Engineers from Macquarie University have developed a new technique to manufacture nanosensors that is more sustainable, cost-effective, efficient, and versatile. This breakthrough significantly improves a key process in the trillion-dollar global nanosensor industry.
The team has discovered a method to treat each sensor using a single drop of ethanol, eliminating the conventional high-temperature heating process.
Their research, titled ‘Capillary-driven self-assembled microclusters for highly performing UV detectors’, was published yesterday in the Journal of Advanced Functional Materials.
Associate Professor Noushin Nasiri, head of the Nanotech Laboratory at Macquarie University’s School of Engineering and corresponding author, explains that nanosensors are typically composed of billions of nanoparticles on a small surface. However, most of these sensors do not function initially.
The nanoparticles self-assemble but are held together by weak natural bonds, resulting in numerous gaps that prevent the transmission of electrical signals, thus rendering the sensor non-functional.
While working to enhance ultraviolet light sensors, Associate Professor Nasiri’s team made this discovery. The technology behind Sunwatch, which made Nasiri a finalist for the 2023 Eureka Prize, relies on ultraviolet light sensors.
Nanosensors have a high surface-to-volume ratio due to their layers of nanoparticles, making them highly sensitive to the substances they are designed to detect. However, most nanosensors require a time-consuming, energy-intensive 12-hour heating process at high temperatures to fuse the layers of nanoparticles, creating channels for electrons to pass through and enable sensor functionality.
Associate Professor Nasiri notes that the furnace used in the conventional process destroys most polymer-based sensors, and nanosensors with tiny electrodes can melt. Furthermore, many materials cannot withstand high temperatures, limiting their use in sensor manufacturing.
However, the Macquarie team’s new technique bypasses this heat-intensive process, allowing for nanosensors to be made from a wider range of materials.
According to Associate Professor Nasiri, “Adding one droplet of ethanol onto the sensing layer, without heating it, causes the atoms on the surface of the nanoparticles to move and the gaps between nanoparticles to disappear as the particles join together.”
“We demonstrated that ethanol significantly improves the efficiency and responsiveness of our sensors beyond what can be achieved with a 12-hour heating process.”
During the process, lead author and postgraduate student Jayden (Xiaohu) Chen accidentally splashed ethanol onto a sensor while washing a crucible. This incident, which would usually destroy the sensitive device, led to the discovery of the new method.
Chen explains, “I thought the sensor was ruined, but later realized that the sample was outperforming every other sample we’ve ever made.”
Although the accident triggered the idea, the method’s effectiveness relied on meticulous research to determine the exact volume of ethanol required.
Associate Professor Nasiri says, “When Jayden obtained this result, we carefully conducted experiments with different ethanol quantities. He repeatedly tested to find the optimal volume that worked.”
“It was like Goldilocks – three microliters was inadequate, 10 microliters was excessive and destroyed the sensing layer, but five microliters was just right!”
The team has filed patents for this discovery, which has the potential to make a significant impact in the nanosensor industry.
Associate Professor Nasiri explains, “We have developed a recipe for making nanosensors work, and we have tested it with UV light sensors and sensors for detecting carbon dioxide, methane, hydrogen, and more. The effect is the same.”
“After applying one correctly measured droplet of ethanol, the sensor becomes active in about a minute. This transforms a slow, highly energy-intensive process into something much more efficient.”
Associate Professor Nasiri has already received interest from Australian and international companies that are eager to collaborate in implementing this technique.