Beyond the impossible

The various phases to manufacture the nano-lens based lens. Nanoparticles are created and then aggregated forming the final lens by undergoing a phase transition. Credit: Wen Fan et al./Science Advances

What we see is the result of photons hitting an object and bouncing back to our eyes. In order to bounce back the photons, that behave both as particles (hence the bounce back) and as waves the object size should be big enough to stop the "wave". If it is too small the photon, behaving as a wave, will just go around the object as a sea wave does when a small rock happens to be on its path. If the rock is big enough the wave "bounces back".

There is, however, another factor that depends on the way we focus the light beam (the lens we use). This is the diffraction limit. When we use a lens on our camera the resolution we can get depends on the aperture of the lens. The bigger it is the more resolution we can get. But this resolution is limited by the wavelength and by the diffraction limit, also known as Abbe limit. This limits the resolution of visible light to about 200nm.

It is a physical limit, like the limit to the amount of information that can be squeezed on a radio link (Shannon limit). 

Well, a team of scientists at Bangor University in UK with colleagues at Fudan University in China has found a way to circumvent this limit by creating a new material made of droplets-like lens structure that can be layered onto the object to be observed. This acts as a magnifying lens moving the object virtual size beyond the Abbe limit and making its observation possible. You cannot see an object that is 100nm (below the Abbe limit) but you can enlarge it and then look at its virtual, enlarged, image.

You may say it is a trick, and indeed yes, it is. Likewise we have found a way to overcome the Shannon limits (that holds for a single radio channel) by using several radio channels at the same time!

The material designed by the team of scientists creates million nano beads that break up the light beam into millions reflecting each one. It is this collection of millions of light beams that allows us to go beyond the Abbe limit.

Beads are made with titanium dioxide and they are cheap to manufacture. Rather than changing your microscope you just pain the beads onto the “invisible object” and voilà, there it is for you to see.


What I find fascinating is the capability and ingenuity of scientists to go beyond limits.


Author - Roberto Saracco

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