Ion Concentration Polarization Tunes Interpore Interactions and Transport Properties of Nanopore Arrays

Biological processes require concerted function of many channels embedded in the cell membrane. While single solid-state nanopores can be designed to mimic properties of individual biological channels, it is not yet known how to connect the pores to achieve biomimetic ionic circuits with interacting components. To identify physical processes that control interactions between nanopores in the same membrane, we designed a model system of nanopore arrays consisting of two and three nanopores with identical surface charge patterns. We also present our first results on arrays of pores with different transport properties, and arrays with a gate electrode. Arrays were fabricated in silicon nitride by electron beam sculpting. The constituent nanopores have opening diameters below 10 nm and the interpore spacing is tuned between 15 nm and 200 nm. Our experimental and modeling results reveal that nanopores interact via overlapping depletion zones created by concentration polarization. Interactions can be controlled by salt concentration and voltage. Our results showcase a possibility of tuning interactions between nanopores and transport properties of arrays by chemical modification of the pore walls. Arrays consisting of nanoporous ionic diodes feature depletion zones with higher concentrations, and lower current suppression than homogeneously charged pores. Our experiments and modeling provide the first steps to leave the constraints of single nanopores and to design biomimetic ionic circuits.