Solid State Nanopores

Our group was among the first groups to study DNA translocation through solid state nanopores. The method of using a TEM to drill nanopores in very thin SiN membranes was developed in our group and we are still actively involved in improving our understanding of pore formation. The detection of single DNA molecules using such pores is very similar to a Coulter counter, where single cells are detected by the current blockade they case as they traverse a narrow channel. The nanopore is mounted in a flow cell seperating two compartments filled with an electrolyte (see the figure).DNA translocation - animation

Using electrodes, a voltage difference is applied between both compartments, leading to an ionic current through the nanopore. As a molecule nears the pore, it will be attracted into the pore, thereby temporarily blocking the ionic current. The nanopore therefore acts as a coulter counter, detecting single molecules. In addition, the magnitude and duration of this current blockade can be used to elucidate structural features of the molecules such as the molecular diameter and its’ charge distribution.

We have recently extended this principle to study more complex molecular constructs, such as DNA-protein complexes. Apart from studying the translocation of these molecules, we also employ a combination of nanopores and optical tweezers to locally exert and measure the forces involved in these processes. Finally, our efforts have shifted towards using these artificial pores to mimic real biologically relevant pores, such as the nuclear pore complex.

Very recently, we have fabricated the ultimately thinnest solid-state nanopore into a graphene monolayer. We demonstrated that single molecules of DNA in water can be pulled through such a graphene nanopore and, importantly, that each DNA molecule can be detected as it passes through the pore.