Microscope Beats Diffraction Limit
MANCHESTER, England, March 3, 2011 — A microscope created by scientists at the University of Manchester shatters the record for the smallest object the eye can see, beating the diffraction limit and likely helping to elucidate the causes of many viruses and diseases.
Dr. Wei Guo, research associate. (Images: University of Manchester)
Standard optical microscopes can see items clearly at only about 1 μm. Electron microscopes can see only the surface of a cell rather than its structure, and there is no tool to see a live virus visually.
But now, by combining an optical microscope with a transparent microsphere, dubbed the “microsphere nanoscope,” the researchers can see down to 50 nm under normal lights.
Experimental configuration of white light microsphere nanoscope with λ/8 to λ/14 imaging resolution. Schematic of the transmission mode microsphere superlens integrated with a classical optical microscope. The spheres collect the near-field object information and form virtual images that can be captured by the conventional lens.
This hugely increased capacity means that the scientists, led by Lin Li and Zengbo Wang, could potentially examine live viruses inside a human cell for the first time to potentially see what causes them. Li and Wang report their work in a recent issue of Nature Communications.
Microsphere superlens imaging in transmission mode: a, Microsphere superlens imaging of 360-nm-wide lines spaced 130 nm apart (top left), the optical nanoscope (ON) image (top right) shows the lines are clearly resolved; b, a gold-coated fishnet anodic aluminum oxide (AAO) sample imaged with microspheres (a = 2.37 μm, borders of two spheres are shown by white lines) superlens. The nanoscope clearly resolves the pores, which are 50 nm in diameter and spaced 50 nm apart (bottom left). The size of the optical image between the pores within the image plane is 410 nm (bottom right). It corresponds to a magnification factor of m = 8.2.
The new nanoimaging system is based on capturing optical, near-field virtual images, which are free from optical diffraction, and amplifying them using a microsphere — a tiny spherical particle that is further relayed and amplified by a standard optical microscope.
“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,” Li said. “Not only have we been able to see items of 50 nm, 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.”
Microsphere nanoscope reflection mode imaging: a, Microsphere superlens reflection mode imaging of a commercial Blu-ray DVD. The 100-μm-thick transparent protection layer of the disc was peeled off before applying the microsphere (a = 2.37 μm). The subdiffraction-limited lines are resolved by the microsphere superlens; b, Reflection mode imaging of a star structure made on a GeSbTe DVD. The complex shape of the star, including a 90-nm corner, was clearly imaged.
Among other tiny objects the scientists will be able to investigate are anodized aluminum oxide nanostructures and the nanoscale patterns on Blu-ray DVDs, not previously visible with an optical microscope.
For more information, visit: www.manchester.ac.uk
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