Fine-tuned ion transport across nanoscale pores is key to many biological processes, including neurotransmission. Recent advances have enabled the confinement of water and ions to two dimensions, unveiling transport properties inaccessible at larger scales and triggering hopes of reproducing the ionic machinery of biological systems. Here we report experiments demonstrating the emergence of memory in the transport of aqueous electrolytes across (sub)nanoscale channels. We unveil two types of nanofluidic memristors depending on channel material and confinement, with memory ranging from minutes to hours. We explain how large time scales could emerge from interfacial processes such as ionic self-assembly or surface adsorption. Such behavior allowed us to implement Hebbian learning with nanofluidic systems. This result lays the foundation for biomimetic computations on aqueous electrolytic chips.

Bipolar electrochemistry (BPE) is a powerful method based on the wireless polarization of a conductive object that induces the asymmetric electroactivity at its two extremities. A key physical limitation of BPE is the size of the conductive object because the shorter the object, the larger is the potential necessary for sufficient polarization. Micrometric and nanometric objects are thus extremely difficult to address by BPE due to the very high potentials required, in the order of tens of kV or more. Herein, the synergetic actions of BPE and of planar micropores integrated in a microfluidic device lead to the spatial confinement of the potential drop at the level of the solid-state micropore, and thus to a locally enhanced polarization of a bipolar electrode. Electrochemiluminescence (ECL) is emitted in half of the electroactive micropore and reveals the asymmetric polarization in this spatial restriction. Micrometric deoxidized silicon electrodes located in the micropore are polarized at a very low potential (7 V), which is more than 2 orders of magnitude lower compared to the classic bipolar configurations. This behavior is intrinsically associated with the unique properties of the micropores, where the sharp potential drop is focused. The presented approach offers exciting perspectives for BPE of micro/nano-objects, such as dynamic BPE with objects passing through the pores or wireless ECLemitting micropores.