A NOVEL TECHNIQUE FOR AUTOMATED DETECTION, COUNT AND MEASUREMENT OF MICROPLASTICS

Microplastics are solid plastic particles composed of different polymers whose dimensions are less or equal to 5 mm. They originate either from primary production or, more frequently, by degradation of plastic materials. Given their interaction with the ecosystems, and their longlived persistence in the environment, they pose a significant threat to the world biota including human life. For that, their detection and continuous monitoring are of paramount importance. Unfortunately, detection and quantification of their abundance require a long work of visual observation and count, which makes the process of a high number of samples a very timedemanding task. Softwares like ImageJ and MP-VAT has been employed with certain success to automate the detection and counting task, although the recognition is not always robust, and a fully automated process is still far. In this context, we report a novel approach in image analysis for detecting, counting, and measuring microplastics on filter membrane substrates with UV-excited fluorescence. The technique relies on a multichannel variant of the Canny edge detection algorithm, which allows an effective microplastic particle segmentation, even in the presence of a strong fluorescence halo. The developed method has been validated against manual count on real sediment samples from Borgio Verezzi (Italy) show cave and water from Po River (Italy). After collection, the samples were treated with 30% hydrogen peroxide to remove fluorescent organic compounds and filtered on glass filter membranes. The filters were imaged with a high-resolution camera under 365 nm UV illumination to stimulate microplastic fluorescence emission. In addition, the staining of microplastic with NileRed dye has also been tested to verify if it can provide improvements in terms of count reliability

Bioresorbable phosphate glass microstructured optical fiber for simultaneous light and drug delivery

Biomedical needs have recently boosted the development of brand-new multifunctional and bioresorbable optical fibers, especially in the field of theranostics. Biocompatible fibers represent great tools for in-body monitoring, diagnostics, and photo-dynamic therapy, thanks to their ability to carry light and act as a drug delivery system in capillary form. Optical fibers are also convenient because of their production scalability since they can be drawn into kilometers starting from a single preform, thus limiting production costs. Furthermore, biocompatible optical fibers can be easily adapted to different applications since they can be well integrated into catheters and other medical instrumentations. In this scenario, calcium-phosphate glass (CPG) optical fibers are promising candidates, thanks to their enhanced thermo-mechanical features and biocompatibility. Moreover, their resorbability, as well as mechanical and optical properties, can be finely tuned by tailoring the specific glass composition. In the present work, we report on our latest results in this field starting from the full characterization of CPG optical fibers by means of in-vitro dissolution tests and in-vivo experiments. Dissolution tests in simulated body fluid revealed that a high amount of MgO can effectively decrease the dissolution time, while in-vivo experiments showed no inflammatory response in the tested animals. The possibility of tailoring the resorption time of the CPG fiber is a key factor in several applications where different operational times are needed, e.g. from few days to few months. In addition, we will show the application of a CPG-based multifunctional fiber to deliver a photosensitive drug and its activation by light carried with the same fiber. Finally, we will report on the design and fabrication of a bioresorbable microstructured CPG fiber by properly combining rotational casting and extrusion techniques

Effect of Partial Crystallization on the Structural and Luminescence Properties of Er3+-Doped Phosphate Glasses

Er-doped phosphate glass ceramics were fabricated by melt-quenching technique followed by a heat treatment. The effect of the crystallization on the structural and luminescence properties of phosphate glasses containing Al2O3, TiO2, and ZnO was investigated. Themorphological and structural properties of the glass ceramics were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and micro-Raman spectroscopy. Additionally, the luminescence spectra and the lifetime values were measured in order to study the influence of the crystallization on the spectroscopic properties of the glasses. The volume ratio between the crystal and the glassy phases increased along with the duration of the heat treatment. The crystallization of the glass ceramics was confirmed by the presence of sharp peaks in the XRD patterns and different crystal phases were identified depending on the glass composition. Sr(PO3)2 crystals were found to precipitate in all the investigated glasses. As evidenced by the spectroscopic properties, the site of the Er3+ ions was not strongly affected by the heat treatment except for the fully crystallized glass ceramic which does not contain Al2O3, TiO2, and ZnO. An increase of the lifetime was also observed after the heat treatment of this glass. Therefore, we suspect that the Er3+ ions are incorporated in the precipitated crystals only in this glass ceramic

Photonic crystal X-shaped waves

We study out-of-plane three-dimensional wave localization in two-dimensional photonic crystals (PCs) and predict the existence of two types of stationary X-shaped waves at frequencies corresponding to either a local top point of a band, where the effective in-plane diffraction turns out to be negative, or at band saddle points. In the former case the X wave is directed along the invariance direction of the PC, whereas in the latter case it lies in the PC plane and directed along one of the principal directions of the diffraction tensor. Numerical results of localized waves for a PC with a square lattice, obtained in the spectral domain by superposition of isofrequency Bloch modes, are presented and confirm the analytical predictions based on an effective mass approach

Integrated devices in ferroelectrics for optical modulations and sensing

We will review the current status of domain inverted lithium niobate acousto- and electro-optic devices and show how the introduction of domain micro-engineering techniques can have a strong impact on modulators' performance enabling for a new class of integrated devices. We will also present potential applications of the proposed devices in increasingly important areas, such as advanced optical communication modulation formats, reconfigurable networks and sensors

Room temperature direct bonding of LiNbO3 crystal layers and its application to high-voltage optical sensing

LiNbO3 is a crystal widely used in photonics and acoustics, for example in electro-optic modulation, nonlinear optical frequency conversion, electric field sensing and surface acoustic wave filtering. It often needs to be combined with other materials and used in thin layers to achieve the adequate device performance. In this paper, we investigate direct bonding of LiNbO 3 crystals with other dielectric materials, such as Si and fused silica (SiO2), and we show that specific surface chemical cleaning, together with Ar or O2 plasma activation, can be used to increase the surface free energy and achieve effective bonding at room temperature. The resulting hybrid material bonding is very strong, making the dicing and grinding of LiNbO3 layers as thin as 15 νm possible. To demonstrate the application potentials of the proposed bonding technique, we have fabricated and characterized a high-voltage field sensor with high sensitivity in a domain inverted and bonded LiNbO3 waveguide substrate