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 in a targeted manner. However, these optical tweezers only work with objects in empty space. 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.
Scientists at the Vienna University of Technology have now shown how virtue can be made of necessity: A special calculation method was developed to determine the perfect wave form to manipulate small particles in the presence of a disordered environment. This makes it possible to hold, move or rotate individual particles inside a sample - even if they cannot be touched directly. The tailor-made light beam becomes a universal remote control for everything small. Microwave experiments have already demonstrated that the method works. The new optical tweezer technology has now been presented in the scientific journal "Nature Photonics".
M. Horodynski et al., Optimal wave fields for micromanipulation in complex scattering environments, Nature Photonics (2019): https://www.nature.com/articles/s41566-019-0550-z
Free version: https://arxiv.org/abs/1907.09956
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