A. Bramanti

Organic light emitting field effect transistors based on an ambipolar p-i-n layered structure

A bottom contact/top gate ambipolar “p-i-n” layered light emitting field effect transistor with the active medium inserted between two doped transport layers, is reported. The doping profile results crucial to the capability of emitting light, as well as to the electrical characteristics of the device. In this sense, high output current at relative low applied gate/drain voltage and light emission along the whole large area transistor channel are observed, putting the basis to full integration of organic light emitting field effect transistors in planar complex devices.

Field-Emission Breakdown and Electromigration in Insulated Planar Nanoscopic Contacts

Planar nanoscopic contacts are observed to undergo early electrical breakdown. The authors show that the cause is high field emission capable of triggering electromigration. The phenomenon is well described by an empirical current-voltage law, well different from that usually found in nonflat field emitters; this is attributed to the particular geometry of the contacts. Although the mathematical form of the law is always the same, the intensity of breakdown current changes from sample to sample, ranging over several orders of magnitude; this is explained by the nanoscopic roughness of the emitting surfaces. They also show that the occurrence of breakdown may be dependent on the polarity of the applied voltage

Retention of nativelike conformation by proteins embedded in high external electric fields.

In this Communication, we show that proteins embedded in high external electric fields are capable of retaining a nativelike fold pattern. We have tested the metalloprotein azurin, immobilized onto SiO2 substrates in air with proper electrode configuration, by applying static fields up to 10(6)-10(7) Vm. The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. Such results are also discussed and supported by theoretical predictions of the inner protein fields.

Azurin for Biomolecular Electronics: a Reliability Study

The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its resilience to high electric fields and ambient conditions, which are crucial reliability issues. Concerning the effect of electric fields, two models of different complexity agree indicating an unexpectedly high robustness. Experiments in device-like conditions confirm that no structural modifications occur, according to fluorescence spectra, even after a 40-min exposure to tens of MV/m. Ageing is then investigated experimentally, at ambient conditions and without field, over several days. Only a small conformational rearrangement is observed in the first tens of hours, followed by an equilibrium state.

A Memristive Pixel Architecture for Real-Time Tracking

We report on a pixel architecture relying on memristive devices to perform pixel-level adaptive background subtraction. Core of the processing is the pixel, containing a light-to-frequency converter. Its output digital pulses, proportional to the intensity of light, are applied in turn to a memristor, changing its resistance accordingly. Two additional memristors are used to store the dynamic boundaries, outside which the behavior of the photo-generated signal is recognized to be anomalous, i.e., unexpectedly fast changing. The main advantages of using memristors over all-CMOS implementations are a smaller pixel pitch and non-volatility, the latter allowing the image background to be modeled with programmable time constants.

Memristor-based pixel for event-detection vision sensor

We report on a vision sensor architecture relying on a pixel-embedded memristive device to perform dynamic background subtraction as basic image processing components, aimed at detecting anomalous events in the scene. A Light-To-Frequency Converter generates digital pulses, which are linearly proportional with the light intensity. During the exposure time, a certain number of pulses, with proper width and amplitude, drive the memristor MS, changing its resistance. The value of MS is then compared with two memristors, MH and ML, used as thresholds. After each frame, the values of MH and ML are adjusted in order to satisfy ML <; MS <; MH. The rate at which the two memristors are updated is application-dependent and can be digitally programmed. If the value of MS trespasses either MH or ML, due to a light change, the pixel behaviour is recognized as anomalous (hot-pixel) By aggregating the hot-pixels of the image, anomalous events can be detected through standard processing techniques. The pixel architecture has been designed in a 0.35μm standard CMOS process and validated through simulation.

Charge transport in disordered films of non-redox proteins

Electrical conduction in solid state disordered multilayers of non-redox proteins is demonstrated by two-terminal transport experiments at the nanoscale and by scanning tunneling microscopy (STM/STS experiments). We also show that the conduction of the biomolecular films can be modulated by means of a gate field. These results may lead to the implementation of protein-based three-terminal nanodevices and open important new perspectives for a wide range of bioelectronic/biosensing applications.

Q3: A Compact Device for Quick, High Precision qPCR

An accurate and easy-to-use Q3 system for on-chip quantitative real-time Polymerase Chain Reaction (qPCR) is hereby demonstrated, and described in detail. The qPCR reactions take place inside a single-use Lab-on-a-Chip with multiple wells, each with 5 to 15 µL capacity. The same chip hosts a printed metal heater coupled with a calibrated sensor, for rapid and accurate temperature control inside the reaction mixture. The rest of the system is non-disposable and encased in a 7 × 14 × 8.5 (height) cm plastic shell weighing 300 g. Included in the non-disposable part is a fluorescence read-out system featuring up to four channels and a self-contained control and data storage system, interfacing with an external user-friendly software suite. Hereby, we illustrate the engineering details of the Q3 system and benchmark it with seamlessly ported testing protocols, showing that Q3 equals the performance of standard commercial systems. Overall, to the best of our knowledge, this is one of the most mature general-purpose systems for on-chip qPCR currently available.

Structural distortions in molecular-based quantum cellular automata: a minimal model based study

Molecular-based quantum cellular automata (m-QCA), as an extension of quantum-dot QCAs, offer a novel alternative in which binary information can be encoded in the molecular charge configuration of a cell and propagated via nearest-neighbor Coulombic cell-cell interactions. Appropriate functionality of m-QCAs involves a complex relationship between quantum mechanical effects, such as electron transfer processes within the molecular building blocks, and electrostatic interactions between cells. The influence of structural distortions of single m-QCA are addressed in this paper within a minimal model using an diabatic-to-adiabatic transformation. We show that even small changes of the classical square geometry between driver and target cells, such as those induced by distance variations or shape distortions, can make cells respond to interactions in a far less symmetric fashion, modifying and potentially impairing the expected computational behavior of the m-QCA.

Metalloprotein-based field-effect transistor: a prototype

A key challenge in nanoelectronics is the use of a bottom-up approach to fabricate nanodevices from molecular building blocks. Here, a field-effect transistor based on the metallo-protein Azurin is demonstrated. Azurin is attractive because of its natural redox properties (provided by the Cu redox site) and self-assembly capability (which allows the chemisorption on suitable surfaces). Our prototype structure consists of two planar nanoelectrodes connected by a protein self-assembled monolayer and a back electrode as gate. The transfer characteristic exhibits a pronounced resonance and transport is explained in terms of equilibrium between the two possible oxidation states of the copper site.