A smart nanofluidic diode that exhibits both ion gating and ion current rectification has been developed using a 1-(4-amino-phenyl)-2,2,2-trifluoro-ethanone-functionalized, conical nanochannel in a polyimide (PI) membrane. The switch-like property can be tuned by controlling the wettability and charge distribution with carbonate ions. Such a nanodevice is advantageous for precisely controlling conductive states with an ultrahigh gating ratio of up to 5000, and a high rectification ratio of 27. By virtue of the high selectivity and sensitivity for carbonate ions, this nanofluidic diode may find applications in carbonate or carbon dioxide detection. 

Angewandte Chemie, 2015 

The operational principle of bioinspired carbonate-activated and tuned nanofluidic diodes. After modification with the hydrophobic molecule APTE, the pore surface can absorb carbonate ions and be recycled by the removal of these absorbed ions with carbonate ionophore VII (CI VII) (bottom). Consequently, ion currents through the functional nanochannel can be precisely controlled. Such control can also be achieved by using different concentrations of carbonate solution, which can function like a tunable switch (top).