Ionic Current Behaviors of Dual Nano- and Micropipettes.

Ionic current rectification (ICR) phenomena within dual glass pipettes are investigated for the first time. We demonstrate that the ionic flow presents different behaviors in dual nano- and micropipettes when the two channels are filled with the same electrolyte KCl and hung in air. Bare dual nanopipettes cannot rectify the ionic current because of their geometric symmetry, but the ICR can be directly observed based on bare dual micropipettes. The phenomena based on dual micropipettes could be explained by the simulation of the Poisson-Nernst-Plank equation. After modification with different approaches, the dual nanopipettes have asymmetric charge patterns and show various ICR behaviors. They have been successfully employed to fabricate various nanodevices, such as ionic diodes and bipolar junction transistors. Due to the simple and fast fabrication with high reproducibility, these dual pipettes can provide a novel platform for controlling ionic flow in nano- and microfluidics, fabrication of novel nanodevices, and detection of biomolecules.