Ion current oscillation of polyelectrolyte modified micropipettes

Here, we report for the first time that ion current oscillation (ICO) with periodic amplitude and frequency can autonomously occur at polyimidazole brush (PvimB) modified pipettes in an asymmetric solution with a pH gradient (e.g. pH 6.0/pH 8.0). Experimental results demonstrated that under a strong bias voltage, the proton responsive PvimB-modified pipettes exhibited significant current switching behavior under negative bias voltages, which contributed to the periodic oscillating ion current under constant biases. Based on this dynamic, the frequency and amplitude of the ICO phenomenon were regulated by adjusting the pH gradient in the asymmetric solution. ICOs under different bias voltages were further explored to show the voltage-dependent nature of this phenomenon. This observation of ICO phenomena offers a new strategy for designing iontronic devices with dynamic conductivity changes induced by surface chemical interactions within spatial confinements.