Electrophoretic time-of-flight measurements of single DNA molecules with two stacked nanopores

Electrophoretic transport through a solid-state nanodevice comprised of two stacked nanopore sensors is used to determine the free-solution mobility of DNA molecules based on their "time-of-flight" between the two pores. Mobility measurements are possible at very low (100 pM) DNA concentration and for low as well as high salt concentrations (here 30 mM and 1 M KCl). The mechanism of DNA transport through the device is elucidated by statistical analysis, showing the free-draining nature of the translocating DNA polymers and a barrier-dominated escape through the second pore. Furthermore, consecutive threading of single molecules through the two pores can be used to gain more detailed information on the dynamics of the molecules by correlation analysis, which also provides a direct electrical proof for translocation.