16 September 2014 Anomalous behavior of a three-dimensional, optically trapped, super-paramagnetic particle
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Super-paramagnetic particles are used extensively in diagnostics and other research applications for the purification of cells, biomolecules and assays. Here, we demonstrate full 3D optical manipulation of such sub-micrometer sized particle using optical tweezers. We report three types of anomalous behavior of such a trapped particle. Firstly, the analysis of particle motion recorded by the quadrant photodiode reveals spikes in the total detected intensity that are formed by a set of very fast oscillations. Secondly, the dependence of trap stiffness on the laser power deviates from the expected linear increase for higher trapping powers. And further, such a particle cannot be optically trapped above certain trapping power threshold. We speculate that these effects are caused by particle internal structure and by its heating.
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Martin Siler, Petr Jákl, Oto Brzobohatý, Jan Jezek, Pavel Zemánek, "Anomalous behavior of a three-dimensional, optically trapped, super-paramagnetic particle", Proc. SPIE 9164, Optical Trapping and Optical Micromanipulation XI, 916436 (16 September 2014); doi: 10.1117/12.2062148; https://doi.org/10.1117/12.2062148

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