Mid-IR source based on a free-standing microhotplate for autonomous CO2 sensing in indoor applications

The measurement of CO₂ by Non-Dispersive InfraRed absorption (NDIR) is often used as a tracer of human occupancy in confined living spaces. The major constraint of commercial sensors comes from the power consumption of the IR source, which makes them unsuitable for autonomous operation.This paper reports the fabrication and the characterization of a black-body IR source based on a microhotplate micromachined in Si and suitable to work above 650 °C. The use of state-of-the-art MEMS technologies allows to lower the power consumption below 50 mW while ensuring a lifetime well beyond 10 years.The radiance of the microhotplate in the spectral range where CO₂ adsorption takes place indicated that the device works as a quasi-perfect blackbody source providing enough power to drive an autonomous NDIR system for CO₂ detection.