FUNDAMENTALS AND ADVANCES IN ULTRA-LOW MOISTURE SENSING: FROM NANOSTRUCTURED INTERFACES TO SMART INDUSTRIAL INFRASTRUCTURE

Abstract

In applications such as semiconductor manufacturing, lithium-ion battery manufacturing, gas purification lines, and aerospace systems the precise detection of very low relative humidity (RH) and low moisture content () is very critical. The physisorption-based Grotthuss ionic conduction mechanisms break down at low moisture content because of the absence of continuous networks of liquid-like water molecules. This extensive review provides the reader with a detailed synthesis of the state-of-the-art fundamental physicochemical mechanisms involved in low-moisture sensing, including chemisorption, dielectric modulation, quantum tunneling and interfacial charge transfer. High performance solid-state trace moisture sensors are comprehensively explored in terms of advanced synthesis, deposition and fabrication routes. This encompasses nanostructured metal oxides, defect-engineered metal-organic frameworks (MOFs), 2D material heterostructures and flexible substrates. Sensitivities, hysteresis limits, response/recovery times and long-term stability under severe drying are among the key performance parameters that are critically evaluated. Lastly, we bring an integrated analytical view on the use of low moisture sensors combined with a calibration model based on artificial intelligence (AI) and automatic edge-computing nodes for the next generation of a smart industrial infrastructure.