric field, while density functional theory (DFT) calculations demonstrate a reduced activation energy for proton (H⁺) migration under humid conditions. These theoretical insights are in excellent agreement with the experimentally observed fast, repeatable response and recovery characteristics, thereby providing a mechanistic understanding of the device’s high-performance humidity-sensing behavior. Owing to its all-2D-materials architecture and flexible COC substrate, the sensor enables practical applications, including real-time physiological monitoring. This work introduces a smart strategy that couples patterned 2DMS electrodes with engineered 2DTS to achieve scalable, metal-free, and flexible humidity sensors, providing a promising platform for wearable and intelligent sensing systems.