Physicists at the ARC Centre of Excellence for Transformative Meta-Optical Systems are developing portable infrared micro-spectrometers aimed at improving consumer access to air quality data. This technology could be integrated into wearable devices to monitor multiple toxic and greenhouse gases, enabling individuals to make better-informed decisions about their health.

Developed by the Centre's University of Melbourne team, the technology is published in Microsystems and Nanoengineering. It uses a machine learning algorithm and metasurface spectral filter arrays to create a microspectrometer (MIMM) that detects the unique infrared signature of multiple gases with a single sensor. The current prototype is the size of a matchbox but has the potential for further miniaturization.

Traditional infrared spectrometers, though excellent at gas detection, are typically bulky and limited to laboratory use. Existing portable multi-gas detectors are bulky due to their use of multiple sensors and chemiresistors, which provide inferior results and have limited lifespans. These limitations prevent current technology from being miniaturized or integrated into wearable devices or the Internet of Things.

A metasurface filter integrated with an off-the-shelf IR detector addresses miniaturization issues by creating sensors from nanometre-thick materials. TMOS researchers created a metasurface spectral filter array to sense all harmful gases. The filter array consists of metallic nanostructures on a silicon substrate, with spectral features tunable by varying the periodicity of the nanostructures. The study demonstrated its effectiveness with carbon dioxide, methane, ammonia, and methyl-ethyl-ketone.

Lead author Jiajun Meng stated, "The microspectrometer is a metasurface filter array integrated with a commercial IR camera that is consumable-free, compact (~ 1 cm3) and lightweight (~1 g). The machine learning algorithm is trained to analyze the data from the microspectrometer and predict the gases present."

TMOS Chief Investigator Kenneth Crozier commented, "The next steps in the research are to increase the sensitivity of the device and make the platform more robust. We are excited about this technology because with a little more development it can be applied to lots of other chemical detection problems (e.g. solids and liquids)."

Research Report:Smart mid-infrared metasurface microspectrometer gas sensing system