E-nose olfactory chips detect multiple gases and odours

For decades, researchers worldwide have been developing artificial olfaction and electronic noses (e-noses) with the aim of emulating the intricate mechanism of the biological olfactory system to effectively discern complex odorant mixtures. But major challenges to their development lie in the difficulty of miniaturising the system and increasing its recognition capabilities in the presence of complex odorant mixtures.

Now a research team led by the School of Engineering of the Hong Kong University of Science and Technology (HKUST) has addressed these challenges with arrays of diverse high-performance gas sensors. The team’s newly developed biomimetic olfactory chips (BOC) are able to integrate nanotube sensor arrays on nanoporous substrates with up to 10,000 individually addressable gas sensors per chip, a configuration that is similar to how olfaction works for humans and other animals.

To tackle the issues, the research team led by Professor Fan Zhiyong, Chair Professor at HKUST’s Department of Electronic & Computer Engineering and Department of Chemical & Biological Engineering, used an engineered material composition gradient that allows for wide arrays of diverse sensors on one small nanostructured chip. Leveraging the power of artificial intelligence, their biomimetic olfactory chips exhibit high sensitivity to various gases with excellent distinguishability for mixed gases and 24 distinct odours. With a vision to expand their olfactory chip’s applications, the team also integrated the chips with vision sensors on a robot dog, creating a combined olfactory and visual system that can accurately identify objects in blind boxes.

The development of the biomimetic olfactory chips will not only improve the existing broad applications of the artificial olfaction and e-nose systems in food, environmental, medical and industrial process control, but also open up new possibilities in intelligent systems, such as advanced robots and portable smart devices, for applications in security patrols and rescue operations.

For example, in their applications in real-time monitoring and quality control, the biomimetic olfactory chips can be used to detect and analyse specific odours or volatile compounds associated with different stages of industrial processes to ensure safety; detect any abnormal or hazardous gases in environmental monitoring; and identify leakage in pipes to facilitate timely repair.

“In the future, with the development of suitable bio-compatible materials, we hope that the biomimetic olfactory chip can also be placed on a human body to allow us to smell odours that normally cannot be smelled,” Fan said. “It can also monitor the abnormalities in volatile organic molecules in our breath and emitted by our skin, to warn us of potential disease.”

The research work, carried out in collaboration with Tsinghua University, Jilin University and Fan’s startup company Ai-Sensing Co. Ltd., was recently published in Nature Electronics, in the paper titled Biomimetic Olfactory Chips Based on Large-Scale Monolithically Integrated Nanotube Sensor Arrays.

Image caption: A smart sensing chip mimicking the human nose. Image credit: HKUST