Showing papers by "Pietro Ferraro published in 2019"
TL;DR: An innovative skin-over-liquid system made of a periodic array of highly compliant microbumps actuated through an electrode-free electrohydrodynamic (EHD) pressure is proposed, demonstrated to be highly repeatable and capable of swelling and deflating easily under a simple thermal stimulation driven by the pyroelectric effect, thus providing a challenging platform that can be actively controlled at the microscale.
Abstract: The unique deformability and the compliance ability of thin sheets on soft substrates attract much interest for studying the phenomena related to elastic instabilities as well as for sensing very weak forces such as those generated by live cells in vitro. However, the techniques used currently for producing such platforms are affected by a high degree of complexity and poor repeatability. Moreover, their deformability is usually used as a passive response to the action of an external force. Herein we propose a novel concept for a reliable and dynamic skin-over-liquid system made of a periodic array of highly compliant microbumps actuated through electrode-free electrohydrodynamic (EHD) pressure. We demonstrate that these structures are highly repeatable and capable of swelling and deflating easily under a simple thermal stimulation driven by the pyroelectric effect, thus providing a challenging platform that can be actively controlled at the microscale. Furthermore, we show the proof of principle by swelling these microbumps for mechanically stimulating live cells in vitro, thus opening the route to more reliable and easy to accomplish assays in the field of mechanobiology. Researchers curious about how mechanical stress impacts cell growth can now turn to silicone plastics that grow microbumps on demand. Simonetta Grilli from Italy’s Institute of Applied Sciences and Intelligent Systems in Pozzuoli and colleagues created a controllable ‘skin-over-liquid’ system by coating a silicone polymer solution onto lithium niobate, a crystal that contains patterned regions of electric charge. An initial plasma treatment produced a flat stiff film on top of the liquid silicone. Thermal heating caused the skin to swell and form dimpled, air mattress-like patterns, corresponding to the underlying lithium niobate domains. Removal of heat restored the sheet to its initial state. The chemically inert skin supported live fibroblast cells and was used to determine reactions to mechanical stress. Significant variations in nuclei and cytoskeletons were observed between cells grown under flat or swollen-skin conditions. We propose an innovative skin-over-liquid system made of a periodic array of highly compliant microbumps actuated through an electrode-free electrohydrodynamic (EHD) pressure. We demonstrate that these structures are highly repeatable and are capable to swell and deflate easily under a simple thermal stimulation driven by pyroelectric effect, thus providing a challenging platform that can be actively controlled at microscale. We show the proof of principle by swelling these microbumps for stimulating mechanically live cells in vitro, thus opening the route to more reliable and easy to accomplish assays in the field of mechanobiology.
120 citations
TL;DR: A multi-look approach with average looks before noise processing performs better than averaging computed with all de-noised looks and the two-dimensional windowed Fourier transform filtering exhibits the best performance in all cases.
Abstract: This paper presents a comparative study of multi-look approaches for de-noising phase maps from digital holographic interferometry. A database of 160 simulated phase fringe patterns with eight different phase fringe patterns with fringe diversity was computed. For each fringe pattern, 20 realistic noise realizations are generated in order to simulate a multi-look process with 20 inputs. A set of 22 de-noising algorithms was selected and processed for each simulation. Three approaches for multi-look processing are evaluated. Quantitative appraisal is obtained using two metrics. The results show good agreement for algorithm rankings obtained with both metrics. One singular and highly practical result of the study is that a multi-look approach with average looks before noise processing performs better than averaging computed with all de-noised looks. The results also demonstrate that the two-dimensional windowed Fourier transform filtering exhibits the best performance in all cases and that the block-matching 3D (BM3D) algorithm is second in the ranking.
33 citations
TL;DR: Researchers in Italy led by Biagio Mandracchia have devised a novel holographic phase imaging technique to watch bubbles as they form, develop, burst and retract, providing unparalleled insight into bubble dynamics through the combination of a full-field thickness estimation, three-dimensional imaging, and a fast acquisition time.
Abstract: The dynamics and stability of thin liquid films have fascinated scientists over many decades. Thin film flows are central to numerous areas of engineering, geophysics, and biophysics and occur over a wide range of lengths, velocities, and liquid property scales. In spite of many significant developments in this area, we still lack appropriate quantitative experimental tools with the spatial and temporal resolution necessary for a comprehensive study of film evolution. We propose tackling this problem with a holographic technique that combines quantitative phase imaging with a custom setup designed to form and manipulate bubbles. The results, gathered on a model aqueous polymeric solution, provide unparalleled insight into bubble dynamics through the combination of a full-field thickness estimation, three-dimensional imaging, and a fast acquisition time. The unprecedented level of detail offered by the proposed methodology will promote a deeper understanding of the underlying physics of thin film dynamics.
26 citations
TL;DR: The b-PES is free from expensive electrodes, nozzles, and masks because it makes use simply of the structured pyroelectric field produced by the PPLN crystal used as collector, and shows clearly the reliability of the technique in producing a wide variety of arrayed fiber mats that could find application in bioengineering or many other fields.
Abstract: The numerous advantages of micro- and nanostructures produced by electrospinning (ES) have stimulated enormous interest in this technology with potential application in several fields. However, ES still has some limitations in controlling the geometrical arrangement of the fiber mats so that expensive and time-consuming technologies are usually employed for producing ordered geometries. Here we present a technique that we call "bipolar pyroelectrospinning" (b-PES) for generating ordered arrays of fiber mats in a direct manner by using the bipolar pyroelectric field produced by a periodically poled lithium niobate crystal (PPLN). The b-PES is free from expensive electrodes, nozzles, and masks because it makes use simply of the structured pyroelectric field produced by the PPLN crystal used as collector. The results show clearly the reliability of the technique in producing a wide variety of arrayed fiber mats that could find application in bioengineering or many other fields. Preliminary results of live cells patterning under controlled geometrical constraints is also reported and discussed in order to show potential exploitation as a scaffold in tissue engineering.
19 citations
TL;DR: It is demonstrated that new optical parameters of RBCs can be measured and analyzed thus opening the route to exploit the bio-lensing modeling as a new biomechanical marker of R BCs.
Abstract: RBCs elasticity is an important parameter for evaluating their health. Many studies have been performed for testing erythrocyte’s membrane stiffness under external stimuli, by means of the most diverse techniques. Here we exploit hydrodynamic deformation of RBCs in microfluidic channels to quantify the membrane shape variations through quantitative phase imaging by digital holography. In particular, two main processing have been employed, i.e. the morphology analysis based on quantitative phase variations and a new way to monitor the entire cell’s deformation, based on the modeling of RBCs as micro-lenses array. In fact, taking advantage of the RBC lens behavior, it is possible to correlate optical aberrations generated by the mechanical deformation to the entire membrane deformation itself, through a numerical analysis based on Zernike polynomials. We demonstrate that new optical parameters of RBCs can be measured and analyzed thus opening the route to exploit the bio-lensing modeling as a new biomechanical marker of RBCs.
16 citations
TL;DR: It is shown that through biospeckle decorrelation it is possible to quantify the shelf-time of alginate-encapsulated probiotic bacteria and their survival rate under simulated gastrointestinal conditions.
Abstract: In recent years, the use of probiotics in food and health has increased so much that usually market offers several functional fermented food or nutraceuticals containing probiotics, often also associated to prebiotics. Both in food industry and in pharmaceutics, it is very important the development and use of methodologies that quickly allow a precise overview about the microbial population present in a specific biological matrix, and to monitor over time any changes that it may undergo. In this paper, we propose biospeckle decorrelation as a tool for the fast evaluation of the effectiveness of microencapsulation as a preservation system. Although speckle grains are often treated as an impairment for imaging, they represent a precious source of information. Such information is rich enough to characterize bacterial dynamics in a fast and simple way suitable for applications in food science and industry. In fact, here we show that through biospeckle decorrelation it is possible to quantify the shelf-time of alginate-encapsulated probiotic bacteria and their survival rate under simulated gastrointestinal conditions.
14 citations
TL;DR: A water-based bottom-up approach for facile encasing of short-lived water silhouettes by a custom-made adaptive suit, opening the way to a breakthrough approach for organ-on-chip and lab-in-a-drop experiments.
Abstract: One of the most important substances on Earth is water. It is an essential medium for living microorganisms and for many technological and industrial processes. Confining water in an enclosed compartment without manipulating it or by using rigid containers can be very attractive, even more if the container is biocompatible and biodegradable. Here, we propose a water-based bottom-up approach for facile encasing of short-lived water silhouettes by a custom-made adaptive suit. A biocompatible polymer self-assembling with unprecedented degree of freedom over the water surface directly produces a thin membrane. The polymer film could be the external container of a liquid core or a free-standing layer with personalized design. The membranes produced have been characterized in terms of physical properties, morphology and proposed for various applications from nano- to macroscale. The process appears not to harm cells and microorganisms, opening the way to a breakthrough approach for organ-on-chip and lab-in-a-drop experiments.
14 citations
TL;DR: This paper proposes a new method, to the best of its knowledge, based on singular value decomposition filtering, to suppress zero-order and twin images in off-axis configuration, thus, automatically selecting the desired real diffraction order.
Abstract: Digital holography is widely used in many fields for imaging, display, and metrology by exploiting its capability to furnish quantitative phase contrast maps. The entire processing pipeline that permits achievement of phase contrast images can be obtained by a cascade of numerical processing, such as zero-order and twin-image suppression, automatic refocusing, phase extraction by aberration compensation, and, if necessary, phase unwrapping. In this paper, we propose a new method, to the best of our knowledge, based on singular value decomposition filtering, to suppress zero-order and twin images in off-axis configuration, thus, automatically selecting the desired real diffraction order. We demonstrate the proposed approach in the case of lack of knowledge about the reference beam's frequency and curvature, which typically occurs in portable off-axis holographic microscope systems for lab-on-a-chip applications. We validate the proposed strategy by a comparison with common Fourier spatial filtering in the case of different experimental conditions and for several biological samples.
13 citations
TL;DR: This study shows that the rotation of linear aggregates of micro-particles can be achieved under the action of acoustic field pressure and demonstrates that it is possible to put in rotation a linear aggregate of erythrocytes and rely on holographic imaging to achieve a full phase-contrast tomography of the aforementioned aggregate.
Abstract: The combined use of ultrasound radiation and microfluidics is a promising tool for aiding the development of lab-on-a-chip devices. In this study, we show that the rotation of linear aggregates of micro-particles can be achieved under the action of acoustic field pressure. This novel manipulation is investigated by tracking polystyrene beads of different sizes through the 3D imaging features of digital holography (DH). From our analysis it is understood that the positioning of the micro-particles and their aggregations are associated with the effect of bulk acoustic radiation forces. The observed rotation is instead found to be compatible with the presence of acoustic streaming patterns as evidenced by our modelling and the resulting numerical simulation. Furthermore, the rotation frequency is shown to depend on the input voltage applied on the acoustic device. Finally, we demonstrate that we can take full advantage of such rotation by combining it with quantitative phase imaging of DH for a significant lab-on-a-chip biomedical application. In fact, we demonstrate that it is possible to put in rotation a linear aggregate of erythrocytes and rely on holographic imaging to achieve a full phase-contrast tomography of the aforementioned aggregate.
12 citations
TL;DR: This work reports a voltage-free pyro-electrification (PE) process able to induce a permanent dipole orientation into polymer sheets under both mono- and bipolar distribution and shows the reliability of the technique for different polymers and for different applications ranging from live cell patterning to biofilm formation tests for bacteria linked to food-processing environments.
Abstract: Localized electric fields have become, in recent years, a source of inspiration to researchers and laboratories thanks to a huge amount of applications derived from it, including positioning of microparticles as building blocks for electrical, optical, and magnetic devices. The possibility of producing polymeric materials with surface charge thus opens new perspectives for applications where process simplicity and cost-effectiveness of flexible electronics are of fundamental importance. In particular, the influence of surface charges is widely studied and is a critical issue especially when new materials and functional technologies are introduced. Here, we report a voltage-free pyro-electrification (PE) process able to induce a permanent dipole orientation into polymer sheets under both mono- and bipolar distribution. The technique makes use of the pyroelectric effect for generating electric potentials on the order of kilovolts by an easy-to-accomplish thermal treatment of ferroelectric lithium niobate (LN) crystals. The PE allows us to avoid the expensive and time-consuming fabrication of high-power electrical circuits, as occurs in traditional generator-based techniques. Since the technique is fully compatible with spin-coating-based procedures, the pyro-electrified polymer sheets are easily peeled off the surface of the LN crystal after PE completion, thus providing highly stable and freestanding charged sheets. We show the reliability of the technique for different polymers and for different applications ranging from live cell patterning to biofilm formation tests for bacteria linked to food-processing environments.
11 citations
TL;DR: It is demonstrated that the gradual formation of a surface relief grating (SRG) in azopolymer thin films under continuous light exposure could be directly observed in situ and in real-time, allowing full-field characterization with high spatial resolution.
Abstract: In this paper, we demonstrated that the gradual formation of a surface relief grating (SRG) in azopolymer thin films under continuous light exposure could be directly observed in situ and in real-time, allowing full-field characterization with high spatial resolution. We reported here for the first time, to the best of our knowledge, that digital holography (DH) can be adopted for investigating and monitoring an inscribed holographic surface relief grating (SRG) of azopolymers by two-beam laser interference lithography over a wide area. The writing process could be assessed through quantitative phase imaging (QPI). The reported results show that the proposed method is a truly valuable diagnostic tool that can be useful for investigating the spatial distribution of the writing process, which can eventually contribute to shedding light on the still unclear origin and related mechanism of SRG formation in azopolymers.
01 Jan 2019
TL;DR: This chapter proposes the use of femtosecond laser micromachining combined with microinjection moulding as a novel highly-flexible microfabrication platform for polymeric LoCs with integrated optical detection, for the realization of low-cost and truly portable biophotonic microsystems.
Abstract: Lab-on-chips (LoCs) are microsystems capable of manipulating small amounts of fluids in microfluidic channels. They have a huge application potential, from basic science to chemical synthesis and point-of-care medical analysis. Polymers are rapidly emerging as the substrate of choice for LoC production, thanks to a low material cost and ease of processing. Two breakthroughs that could promote LoC diffusion are a microfabrication technology with cost-effective and rapid prototyping capabilities and also an integrated on-chip optical detection system. This chapter proposes the use of femtosecond laser micromachining combined with microinjection moulding as a novel highly-flexible microfabrication platform for polymeric LoCs with integrated optical detection, for the realization of low-cost and truly portable biophotonic microsystems. We demonstrate a LoC for the relevant application of non-invasive and contactless mechanical phenotyping of single cancer cells.
04 Mar 2019
TL;DR: The recent advancements of DH in transmission microscopy mode are shown, when this is applied to microfluidics to yield 3D imaging capabilities and medical diagnostic applications based on DH are shown.
Abstract: In global healthcare and point-of-care diagnostics there is an increasing request of medical equipment with devices able to provide fast and reliable testing for clinical diagnosis. In developing countries that lack of adequate facilities, this need is even more urgent. Lab-on-a-Chip devices have undergone a great growth during the last decade, supported by optical imaging techniques more and more refined. Here we present recent progresses in developing imaging tools based on holographic microscopy that can be very useful when applied into bio-microfluidics. Digital Holography (DH) is label-free, non-invasive, potentially high-throughput and, above all, quantitative. We show the recent advancements of DH in transmission microscopy mode, when this is applied to microfluidics to yield 3D imaging capabilities. Holographic flow cytometry through quantitative phase imaging and in-flow tomography for the analysis and manipulation of micro-particles and cells will be shown [1-3]. Medical diagnostic applications based on DH will be also shown. Moreover, we present a portable common-path holographic microscope embedded onboard a microfluidic device that paves the way to the application of DH on the field [4].
TL;DR: It is predicted that such a dehydrating process can be effective for improving phase contrast, thus permitting better imaging of plant cells with the scope of learning more about cellular dynamics and related phenomena.
Abstract: The intracellular dynamics of onion epidermal cells during the dehydration process is observed by holographic microscopy. Both the nucleus and cytoplasm are accurately revealed by quantitative phase imaging while dehydration takes place. Indeed, we notice that the contrast of phase images increases with the decrease in cellular water content. We foresee that such a dehydrating process can be effective for improving phase contrast, thus permitting better imaging of plant cells with the scope of learning more about cellular dynamics and related phenomena. Exploiting this concept, we observe intracellular cytoplasmic circulation and transport of biological material.
TL;DR: In this paper, the authors demonstrated the potential use of digital holography in the far infrared region of the spectrum (far-infrared region of spectrum) and demonstrated the feasibility of using holographic technology in the future.
Abstract: Recent advances in digital holography in the far‐infrared region of the spectrum have demonstrated the potential use of digital holography...
04 Mar 2019
TL;DR: A very accurate classifier is obtained using a simple machine learning approach, which does not require a large amount of training data and identifies micro-plastics of various morphology and optical properties over a wide range of characteristic scales.
Abstract: Micro-plastics dispersion in water is one of the major global threats due to the potential of plastic items to affect the food chain and reproduction of marine organisms. However, reliable and automatic recognition of micro-plastic in water is still an unmatched goal. Here we identify micro-plastics in water samples through digital holography microscopy combined to machine learning. We exploit the rich content of information of the holographic signature to design new distinctive features that specifically characterize micro-plastics and allow distinguishing them from marine plankton of comparable size. We use these features to train a plain support vector machine, remarkably improving its performance. Thus, we obtain a very accurate classifier using a simple machine learning approach, which does not require a large amount of training data and identifies micro-plastics of various morphology and optical properties over a wide range of characteristic scales. This is a first mandatory step to develop sensor networks to map the distribution of micro-plastics in water and their flows.
01 Jan 2019
TL;DR: The capability for recovering the complex amplitude distribution scattered by the sample permits numerical refocus after acquisition and quantitative phase imaging and makes DHM a very versatile microscopy technique.
Abstract: Digital holographic microscopy (DHM) has become a technique utilized widely for sample inspection, having many applications in different fields of science and technology. The capability for recovering the complex amplitude distribution scattered by the sample permits numerical refocus after acquisition and quantitative phase imaging. These are two of the features that make DHM a very versatile microscopy technique. The standard DHM system is based on a Mach–Zehnder interferometer that can be configured for operating in transmission or reflection modes, working in either the in-line or off-axis architecture. With the benefit of such special characteristics, DHM is used in basic research as much in the industry. Here we review some of the recent advancements for the label-free inspection of biological samples and the study of thin films.
TL;DR: In this article, the impact area due to low-velocity impact tests at different impact energy values and different temperatures on glass fiber-reinforced plate laminates was investigated by two nondestructive evaluation (NDE) techniques, electronic speckle pattern interferometry (ESPI) and ultrasound testing (UT).
Abstract: In this work, the evaluation of damage area due to low-velocity impact tests at different impact energy values and different temperatures on glass fiber-reinforced plate laminates was investigated by two nondestructive evaluation (NDE) techniques, electronic speckle pattern interferometry (ESPI) and ultrasound testing (UT). Composites are characterized by several interacting failure modes such as matrix breakage, fiber failure and delaminations, which can be simultaneously induced by low-velocity impacts and can be different depending on the temperature. It can be complicated to detect by visual inspections of the structures for such phenomena. This paper aims to investigate the dependence of the damaged area with respect to temperature variation on glass fiber composite laminates. GF composite laminates were impacted with three energy levels (5, 10, 20 J) and at different temperatures (room temperature, − 25, − 50 °C) by a drop weight impact machine. The results show that at decreasing temperature, a decrease in the damage extension was observed, which is more evident at increasing impact energy. Moreover, as expected, the results confirm UT and ESPI techniques are able to identify the barely visible low-velocity impact damage. However, some limitations for detection were found in ESPI. Nonetheless, the ESPI technique can be considered as one of the useful NDE methods if the calibration and the post-processing methods are improved.
21 Jun 2019
TL;DR: In this article, the use of ESPI as optical metrology tool for new industrial applications, biomaterials and non-destructive evaluation technique for novel materials is reviewed and discussed.
Abstract: Electronic Speckle Pattern Interferometry (ESPI) is a full-field technique based on interferometry that has found applications in a wide range of domains mostly related in the field of non-destructive testing. The continuous progress of electronics, image analysis and processing has allowed during the last years this technique to expand its application horizons. In this contribution we review the use of ESPI as optical metrology tool for new industrial applications, biomaterials and non-destructive evaluation technique for novel materials. For the first topic different examples found in literature have been shown and discussed. In fact, ESPI has been successfully employed for assessing the integrity of stainless steel kegs or for measuring the deformation of the surface of a heated mirror, and also for evaluating residual stress fields in pipes. Further interesting studies were about thermomechanical behavior of a Printed Wired Board. Biomedical field can benefit of ESPI technology since ESPI has been employed for measuring surface displacements during inflation testing of ocular tissues or to assessing strain in bone-implant interfaces. Finally, one more example of application regarding non-destructive testing technique describes some interesting results for characterizing novel “green” and thus sustainable composite materials.
21 Jun 2019
TL;DR: In this paper, a pyroelectrodynamic jet (p-jet) was used to concentrate the lactose molecules onto a solid amine support for easy and rapid detection through a fluorescence measurement.
Abstract: A novel method for sensing low abundant lactose in small sample volumes is proposed. It is based on a pyroelectrodynamic jet (p-jet) system able to concentrate the lactose molecules onto a solid amine support for easy and rapid detection through a fluorescence measurement. The p-jet produces droplets with sub-picoliter volumes accumulated onto a microscale area of the solid support in order to reduce the diffusion limits typically occurring in standard well-based assays. A highly reproducible linear response for lactose was obtained between 2 pM/μL and 10 pM/μL. The great advantage of the technique is the ability to concentrate the molecules directly onto the solid support ready for the readout measurement by a standard fluorescence scanner. No time-consuming and expensive sample treatments are needed. The proposed method is rapid, suitable for repeated use providing a built-in quality assurance.
04 Mar 2019
TL;DR: Through bio-speckle decorrelation, the shelf-time of alginate-encapsulated Lactobacillus rhamnosus and LactOBacillus plantarum probiotic bacteria and their survival rate under simulated gastro-intestinal conditions is quantified.
Abstract: Probiotics are microbial species that have been demonstrated to confer benefits to health. In recent years, the use of probiotics in food and health has increased enormously. A sufficient concentration of probiotics in the intestine acts against pathologies such as obesity, diabetes, etc. However, if probiotics are not able to maintain their viability during their transit through the gastro-intestinal apparatus, they cannot act to enhance the immune system. Hence, protection and preservation of probiotics are essential to both food industry and in pharmaceutics. Microencapsulation is one of the most common methods of preservation, applicable to several biological matrices, including probiotics. Whenever food products or pharmaceutical formulations contain microencapsulated probiotics, it is important to quantify the effectiveness of micro-encapsulation as a microbial protection system over the time, e.g. during the shelf life of a functional product containing encapsulated probiotics, conserved in the supermarket, and during gastro-intestinal transit. Here we use bio-speckle decorrelation as a tool for the rapid assessment of microencapsulation effectiveness. Although speckles are often thought as a noise to get rid of, they represent a precious source of information, increasing the sensitivity of image sensors based on coherent illumination. Such information is exploitable to characterize bacterial dynamics in a fast and simple way suitable for applications in food science and industry. Through bio-speckle decorrelation, we quantify the shelf-time of alginate-encapsulated Lactobacillus rhamnosus and Lactobacillus plantarum probiotic bacteria and their survival rate under simulated gastro-intestinal conditions.
21 Jun 2019
TL;DR: A test case is analyzed by using a holographic image dataset for classification, by extracting unique features that can be solely obtained by holographic images.
Abstract: The identification and classification of biological samples is high-demanded in biomedical imaging for diagnostic purposes. Among all imaging modalities, digital holography has gained credits as a powerful solutions, thanks to its ability to perform full-field and label –free quantitative phase imaging. On the other hand, machine learning is nowadays the most used approach for classification purposes. The robustness and the accuracy of the classification depend of the features used for the training step. Therefore, the identification of micro-organism becomes strictly related to the features that can be extracted from their images. In other word, the more the image contains information, the higher the possibility of extracting highly distinctive descriptors to differentiate biological phenotypes. Digital holography can be considered one of the richest in terms of information content due to the fact that a single digital hologram encode both amplitude and phase information about the imaged cells. This opens the way to improve the features extraction, thus making more accurate the classification step. In this paper we analyze a test case by using a holographic image dataset for classification, by extracting unique features that can be solely obtained by holographic images.
23 Jun 2019
TL;DR: All steps need to obtain the tomographic reconstruction of flowing cells, including a holographic 3D tracking algorithm to follow each cells that moves in the field of view, along with a suitable tracking angle method for the cell’s tumbling are investigated.
Abstract: The complete cells characterization in microfluidic flow can be achieved by using the quantitative phase imaging by digital holography as imaging tool. In fact, by assuring the complete 3D rotation of flowing cells, it is possible to recover their 3D refractive index mapping by using the tomographic phase-contrast reconstruction. In this paper, we investigate all steps need to obtain the tomographic reconstruction of flowing cells. In particular, we employ a holographic 3D tracking algorithm to follow each cells that moves in the field of view, along with a suitable tracking angle method for the cell’s tumbling. Moreover, a fluid modeling is used to characterize the cell rotation effect. We test the proposed processing pipeline for circulating tumor cells.
21 Jun 2019
TL;DR: A reverse modality in which holographic imaging boosts the performance of machine leaning algorithms and identifies several descriptors solely related to the type of data to be classified, i.e. the holographic image.
Abstract: Nowadays, digital holography can be considered as one of the most powerful imaging modality in several research fields, from the 3D imaging for display purposes to quantitative phase image in microscopy and microfluidics. At the same time, machine learning in imaging applications has been literally reborn to the point of being considered the most exploited field by optical imaging researchers. In fact, the use of deep convolutional neural networks has permitted to achieve impressive results in the classification of biological samples obtained by holographic imaging, as well as for solving inverse problems in holographic microscopy. Definitely, machine learning approaches in digital holography has been used mainly to improve the performance of the imaging tool. Here we show a reverse modality in which holographic imaging boosts the performance of machine leaning algorithms. In particular, we identify several descriptors solely related to the type of data to be classified, i.e. the holographic image. We provide some case studies which demonstrate how the holographic imaging can improve the performance of a plain classifier.
19 May 2019
TL;DR: This work investigates the possibility to probe micro-plastics with coherent light and to image them by digital holography microscopy and shows that the phase-contrast map can be used as a distinctive fingerprint to identify microplastics in water.
Abstract: Detection of micro-plastics in water samples is a highly pursued goal to map the distribution and abundance of these pollutants. Here we investigate the possibility to probe micro-plastics with coherent light and to image them by digital holography microscopy. From the recorded hologram, we access the phase-contrast map of the object. We show that this map can be used as a distinctive fingerprint to identify microplastics in water.
21 Jun 2019
TL;DR: Through bio-speckle decorrelation, the presence of bacteria in food without any chemical analysis is detected, and the shelf-time of alginate-encapsulated Lactobacillus rhamnosus and LactOBacillus plantarum probiotic bacteria and their survival rate under simulated gastro-intestinal conditions are quantified.
Abstract: Bacteria are often associated with the insurgence of diseases and many efforts have been made to develop methods for accurate identification of bacteria in food for industry and new generation smart farms. On the other hand, there is a wide category of “good” bacteria that are used in food and pharmaceutic industry. In particular, probiotics are microbial species that have been demonstrated to confer benefits to health, acting against pathologies such as obesity, diabetes, etc. Probiotics have to maintain their viability during their transit through the gastro-intestinal apparatus in order to act to enhance the immune system. The use of alginate microcapsules is one of the most common methods of preservation, applicable to several biological matrices, including probiotics. Here we use bio-speckle decorrelation as a tool for the rapid assessment of microencapsulation effectiveness. Although speckles are often thought as a source of noise, these can be fruitfully used to increase the sensitivity of coherent imaging sensors. Thus, it is possible to characterize bacteria motion and to use it as a contrast agent for applications in food science and industry. Through bio-speckle decorrelation, we detect the presence of bacteria in food without any chemical analysis. Moreover, we quantify the shelf-time of alginate-encapsulated Lactobacillus rhamnosus and Lactobacillus plantarum probiotic bacteria and their survival rate under simulated gastro-intestinal conditions.
21 Jun 2019
TL;DR: This work provides a DH characterization of the “plastic” class that can be used as a global identifier independently on the plastic material under analysis and shows that the phase contrast map of microplastics can beused to define a fingerprint for the microplastic population.
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.
21 Jun 2019
TL;DR: In this paper, a smart solution to obtain Tomographic Phase Microscopy (TPM) of samples in microfluidic environment, by exploiting their tumbling while flowing in a microchip, is presented.
Abstract: We report on a smart solution to obtain Tomographic Phase Microscopy (TPM) of samples in microfluidic environment, by exploiting their tumbling while flowing in a microchip. This method permits to observe full 360° of rotating cells, this avoiding the limitation in the accuracy of tomograms, and no mechanical contact neither holographic optical tweezers are needed to rotate the sample. Moreover, it is suitable for application in flowing conditions with high-throughput performances. In fact, it allows to monitor a large number of cells, the only limit being the frame rate of the camera used to acquire data, and to analyze in principle each single cell with high resolution, regardless of its shape or symmetry. This would allow real microfluidic biomedical applications on a large scale. Summarizing, the whole process is accomplished following the subsequent steps: (i) holograms acquisition of cells flowing in microfluidic channels; (ii) 3D tracking and realignment by using either biolens effect or particular symmetries (depending on the object’s structure); (iii) connection between rotation angles and phase maps; (iv) complete 3D image retrieving, displaying the inner structure of the object (i.e. tomography).
23 Jun 2019
TL;DR: A panel of label-free optical markers are introduced to identify red blood cell (RBC) phenotypes, demonstrating that an optical fingerprint of RBC is related to erythrocyte disease through modeling RBC as biological lens.
Abstract: We propose a new diagnostic tool for anemias identification based on quantitative phase imaging. We introduce a panel of label-free optical markers to identify red blood cell (RBC) phenotypes, demonstrating that an optical fingerprint of RBC is related to erythrocyte disease through modeling RBC as biological lens.
01 Mar 2019
TL;DR: The joint action of numerical ML (thought as a preprocessing filter) and 3D Block Matching in post-processing permits to overcome the theoretical limit of ML and to outperform the BM3D for the denoising of holograms.
Abstract: Digital Holography (DH) suffers from severe degradation of the reconstruction quality due to the presence of speckles. Speckle is due to the source coherence and shows on the hologram as a multiplicative, correlated noise. Due to the larger size of the speckle grains, the lower resolution, and the worse features of the available hardware, long wavelength digital holography is more severely degraded by noise than its visible wavelength counterpart is. Non-Bayesian approaches to the denoising problem suffer from resolution loss or complex acquisition systems required to record multiple uncorrelated holograms to be averaged. Instead of providing multiple captures, these can be simulated to yield a number of reconstructions from one single hologram (generally referred to as numerical Multi-Look, ML). However, the ML improvement is inherently bounded to a theoretical limit. On the other hand, image processing has offered a wide literature on the topic over the last decades. Among the most efficient methods to reduce additive Gaussian noise, 3D Block Matching (BM3D) has emerged and it is nowadays widely used in the image processing framework. However, BM3D performance worsens in the presence of speckle and cannot be effectively applied to long wavelength DH. Here we show that the joint action of numerical ML (thought as a preprocessing filter) and BM3D in post-processing permits to overcome the theoretical limit of ML and to outperform the BM3D for the denoising of holograms. The quasi noise free reconstruction of long wavelength holograms of famous artworks will be shown.