Study on LC wireless passive humidity sensor using MoS2/CS composite material: examination of high sensitivity and the chemical-physical synergistic adsorption mechanism

This paper introduces a wireless passive humidity sensor based on a molybdenum disulfide (MoS 2 ) nanoflower and chitosan (CS) composite material, designed to address the limitations of traditional humidity sensors, including weak response, complex structure, and high cost, particularly in extreme humidity environments. The innovative MoS 2 /CS composite dielectric layer was developed by leveraging the high specific surface area and active sites of MoS 2 , in conjunction with the hydrophilicity and biocompatibility of CS. Experimental results demonstrate that an optimized composite material ratio (MoS 2 :CS = 1:20) yields an ultra-high sensitivity (660 kHz/%RH), faster response/recovery time (70 s/120 s), The device demonstrates a strong linear response within a humidity range of 40 %–60 %RH, evidenced by a linearity value of 0.98779. However, between the humidity range of 60 %–95 %RH, the resonant frequency exhibits a quintic relationship with humidity. In this range, the linearity R 2 value is 0.99656. and minimal hysteresis (approximately 3 %) across a broad humidity range (40 %–95 % RH). Furthermore, the chemical-physical synergistic adsorption mechanism of the composite material was elucidated using characterization methods such as FTIR, XPS, and SEM. Chemical adsorption (hydrogen bonding and coordination bonding) predominates at low humidity, while physical adsorption (swelling and interlayer hydration) is more prevalent at high humidity. The sensor offers several advantages, including low cost, long-term stability (no drift for 30 days), and environmental compatibility, thereby providing a high-performance solution for the Internet of Things and closed monitoring systems. This also expands the potential application of two-dimensional materials and biopolymers in the field of wireless sensing.