Scalable fabrication of gas sensors via spark-ablation printing of semiconductive metal oxide nanoparticles and heterostructures.

Semiconductive metal oxide (SMO) gas sensors are extensively used in air monitoring, industrial safety, and hazardous-gas detection due to their high sensitivity, low cost and low power consumption. Advances in nanotechnology have enabled precise control over the morphology and electronic structure of SMOs, thereby enhancing their sensing performances. However, the implementation of nanoscale SMOs into gas sensors typically involves two steps consisting of material synthesis and subsequent transfer onto device substrates, which face challenges in ensuring high uniformity and reproducibility. Here, we report a scalable gas sensor fabrication strategy based on spark-ablation printing, which enables the simultaneous synthesis and direct deposition of SMO films onto micro hotplate sensor chips. This one-step process allows the integration of both pristine and noble-metal-decorated SMOs, achieving ppb-level gas detection limit with excellent device-to-device consistency. Furthermore, sensor arrays composed of diverse SMO materials, when integrated with machine-learning algorithms, enable the accurate classification of four gases (>99%), demonstrating the potential of this approach for scalable and intelligent gas-sensing applications. Spark-ablation printing employs pulsed high-voltage discharges to vaporize electrode materials, generating nanoparticles that are transported by the gas flow and deposited onto MEMS microheater arrays as porous sensing films. This solvent-free and region-selective deposition technique enables scalable integration of diverse metal oxides, providing a robust platform for high-performance gas sensing.