Since their prediction, memristive devices revolutionized the world of computing and nowadays they have been widely considered as promising candidate for mimicking synapses. In particular, organic-based memristors allow the construction of circuits capable of learning. Physarum Polycephalum slime mold is well suited for the implementation of the functional properties of smart living systems into electronic devices. Physarum has memory patterns that can be associated to learning, generally considered a feature of more complex species. Here we presents the characteristics of an hybrid memristor developed by interfacingpoly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate), (PEDOT: PSS), with Physarum Polycephalum (PP). The device has memristive features resulting by electrochemical changes occurring into the polymer upon application of anodic potentials across the semiconducting PEDOT: PSS channel.

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.

Clay nanotubes are recently attracting interest as micro-metric-scale vehicles for smart release of drugs and proteins being also biocompatible, nontoxic, and abundantly available. Halloysite nanotubes can be easily mixed with both polar and low-polar polymers; this feature opens many possibilities of functional biocomposites. The latter can be enhanced in mechanical strength, adhesion, and slow release of chemical agents because of the addition of clay nanotubes that work as an inorganic reinforcement material of polymers. Here, we inserted halloysite tubes in a polyethylene oxide gel doped with a lithium salt. The resulting material, placed between two gold electrodes, revealed anisotropic features and had been characterized by electrical pulsed mode measurements.

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.

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 development of devices able to detect and record ion fluxes is a crucial point in order to understand the mechanisms that regulate communication and life of organisms. Here, we take advantage of the combined electronic and ionic conduction properties of a conducting polymer to develop a hybrid organic/living device with a three-terminal configuration, using the Physarum polycephalum Cell (PPC) slime mould as a living bio-electrolyte. An over-oxidation process induces a conductivity switch in the polymer, due to the ionic flux taking place at the PPC/polymer interface. This behaviour endows a current-depending memory effect to the device.

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.

Asymmetric electrical contact (gold and indium) was performed to the slime mold. Electrical characterization of such structure revealed rectifying behavior due to the Schottky effect and a hysteresis due to the electrochemical activity within the slime mold.

Similarly to inorganic memristors, the organic memristive devices reveal a variation of the hysteresis loop upon the frequency of the applied bias voltage. The on/off ratio of the conductivity increases from 4 to 1000 Limes for the variation of time delay (equilibration after the application of the voltage increment) from 5 to 60 s. Being implemented in multi-element electrical circuits memristive devices provide a cross-talk, leading to an equilibration trend of the conductivity values. This effect is mainly related to the formation of stable signal pathways. (C) 2014 Elsevier Ltd. All rights reserved.

This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps (with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled by a custom hardware and the related software system. The studies were carried out through experiments and simulations of organic molecules, in particular oligothiophenes.

Molecular nanoelectronics is attracting much attention, because of the possibility to add functionalities to silicon-based electronics by means of intrinsically nanoscale biological or organic materials. The contact point between active molecules and electrodes must present, besides nanoscale size, a very low resistance. To realize Metal-Molecule-Metal junctions it is, thus, mandatory to be able to control the formation of useful nanometric contacts. The distance between the electrodes has to be of the same size of the molecule being put in between. Nanogaps technology is a perfect fit to fulfill this requirement. In this work, nanogaps between gold electrodes have been used to develop optoelectronic devices based on photoactive proteins. Reaction Centers (RC) and Bacteriorhodopsin (BR) have been inserted in nanogaps by drop casting. Electrical characterizations of the obtained structures were performed. It has been demonstrated that these nanodevices working principle is based on charge separation and photovoltage response. The former is induced by the application of a proper voltage on the RC, while the latter comes from the activation of BR by light of appropriate wavelengths.