Runner up of the 2016 UNSW Bragg Student Prize for Science Writing, Chelsy Teng, reveals the wonders of the scanning helium microscope.
Over the years Australians have been at the forefront of numerous innovations and discoveries. The nation’s natural tendency to solve problems has led to breakthroughs in many scientific fields.
Professor Paul Dastoor had a particular predicament. Examining delicate samples under a conventional microscope is less than ideal because they can become easily damaged when exposed to the microscope’s beams of light. So when Professor Dastoor and his team at the University of Newcastle in NSW announced the development of a new microscope in May 2016, they were met with excitement. Along with collaborators at the University of Cambridge in the UK, Professor Dastoor and his team had created the scanning helium microscope (SHeM) – the first prototype of its kind in the world.
Unlike conventional light or electron microscopes that fire energising beams of light or particles at a surface, the SHeM uses a beam of neutral helium atoms. This prevents damage to delicate materials as the high energy from conventional microscopes can cause samples to boil.
The charged nature of fired electrons from an electron microscope can create difficulties when imaging with electric or magnetic fields. This is also problematic when scanning insulating materials, as electrons will collect and add a conductive coating. To prevent this, SHeM samples are coated with gold. This means that the actual sample is never viewed – only a gold-coated image. So with the SHeM, scientists and researchers will be able to see what has never been seen before.
But why use helium? This element is more commonly used in balloons and is known for its squeaky effect on voices when inhaled.
Helium is used for two main reasons. Firstly, it is a noble gas with a full valence shell of electrons. It is highly stable as it does not chemically react with other substances, and its atoms are neutral. Due to its lack of electrical charge, it can image surfaces without causing damage.
Secondly, it has very low energy. The energy from a helium atom beam is 0.1 electron volts, compared to the 100,000 electron volt beam from an electron microscope. This is important because if too much energy is used, it can break chemical bonds and damage the sample being viewed. Thus, under a conventional electron microscope, many samples can only be viewed once or very few times, severely restricting the experimental period.
However, this is not the first time helium atoms have been used in microscopy. Helium atom scattering is a surface analysis technique that also exploits helium’s useful properties to probe substances. The difference between the SHeM and other designs is the SHeM’s pinhole concept, inspired by the design of the pinhole camera. Dastoor’s breakthrough was managing to form the helium atoms into a single beam so that they would capture images.
The SHeM microscope works by compressing helium gas and squirting it through a tiny hole into a vacuum chamber. It forms a beam that lands on the surface being imaged. This bounces into the detector and computer software then maps the image.
So why is the SHeM important? Its development has opened up a variety of new areas and applications, such as in pharmaceuticals, solar energy, defense, explosives and information technology. For example, delicate organic materials will no longer risk being damaged under examination. Currently, the SHeM has been used to view a spider’s fang and chitin on a butterfly’s wing, with stunning results. And explosives, which were unstable under conventional microscopes, can now be safely imaged. Further applications include removing carbon monoxide from exhaust gases and cleaning up toxic spills without harming surrounding flora and fauna, thus minimising environmental damage.
The SHeM also has the ability to reveal the chemical content of substances imaged. It can chemically ‘fingerprint’ thin coatings of metal and examine the composition of different surfaces. Different coatings reflect helium in different ways, allowing scientists to detect differences in the chemistry of surfaces. This will lead to further understanding of surface physics, and possibly many new discoveries. This also has implications for industries, as the ability to distinguish between similar materials is crucial in areas like electronics.
The scanning helium microscope will revolutionise the way scientists examine materials, increasing knowledge and creating solutions in numerous fields. Though it is yet to be adapted for commercial purposes, and further development is needed to increase the range of its imaging resolution and make it fit on a laboratory bench, it is definitely a step in the right direction. Regardless of the fact that it still has a way to go, this Australian breakthrough is set to forever change how we view the microscopic and the minuscule.
– Chelsy Teng
Year 9, James Ruse Agricultural High School
References
Barr, M. et al. (2016). Unlocking new contrast in a scanning helium microscope. Retrieved 29th May 2016
Cox, D. (2016). World-first scanning helium microscope looks at spider fangs and butterfly wings. Retrieved 22nd May 2016
Nicholson, J. (2016). World-first scanning helium microscope opens new scientific world. Retrieved 22nd May 2016
Pool, R. (2016). Helium microscope breakthrough. Retrieved 29th May 2016
Shih, I. (2016). New helium microscope reveals startling details without frying the sample. Retrieved 22nd May 2016
The University of Newcastle. (2016). Scanning Helium Microscopy. Retrieved 29th May 2016
Turner, S. (2016). Physicists unveil helium microscope. Retrieved 22nd May 2016
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