Annalisa Chiappone

3D Printing of Conductive Complex Structures with in Situ Generation of Silver Nanoparticles

Coupling the photoreduction of a metal precursor with 3D-printing technology is shown to allow the fabrication of conductive 3D hybrid structures consisting of metal nanoparticles and organic polymers shaped in complex multilayered architectures. 3D conductive structures are fabricated incorporating silver nitrate into a photocurable oligomer in the presence of suitable photoinitiators and exposing them to a digital light system.

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.

Effect of Different Green Cellulosic Matrices on the Performance of Polymeric Dye-Sensitized Solar Cells

Carboxymethyl cellulose (CMC) and microfibrillated cellulose (MFC) are here employed as bio-sourced fillers in quasi-solid electrolytes for polymeric dye-sensitized solar cells (DSSCs). High and durable photovoltaic performances are obtained, due the influence of the different cellulosic fillers on the cell parameters which are here compared and discussed. The present findings open up new intriguing prospects in the design of efficient energy conversion devices with eco-friendly/natural additives

3D Printed PEG-Based Hybrid Nanocomposites Obtained by Sol–Gel Technique

In this work, three-dimensional (3D) structured hybrid materials were fabricated combining 3D printing technology with in situ generation of inorganic nanoparticles by sol-gel technique. Those materials, consisting of silica nanodomains covalently interconnected with organic polymers, were 3D printed in complex multilayered architectures, incorporating liquid silica precursors into a photocurable oligomer in the presence of suitable photoinitiators and exposing them to a digital light system. A post sol-gel treatment in acidic vapors allowed the in situ generation of the inorganic phase in a dedicated step. This method allows to build hybrid structures operating with a full liquid formulation without meeting the drawbacks of incorporating inorganic powders into 3D printable formulations. The influence of the generated silica nanoparticle on the printed objects was deeply investigated at macro- and nanoscale; the resulting light hybrid structures show improved mechanical properties and, thus, have a huge potential for applications in a variety of advanced technologies.

In Situ Thermal Generation of Silver Nanoparticles in 3D Printed Polymeric Structures

Polymer nanocomposites have always attracted the interest of researchers and industry because of their potential combination of properties from both the nanofillers and the hosting matrix. Gathering nanomaterials and 3D printing could offer clear advantages and numerous new opportunities in several application fields. Embedding nanofillers in a polymeric matrix could improve the final material properties but usually the printing process gets more difficult. Considering this drawback, in this paper we propose a method to obtain polymer nanocomposites by in situ generation of nanoparticles after the printing process. 3D structures were fabricated through a Digital Light Processing (DLP) system by disolving metal salts in the starting liquid formulation. The 3D fabrication is followed by a thermal treatment in order to induce in situ generation of metal nanoparticles (NPs) in the polymer matrix. Comprehensive studies were systematically performed on the thermo-mechanical characteristics, morphology and electrical properties of the 3D printed nanocomposites.

3D printable light-responsive polymers

New photo-curable polymers for 3D printing are provided, exhibiting mechanical light-responsivity upon laser irradiation. Azobenzene moieties are employed both as dyes in the 3D printing process and as active groups providing the desired light responsivity. The incorporation of azobenzene units into polymeric matrices allows a reversible and controllable change of the Youngs modulus of a crosslinked micrometric structure. Depending on the temperature of operation, laser irradiation induces either a decrease (photo-softening) or an increase (photo-hardening) of the Youngs modulus. Such a behaviour can be spatially controlled in order to locally modify the mechanical features of 3D printed objects such as microcantilevers.

Ionic liquid-enhanced soft resistive switching devices

Resistive switching phenomena are of paramount importance in the area of memory devices. In the present study, we have fabricated a simple resistive switching device using a solution processable nanocomposite based on silver nitrate and poly(vinylidene fluoride-hexafluoropropylene). The change in resistance is ascribed to an initial ionic conduction, followed by a non-continuous field induced filament formation. The switching device fabricated with the above-mentioned active matrix displayed a volatile switching behavior. The addition of room temperature ionic liquid plays a fundamental role in triggering permanent memory and reducing the set voltage range up to ten-fold. The change in switching behavior with respect to the applied voltage bias and compliance level set during electrical characterization was studied thoroughly. The present work also gives a glimpse into the importance of device architecture on resistive switching phenomena.

UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices.

In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10-3 S cm-1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices.

Self-standing polymer-functionalized reduced graphene oxide papers obtained via a UV-process

Graphene based materials are attracting great attention every day due to their outstanding properties. Widening their potentialities through synergic effects in conjunction with other materials represents an intriguing challenge in order to obtain lighter and multi-functional composites. In this paper, novel self-standing graphene-based paper-like sheets are investigated, obtained via a facile dual step UV-induced process. This method, employing graphene oxide as a starting material, allows the obtaining of polymeric functionalized reduced graphene oxide papers that could be easily handled, featuring improved mechanical and peculiar electrical properties. The mechanical and thermal properties were investigated as well as their electrical response under different stimuli, such as temperature and humidity, showing remarkable changes.

Tunable electromechanical actuation in silicone dielectric film

Dielectric elastomer actuator films were fabricated on transparent conductive electrode using bi-component poly(dimethyl)siloxane (PDMS). PDMS is a well-known material in microfluidics and soft lithography for biomedical applications, being easy to process, low cost, biocompatible and transparent. Moreover its mechanical properties can be easily tuned by varying the mixing ratio between the oligomer base and the crosslinking agent. In this work we investigate the chemical composition and the electromechanical properties of PDMS thin film verifying for the first time the tuneable actuation response by simply modifying the amount of the curing agent. We demonstrate that, for a 20:1 ratio of base:crosslinker mixture, a striking 150% enhancement of Maxwell strain occurs at 1 Hz actuating frequency.