Advances and Prospects of Chemiresistive Breath Humidity Sensors

Chemiresistive breath humidity sensors (CRBHSs) have emerged as a promising technology for non-invasive health monitoring, offering high sensitivity, a simple device architecture, strong miniaturization potential, and low power consumption. This review summarizes recent progress in CRBHSs from three core perspectives: sensing mechanisms, material systems, and device applications. First, we outline the fundamental sensing principles, emphasizing the Grotthuss proton-hopping mechanism and the resistance modulation associated with water adsorption/desorption. Next, we discuss structural engineering strategies for zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) sensing materials, highlighting how dimensional design can balance water uptake, charge transport, mechanical compliance, and wearability. Finally, we review representative applications ranging from healthcare diagnostics and respiratory monitoring to emotion- and behavior-related assessment. Overall, this review integrates the mechanism–material–application relationship to provide a cohesive understanding of CRBHSs; identifies key challenges such as environmental stability and anti-interference performance; and outlines future directions, including performance optimization, flexible/wearable integration, and intelligent sensor systems.