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An Artificial Nose! - Explained in Two Minutes - WA Node

June 2013

Gino Putrino is a PhD student at the University of Western Australia and one of 12 winners of a world-wide competition for researchers to reduce their work to simple visual ideas that can be understood by everybody. Gino was the only West Australian finalist chosen from among more than 200 competitors that entered an international 'PhD TV 2 Minute Thesis' contest (see here for the full animated version).

Gino's project attempts to bring together vibrating mechanical beams, lasers, and butterfly wings to aid in the early detection of lung cancer.

How does it do this? Let Gino explain.

Gino Putrino in his lab  

Above - Gino Putrino in his lab (image coutesy of UWA).

Below - Green Hairstreak Butterfly (image courtesy of The Dublin Naturalists' Field Club)

 
Green Hairstreak Butterfly  

"The air we breath is packed full of invisible chemicals that carry a huge amount of useful information. A sensitive enough artificial nose could decipher this information, making possible the ability to tell if someone has lung cancer simply by sniffing their breath, detecting explosives in an airport, or just telling if vegetables in a supermarket are fresh."

Micro-electro-mechanical sensors (MEMS), a specialty area of research and development at the School of Electrical, Electronic and Computer Engineering and supported by the WA Node of the ANFF at UWA, are a new class of device which have been shown to be sensitive enough to do all these things.

"The way in which they work is like this. You make a suspended mechanical beam, clamped at one end. You then coat it with an substance which sticks to the specific chemical you want to sense. If you hit this beam, it will start vibrating at a speed that is called its natural frequency. If the chemicals you are trying to sense then stick to the beam, that speed will change, and if you are able to detect that change, you have an incredibly sensitive device."

"The problem is that these beams need to be tiny, typically one tenth of a mm long, and the frequency that they vibrate at is over 20,000 times a second. Humans are just too big and slow to see them, so we need to find a way to see what these sensors are doing."

To explain how his PhD solves this problem you need to understand the optical properties of the wings of the Green Hairstreak butterfly. The shimmering colours of these wings are not created by pigments, but rather by nano-structured shapes which create an effect called diffraction, where different colours of light are bent in different directions.

"If nature can do it, then so can we: by fabricating a similar nano-structure underneath the beam, and aiming a laser through it, the amount of light that reaches the other side will depend on the height of the mechanical beam."

And so by bringing all these things together: what mechanical engineers know about vibrating beams; what chemists and biochemists know about which chemicals stick to each other; what micro-electronic engineers know about making tiny things; and strangely, what physicists know about how butterfly wings bend light, then we can build such a device to check if groceries are fresh, to remotely pick up explosives in an airport, or to test for lung cancer without needing a biopsy.

Gino Putrino's PhD TV entry

Gino's work on this project, which has three patents pending so far, is in collaboration with Winthrop Professor John Dell, Dean of the Faculty of Engineering, Computing and Mathematics; Winthrop Professor Lorenzo Faraone, Director of the Centre for Semiconductor Optoelectronics and Microsystems and Director of the ANFF WA Node; Professor Adrian Keating in the School of Mechanical and Chemical Engineering; and Professor Mariusz Martyniuk, (Facility Manager of the ANFF WA Node) in the School of Electrical, Electronic and Computer Engineering.

Story and images provided by Gino Putrino, PhD student at the School of Electrical, Electronic & Computer Engineering - UWA.