One of the most exciting things about working in nanoscience is the incredible level of precision with which we can probe the world around us. This includes not just the physical world but also the biological world, which is a lot messier than most physicists are comfortable with!
There is currently intense interest in sequencing DNA via translocation through a nanopore, like threading a needle with the molecule that contains instructions for building life. Protein nanopores are the basis of new technology for DNA sequencing that made the news recently, costing only $1000 for full DNA sequencing with a palm-sized device from Oxford Nanopore. The protein nanopore is pictured in the image below, with DNA unspooling to pass through the pore.
But these nanopores can also be created in silicon, graphene or other thin materials. These solid state nanopores emulate the very small biological pores which can be found in the lipid bilayer around cells and their nuclei. Macroelectrodes in solution on either side of a solid state nanopore drive an ionic current in the carrier solution through the nanopore. As the DNA passes through the nanopore, it physically blocks the ionic current through the nanopore, allowing detection of translocation events. Additional electrodes can be added across the nanopore to enhance sensitivity to DNA. While research in this area is ongoing, it is thought that noise in the electrical signal through the nanopore can eventually be lowered—by applying coatings, slowing translocation speeds and improving fabrication techniques—to enable base pair sensitivity for DNA sequencing. Using solid state nanopores for sequencing could lead to more reliability and lower costs than protein sequencing, and is a major research area of the Drndić group at UPenn, the group I worked in for my PhD!
To me, nanopore sequencing is an amazing example of how direct electrical interaction with nanostructures can yield important information about not just the world around us, but our own place in it.