Like bees to honey, a Schulich School of Engineering research team is quickly finding its way to developing a powerful new sensor for tiny amounts of airborne chemicals.
And they are doing it with inspiration from Mother Nature.
The team's nanoscale technology detects molecules in the air by mimicking how insects and animals track scents, down to just 100 parts per billion (ppb), far more sensitive than the human nose, which typically only detects scents at parts per million (ppm).
Seonghwan (Sam) Kim (left) and Arindam Phani are refining the sensitivities of sensors to more accurately mimic those of insects and animals. Photo Credit: Joe McFarland
Lead researcher Dr. Arindam Phani, PhD, says this work opens new doors in the areas of monitoring air quality in real-time and detecting disease biomarkers from breath.
"Nature doesn't wait for molecules to settle," says Phani, an acting research associate in the Department of Mechanical and Manufacturing Engineering. "Insects, for example, sense changes and fluctuations in the air around them. We wondered: what if we could build that into a sensor?"
The team's findings, reported in Tracking Molecular Signatures at ppb Sensitivity Using Fluctuational Kinetics in Metal-Organic Frameworks, has been published in the journal Nano Letters.
Strong sense of smell
Conventional sensing technologies rely on adsorption, which is a molecule of one substance sticking to the surface of the sensor.
Phani, however, says that this traditional method struggles to distinguish between molecules with similar properties and often takes time to reach a stable reading, especially when the concentration is very low.
He says adsorption is governed by a molecule's adsorption energy, and the differences in these energies are often very small across different molecules, making it difficult to achieve precise readings using conventional approaches.
Working with co-first author Dr. Balasubramanian Srinivasan and corresponding author Dr. Seonghwan (Sam) Kim, both PhDs, of Schulich's Nano/Micro-Sensors and Sensing Systems Lab, the team wanted to replicate how insects find their way to smells so quickly.
"Say you open a bottle of wine or peel a banana while your window is slightly open," Phani says. "In no time, you will find a fruit fly there anticipating food."
Coating a vibrating quartz crystal with a thin layer of porous material called a metal-organic framework, the team exposed the sensor to different gases to see how it reacted.
Srinivasan says subtle changes in how molecules moved in and out of the sensor's pores created a "distinct, kinetic fingerprint" for each type of molecule, allowing them to detect each gas separately.
Creating a buzz for industry
Just as insects have natural amplifiers and filters to detect minute chemical cues, the team's sensor has already demonstrated its ability to detect trace amounts of organic compounds at extremely low concentrations.
"This dynamic behaviour - captured in real-time - offers a new way of recognizing chemical signatures that would otherwise go unnoticed using traditional methods," says Kim, a professor and Canada Research Chair in Nano Sensing Systems.
Phani says their findings represent a major step forward in translating biological principles into advanced material technologies for environmental safety, medical diagnostics and even food-quality monitoring.
"This is about more than just detection," he says. "We're unlocking a new way to understand how molecules behave, which opens the door to smarter, faster and more selective sensors."
The team is looking to refine their current sensor's design while building on their findings by looking at how temperature and humidity impact adsorption on the sensor.
The research is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, Canada Research Chairs Program and Mitacs Accelerate Program.
