Nanotube Nanofluidics

Ionic transport through nanoscale channels is receiving increasing attention due to recent experiments that report modulation of ion currents during the passage of single molecules of DNA or protein through the protein ion channel ?-hemolysin. The possibility of rapid DNA sequencing by monitoring the ionic conductance signatures of passing nucleotide oligomers has prompted the synthesis of artificial nanopores and the study of biomolecular transport through them. Nanotubes provide a unique high aspect ratio channel in which to study ion transport and fluid flow. A theoretical treatment of ion behavior in gated silica nanotubes suggests that when the tube diameter is smaller than the Debye length, an applied gate bias can completely expel ions of like charge and produce a unipolar solution of counter-ions within the channel. Modifying the surface charge on the nanotube with the gate electrode modulates the ionic current through the tube – the basis for a unipolar ionic field-effect transistor. Also, the 5-20 ?m length of the nanotube channels now being fabricated in this lab opens up the possibility of imaging and manipulating single molecules as they pass through a tube.


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