When you enter the nanoscale, it’s a different world. With enormous possibilities.
When I started my PhD, I didn’t have a background in nanotechnology, and I really struggled to grasp the concepts that exist at nanoscale.
I remember talking to my supervisor about one of the concepts that contradicted the whole understanding that I had learned from seven years of study of material science and engineering technology.
There was a rubbish bin outside of his office window, and he said to me, “Could you please just go outside to that bin and vomit everything you’ve learnt into it? It doesn’t help you. What you’ve learned is the knowledge of the micro, but I want you to learn the knowledge of atoms and molecules. And these two scales do not work together in parallel.”
He believed it would be easier to teach me if I knew nothing…
The best example is gravity, which we learn from a very young age impacts everything, from the rain that falls to the movement of the stars and planets.
Yet gravity doesn’t exist at all in the nanoscale. When you work in atoms and molecules, you are dealing with a very new set of rules, and a new bunch of forces that are impacting your nano particles.
We usually don’t even consider gravity at all in our calculations: the chance of that matter particle being hit by another molecule, and then being moved in the other direction, is much greater. Forces like electromagnetism and Brownian motion – even the tiny magnetic force between two charged particles – are far more likely to change behaviour.
Read more on nanoscale science: Teeny tiny transistors
Nano, remember, means one billionth. One nanometre is one billionth of a metre. Very very very tiny.
The irony here is that because we work on such a very small size, we need to use huge pieces of equipment. We have to create a very controlled environment inside that equipment to control the movement of molecules.
The challenge for us is to use nanotechnology to bring down the size of this kind of infrastructure.
My PhD project was a UV sensor that is so tiny that you can have it on your sunglasses or clip onto your clothing to measure how much UV is absorbed by your skin.
I wanted to work on something that would benefit society, and had read that Australia has the highest mortality rate of melanoma in the world – and only 4% is genetic, meaning 96% can be prevented by reducing UV exposure. But you can’t see UV and you can’t feel UV, so it makes it very difficult to estimate how much you’ve absorbed through your skin.
So I thought, what if we can create a device that can just talk to the end user and tell them, “Hey, you’ve absorbed 80% of the recommended exposure. Time to take cover.”
The first version was a little bit chunky, like a watch, but over time it has become as small as a Fitbit. Right now, my students are working on making it even smaller, like a five-cent coin.
When I was researching these nanoscale sensors, I realised that some are also sensitive to gases. This realisation opened a new door and I began work on a different type of project. What if we can make a tiny sensor that is sensitive to particular gases? It can have many different applications.
I chose to work on the detection of acetone in our breath, because acetone is a biomarker for diabetes – the level of glucose in the blood. People living with diabetes have to prick their fingers for blood four times a day to get that measurement – which is around 3000 times a year. It’s a very invasive test, and even adults can mentally struggle to accept that they have to do the test again and again. For kids, it’s even more challenging and painful.
So I built a very spongy, tiny sensor – one that is super porous. Even though the acetone trace is very, very low, we can still detect the disease by analysing human breath.
This is not my idea – everyone knew it. And we already have machines that can make this measurement – but they are huge infrastructure. The challenge has been to do it in real time, with a tiny device. What if the end user can just pick up the device and breath onto the sensor and see the level of glucose in their blood?
A normal level of acetone in the breath of a non-diabetic is one part per million. But if you have two parts per million of acetone, you are diabetic. So it’s not enough for the sensor to be sensitive to parts per million. It should be sensitive to parts per billion.
I now have a sensor that can detect 10 parts per billion.
The next challenge is to improve this even more.
To do this, the answer might be found in nature, because dogs and bees can detect parts per trillion.
Researchers are still struggling to understand how these creatures do this, but they’ve been digging into how they smell, how they analyse, and how they can be trained. We already have very good information, and I used some of this information in building my sensor.
But if we can detect parts per trillion with devices built at nanoscale, that would be the next big thing. It would open up the potential to create sensors for virtually every disease – especially many cancers. Medical doctors have already published papers that demonstrate that the biomarkers for around 30 diseases can be found in human breath. We know they’re there, but they’re often in parts per billion – so we need to be able to measure parts per trillion.
If I can push these sensors to parts per trillion . . . That’s my passion, my motivation. We’re not there yet, but we are making great advances.
Dr Noushin Nasiri is the Head of the NanoTech Laboratory at Macquarie University. Her research is focused on design and fabrication of nanostructured materials, miniaturised sensor technologies, and wearable electronics for personalised and preventive medicine. She is a 2022 L’Oreal/UNESCO For Women In Science fellow.