'Nanoscope' makes live viruses visible for first time

High-tech microscope breaks record for tiniest object viewable under normal light. And with no limit on imaging capacity, who knows what life forms may soon be seen?

Viruses are small. Very small. There are millions of types, and the 5,000 or so that have been studied in detail are typically between 10 and 300 nanometers (one-billionth of a meter) in diameter.

These microspheres collect evanescent waves to form virtual images that can be captured by a conventional lens. University of Manchester

Because the wavelengths of visible light range from roughly 300 to 800 nanometers, viruses aren't exactly visible under normal lighting. Only optical fluoresce microscopes can see inside a virus, and then only indirectly, using dye, which cannot actually penetrate a virus.

So the "microsphere nanoscope" developed by scientists at the University of Manchester's School of Mechanical, Aerospace, and Civil Engineering in the U.K. and described in the journal Nature Communications is remarkable on two counts: It breaks the world record of direct imaging under normal lights by 20 times, viewing objects as small as 50 nm wide, and what's more, the tech behind it imposes no theoretical limit in the size of feature that can be seen.

This incredible jump in capacity could allow humans to see inside human cells and even live viruses for the first time, which in turn could give us many new insights into their structures and behaviors.

"This is a world record in terms of how small an optical microscope can go by direct imaging under a light source covering the whole range of optical spectrum," says Professor Lin Li, who initiated and led the research with academics at the National University and Data Storage Institute of Singapore. In a news release, Li adds:

Not only have we been able to see items of 50 nanometers, 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 will be able to see. Seeing inside a cell directly, without dying, and seeing living viruses directly could revolutionize the way cells are studied and allow us to examine closely viruses and biomedicine for the first time.

Because light waves inevitably spread out as they travel through space, there is a diffraction limit that caps the degree to which light waves can be focused, which in turn caps the size of an object that can be viewed.

The surfaces of objects, even objects as tiny as viruses, emit "evanescent waves" that fade so quickly they are usually lost, but this fast fading also frees them from the diffraction limit. The microscope, which is technically a nanoscope, uses tiny (between 2 and 9 micrometers--millionths of a meter--across) glass beads (called microspheres) to gather these evanescent waves, refocus them, and channel them into a standard microscope viewable under normal lights.

This method is entirely novel. It's as if the researchers are capturing the ghostly auras of invisible objects in order to see them. With no upper limit in terms of imaging capacity, who knows what life forms may soon be visible?

 

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