Electrophoretic Translocation of Star-Shaped Polymers through Single Solid-State Nanopores

While the translocation of linear polymers through nanopores is well-understood, the underlying mechanism of transport of branched polymers through nanopores is yet to be fully developed. In this general premise, we have investigated the translocation of multiarm star-like polyethylene glycols (PEGs) through single solid-state nanopores, using single-molecule electrophoresis. Our experiments reveal the conformational trajectories of multiarm-PEGs during their sojourn inside the nanopore in exquisite detail. We quantify these pathways in terms of the number of leading arms (fin) and the number of lagging arms (fout), which depend on the pore diameter (d) and the total number of arms (f). We have measured the average translocation time (τ), polymer capture rate (Rc), and polymer conformations during translocation in terms of d, f, and applied voltage (Vm). We find a direct proportionality between Rc and fVm, and between τ and f/Vm. Interestingly, star polymers with more arms inside the nanopore (fin) than outside (fout) also translocate successfully, in contrast with previous suggestions of fin < fout. As the pore size increases, the optimal fin shifts from 0.25f to 0.5f. In addition to gaining insight into the mechanism of translocation of star-like polymers, the present experimental strategy opens new opportunities to characterize and separate polymers with different branching architectures.