The idea behind nanopore-based DNA sequencing is relatively simple – pass a DNA molecule through a nanopore channel, sort of the same way you pass a thread through an eye of the needle. As the DNA is passing through the pore, it can be “read out” by looking for specific signatures of the four bases in, for example, electrical capacitance. Experimental implementation of this idea is of course very challenging.
Gershow and Golovchenko demonstrate that they have ability to “suck” the DNA molecule back into the pore, sufficiently long time after it left the pore. The figure above demonstrates this process schematically.
See also a News and Views by Derek Stein, as well as “Colloquium” review of DNA sequencing approaches in Review of Modern Physics paper by DiVentra and Zwolak.