Atoms, Molecules Or Even Living Cells Can Be Manipulated With Light Beams
Arthur T Knackerbracket has found the following story:
They are reminiscent of the "tractor beam" in Star Trek: special light beams can be used to manipulate molecules or small biological particles. Even viruses or cells can be captured or moved. However, these optical tweezers only work with objects in empty space or in transparent liquids. Any disturbing environment would deflect the light waves and destroy the effect. This is a problem, in particular with biological samples because they are usually embedded in a very complex environment.
[...] "However, this scattering effect can be compensated," says Michael Horodynski, first author of the paper. "We can calculate how the wave has to be shaped initially so that the irregularities of the disordered environment transform it exactly into the shape we want it to be. In this case, the light wave looks rather disordered and chaotic at first, but the disordered environment turns it into something ordered. Countless small disturbances, which would normally render the experiment impossible, are used to generate exactly the desired wave form, which then acts on a specific particle.
To achieve this, the particle and its disordered environment are first illuminated with various waves and the way in which the waves are reflected is measured. This measurement is carried out twice in quick succession. "Let's assume that in the short time between the two measurements, the disordered environment remains the same, while the particle we want to manipulate changes slightly," says Stefan Rotter. "Let's think of a cell that moves, or simply sinks downwards a little bit. Then the light wave we send in is reflected a little bit differently in the two measurements." This tiny difference is crucial: With the new calculation method developed at TU Wien, it is possible to calculate the wave that has to be used to amplify or attenuate this particle movement.
Journal Reference:
Michael Horodynski, Matthias Ki1/4hmayer, Andre Brandstitter, Kevin Pichler, Yan V. Fyodorov, Ulrich Kuhl, Stefan Rotter. Optimal wave fields for micromanipulation in complex scattering environments[$]. Nature Photonics, 2019; DOI: 10.1038/s41566-019-0550-z
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