Integrated Passive Device-Based Gas Sensor Combined with PANI/SnO₂ Composites for Ammonia Detection

This paper investigates the application of microwave-transduction-based sensors in gas detection. An optimized microwave resonator sensor based on integrated passive device (IPD) technology coated with PANI/SnO 2 composites that changes its dielectric properties under ammonia (NH 3 ) exposure is developed. PANI/SnO 2 is an organic–inorganic composite that exhibits good response and recovery capability to ammonia at room temperature, establishing the foundation for a microwave detection scheme. The performance of the gas sensor under a 10–120 ppm ammonia environment is studied by observing the microwave parameters of the microwave sensor, with the frequency shifts of 0.299 and 0.925 MHz/ppm at low (10–60 ppm) and high (60–120 ppm) concentration levels at room temperature (20 °C) and 40% relative humidity (RH). In addition, a capacitive device based on micro–nano processing technology is fabricated to study the gas sensing mechanism and observe the relationship between PANI/SnO 2 composites under different ammonia environments and the variation of dielectric properties.