Hydrodynamic Slip on DNA Observed by Optical Tweezers-Controlled Translocation Experiments with Solid-State and Lipid-Coated Nanopores

We use optical tweezers to investigate the threading force on a single dsDNA molecule inside silicon-nitride nanopores between 6 and 70 nm in diameter, as well as lipid-coated solid-state nanopores. We observe a strong increase of the threading force for decreasing nanopore size that can be attributed to a significant reduction in the electroosmotic flow (EOF), which opposes the electrophoresis. Additionally, we show that the EOF can also be reduced by coating the nanopore wall with an electrically neutral lipid bilayer, resulting in an 85% increase in threading force. All experimental findings can be described by a quantitative theoretical model that incorporates a hydrodynamic slip effect on the DNA surface with a slip length of 0.5 nm.