Fig. 4: Learning and forgetting in a hydrophobically gated memristive nanopore (HyMN) device.

a Experimental setup. The HyMN, here represented in the red inset, is composed of multiple engineered FraC nanopores (less than 5, white pores), immersed into a lipid bilayer (gray and red membrane) separating two electrolyte reservoirs (green and blue spheres, water not shown). The lipid membrane is suspended on a Delrin partition (Warner, USA) containing an aperture of approximately 150 μm in diameter, see Materials and Methods for more details. The current that passes through a HyMN depends on the previous voltage applied at its terminals. b The average of measured current (black line) through the HyMN subjected to a voltage signal (golden line) composed of 4 positive excitatory triangular waves, 2 negative inhibitory ones, and 4 positive ones. The current response increases during the excitatory pulses and decreases during the inhibitory ones. c HyMN device response to the opposite protocol, starting with 4 inhibitory pulses, followed by 2 excitatory ones, and ending with 4 inhibitory pulses. Again, during the inhibitory stage the maximum current goes down, while it increases after excitatory pulses. For both (b) and (c) the capacitive current was subtracted; the measured current is the average over 35 realizations. d, e Change in the average conductance (%), computed with respect to the conductance during the first spike in b and c, respectively. The conductance is averaged over each pulse. Note that the pore is more conductive at negative voltages, see Fig. 3d, a behaviour usually observed in biological nanopores and also reported for the FraC WT and other mutants⁴⁰. f, g Cumulative dissipated energy during the cycles reported in b and c, respectively. The dissipated energy is computed by integrating the mean electric power during the cycle, obtained by averaging the current trace over 35 realizations.