In this paper we demonstrate a dark field video imaging system for the detection and size characterization of individual magnetic micromarkers suspended in liquid and the detection of pathogens utilizing magnetically labelled E.coli. The system follows dynamic processes and interactions of moving micro/nano objects close to or below the optical resolution limit, and is especially suitable for small sample volumes (~ 10 μl). The developed detection method can be used to obtain clinical information about liquid contents when an additional biological protocol is provided, i.e., binding of microorganisms (e.g. E.coli) to specific magnetic markers. Some of the major advantages of our method are the increased sizing precision in the micro- and nano-range as well as the setup’s simplicity making it a perfect candidate for miniaturized devices. Measurements can thus be carried out in a quick, inexpensive, and compact manner. A minor limitation is that the concentration range of micromarkers in a liquid sample needs to be adjusted in such a manner that the number of individual particles in the microscope’s field of view is sufficient.

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A. Malec, C. Haiden, G. Kokkinis, F. Keplinger, and I. Giouroudi, "Dark field imaging system for size characterization of magnetic micromarkers," Proc. SPIE 10247, Bio-MEMS and Medical Microdevices III, 102470B (Presented at SPIE Microtechnologies: May 10, 2017; Published: 30 May 2017); https://doi.org/10.1117/12.2267943.