Nanopores with Ionic Memory in Oscillating Ion Current Signals

Nanopores provide controlled nanoconfinement that can be used to induce localized chemical reactions. Here, we present a nanopore exhibiting memory in the frequency of ion current oscillations induced by the dynamic formation and removal of nanoprecipitates within the pore volume. We find that the onset and characteristics of these current oscillations depend on the direction of the voltage scan, with memory effects evidenced in the frequency of switching between high and low conductance states and the probability of the pore to be in the open state. We have also emulated conductive synaptic switching behavior by applying voltage pulses and demonstrated an ability for the system to exhibit long-term potentiation (LTP) and long-term depression (LTD) that mimic learning and memory of synapses. A hypothesis is presented stating that the memory effects arise from the delayed formation and clearing of nanoprecipitates due to spatial-temporal asymmetry as well as from long-term variations in the effective surface charge. We propose a model in which precipitate formation is limited by the cation arrival rate. Our delayed logistic expression successfully recreates steady-state and oscillatory features in the transmembrane current. Nanopores with memory encoded in the frequency of ion current oscillations emulate how the brain stores information, open the possibility to achieve high-dimensional ionic memory, and move beyond the hysteresis in average conductance of ionic memristors.