Sébastien Pecqueur

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 and 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 samples, 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 complexity 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 shows that low material resources and low voltage fabrication processes based on electrochemistry can be exploited for practical electronic applications in future-emerging sensing technologies.

Machine olfaction is still not embedded in portable devices. Relationships between electronic materials and chemical environments are hard to decipher to build phenomenologic models that formalize smells’ and odors’ subjectivity. Also, machine olfaction requires norms to generate large datasets: a generic technology, easy to manufacture and integrable to the broadest range of electronic devices must be identified. To this aim, this study reports on relevant materials to be processed on cost-effective electronic noses. Using a single water-soluble conducting polymer but sensitized with various p-dopants deposited directly on the circuit board, solvent vapors are successfully recognized on a USB-powered small-sized prototype. The chosen doped polymers are easy and safe to process, particularly sensitive to water, but successfully discriminate moist from acetone and ethanol vapors. Diversifying the nature of the doping metal salts increases the prototype receptive field and allows better identification of the nature of volatile chemical compounds. This study contributes to identifying relevant materials to be processed in an easy way on electronic circuits to implement machine olfaction in portable IoT systems, by the use of various mildly doped conducting polymers. By its statistical approach, this study also raises several hypotheses on the physical origin of the sensitivity of a specific class of polymer which transports both electrons and ions. The development of such cost-effective platform allows effectively to compare the performances of multiple materials in a reproducible and systematical way, to ease multi-material performance screening supported by multivariate data analysis.

Fabricating electronic devices spoiling the least resources is of an increasingly high importance. Also, micro-electronics hardly embeds chemical functionalities on silicon, as soft materials suffer from harsh conditions of conventional processes. In this study, electrochemistry on a chip is investigated to pattern conductivity-based measurement devices at small scale via electropolymerization. To comply with additive manufacturing, a dewetting coating and local quasi-reference/counter micro-electrodes shall be integrated on each chip. The process reliability is challenged using minimalist chemical and energy resources, such that a μ L droplet of an electro-active solution composed mostly of a non-toxic and affordable solvent suffices to coat 16 elements on a 3×3 mm ² chip. Despite the complexity of electrochemistry at such scales, the coatings variability is dominated by the chemical composition of the droplet. Avoiding a vessel to confine large volumes of solutions and integrating all electrodes is required to reduce drastically the electrochemical signal noise. This demonstrates its sufficient stability to screen conducting polymer materials when their precursors are not available in large amount to be coated with conventional techniques. It also demonstrates its compliance for chips microfabrication using conducting polymers as functional materials for electrochemically-assisted additive manufacturing production.

Conducting polymer dendrite (CPD) morphogenesis is an electrochemical process that enables in materio evolving intelligence in wetware devices. During CPD morphogenesis, voltage transients drive the physical evolution of electrically conductive structures, thereby programming their filtering properties as nonlinear analog devices. Whether studied in an electrochemical experiment or in neuromorphic devices, the dependence of the electrical properties of the electrogenerated structures on the chemical composition of their growth environment is still unreported. In this study, we report the existing interconnection between the nature and concentration of the electrolytes, electroactive compounds and co-solvents and the electrical and electrochemical properties of CPDs in an aqueous electrolyte. CPDs exhibit various chemical sensitivities in water: their morphology is highly dependent on the nature of the chemical resources available in their environment. The selection of these resources therefore critically influences morphogenesis. In addition, the concentrations of the different electrochemical species have varying impacts on growth dynamics, modulating the balance between thermodynamic and kinetic control over polymer electrosynthesis. By correlating the dependencies of these evolving objects with the availability of the chemical resources in an aqueous environment, this study offers guidelines to tune the degree of evolution of electronic materials in water and highlights potential avenues for their application. Such evolving hardware is envisioned to exploit the chemical complexity of real-world environments as part of information processing technologies.

Fabricating electronic devices spoiling the least resources is of an increasingly high importance. Also, micro-electronics hardly embeds chemical functionalities on silicon, as soft materials suffer from harsh conditions of conventional processes. In this study, electrochemistry on a chip is investigated to pattern conductimetric devices at small scale via electropolymerization. To comply with additive manufacturing, a dewetting coating and local quasi-reference/counter micro-electrodes shall be integrated on each chip. The process reliability is challenged using minimalist chemical and energy resources, such that a µL droplet of an electro-active solution composed mostly of a non-toxic and affordable solvent suffices to coat 16 conductimetric elements on a 3×3 mm 2 chip. Despite the complexity of electrochemistry at such scales, the coatings variability is dominated by the chemical composition of the droplet. Avoiding a vessel to confine large volumes of solutions and integrating all electrodes is required to reduce drastically the electrochemical signal noise. This demonstrates its sufficient stability to screen conducting polymer materials when their precursors are not available in large amount to be coated with conventional techniques. It also demonstrates its compliance for chips microfabrication using conducting polymers as functional materials for electrochemically-assisted additive manufacturing production.

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 living organisms and exploit topological plasticity as a low-resource mechanism for in operando manufacturing and computation. Often fractal, the resulting topologies feature an inherent disorder: a property that is never exploited in conventional electronics manufacturing, 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 discharge 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 not only on the temporality 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.

Process variation is always a challenge to mitigate in electronics. This especially holds true for organic semiconductors, where reproducibility concerns hinder industrialization. Challenging this concept, it shows AC‐electropolymerization to be a powerful platform for the development of morphology‐dependent computing hardware, thanks precisely to its intrinsic stochasticity. The findings reveal that electropolymerized polymer dendrite networks exhibit a complex structure‐operation relationship that allows to implement nearly linear to nonlinear functions. Moreover, dendritic networks can integrate a limitless number of inputs from their environment, which can be used to the advantage in the context of in materio computing to discriminate between different spatiotemporal inputs. These results position electropolymerization as a pivotal technique for the bottom‐up implementation of computationally powerful objects. This study anticipates this study to help shifting the negative perception of variability in the material science community and promote the electropolymerization framework as a foundation for the development of a new generation of hardware defined by its topological richness.

Conducting polymer dendrite (CPD) morphogenesis is an electrochemical process that unlocks the potential to implement in materio evolving intelligence in electrical systems: As an electronic device experiences transient voltages in an open-space wet environment, electrically conductive structures physically change over time, programming the filtering properties of an interconnect as a non-linear analog device. Mimicking the self-preservation strategies of some sessile organisms, CPDs adapt their morphology to the environment they grow in. Either studied as an electrochemical experiment or as neuromorphic devices, the dependence of CPDs' electrical properties on the chemical nature of their environment is still unreported, despite the inter-dependence between the electrical properties of the electrogenerated material and the chemical composition of their growth medium. In this study, we report on the existing intrication between the nature and concentration of the electrolytes, electroactive compounds and co-solvents and the electrical and the electrochemical properties of CPDs in water. CPDs exhibit various chemical sensitivities in water: their morphology is highly dependent on the nature of the chemical resources available in their environment. The selection of these resources therefore critically influence morphogenesis. Also, concentrations have different impacts on growth dynamics, conditioning the balance between thermodynamic and kinetic control on polymer electrosynthesis. By correlating the dependencies of these evolving objects with the availability of the chemical resources in an aqueous environment, this study proposes guidelines to tune the degree of evolution of electronic materials in water. Such hardware is envisioned to exploit the chemical complexity of real world environments as part of information processing technologies.

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 living 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 manufacturing, 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 discharge 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 temporality 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.