Application-oriented surface acoustic wave humidity sensors: a review

Purpose This paper aims to present an application-oriented systematic review of surface acoustic wave (SAW) humidity sensors, covering the entire chain from sensitive materials and device structures to system integration. Design/methodology/approach The differentiated requirements of six major application scenarios are analyzed. Key strategies for sensitive material innovation device structure optimization and system integration are reviewed for each scenario. Findings Different scenarios impose multidimensional constraints on sensitivity, response speed, stability, biosafety and cost. Polymers offer high sensitivity in medical applications but require improved stability. Metal oxides are suitable for industrial environments yet exhibit relatively low sensitivity. Carbon-based materials show great potential for ultra-trace detection but suffer from poor consistency. Natural materials meet safety requirements for food packaging but lack sufficient sensitivity. For system integration, wireless passive operation, signal demodulation, temperature compensation and robust packaging are key technological pillars for practical use. Originality/value This work constructs an application-oriented technical roadmap for SAW humidity sensors along the “material–device–system” chain. It clarifies the rationale for selecting technical paths in different scenarios and identifies breakthrough directions in material stability, process consistency and multifield decoupling.