Iontronic memristor in funnel-shaped Ångström channels

Herein we present an iontronic memristor using funnel-shaped Ångström channels, exhibiting behavior that differs from conventional conical nanochannel systems. Funnel-shaped channels were fabricated using ion-track technology, which consists of an Ångström tip and a conical nano-opening as the base. The voltage sweeping measurements showed current hysteresis as an essential feature of the memristor, with the hysteresis area increasing with frequency, reaching a peak, and subsequently decreasing. The current rectification becomes reversed compared to the classical conical nanochannel at low bias voltages, returning once the bias voltage surpasses a specific threshold. The reversed current rectification and unconventional hysteresis area change are likely attributed to energy barriers at the Ångström-scale tip, resulting in a decrease in ionic fluxes from the tip to the base. When the bias exceeds this threshold, the system returns to the standard conical nanochannel feature. Our research demonstrates a nanofluidic memristor in which the hysteresis and rectification are dependent on both voltage and frequency. This indicates potential applications in neuromorphic computing which can enhance the understanding of ionic transport in sub-nanometer confinement.