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Mechanical properties of polymer biocomposites are influenced by the interaction between the matrix and the filler surface. In this work, composites based on poly(butylene-adipate-terephthalate) (PBAT) filled with micrometric particles of zein-TiO2 complex (ZTC) were realized via solvent casting technique at different concentrations, equal to 0, 5, 10, and 20 wt%. After pelletization, the resulting materials were injection molded into standard specimens, employed for the uniaxial tensile test (UTT) characterization. From the stress-strain curves, Young’s modulus ( E ), yield stress ( σ y ), stress at break ( σ B ), elongation at break ( ε B ), and toughness ( T ) were collected. The addition of the ZTC proved to show a reinforcing effect on the polymeric matrix, with an increase in both E and σ y . Modelling of the mechanical properties was performed by applying Kerner’s and Pukánszky’s equations. Kerner’s model, applied on experimental E values, returned a very good correspondence between collected and theoretical values. From the application of Pukánszky’s model to σ y , the obtained B value showed a good interfacial interaction between the matrix and the filler. Due to the enhanced stiffness of the composites, a reduction in the true stress at break ( σ T , B ) was observed. The modified Pukánszky’s model gave a B value lower than the one obtained for the yield, but still in the range of acceptable values for microcomposites.

The formation of elemental trigonal tellurium (t-Te) on tellurite glass surfaces exposed to femtosecond laser pulses is discussed. Specifically, the underlying elemental crystallization phenomenon is investigated by altering laser parameters in common tellurite glass compositions under various ambient conditions. Elemental crystallization of t-Te by a single femtosecond laser pulse is unveiled by high-resolution imaging and analysis. The thermal diffusion model reveals the absence of lattice melting upon a single laser pulse, highlighting the complexity of the phase transformation. The typical cross-section displays three different crystal configurations over its depth, in which the overall thickness increases with each subsequent pulse. The effect of various controlled atmospheres shows the suppressing nature of the elemental crystallization, whereas the substrate temperature shows no significant impact on the nucleation of t-Te nanocrystals. This research gives new insight into the elemental crystallization of glass upon femtosecond laser irradiation and shows the potential to fabricate functional transparent electronic micro/nanodevices.

In this work new biodegradable composite materials based on poly(butylene-adipate-co-terephthalate) (PBAT) reinforced with water-soluble calcium-phosphate glass (CPG) microparticles at different filler concentration (0, 4, 10, 20 and 40 wt%) were characterized by dynamic-mechanical analysis (DMA), aging and fragmentation tests. DMA results showed increasing storage modulus (E′) values with the filler content, without a significant modification of the glass transition temperature (Tg), translating in a reinforcing effect of the filler particles with good interphase adhesion. The creep compliance decreased with the increase of the CPG content, confirming a greater resistance of the composites to deformation under constant stress. The stability to weathering agents and the degree of fragmentation in laboratory-scale composting conditions were also tested, obtaining a higher sensitivity to degradation of the PBAT-based composites with the increase of CPG content. Overall, the addition of CPG particles in a PBAT matrix produced stiffer composites, with modulation of the properties based on the filler content, enhancing at the same time their degradation rate, making them a promising and more sustainable alternative to traditional polymers. Graphical Abstract

Biobased composites with peculiar properties offer an attractive route for producing environmentally friendly materials. The reinforcement for poly(butylene adipate

In recent years, there has been a growing interest towards compact high peak-power pulsed laser sources for applications such as LIDAR, range findings, remote sensing, communications and material processing. A common laser architecture used to realize these sources is the Master Oscillator Power Amplifier (MOPA), in which a master oscillator produces a highly coherent beam and a fiber amplifier boosts the output power, while preserving its main spectral properties. Phosphate glasses are recognized to be an ideal host material for engineering the amplification stage of a pulsed MOPA since they enable extremely high doping levels of rare-earth ions to be incorporated in the glass matrix without clustering, thus allowing the fabrication of compact active devices with high gain per unit length. With the aim of realizing compact optical fiber amplifiers operating at 1 and 1.5 µm, a series of highly Yb3+- and Yb3+/Er3+-doped custom phosphate glass compositions were designed and fabricated to be used as active materials for the core of the amplifiers. Suitable cladding glass compositions were explored and final core/cladding glass pairs were selected to realize single-mode and multi-mode optical fibers. Core and cladding glasses were synthesized by melt-quenching technique. The core glass was then cast into a cylindrical mold to form a rod, while the cladding glass was shaped into a tube by rotational casting method or extrusion technique. The latter has been extensively employed for the manufacturing of tellurite and germanate glass preforms, but only recently the first example of active phosphate fiber preform fabricated by this method has been reported by our research team. Phosphate fibers were then manufactured by preform drawing, with the preform being obtained by the rod-in-tube technique. Preliminary results of pulsed optical amplification at 1 and 1.5 µm are presented for a single-stage MOPA.

Ion-exchange in molten nitrate salts containing metal ions (i.e. silver, copper, etc.) represents a well-established technique able to modify the chemical-physical properties of glass materials. It is widely used not only in the field of integrated optics (IO) but also, more recently, in plasmonics due to the possibility to induce the formation of metal nanoparticles in the glass matrix by an ad hoc thermal post-process. In this work, the application of this technology for the realisation of low-cost and stable surface-enhanced Raman scattering (SERS) active substrates, based on soda-lime glass microrods, is reported. The microrods, with a radius of a few tens of microns, were obtained by cutting the end of an ion-exchanged soda-lime fibre for a length less than 1 cm. As ion source, silver nitrate was selected due to the outstanding SERS properties of silver. The ion-exchange and thermal annealing post-process parameters were tuned to expose the embedded silver nanoparticles on the surface of the glass microrods, avoiding the use of any further chemical etching step. In order to test the combined SERS/fluorescence response of these substrates, labelled molecular beacons (MBs) were immobilised on their surface for deoxyribonucleic acid (DNA) detection. Our experiments confirm that target DNA is attached on the silver nanoparticles and its presence is revealed by both SERS and fluorescence measurements. These results pave the way towards the development of low-cost and stable hybrid fibres, in which SERS and fluorescence interrogation techniques are combined in the same optical device.

Recently developed calcium-phosphate glass formulations are proposed in this chapter as a new class of materials for biomedical optics and photonics. The glasses have been designed and carefully prepared in our laboratory to be dissolvable in biological fluids while being optically transparent, mechanically reliable both in dry and humid environments, and suitable for both preform extrusion and fiber drawing. Optical fibers have been drawn from these glasses using our custom-made induction heated drawing tower and showed attenuation loss values from one to two orders of magnitude lower than the counterpart polymeric-based bioresorbable devices reported in literature. In addition, the optical fibers have been implanted in living rats for several weeks and no clinical signs of any adverse effect have been found. Results on the inscription and characterization of different types of fiber Bragg grating-based optical filters will be also shown, together with the demonstration of the suitability of the above-mentioned bioresorbable optical fibers for time-domain diffuse optical spectroscopy.

Silica optical fibers are employed in endoscopy and related minimally invasive medical methods thanks to their good transparency and flexibility. Although silicon oxide is a biocompatible material, its use involves a serious health risk due to its fragility and the fact that potential fiber fragments can freely move inside the body without the possibility of being detected by conventional methods such as X-ray imaging. A possible solution to this issue can be the development of optical fibers based on bioresorbable (i.e., biodegradable and biocompatible) materials, which exhibit the important benefit of not having to be explanted after their functionality has expired. The optical power transmission tests of recently developed single-mode (SM) and multi-mode (MM) bioresorbable optical fibers based on calcium-phosphate glasses (CPGs) are here reported. A continuous-wave (CW) fiber laser at 1080 nm with output power up to 13 W and picosecond laser sources at 515 and 1030 nm with MW pulse peak power were used to test the transmission capabilities of the CPG fibers. No degradation of the CPG fibers transmission under long-term illumination by CW laser was observed. A laser-induced damage threshold (LIDT) at a fluence higher than 0.17 J/cm2 was assessed with the picosecond laser sources.

We present an experimental characterization of the amplification of sub-nanosecond duration laser pulses at a wavelength of 1538 nm in short custom-made Er:Yb phosphate glass fibers with different core diameters. The fibers vary in their diameter from 100 µm (highly multi-mode) down to 12 µm (single-mode). The peak power, energy per pulse, and spectral shape of the amplified signal are presented. With our input pulses, the measurements show that the large core diameter fibers do not increase the amplification of the 1538 nm signal. We believe this is due to the high re-absorption of the E r 3 + ions in the phosphate fiber. The optimal fiber geometry was found to have a core diameter of 20 µm with a length of 14 cm. The maximum peak power is 8.25 kW, corresponding to a net gain of 10.9 dB, with a pulse duration of 0.7 ns and a repetition rate of 40 kHz.

This paper reports the results of the designing, manufacturing and characterization of a jewel obtained by means of coupling the dogmas of industrial design to the analytical engineering approach. The key role in the design of the jewel was played by an in-house synthesized Neodymium (Nd)-doped phosphate glass, selected due to its easy handling and capability to change color according to the incident light wavelength. The glass core was covered by a metal alloy to mitigate its relatively high fragility and sensitivity to thermal shock and, at the same time, to highlight and preserve its beauty. The selection of the proper metal alloy, having thermo-mechanical properties compatible with those exhibited by the glass, was carried out by means of Ashby&rsquo, s maps, a powerful tool commonly adopted in the field of industrial design.

This Conference Presentation, “Bioresorbable phosphate glass microstructured optical fiber for simultaneous light and drug delivery,” was recorded for the SPIE Photonics Europe 2020 Digital Forum.

The well-known enhancement effect of surface-enhanced Raman spectroscopy (SERS) is associated with the presence of metallic nanostructures at the substrate surface. Different bottom-up and top-down processes have been proposed to impart the substrate with such a nanostructured layer. The former approaches are low cost but may suffer from reusability and stability. The latter strategies are expensive, time consuming and require special equipment that complicate the fabrication process. Here, we present the possibility to obtain stable and reusable SERS substrates by a low-cost silver-sodium ion-exchange process in soda-lime glass microrods. The microrods were obtained by cutting the tip of the ion-exchanged soda-lime fiber, resulting in disks of about few millimeters in length and one hundred microns in diameter. A thermal annealing post-process was applied to trigger the reduction of Ag+ ions into nanoparticles (AgNPs) within the ion-exchanged glass microrods. Afterwards, ion-exchange and thermal treatments were carefully tuned to assure the presence of silver NPs exposed on the surface of the microrods, without using any chemical etching. An AFM analysis confirmed the presence of AgNPs with size of tens of nm on the surface of the fiber probe. A SERS affinity bioassay was developed on the probe with the final aim of detecting microRNA fragments acting as biomarkers of different diseases. Specifically a DNA hybridization assay was built up by anchoring a molecular beacon containing a Raman tag on the Ag surface via thiol chemistry. Initial SERS experiments confirmed the presence of the beacon on the NPs embedded on the microrods surface, as monitored by detecting main spectral bands ascribed to the oligonucleotide chain. Finally, the ability of the platform to interact with the target microRNA sequence was assessed. The analysis was repeated on a number of miRNA sequences differing from the target to evaluate the specificity of the proposed assay.

The steps toward the fabrication of directly-extruded microstructured fibre preforms made of a bioresorbable phosphate glass are herein presented. Microstructured fibres show a wide range of applications, i.e. photonic crystal fibres, large mode area fibres, hollow gas/liquid sensors, etc. Nevertheless, the fabrication of bioresorbable microstructured fibres has not been feasible so far due to a lack of bioresorbable transparent glass and more flexible fibre preform fabrication techniques. A custom developed calcium-phosphate glass has been designed and carefully prepared in our laboratory to be dissolvable in a biological fluid while being optically transparent and suitable for both preform extrusion and fibre drawing. This glass has been characterised both in terms of mechanical and optical properties as well as for dissolution in aqueous medium. Furthermore, the proposed glass is thermally stable, i.e. can be processed both in the extruder and in the drawing tower. Several extrusion experiments have been carried out with different glass preforms’ shapes. Analyses of these preforms by means of Optical Profilometry and Atomic Force Microscopy have been carried out to assess the roughness of the surface of the extrudate. To support the production of an optimized die for the preform extrusion, a simplified laminar flow model simulation has been employed. This model is intended as a tool for a fast and reliable way to catch the complex behaviour of glass flow during each extrusion and can be regarded as an effective design guide for the dies to fulfil specific needs for preform fabrication. After die optimisation, extrusion of a capillary was realised, and a stacking of extruded tubes was drawn to produce a microstructured optical fibre made of bioresorbable phosphate glass. The combination of bioresorbability and fibre microstructure, show a promising pathway toward a new generation of implantable biomedical devices.

The environmental impacts of cement and concrete industries are increasingly taken into consideration by regulatory agencies and new solutions must be found to turn into more sustainable productions. The use of waste materials as partial replacement of cement and/or aggregates or also as fillers into cement-based admixtures is a possible way to reduce the related negative impacts, such as carbon dioxide emissions and raw materials consumption. This work explores the possibility of using biochar, a carbon-rich and porous solid by-product resulting from thermochemical conversion of residual biomass under controlled conditions, as filler in concrete for structural use. The biochar used in this study derives from a commercial plant, which produces energy from pyro-gasification of woodchips. Biochar is at first chemically and morphologically characterized, then it is added as filler in concrete in different percentages, up to 10% by weight of cement. The effects of its introduction on fresh and hardened physical and mechanical properties of concrete, as well as on the internal matrix microstructure, are evaluated and compared to a reference concrete. Different curing conditions (wet and dry) and curing times (up to 365 days) are processed, also in order to evaluate biochar effect on concrete in terms of internal curing action and long-term behavior.

High-power, single-frequency, pulsed fiber amplifiers are required in light detection and ranging, coherent laser detection, and remote sensing applications to reach long range within a short acquisition time. However, the power-scaling of these amplifiers is limited by nonlinearities generated in the optical fibers, in particular by stimulated Brillouin scattering (SBS). In this regard, the use of multicomponent phosphate glasses maximizes the energy extraction and minimizes nonlinearities. Here, we present the development of a single-stage, hybrid, pulsed fiber amplifier using a custom-made multicomponent Yb-doped phosphate fiber. The performance of the phosphate fiber was compared to a commercial Yb-doped silica fiber. While the latter showed SBS limitation at nearly 6.5 kW for 40 cm length, the maximum achieved output peak power for the multicomponent Yb-doped phosphate fiber was 11.7 kW for 9 ns pulses using only 20 cm with no sign of SBS.

A high power, ultra-compact, lightweight, and low cost eye-safe laser source for a Light Detection and Ranging (LIDAR) system is currently under development in the framework of the NATO Science for Peace and Security project “CALIBER”, with the aim to be installed on small Unmanned Aerial Vehicles (UAVs) for surveillance of borders and sensitive areas, with saving in manpower and equipment.

This work presents the fabrication and experimental evaluation of instrumentation designed to enable higher spatial resolution neutron radiography for those performing research at neutron scattering facilities. Herein, we describe a proof-of-concept array of microstructured silicate fibers with 6Li doped cores that shows progress towards a design for μ m resolution neutron radiography. The multicore fiber was fabricated by drawing stacked unit elements of Guardian Glass (Nucsafe Inc., Oak Ridge, TN, USA), a 6Li scintillating core glass, and a silicate cladding glass. These structured fibers function as an array of sub-10- μ m waveguides for scintillation light. Measurements have shown a significantly increased integrated charge distribution in response to neutrons, and the spatial resolution of the radiographs is described by edge response and line spread functions of 48 ± 4 μ m and 59 ± 8 μ m , respectively.

We report on the design and development of microstructured phosphate glass optical fibers for minimally invasive diagnosis and therapy. We discuss preliminary results of fiber drawing and characterization.

The well-known enhancement effect of surface-enhanced Raman spectroscopy (SERS) is associated with the presence of metallic nanostructures at the substrate surface. Different bottom-up and top-down processes have been proposed to impart the substrate with such a nanostructured layer. The former approaches are low cost but may suffer from reusability and stability. The latter strategies are expensive, time consuming and require special equipment that complicate the fabrication process. Here, we present the possibility to obtain stable and reusable SERS substrates by a low-cost silver-sodium ion-exchange process in soda-lime glass microrods. The microrods were obtained by cutting the tip of the ion-exchanged soda-lime fiber, resulting in disks of about few millimeters in length and one hundred microns in diameter. A thermal annealing post-process was applied to trigger the reduction of Ag+ ions into nanoparticles (AgNPs) within the ion-exchanged glass microrods. Afterwards, ion-exchange and thermal treatments were carefully tuned to assure the presence of silver NPs exposed on the surface of the microrods, without using any chemical etching. An AFM analysis confirmed the presence of AgNPs with size of tens of nm on the surface of the fiber probe. A SERS affinity bioassay was developed on the probe with the final aim of detecting microRNA fragments acting as biomarkers of different diseases. Specifically a DNA hybridization assay was built up by anchoring a molecular beacon containing a Raman tag on the Ag surface via thiol chemistry. Initial SERS experiments confirmed the presence of the beacon on the NPs embedded on the microrods surface, as monitored by detecting main spectral bands ascribed to the oligonucleotide chain. Finally, the ability of the platform to interact with the target microRNA sequence was assessed. The analysis was repeated on a number of miRNA sequences differing from the target to evaluate the specificity of the proposed assay.

Rare earth doped phosphate glasses are attractive materials for the engineering of photonic devices, due to their easy processing, good thermal stability, excellent optical properties and high rare-earth ions solubility [1]. Besides, phosphate glasses with a P 2 O 5 content of 50 mol% have been shown to be suitable for fiber drawing. It is well known that if the rare-earth ions are located in crystalline phase of desired nature and structure, the spectroscopic properties of the glasses can be enhanced [2]. Therefore, efforts have been focused on the development of new glass-ceramics (GCS) obtained from the heat treatment of glasses, as these engineered materials possess some of the glass properties (large flexibility of composition and geometry) but also some advantages of the RE-doped single crystals (high absorption and emission as well as long lifetimes).

The use of bioresorbable fibers represents an innovative way to build optical implantable devices and to look inside the body. Recently, a new kind of bioresorbable fibers, based on calcium-phosphate glasses, has been introduced by some of us. They show a good biocompatibility and improved attenuation loss coefficient with respect to other bioresorbable fibers. In this work, we used those fibers to explore their suitability in diffuse optics. Indeed, the time-domain technique is a non-invasive methodology which allows to have an absolute estimate of the absorption and reduced scattering spectra of the diffusive medium. It allows to bring information about concentration of chemical components (water, oxyand deoxy-hemoglobin), thus conveying information about the functional status and/or the scattering properties (changes in tissue microstructure, edema). Such information can then be related to the tissue regeneration, healing process, or to a harmful evolution. This makes the time domain optical spectroscopy coupled to bioresorbable fibers a good candidate for future medical devices. Here we demonstrate the suitability of these fibers for diffuse optics by means of standardized tests and then we use them for a proof-of-principle measurement on ex-vivo chicken breast, obtaining results comparable with standard fibers. Thanks to the encouraging results, we are working on a system based on a single fiber (serving as both injection and collection fiber) to go closer to a single interstitial fiber which can lessen the effect of the implant.