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Nanoparticle Translocation through Conical Nanopores: A Finite Element Study of Electrokinetic Transport

Recent years have seen a surge of interest in nanopores because such structures show a strong potential for characterizing nanoparticles, proteins, DNA, and even single molecules. These systems have been extensively studied in experiment as well as by all-atom and coarse-grained simulations, with a strong focus on DNA translocation. However, the equally interesting problem of particle characterization using nanopores has received far less attention. Here, we theoretically investigate the translocation of a nanoparticle through a conical nanocapillary. We use a model based on numerically solving the coupled system of electrokinetic continuum equations, which we introduce in detail. Based on our findings, we formulate basic guidelines for obtaining the maximum current signal during the translocation event, which should be transferable to other nanopore geometries. In addition, the dependence of the signal strength on particle properties, such as surface charge and size, is evaluated. Finally, we identify conditions under which the translocation is prevented by the formation of a strong electro-osmotic barrier and show that the particle may even become trapped at the pore orifice, without imposing an external hydrostatic pressure difference.