Slip-Coupled Electroosmosis and Electrophoresis Dictate DNA Translocation Speed in Solid-State Nanopores

Controlling the DNA translocation speed is critical in nanopore sequencing, but remains rather challenging in practice, as attributable to a complex coupling between nanoscale fluidics and electrically mediated migration of DNA in a dynamically evolving manner. One important factor influencing the translocation speed is the DNA-liquid slippage stemming from the hydrophobic nature of the oligonucleotide, an aspect that has been widely ignored in the reported literature. In an effort to circumvent this conceptual deficit, here we first develop an analytical model to bring out the slip-mediated coupling between the electroosmosis and DNA-electrophoresis in a solid-state nanopore at low surface charge limits, ignoring the end effects. Subsequently, we compare these results with the numerical simulation data on electrokinetically modulated DNA translocation in such a nanopore, albeit of finite length with due accommodation of the end effects, connecting two end reservoirs by deploying a fully coupled Poisson-Nernst-Plank-Stokes flow model. Both the numerical and analytical results indicate that the DNA translocation speed is a linearly increasing function of the slip length, with more than four-fold increase being observed for a slip length as minimal as 0.5 nm as compared to the no-slip scenario. Considering specific strategies on demand for arresting high translocation speeds for accurate DNA sequencing, the above results establish a theoretical proposition for the same, premised on an analytical expression of the DNA-hydrophobicity modulated enhancement in the translocation speed for designing a nanopore-based sequencing platform─a paradigm that remained to be underemphasized thus far.