Alice Dimonte

Nanogap structures for molecular nanoelectronics

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.

Nanosized Optoelectronic Devices Based on Photoactivated Proteins

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.

Hysteresis loop and cross-talk of organic memristive devices

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 times for the variation of time delay (equilibration after the application of the voltage increment) from 5 to 60s. 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. Display Omitted

Hybrid slime mould-based system for unconventional computing

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.

Magnetic nanoparticles-loaded Physarum polycephalum: Directed growth and particles distribution.

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.

Use of nanogap structures for molecular nanoelectronics

This work is focused on the realization of nanodevices for electronics based on molecular interactions. The electronic function is a property of the Metal-Molecule-Metal (M-M-M) structure and consists in the I-V characterization. The contact between the metals and the molecule is obtained by gold nanogaps (with a dimension less than 10 nm) through electromigration. This phenomenon is controlled by a custom hardware and software system. The M-M-M junction is what authors have studied through experiments and simulations of molecules made mainly by organic carbon rings. The characterizations of the molecules are done with an electrometer.

Organic Memristor Based Elements for Bio-inspired Computing

Bio-based/bio-inspired systems are attracting the interest of many studies even if we are far from reproducing the simplest living cell property. The concept of memory is particularly well suited for mimicking learning behavior in biosystems and in information processing systems being capable of coupling inherently memory and logic capabilities. Bio-electronics is another challenging platform, mostly if we consider organic devices based on conductive and biocompatible polymers. This chapter deals with several examples of devices developed by joining unconventional computing, organic memristors and living being. Starting from organic memristors we realized logic gates with memory and a single layer perceptron. We developed hybrid systems based on living beings as key elements for the proper device working, in particular with Phyarum polycephalum and neurons. These devices enable new and unexplored opportunities in such emerging field of research.

Physarum in Hybrid Electronic Devices

We discuss hybrid systems where the slime mould is interfaced with organic electronics devices. We demonstrate the realisation of slime mould Schottky diode and organic electrochemical transistor . A central part of the chapter is dedicated to the integration of the Physarum into organic memristive device , an electronic element with synapse-like properties. We describe an architecture and working principles of the hybrid devices and variations of their electrical and optical properties as a result of the interaction with slime mould. We demonstrate that the slime mould is a smart candidate for the implementation of functional properties of smart living systems into electronic devices.

Basic transitions of Physarum polycephalum

The main charter of this work is the organism Physarum polycephalum, in particular plasmodium, Physarums 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.

Hybrid slime mold - containing systems for unconventional computing

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.