Experimental configuration of white light microsphere nanoscope. The spheres collect the near-field object information and form virtual images that can be captured by the conventional lens.
Credit: Daniel Cochlin
SYDNEY: Researchers have created an optical microscope with the capability to observe objects as small as 50 nanometres (nm) using an ordinary white light – a record-setting breakthrough in magnification technology that could revolutionise the study of cells.
This development means people can now examine nano materials using relatively inexpensive equipment. It could also allow scientists to look inside human cells and live viruses for the first time without using fluorescent dyes – though researchers are still investigating this potential application.
“We have developed a very simple way of achieving high magnification optical microscopy, well beyond the theoretical limits of light,” said co-author Lin Li, professor of laser engineering at the University of Manchester in England. “It offers the opportunities to examine live cells, bacteria and virus interactions to understand the causes of disease.”
Breaching the nanoscale with light
Previously, standard optical microscopes were limited in what they could view by light diffraction – the slight bending of light as it passes around an obstacle – and could only view objects around one micrometre in size. This is equivalent to 0.001 millimetres or 1,000 nm, roughly the size of a single bacterium.
In order to get around this limitation, researchers combined an ordinary optical microscope with transparent microspheres – tiny spherical particles made of glass. These essentially act like super magnifying glasses.
The new imaging system captures virtual images free from light diffraction, amplifies these images using the microspheres, and then magnifies them even further using a standard optical microscope.
20 times smaller than before
With this new microscope – labelled the ‘microsphere nanoscope’ – researchers have found a way around the diffraction limit of light to observe objects 20 times smaller than previously possible, and in so doing could push the boundaries even further.
“Not only have we been able to see items of 50 nanometres, we believe that is just the start and we will be able to see far smaller items... Theoretically, there is no limit on how small an object we can see,” Lin said, though he acknowledged certain practical obstacles.
Limitations can arise depending on how samples are collected and magnified, Lin said. This is particularly important as researchers move away from fixed structure observations toward viewing living cells and viruses, which are not flat and move around.
Another important obstacle preventing this limitless theoretical notion is resolution-quality, which would need to be maintained as researchers progress further down the nanoscale.
