Single Artificial Ion Channels with Tunable Ion Transport Based on the Surface Modification of pH-Responsive Polymers.

Artificial ion channels with tunable ionic transport control and intelligent iontronic functions at the nanoscale have a wide application in logic computing and biosensing. Although some artificial ion channels with smart ion transport characteristics have been developed, most of them are constructed on porous membranes with undefined channel numbers. It is still challenging to achieve multiple ion transport features in single nanochannels and to control the ion flow more accurately with excellent repeatability. In this paper, a design strategy is presented to fabricate pH-responsive ion channels with various ion transport features based on a single polydimethylsiloxane (PDMS) nanochannel. The single-ion nanochannel developed by this approach can be further integrated into electronic systems on a chip. Three types of artificial ion channels are demonstrated and investigated systematically in this work. With symmetric or asymmetric pH stimuli, these ion channels can alternatively change their working states among an opened state, a closed state, and an ionic diode state. Four different ion transport features can be realized in a triple-gated ion channel system. With these advantages of the design, it is promising to build smart nanofluidic iontronic devices with widespread applicability in energy conversions, active ion transport control, and biological analysis.