Negative Differential Resistance in Conical Nanopore Iontronic Memristors

Abstract

Emerging ion transport dynamics with memory effects at nanoscale solution−substrate interfaces offers a unique opportunity to overcome the bottlenecks in traditional computational architectures, trade-offs in selectivity and throughput in separation, and electrochemical energy conversions. Negative differential resistance (NDR), a decrease in conductance with increasing potential, constitutes a new function from the perspective of time-dependent instead of steady-state nanoscale electrokinetic ion transport but remains unexplored in ionotronics to develop higher-order complexity and advanced capabilities. Herein, NDR is introduced in hysteretic and rectified ion transport through single conical nanopipettes (NPs) as ionic memristors. Deterministic and chaotic behaviors are controlled via an electric field as the sole stimulus. The NDR arises fundamentally from the availability and redistribution of the ionic charges during the hysteretic and rectified transport at asymmetric nanointerfaces. The elucidated mechanism is generalizable, and the drastically simplified operations enable tunable state-switching dynamics with higher-order complexity besides the first-order synaptic functions in multiple excitatory and inhibitory states.

Nanofluidic Ionic Memristors

“…However, they are under-explored in nanostructures operating in the liquid state. Previous efforts in the field have addressed different phenomena, including negative incremental resistance and millimolar concentration calcium-induced gating observed in asymmetric nanopores, NDR induced by externally applied mechanically forced electroosmotic flow through nanopores, quasi-stable ionic NDR effect in SiN x nanopore under a salinity gradient, electrodiffusion osmosis induced by NDR in pH-modulated mesopores, NDR phenomena in conical nanopores with KF solution. , When the NDR phenomenon occurs, it will cause a gradual accumulation/depletion of ions in the entrance region of the nanopore/channel, resulting in a switch of high/low ionic conductance . This negative differential resistance effect is attributed to the ions’ CP; thus, the conductance switching can be explained by CP.…”