Synergistic Li⁺-functionalised Mo₂CTₓ MXene and polyaniline composite for rapid and stable moisture sensing in wearable wound monitoring application

Abstract

Managing optimal moisture balance is essential for chronic wound healing, yet current clinical assessments are often subjective and intermittent. This study reports the development of a high-performance, flexible resistive moisture sensor designed for real-time, quantitative wound monitoring. The active sensing layer consists of a lithium-ion (Li+) functionalized Mo2CTx MXene and polyaniline (PANI) composite. Li+ intercalation was utilized to expand the MXene interlayer spacing, enhancing water adsorption and ion transport. Simultaneously, in situ polymerized PANI was introduced to provide stable proton-conductive pathways. Current-voltage (I-V) characterization verified that the Li⁺–Mo₂CTₓ/PANI composite forms robust Ohmic contacts with the electrodes, exhibiting over a 40-fold enhancement in baseline electrical conductance compared to pristine Mo2CTx. The composite was integrated onto screen-printed circular interdigitated electrodes on a flexible PET substrate and encapsulated with poly(diallyldimethylammonium chloride) (PDAC). This protective PDAC layer acts as a semi-permeable moisture-diffusion barrier that regulates water molecule transport, prevents surface fouling and uncontrolled hydration saturation, and ensures environmental stability without compromising response speed. The sensor demonstrates a linear response across a wide relative humidity (RH) range of 20–80%, featuring sensitivity of approximately 2.0 ΔR/%ΔRH, with a rapid response time of ~1 s and a recovery time of ~11 s. The device demonstrates high mechanical flexibility, and stable operation over a 15-day period. Real-time assessments using finger-touch tests and PVA-hydrogel wound models successfully distinguished between dry, normal, and wet clinical states. The superior performance is attributed to the synergistic effects of Li⁺-assisted interlayer hydration, Grotthuss-type proton hopping, and moisture-induced PANI protonation. These findings position the Li⁺–Mo₂CTₓ/PANI composite as a promising candidate for next-generation smart dressings in digital wound management.