Trapping single molecules with a solid state nanopore

I describe a system for measuring and manipulating single molecules using a solid state nanopore, a small hole in an insulating film fashioned using solid-state Silicon processing techniques. In this work, pores less than 10 nanometers in diameter in 20-30 nm thick Silicon Nitride membranes are used to join two reservoirs of salt water. DNA molecules added to one reservoir are forced through the nanopore by an applied voltage bias. Single molecules of DNA are detected passing through the pore by a blockage of the ionic current between the reservoirs. The depth and duration of the current blockages reveal information about the molecule's geometry while the shape of the blockage depends on the molecule's conformation. If the driving voltage is reversed soon after a molecule has passed through the nanopore, the same molecule can be "recaptured," induced to pass through the pore a second time. This process reveals information about the dynamics of the molecule outside of and its interaction with the nanopore. The recapture process can be repeated multiple times to form a single molecule trap.