Iontronic neuromorphic signalling with conical microfluidic memristors

Abstract

Experiments have shown that the conductance of conical channels, filled with an aqueous electrolyte, can strongly depend on the history of the applied voltage. These channels hence have a memory and are promising elements in brain-inspired (iontronic) circuits. We show here that the memory of such channels stems from transient concentration polarization over the ionic diffusion time. We derive an analytic approximation for these dynamics which shows good agreement with full finite-element calculations. Using our analytic approximation, we propose an experimentally realisable Hodgkin-Huxley iontronic circuit where micrometer cones take on the role of sodium and potassium channels. Our proposed circuit exhibits key features of neuronal communication such as all-or-none action potentials upon a pulse stimulus and a spike train upon a sustained stimulus.

Unveiling the capabilities of bipolar conical channels in neuromorphic iontronics

“…A particularly exciting direction is that of neuromorphic (brain-inspired) iontronic circuits [1][2][3][4][5][6], which offer the unique feature of closely resembling biological processes as signalling in the brain also relies on ion transport [11,12]. A promising candidate for the realisation of such circuits are ionic microfluidic memristors (memory-resistors) [7][8][9][10][13][14][15][16][17][18][19][20][21][22][23][24]. The dynamical properties of memristors make them artificial analogues to biological synapses, the connections between neurons [25][26][27][28][29].…”

“…In the past few years, however, some interest has been shown in microfluidic neuromorphic components [7][8][9][10][13][14][15][16][17][18][19][20][21][22][23]. Candidates of specific interest for the present work are conical channels containing an aqueous electrolyte and a homogeneous surface charge, which are known to act as iontronic microfluidic memristors [13][14][15][16][17][18][19][20][21][22][23].…”

“…Candidates of specific interest for the present work are conical channels containing an aqueous electrolyte and a homogeneous surface charge, which are known to act as iontronic microfluidic memristors [13][14][15][16][17][18][19][20][21][22][23]. Recently, an analytical model was derived that explains in a quantitative manner how transient concentration polarisation in such channels is responsible for a volatile conductance memory and it was demonstrated that these channels could carry the potential to be used in experimentally accessible neuromorphic iontronic circuits [8]. The underlying functionality which underpins the memristive behaviour of conical channels is that they exhibit current rectification in steady-state [54][55][56][57][58].…”

“…In this work we present an analytical model that quantitatively captures both the steady-state and the dynamical behaviour of conical channels with an inhomogeneous surface charge distribution, based on the methodology in Refs. [8,55]. Our model contains no free parameters and can quantitatively predict the steady-state and time-dependent ionic charge currents as a result of static and dynamic applied voltages, respectively.…”

“…Recently some fully microfluidic circuits that display neuronal behaviour have been theoretically and numerically explored. These circuits, through which an imposed current can be driven, consist of artificial ion channels, batteries, and a capacitor [7,8]. In Ref.…”