Using Dynamic Impedance Spectroscopy to Deconvolute Memory Elements in Droplet Interface Bilayers

Abstract

The underlying principles for generating and storing memory in living organisms differ significantly from traditional hard-matter-based circuits. Bio-inspired membranes are ideal platforms for exploring biomimetic neuromorphic equivalents as they offer novel forms of tunable plasticity and diverse mechanisms to control functionality. Droplet interface bilayers (DIBs) are inherently nanostructures that show electrical properties that are extremely sensitive to nano-scale perturbation. We will demonstrate how dynamic electrochemical impedance spectroscopy (dEIS) can follow molecular-level restructuring in DIBs that lead to hysteretic loops and mem-behaviors in lipid bilayers in response to electrical biasing. We deconvoluted the DIB system’s memristance and memcapacitance by measuring the time-dependent complex impedance to show that if the bilayer’s structure (thickness or area) changes, these quantities contain the same information; however, if a phase transition occurs, then these responses have additional information. Figure 1, demonstrates both the DIBs platform two major modes of voltage-inducing physical change that can occur in bilayers. Through correlation analysis of the capacitance/resistance, we show that memory processes caused by lipid bilayer expansion, or contraction, do not affect the observed electrical charge/discharge time constant. However, phase transitions resulting in new solvation or lipid structures affect the extracted electrical time constant. In short, dEIS coupled with time-constant analysis provides a means for extracting individual memory elements from a simple two-terminal device, thereby multiplexing the function and potential computational throughput. Figure 1