One-Step In Situ Inkjet Printing Fabrication of Au-Decorated Polyaniline on MEMS Platforms for Sensitive Ammonia...

High-performance ammonia (NH₃) sensors play a critical role in environmental protection and noninvasive medical diagnosis. This work reports a new NH₃ sensor based on Au-microsphere-decorated polyaniline (PANI) manufactured by a precise in situ inkjet printing method on a MEMS micro-hotplate. The in situ oxidative polymerization of aniline was performed directly on the MEMS platform using AuCl₃ as a bifunctional oxidant and precursor, with a hierarchical morphology of microspheres (~750 nm) and nanorods (~250 nm). Reduced from Au³⁺ in the polymerization reaction, Au microparticles achieve substantial catalytic promotion by virtue of chemical sensitization and spillover effect. The optimized Au-PANI MEMS sensor exhibits a superlative response of 201% toward 1 ppm NH₃ at room temperature, with an ultra-low theoretical limit of detection (LOD) of 0.42 ppb. Furthermore, the device demonstrates rapid response/recovery kinetics (76 s/72 s), exceptional selectivity against common interfering gases (SO₂, CO, H₂, etc.), and robust long-term stability with high response retention over two months. This research provides a scalable, cost-effective strategy for the mass production of miniaturized, high-sensitivity gas sensors for industrial and healthcare applications.