Design and fabrication of a three-dimensional folded MEMS infrared emitter for photoacoustic spectroscopy gas sensor

In this study, a three-dimensional folded nickel–chromium thin-film infrared emitter is proposed. The dimensions of the emitter, as well as their relationship with operating temperature and irradiance, are investigated through theoretical calculations and finite element simulations. To enhance infrared emissivity, an oblique angle physical vapor deposition process is employed to create nanostructures on the surface of the thin film, enabling blackbody-like infrared emission. Using a set of high-precision graphite molds, the emitter can be folded into a three-dimensional structure, effectively increasing its operating temperature. Experimental results show that under an input power of 410 mW, the emitter achieves a maximum operating temperature of 946 K. At a modulation frequency of 10 Hz, it maintains a modulation depth of 62%. The infrared emitter is integrated into a self-developed miniaturized photoacoustic spectroscopy gas sensor and achieves carbon dioxide detection with a sensitivity of 0.293 mV/ppm. In the long-term experiments, the infrared emitter exhibited excellent temperature stability over 2.4 × 106 operating cycles. These experiments demonstrated the feasibility and reliability of the infrared emitter, confirming its suitability for use in miniaturized PAS sensor applications.