Alessandro Chiolerio

An NCL-HDL Snake-Clock-Based Magnetic QCA Architecture

The International Technology Roadmap of semiconductors suggests that quantum-dot cellular automata (QCA) technology might be a possible CMOS substitute. In particular, magnetic quantum-dot cellular automata (MQCA) have recently drawn the attention of the researchers. Previous experimental works have demonstrated that MQCA are feasible, and can be fabricated with existing technological processes. They are also attractive due to their compactness and an extremely small power dissipation. Unlike in previous contributions, where architectural blocks are often presented without or only slightly considering their relations with technology, here we conceived, implemented, and described a complex MQCA computational block maintaining a clear link with technology. This link is achieved at different levels. At an architectural level, we propose the use of delay insensitive null convention logic (NCL) . It is implemented for MQCA in order to solve the “layout=timing” problem in the specific case of MQCA. We, thus, describe an architectural block at system level using a hardware description language (HDL). This NCL-HDL idea is adapted to a new structure, which we have called “snake clock,” proposed as a feasible solution for the problem of clock delivery, essential for MQCA operations. Furthermore, we demonstrated by means of accurate micromagnetic and finite element method simulations that the three-phase “snake-clock” NCL structure works correctly.

Inkjet printed acrylic formulations based on UV-reduced graphene oxide nanocomposites

This work reports the formulation of water-based graphene oxide/acrylic nanocomposite inks, and the structural and electrical characterization of test patterns obtained by inkjet direct printing through a commercial piezoelectric micro-fabrication device. Due to the presence of heavily oxygenated functional groups, graphene oxide is strongly hydrophilic and can be readily dispersed in water. Through a process driven by UV irradiation, graphene oxide contained in the inks was reduced to graphene during photo-curing of the polymeric matrix. Printed samples of the nanocomposite material showed a decrease of resistivity with respect to the polymeric matrix. The analysis of the influence of printed layer thickness on resistivity showed that thin layers were less resistive than thick layers. This was explained by the reduced UV penetration depth in thick layers due to shielding effect, resulting in a less effective photo-reduction of graphene oxide.

Direct patterning of silver particles on porous silicon by inkjet printing of a silver salt via in-situ reduction

We have developed a method for obtaining a direct pattern of silver nanoparticles (NPs) on porous silicon (p-Si) by means of inkjet printing (IjP) of a silver salt. Silver NPs were obtained by p-Si mediated in-situ reduction of Ag+ cations using solutions based on AgNO3 which were directly printed on p-Si according to specific geometries and process parameters. The main difference with respect to existing literature is that normally, inkjet printing is applied to silver (metal) NP suspensions, while in our experiment the NPs are formed after jetting the solution on the reactive substrate. We performed both optical and scanning electron microscopes on the NPs traces, correlating the morphology features with the IjP parameters, giving an insight on the synthesis kinetics. The patterned NPs show good performances as SERS substrates.

Silver nanoparticle ink technology: state of the art

Printed electronics will bring to the consumer level great breakthroughs and unique products in the near future, shifting the usual paradigm of electronic devices and circuit boards from hard boxes and rigid sheets into flexible thin layers and bringing disposable electronics, smart tags, and so on. The most promising tool to achieve the target depends upon the availability of nanotechnology-based functional inks. A certain delay in the innovation-transfer process to the market is now being observed. Nevertheless, the most widely diffused product, settled technology, and the highest sales volumes are related to the silver nanoparticle-based ink market, representing the best example of commercial nanotechnology today. This is a compact review on synthesis routes, main properties, and practical applications.

Sonochemical synthesis of versatile hydrophilic magnetite nanoparticles.

Hydrophilic magnetite nanoparticles in the size range 30-10nm are easily and rapidly prepared under ultrasonic irradiation of Fe(OH)(2) in di- and tri-ethylene glycol/water solution with volume ratio varying between 7:3 and 3:7. Structural (XRD) and morphological (SEM) characterization reveal good crystalline and homogeneous particles whereas, when solvothermally prepared, the particles are inhomogeneous and aggregated. The sonochemically prepared particles are versatile, i.e. well suited to covalently bind molecules because of the free glycol hydroxylic groups on their surface or exchange the diethylene or triethylene glycol ligand. They can be easily transferred in hydrophobic solvents too. Room-temperature magnetic hysteresis properties measured by means of Vibrating Sample Magnetometer (VSM) display a nearly superparamagnetic character. The sonochemical preparation is easily scalable to meet industrial demand.

Radical diffusion engineering: tailored nanocomposite materials for piezoresistive inkjet printed strain measurement

We present a comprehensive study related to UV-curable nanocomposite (NC) materials, based on acrylic matrix containing Ag nanoparticles (NPs) formed by in situ reduction and co-formulated with titania NPs. Addition of titania produces a diffusion limited aggregation of in situ formed Ag NPs during photocuring due to radical propagation, allowing to obtain electromechanical percolation at very low solid content. Keeping low the solid content is important, considering the cost of raw materials. Compared to NCs based on spherical fillers, where percolation is reached at very high solid contents (around 70%), by radical engineering we could approach it by adding 5 to 30% of Ag precursor (Ag content 2 to 10%). These NCs are characterized by a low viscosity at room temperature, allowing full processability by means of inkjet printing (IjP), as well as good electrical properties after curing, ranging from metallic to dissipative, in their annealed state. We present morphological, chemo-physical and electrical characterisation, as well as outstanding piezoresistive properties of these materials in the thin film state and after direct patterning by means of IjP. The goal was to realize low cost printed strain-gages featuring improved characteristics when compared to available commercial products. We obtain diffusion-engineered unstructured materials featuring gauge factors (GF) as high as 13.4, corresponding to a seven-fold increase with respect to commercial metallic alloys. Measurements performed on structured NC IjP strain gauges produce GF up to 220, corresponding to a hundred-fold increase in comparison with commercial devices.

Inkjet-printed PEDOT:PSS electrodes on plasma-modified PDMS nanocomposites: Quantifying plasma treatment hardness

Nanostructured polymeric composites are promising materials for the fabrication of piezoresistive devices because they show a huge variation in electrical resistance when subjected to mechanical deformation. Quantum tunneling composites feature a conduction mechanism occurring between the metallic filler and copper particles embedded in a polydimethylsiloxane (PDMS) insulating matrix, and the mechanism is enhanced by the spiky morphology of the particles. PEDOT:PSS electrodes are patterned on either side of the composite by inkjet printing, a technology that allows one-step fabrication processes. The adhesion and spreading of conductive printed ink drops are controlled and enhanced by pre-treating the samples surface in an atmospheric pressure plasma customized system. Because of an extremely high metal to polymer ratio, which results in the different surface and dielectric properties of the composite, conventional plasma conditions are not suitable to allow the control of spreading. The optimal plasma conditions for ink/surface compatibility were found using quantitative comparison based on image analysis and numerical interpretation of the adhesion/roughness properties such as bulging and spread.

Synthesis of polyaniline-based inks for inkjet printed devices: Electrical characterization highlighting the effect of primary and secondary doping

Engineering applications for printed electronics demand solution processable electrically conductive materials, in the form of inks, to realize interconnections, piezoresistive pressure sensors, thermoresistive temperature sensors, and many other devices. Polyaniline is an intrinsically conductive polymer with modest electrical properties but clear advantages in terms of solubility and stability with temperature and in time. A comprehensive study, starting from its synthesis, primary doping, inkjet printing and secondary doping is presented, with the aim of elucidating the doping agent effects on its morphology, printability and electronic performance.

Effect of the fabrication method on the functional properties of BaTiO3: PVDF nanocomposites

This paper deals with the preparation and characterization of nanocomposite (NC) materials, comparing different technologies for sample fabrication, in view of their possible application as piezoelectric sensors. Those NCs consist on BaTiO3 nanoparticles embedded into a polyvinylidene fluoride matrix, where both the ceramic and the polymeric phases could exhibit ferroelectricity. In particular, we compare the properties of samples prepared through three different methods, i.e., solvent casting, enabling a fast realization, spin-coating, which allows to realize thin flexible films particularly interesting for large area sensors, and hot embossing, which is exploited to modify the residual porosity in the thick films. The influence of the fabrication techniques on the physical and chemical properties is investigated. Different electrode materials have been tested and compared, ranging from sputtered Pt to an engineered thermally evaporated Ti/Au bilayer. Leakage current, polarization, displacement curves, and piezoelectric coefficient d33 are evaluated by small signal indirect measurements, comparing the properties of different materials and understanding how processing technologies influence the sensor performances by acting on the functional materials.

SERS active silver nanoparticles synthesized by inkjet printing on mesoporous silicon

Inkjet printing technique is exploited for the synthesis of Ag nanoparticles (NPs) patterned on electrochemically etched silicon-based substrates. The nanostructure morphology, here analyzed by scanning electron microscopy, is dictated by the ink composition and the printing parameters. Under suitable excitation conditions, resonant surface-enhanced Raman scattering (SERS) performed on such metal-dielectric nanostructures can approach single-molecule detection as recently demonstrated on silvered porous silicon synthesized by immersion plating.PACS78.67.Bf; 78.30.-j