Synergistic MXene/GO composites for flexible capacitive humidity sensors with ultrahigh sensitivity and fast response

High-performance flexible humidity sensors are critical enabling components for next-generation wearable systems and electronic skin (e-skin), although achieving concomitant ultrathin geometries, mechanical flexibility, and ultrahigh sensitivity remains challenging. This study presents a significant advancement through the development of a capacitive flexible humidity sensor based on engineered Ti 3 C 2 T x (MXene)/graphene oxide (GO) heterostructures. The synergistic interactions between the polar surface terminations of MXene (rich in –OH and –F groups) and the facilitated water transport properties of GO are exploited to yield a humidity-sensing layer exhibiting a significantly enhanced dielectric response to moisture. The optimized MXene/GO device achieves a striking ultrahigh sensitivity ( S = 1.24 × 10 6 % ΔC/C₀), representing a 228-fold improvement over its pristine MXene counterpart, across a wide operational range of 11 % to 97 % relative humidity (RH). The sensor further exhibits rapid dynamic responses (adsorption/desorption times of 17 s / 7 s, respectively) and maintains excellent linearity (R 2 = 0.99). This work highlights the efficacy of MXene/GO heterostructures for developing ultra-sensitive flexible humidity sensors, paving the way for innovative applications in non-contact interfaces, skin hydration diagnostics, and physiological monitoring.