Functional coupling live neurons through artificial synapses is the primary requirement for their implementation as prosthetic devices or in building hybrid networks. Here, the first evidence of unidirectional, activity dependent, coupling of two live neurons in brain slices via organic memristive devices (OMD) is demonstrated. ODM is a polymeric electrochemical element, which has two terminals for the connection in electrical circuits and which displays hysteresis and rectifying features. OMD coupling is characterized by nonlinear relationships determined by the instantaneous values of OMD resistance that can be controlled by the neuronal activity, and the excitation threshold in the postsynaptic neuron. OMD coupling also has the spike-timing features similar to that of the natural excitatory synapses. Also, OMD-synapses support synchronized delta-oscillations in the two-neuron network. It is proposed that OMD-synapses may enable realization of prosthetic synapses and building hybrid neuronal networks endowed with a capacity of learning, memory, and computation.

The biomimetic devices such as the artificial synapses are of great significance because they can emulate the functions of biological systems. The development of memristive devices represents one of the most promising pathways towards adaptive and neuromorphic computing. This study reports the characterization of the first organic memristive element based on polyaniline-Chitosan (PANI-CS) junction. The Chitosan is used as solid polyelectrolyte in the active area of organic memristive element. Its working principle is based on the significant variation of the resistance of PANI in the oxidized and reduced states in junction area. The experimental parameters that influence the memristive behavior of Chitosan-based devices were studied by means of voltage-current measurements. The application of biocompatible material, the Chitosan, in organic memristive devices pave the way towards the application of organic memristor in bio-integrated systems.

A phenomenological model of the polyaniline (PANI) based memristive element's conductivity evolution during the application of varying voltages is presented in this work. The model is based on the experimental data on the conductance versus time dependencies for a set of applied voltages. The model could be used for simulation of complex artificial neural networks (ANNs) based on PANI memristive elements. We have experimentally shown that organic PANI-based memristive element could be trained by the biologically inspired spike-timing-dependent plasticity mechanism. The results obtained by the simulation using the developed model are in a good agreement with the experimental data. It allows considering the usage of the organic memristive element as a synaptic element in a hardware realization of spiking ANNs capable of non-supervised learning.

Novel architectures of organic memristive device with pectin as a solid polyelectrolyte have been developed and studied. The assembled devices exhibit memristive properties (hysteresis and rectification) emulating the signal process and memory functions of biological synapses. This work reveals for the first time that pectin from fruit peel is a promising material for nonvolatile memory applications based on polyaniline electrochemistry. In addition, we have demonstrated that under well-defined conditions, pectin can play the role of an intermediate biocompatible layer interfacing the electronic device with the living organism preserving functions of both. In particular, the pectin interfacing layer in this case maintains polyaniline conductivity without the presence of strong inorganic acids. The method was successfully validated by developing a hybrid bio-memristive electrochemical device with living organism Physarum polycephalum.

Slime mould Physarum polycephalum develops intricate patterns of protoplasmic networks when foraging on a non-nutrient substrates. The networks are optimised for spanning larger spaces with minimum body mass and for quick transfer of nutrients and metabolites inside the slime mould's body. We hybridise the slime mould's networks with conductive polymer polyaniline and thus produce micro-patterns of conductive networks. This unconventional lithographic method opens new perspectives in development of living technology devices, biocompatible non-silicon hardware for applications in integrated circuits, bioelectronics, and biosensing.

A new architecture of organic memristive device is proposed with a double-layered polyelectrolyte, one of which is a biological system that alone drives the memristive behavior. In the device the Physarum polycephalum was used as living organism, the polyaniline as conducting polymer for the source-drain channel. The key choice for the device functioning was the interposition of a biocompatible solid layer between polyaniline and living organism, that must result both electrochemically inert and able to preserve a good electrical conductivity of the polyaniline, notwithstanding the alkaline pH environment required for the surviving of living being, by avoiding strong acids. Pectin with a high degree of methylation and chitosan were tested as interlayer, but only the first one satisfied the essential requirements. It was demonstrated that only when the living organism was integrated in the device, the current-voltage characteristics showed the hysteretic rectifying trends typical of the memristive devices, which however disappeared if the Physarum polycephalum switched to its sclerotic state. The mould resulted to survive a series of at least three cycles of voltage-current measurements carried out in sequence.

Growth of gallium oxide thin films was carried out by Metalorganic Chemical Vapor Deposition (MOCVD) at different temperatures. Pure epsilon-phase epilayers of Ga2O3, with good morphology and structural properties, were obtained, for the first time with this technique, on sapphire at the temperature of 650 degrees C. XRD analysis performed by high-resolution diffractometry confirmed the good crystallographic quality of the grown layers. At temperatures higher than 700 degrees C the usual stable beta-Ga2O3 phase was obtained. The epsilon-films were successfully deposited also on (0001)-oriented GaN and (111)- and (001)-oriented 3C-SiC templates, provided that the appropriate temperature was chosen. This indicates that the temperature, rather than substrate structure, is the growth parameter which decides what phase actually forms. The growth proceeds via coalescence of hexagonal islands and is favored when a substrate with an in-plane hexagonal arrangement of the atoms is employed. By applying Atomic Layer Deposition (ALD), epitaxial growth of the e-phase was achieved at lower temperature, while the overall uniformity resulted improved, even on large sapphire substrates. (C) 2016 Elsevier B.V. All rights reserved.

Physarum polycephalum slime mould can modify polyaniline (PANI) features due to its internal activity. We created networks with different conductivity made by the slime mould on PANI substrates. Thus, Physarum's growth results in changing the conductivity state of PANI layers, providing negative and positive patterning of the samples. A spectrophotometric scanner is here exploited to investigate and characterize the effects coming out from the interaction between Physarum polycephalum and PANI. The latter is an electro-chromic polymer that vary its colour and conductive properties according to its redox state.

The main charter of this work is the organism Physarum polycephalum, in particular plasmodium, Physarum's vegetative phase. During this latter form, the organism is more active and moves searching for food. Plasmodium behaves like a giant amoeba, and more interestingly, its way of foraging can be interpreted as a computation. By comparing the reaction of this organism with attractors and repellents, knowing its capability of solving computational problems with natural parallelism, we dedicated the present work to study the behavior of Physarum polycephalum slime mold under different conditions.

In this present work, initial results of the growing of neuronal like cells on the memristive substrate are going to be presented. SH-SY5Y line cells where chosen for this test, thanks to their features similar to neurons and they were grown on Polyaniline (PANI) multilayer. PANI is a well known conductive polymer and it's also the active layer of a special class of device, the organic memristors. It's deposited by Langmuir-Schaefer technique on a round cover glass support.

Physarum polycephalum is considered to be promising for the realization of unconventional computational systems. In this work, we present results of three slime mould-based systems. We have demonstrated the possibility of transporting biocompatible microparticles using attractors, repellents and a DEFLECTOR. The latter is an external tool that enables to conduct Physarum motion. We also present interactions between slime mould and conducting polymers, resulting in a variation of their colour and conductivity. Finally, incorporation of the Physarum into the organic memristive device resulted in a variation of its electrical characteristics due to the slime mould internal activity.

Three systems containing slime mold are under the consideration in this paper. In the first case, slime mold was loaded with microparticles, demonstrating the possibility of their transport during the growth. In a case of magnetic particles, it was introduced a new method of the affecting the growth direction: deflector - direction control by the external magnetic field. In the second case, we have demonstrated the variation of the polyaniline layer conductivity in zones where slime mold passed. In the third case, slime mold was used as an electrolyte in organic memristive device.

A hybrid bio-organic electrochemical transistor was developed by interfacing an organic semiconductor, poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate), with the Physarum polycephalum cell. The system shows unprecedented performances since it could be operated both as a transistor, in a three-terminal configuration, and as a memristive device in a two terminal configuration mode. This is quite a remarkable achievement since, in the transistor mode, it can be used as a very sensitive bio-sensor directly monitoring biochemical processes occurring in the cell, while, as a memristive device, it represents one of the very first examples of a bio-hybrid system demonstrating such a property. Our system combines memory and sensing in the same system, possibly interfacing unconventional computing. The system was studied by a full electrical characterization using a series of different gate electrodes, namely made of Ag, Au and Pt, which typically show different operation modes in organic electrochemical transistors. Our experiment demonstrates that a remarkable sensing capability could potentially be implemented. We envisage that this system could be classified as a Bio-Organic Sensing/Memristive Device (BOSMD), where the dual functionality allows merging of the sensing and memory properties, paving the way to new and unexplored opportunities in bioelectronics.

The features of spectrophotometric scanner, generally exploited in the artwork field, are here considered in a non-conventional context to characterize the networks created by Physarum polycephalum slime mold during its motion on glass substrates covered with polyaniline: a polymer that varies its color and conductive properties according to the redox state. The used technique allowed the investigation of the effects coming out from the interaction between P. polycephalum and polyaniline. Thus, the contactless method of the analysis of polyaniline conductivity state resulted from the slime mold metabolism was suggested. Indeed, it is here demonstrated that P. polycephalum can modify properties of polyaniline due to its internal activity in contact zones.

Slime mold Physarum polycephalum is a single cell visible by an unaided eye. The slime mold optimizes its network of protoplasmic tubes to minimize expose to repellents and maximize expose to attractants and to make efficient transportation of nutrients. These properties of P. polycephalum, together with simplicity of its handling and culturing, make it a priceless substrate for designing novel sensing, computing and actuating architectures in living amorphous biological substrate. We demonstrate that, by loading Physarum with magnetic particles and positioning it in a magnetic field, we can, in principle, impose analog control procedures to precisely route active growing zones of slime mold and shape topology of its protoplasmic networks.

We propose a multi-technique approach based on in-vacuum synthesis of metal oxides to optimize the memristive properties of devices that use a metal oxide thin film as insulating layer. Pulsed Microplasma Cluster Source (PMCS) is based on supersonic beams seeded by clusters of the metal oxide. Nanocrystalline TiO2 thin films can be grown at room temperature, controlling the oxide stoichiometry from titanium metal up to a significant oxygen excess. Pulsed Electron beam Deposition (PED) is suitable to grow crystalline thin films on large areas, a step towards producing device arrays with controlled morphology and stoichiometry. Atomic Layer Deposition (ALD) is a powerful technique to grow materials layer-by-layer, finely controlling the chemical and structural properties of the film up to thickness of 50-80 nm. We will present a few examples of metal-insulator-metal structures showing a pinched hysteresis loop in their current-voltage characteristic. The structure, stoichiometry and morphology of the metal oxide layer, either aluminum oxide or titanium dioxide, is investigated by means of scanning electron microscopy (SEM) and by Raman scattering.

Organic memristive device is an electronic system mimicking some properties of biological synapses. Slime mold - Physarum polycephalum - is a single cell living being, widely considered now for the unconventional computing application. This work is dedicated to the realization of hybrid organic memristive device/Physarum polycephalum system and studying of its electrical properties. It was found that the slime mold remains alive only when the appropriate biocompatible layer is inserted into the structure and that the characteristics of the system are very different from those of the standard organic memristive devices.

The present work is dedicated to the use of Physarum polycephalum slime mold, an unicellular organism self-adapting, self-repairing and self-repellent, for the realization of elements for unconventional computational systems. Physarum continuously changes its shape under the influence of different stimuli like attractors (food in the most of cases) and repellents (light, temperature, humidity, chemicals), creating optimized networks. Here we introduced a new, softer, element able to influence the motion and the shape of Physarum: the DEFLECTOR. Physarum polycephalum, loaded with magnetic particles and placed under a magnetic field, is conditioned in its active zones routing and shape topology networks. Thus, slime mold can be used as particles carrier and, moreover, it is possible to deflect the mold movement and realize chemical composites in defined places what allows to consider Physarum as a simple version of bio-robot. On the other hand, we have realized the idea of creating networks with the varied conductivity with the slime mold on polyaniline (PANI) substrates. As the result, it was shown that Physarum growth results in the changing of the conductivity state of PANI layers in different ways, providing negative and positive patterning of the sample. The possibility to control mold's direction with a deflector together with the capability of Physarum to pattern PANI surfaces are the main points of this work. This paper opens new possibilities of the development in many fields and areas from the electrical circuit design and the bio-actuators (bio-) robot research, up to the unconventional computing and realization of a novel category of polymer-mold-modified.

The plasmodium of Physarum polycephalum is a large single cell visible with the naked eye. The plasmodium realizes a pattern of protoplasmic veins which span sites of sources of nutrients, producing efficient network structures like cycles and Steiner minimum trees. Besides, the plasmodium can embed different chemicals; therefore, it should be possible to program the plasmodium to realize deterministic adaptive network and spatial distribution of nanoscale and microscale materials. The transported particles can be used for the modification of the physical properties of the system (electrical, optical, magnetic) facilitating the readout of the information, processed by the slime mold. Experiments with polystyrene microparticles and MnCO3 microparticles demonstrate that the plasmodium of Physarum can propagate nanoscale objects using a number of distinct mechanisms. The results of our experiments could be employed in the field of the unconventional computing and bio-computing application devices, using Physarum network as scaffolds for the development of hybrid nanocircuits and microcircuits and devices.

We propose a multi-technique approach based on in-vacuum synthesis of metal oxides to optimize the memristive properties of devices that use a metal oxide thin film as insulating layer. Pulsed Microplasma Cluster Source (PMCS) is based on supersonic beams seeded by clusters of the metal oxide. Nanocrystalline TiO2 thin films can be grown at room temperature, controlling the oxide stoichiometry from titanium metal up to a significant oxygen excess. Pulsed Electron beam Deposition (PED) is suitable to grow crystalline thin films on large areas, a step towards producing device arrays with controlled morphology and stoichiometry. Atomic Layer Deposition (ALD) is a powerful technique to grow materials layer-by-layer, finely controlling the chemical and structural properties of the film up to thickness of 50-80 nm. We will present a few examples of metal-insulator-metal structures showing a pinched hysteresis loop in their current-voltage characteristic. The structure, stoichiometry and morphology of the metal oxide layer, either aluminum oxide or titanium dioxide, is investigated by means of scanning electron microscopy (SEM) and by Raman scattering.