Shiyu Wei is working on tiny pillars made from indium phosphide. With diameters less than one hundredth the diameter of human hair, these nanowires, as they are called, have remarkable properties that can be used for building microscopic lasers, antennae or light detectors.
But they have a drawback – their surface is sensitive, easily damaged by chemicals, and usually needs to be treated to prevent damage degrading performance.
“We know nanowires have a drawback, they are not that robust, and need to be protected from their surrounding environment,” Shiyu says.
“But that kind of behaviour is perfect for sensing chemicals – so I’m making use of the drawback.”
She has put that sensitivity to work in a tiny sensor that detects nitrogen dioxide, a vehicle pollutant, and ingredient in acid rain. Her array of indium phosphide nanowires can detect parts per billion of nitrogen dioxide, and is much smaller and lighter than existing technology, which needs a trained technician to operate it. Better yet, it is self-powered, operating as a miniature solar cell.
To test it, she wired in a USB connection, and held it next to her car’s exhaust, seeing a clear signal from the pollutant.
By tweaking the surface of the nanowires, Shiyu and the team in the Electronic Materials Engineering Department are now optimising sensitivity to other gases, for example acetone, which could be used in a breath test for diabetes, carbon dioxide, and also for human pulse and temperature. [LF1]
Shiyu’s gas sensors are an exciting departure for the group in EME, run by Professor Lan Fu, who have to date focused on the optical and optoelectronic properties of nanowires.
In contrast, Shiyu had studied ammonia sensors in her masters. She knew Professor Fu through a collaboration with her supervisor at the Heifei University of Technology in China, and reached out to her for a PhD position.
Professor Fu saw the potential in bringing Shiyu into the group to add to the breadth of the ANU research.
“Shiyu has taken up the challenge and quickly developed a novel nanowire array gas sensor and successfully demonstrated it,” Professor Fu says
“In a short period of time, Shiyu has mastered many complicated experimental techniques and has developed excellent understanding of the properties and operation mechanism of nanowire materials and devices.”
“She is a very good thinker and always comes up solutions to problems encountered during her research.”
For Shiyu a move to Australia was attractive.
“I was normally working 12 hours a day, and the environment in Australia is not so pushy,” she says.
“I’ve got a lot of support, the engineers are willing to help and very professional.”
“Everyone is friendly, and the city is clean. But there are no people on the streets, and not so much entertainment. And the sun is so hot!”
She is also part of the Centre of Excellence for Transformative Meta Optical Systems (TMOS).
“TMOS has broadened my horizons about what others are doing, and I have plenty of opportunity to have access to other labs, and their equipment. This is really great for us. ”
As well as helping to develop technology that might save lives, improve the environment, and reduce global power consumption, Shiyu is motivated by her voyage of discovery.
“Research is about finding a land that no one has been to before. My own curiosity to explore unknown worlds is what motivates me to keep working.”
Ms Shiyu Wei