Pietro Ferraro

Bio: Pietro Ferraro is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 61, co-authored 653 publications receiving 12666 citations. Previous affiliations of Pietro Ferraro include Aeritalia & Centre national de la recherche scientifique.

Instant in situ formation of a polymer film at the water–oil interface

Abstract: The water–oil interface is an environment that is often found in many contexts of the natural sciences and technological arenas. This interface has always been considered a special environment as it is rich in different phenomena, thus stimulating numerous studies aimed at understanding the abundance of physico-chemical problems that occur there. The intense research activity and the intriguing results that emerged from these investigations have inspired scientists to consider the water–oil interface even as a suitable setting for bottom-up nanofabrication processes, such as molecular self-assembly, or fabrication of nanofilms or nano-devices. On the other hand, biphasic liquid separation is a key enabling technology in many applications, including water treatment for environmental problems. Here we show for the first time an instant nanofabrication strategy of a thin film of biopolymer at the water–oil interface. The polymer film is fabricated in situ, simply by injecting a drop of polymer solution at the interface. Furthermore, we demonstrate that with an appropriate multiple drop delivery it is also possible to quickly produce a large area film (up to 150 cm2). The film inherently separates the two liquids, thus forming a separation layer between them and remains stable at the interface for a long time. Furthermore, we demonstrate the fabrication with different oils, thus suggesting potential exploitation in different fields (e.g. food, pollution, biotechnology). We believe that the new strategy fabrication could inspire different uses and promote applications among the many scenarios already explored or to be studied in the future at this special interface environment.

Holographic imaging boosts machine learning for accurate micro-plastics recognition in seawater sample

Abstract: An effective strategy, that combines Digital Holography with machine learning, for achieving accurate and automatic identification of microplastics in filtered water sample, is proposed, reaching over 99% in classification performance among microplastics and diatoms.

Characterization of microplastics by holographic features for automatic detection in heterogeneous samples

Abstract: Microplastics are worrisome water pollutants that are more and more spread in deep sea and coastal waters. Plastic items can take decades to biodegrade, have the potential to affect the food chain and are harmful to marine life. Hence, there is the urgent need to define protocols and to create reliable tools to map the presence of microplastics in heterogeneous liquid samples. However, well established protocols and tools to identify microplastics in water have not been proposed yet. Here we investigate this class of objects by means of coherent imaging, in particular relying on Digital Holography (DH) microscopy. We provide a DH characterization of the “plastic” class that can be used as a global identifier independently on the plastic material under analysis. We probe microplastics of various materials through our DH microscope and show that the phase contrast map of microplastics can be used to define a fingerprint for the microplastics population. Thanks to the DH flexible refocusing, volumetric counting of microplastics in flow is feasible by DH with high-throughput. Remarkably, field-deployable, cost effective DH microscopes exist that can bring the DH characterization potential out of the lab for in situ environmental monitoring.

Manipulating liquid crystals by pyroelectric effect

Abstract: Liquid crystals (LCs) are substances that flow like liquids but have molecules ordered in a crystal-like way. These properties allow LCs to organize themselves in mesophases, states where they present features of both liquid and solid states, under particular conditions. This peculiarity has allowed these materials to find wide applicability in many fields, from display systems to optics and photonics.1, 2 An attractive property of LCs is the ability to modulate their optical properties using electric, optical, or magnetic fields. At present, different techniques exist for manipulating LCs that have found applications in various areas. For example, researchers have extensively studied LC tunable lenses and have designed and experimentally demonstrated many successful configurations.3 Other groups have proposed optical microresonators (light-trapping microspheres that have applications in laser sources)4 and LC-based optical devices such as electrooptic switches and beam scanners.5 Nevertheless, faster and more versatile approaches to modulate the properties of LCs are desirable, particularly in emerging fields of technology. The selective patterning of LCs into optical devices is often achieved by ink-jet printing approaches where a nozzle is scanned onto the target support for precise delivery of LC droplets. However, these techniques make use of expensive systems based on external voltage generators and, due to the scanning-mode operation, are relatively time-consuming. We found that the spatial self-assembly of LC droplets can be an efficient alternative to these techniques since, in particular conditions, the droplets can be driven to desired locations following electric-field lines (see Figure 1). Our approach is easier to accomplish than the ink-jet printing methods, even over relatively large areas, thus providing a cost-effective and rapid manipulation of LC droplets. Figure 1. Liquid-crystal (LC) droplets aligned onto a lithium niobate (LN) substrate following electric-field lines that were pyroelectrically generated. Droplet dimensions are of the order of microns or submicrons.

MEMS inspection by Digital Holographic

Abstract: We employed Digital Holographic Microscope (DHM) as a useful method for determining, with high accuracy, the MEMS out-of-plane deformations due to the residual stress introduced by fabrication process and to understand the effect of a thermal load on MEMS profile. The measured profiles can be employed for a quantitative estimation of the residual stresses by mean of some analytical and numerical models. Moreover, DHM also allows determination of variation of the profile of the object due to some external dynamic load (e.g. change in temperature, pressure, electrostatic). In this paper, MEMS behavior subjected to thermal load has been evaluated. In particular, the variation of profiles of cantilever beams subjected to a thermal treatment from 23/spl deg/C to 130/spl deg/C has been measured.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fiber grating sensors

Abstract: We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.