Abstract: If electronics drives only electrons to charge electrodes, natural systems learn by moving matter to evolve. Morphogenesis in sessile organisms can be seen both as a fabrication process and as an operative mechanism. However, intricating manufacturing an d programming functionalities in electronic hardware is not conventional. In this study, we experimentally implement such a concept of an evolutionary electrical system using a neuro-inspired electronic nose as a model, to store a history of sensory data in the physical properties of the electrical interconnects of sensing elements. Triggered only by volatile molecule exposures, different sensing elements change instantaneously and reversibly their impedance, so pulse voltages enable the electrochemical growth of conducting polymer dendrites. The strength of the evolving interconnects is specific to the sensing materials and to the nature of volatile molecules to which they are exposed. The dendritic growths occur exclusively when exposed to volatile s amples, and stop immediately after interrupting the exposure. The capability of such "passive memory" was also assessed by simulating a network architecture, which showed that this way of storing information should greatly diminish the fabrication comple xity of a highly dense sensing array while realistically enabling its calibration to classify user-specific environment exposures. By demonstrating that memory in electronics can be a concept linked to manufacturing like in living organisms, this study s hows that low material resources and low voltage fabrication processes based on electrochemistry can be exploited for practical electronic applications in future-emerging sensing technologies.
Baron A., Hafsi B., Hernández-Balaguera E., Pecqueur S.*
Abstract: The brain exploits electrochemistry both to process chemical information and to fabricate itself: two functionalities that silicon cannot achieve by itself. In a complementary approach, this presentation reports on a few elements suggesting that electrop olymerization on a chip is a way to gather sufficiently rich chemistries on a miniaturized electronic nose, and that "letting" sensors connect during an application could be a solution for electronics to self-manufacture, reducing its environmental footp rint, while unlocking unprecedented computing functionalities beyond charging and discharging memory cells. By controlling the electrochemical growth of conducting polymers on micro-electrode arrays in a microliter sized droplet, conducting polymers with various chemistries can be confined additively at a micrometer scale on conductimetric devices. Since conducting polymers are both macromolecular materials and doped semiconductors, they intrinsically feature both chemical detection and electrical trans duction, like G-coupled proteins on olfactory receptor neurons, to generate relevant information on a sugar-cube sized electronic nose. Electropolymerization allows growing films on devices, but also interconnecting them with an incredibly versatile way. Branching out from electrodes, conducting polymer dendrites grow by the action of voltage pulses. The temporality of the voltage and the chemistry of their growth medium allow them to form various sizes and shapes, which program their equivalent circuit deeply through their structural evolution. Because polymers can drive both electrons and ions, their fractal structure relates to diffusion-limited capacitive decays, offering a second degree of freedom, unexploited in analog electronics, to program the fading memory time window of a dendritic junction between neighboring devices. By embedding such bio-inspired functionalities as neurogenesis and morphogenesis into electronics, conducting polymers electrochemistry could greatly contribute in fabricatin g electronic chips in a more sustainable manner while unlocking new programming functionalities to generate and process information.
Pecqueur S., Baron A., Viala A., Moustiez P., Guérin D., Dargent T., Hernández-Balaguera E.
Abstract: Understanding the electrical mechanisms underlying artificial synaptic plasticity is essential for neuromorphic engineering. This work presents a unified electrical perspective connecting the simple bioelectrochemical dendrites and the greater complexity of memristors as complementary platforms for studying memory effects in artificial brain-inspired synapses. First, we show how conducting polymer dendrites exhibit fractional-order transient responses arising from coupled ionic and electrochemical proce sses, reproducing key features of synaptic plasticity such as history-dependent dynamics and synaptic learning behavior during morphogenesis. Similar electrical signatures are observed in halide perovskite memristors, where ion migration and charge accum ulation govern conductance modulation and short-/long-term potentiation. By combining Impedance Spectroscopy and transient analysis, we explain the electrical tools for quantifying the physics-based memory effects across biology and neuromorphic engineer ing. This electrical approach bridges bioelectrochemistry and neuromorphic hardware, offering new insights into the physical origins of synaptic functionality while providing practical guidance for the design and interpretation of next-generation brain-i nspired electronic systems.
Hernández-Balaguera E., Baron A., Pecqueur S., Bisquert J.
Abstract: Understanding and reproducing the brain's ability to store and process information remains a central challenge in neuromorphic engineering. Here, we identify the physical origin and provide a phenomenological interpretation of memory effects underlying s ynaptic-like plasticity, realized in brain-inspired electrochemical dendrites, from fractional calculus. Using hybrid ion-electron conduction pathways, such artificial dendrites exhibit anomalous transient responses arising from the complex dynamics of i onic diffusion and electronic transport across the nanostructured interfaces, effectively embedding history-dependent behavior in the electrochemical junctions. These insights show that the constant phase element (CPE) is more than a simple fitting const ruct used commonly in Electrochemistry: It provides a fundamental description of multiscale transients, capturing the complex dynamical behavior associated with memory effects and their analogy to synaptic functionality. Beyond the classical Mittag-Leffl er responses obtained under previous equilibrium conditions, the hereditary behavior behind artificial synaptic activity emerges as fractional-order dynamics with cumulative Mittag-Leffler patterns in the current responses, offering a natural platform fo r understanding device-level short- and long-term potentiation effects. Our approach, faithfully captured by a quantitative physical model validated through experiments and simulations, encodes past-state memory in neuromorphic devices, bridging physical processes and system-level modeling while enabling dendrite-inspired circuits capable of learning and temporal information processing.
Baron A.*, Pecqueur S., Hernández-Balaguera E.*
Abstract: Electropolymerization under an alternating-current results in the formation of conducting polymers dendrites (CPDs), that conduct both ionic matter and electronic charges simultaneously, offering features from both the worlds of electronics and electroch emistry. Versatile, they can be grown in various electrolytes to develop classes of electronic components that are evolvable and process information using mass-transfer mechanisms. By self-healing or resorbing, CPD have the potential to enable new functi onalities in conventional electronic systems with low material and energy costs, making them a promising avenue for bio-inspired information processing. They also offer a simple, low-voltage alternative to address the ongoing problem of high manufacturin g costs in the microelectronics industry. In this work, we investigate the control of poly(3,4-ethylenedioxythiophene) (PEDOT) based CPD morphology through electrolyte chemistry and its impact on impedance patterns in a two-electrode system, particularly in relation to their observed constant phase element (CPE) behavior. We also explore how morphology influences the charge/discharge dynamics when the dendritic connection is not yet completed. Specifically, it is shown that the electrical parameters of the CPDs, extracted by fitting the transient curves using the Mittag-Leffler function, are defined early during the growth, and that thicker CPDs will allow longer relaxation times. By changing the voltage pulse duration in the growth signal, one has the refore the ability to tune both the characteristic times and the non-ideality of a CPD charge. Ultimately, we aim to demonstrate the applicability of these concepts for programming sensors and integrating neuro-inspired functionalities into electronic no ses, which exploit electrochemistry for the recognition of complex environmental patterns.
Baron A., Scholaert C., Hernández-Balaguera E., Guérin D., Moustiez P., Coffinier Y., Alibart F., Pecqueur S.
Abstract: Conventional electronics is founded on a paradigm where shaping perfect electrical elements is done at the fabrication plant, so as to make devices and systems identical, "eternally immutable". In nature, morphogenic evolutions are observed in most livin g organisms and exploit topological plasticity as a low-resource mechanism for in operando manufacturing and computation. Often fractal, the resulting topologies feature inherent disorder: a property which is never exploited in conventional electronics m anufacturing, while necessary for data generation and security in software. In this study, we present how such properties can be exploited to implement long-term and evolvable synaptic plasticity in an electronic hardware. The rich topology of conducting polymer dendrites (CPDs) is exploited to program the non-ideality of their electrochemical capacitances containing constant-phase-elements. Their evolution through structural changes alters the characteristic time constants for them to charge and discha rge with the applied voltage stimuli. Under a train of voltage spikes, the evolvable current relaxation of the electrochemical systems promotes short-term plasticity with timescales ranging from milliseconds to seconds. This large window depends on the t emporality of the voltage pulses used for reading, but also on the structure of a pair of CPDs on two electrodes, grown by voltage pulses. This study demonstrates how relevant physically transient and non-ideal electrochemical components can be exploited for unconventional electronics, with the aim to mimic a universal property of living organisms which could barely be replicated in a silicon monocrystal.
Baron A., Hernández-Balaguera E., Scholaert C., Alibart F., Pecqueur S.*
Abstract: Conducting Polymer Dendrites (CPD) can engrave sophisticated patterns of electrical interconnects in their morphology, networking input with output nodes, from low-voltage spikes and with very minimal amounts of resources: they may unlock in operando man ufacturing functionalities for an electronics framework using metamorphism conjointly with electron transport as part of the information processing. The relationship between their structure and the information transport is still however very unclear and hinders the exploitation of the versatility of their morphologies to store and process electrodynamic information. This study details the evolution of CPD's circuit parameters with their growth and shape. By the means of electrochemical impedance spectro scopy (EIS), multiple distributions of relaxation times (DRT) are evidenced and evolve specifically upon growth. Correlations are established between the dispersive capacitance of dendritic morphologies and their growth duration, independently from exoge nous physical variables, such as distance, multi-component evaporation or aging. Deviation of the anomalous capacitance from the conventional Debye dielectric relaxation can be programmed within the morphology, as the growth controls the dispersion coeff icient of the dendrite's constant-phase elements relaxation. These results suggest that the fading-memory time window of pseudo-capacitive interconnects can practically be conditioned using electrogenerated CPD morphogenesis as an in materio learning mec hanism. This study confirms the perspective of using electrochemistry for unconventional electronics, engraving information with low voltage events in the physics of conducting polymer objects, and storing information in their morphology, accessible by i mpedance spectral analysis.
Baron A., Hernández-Balaguera E., Pecqueur S.*
Abstract: Conducting Polymer Dendrites (CPD) are truly inspiring for unconventional electronics that shapes topological circuitries evolving upon an application. Driven by electrochemical processes, an electrochemical impedance rules signal propagation from one no de to another. However, clear models dictating their behavior in an electroactive electrolyte have not been identified yet. In this study, we investigate on CPD in an aqueous electrolyte by impedance spectroscopy to unify their signal transport with an e lectrical model, aiming to define a circuit simulation block to integrate these objects in systems for in materio information processing.
Baron A., Hernández-Balaguera E., Pecqueur S.
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