Showing papers by "Giuseppe Coppola published in 2015"

Recent advances in holographic 3D particle tracking

Abstract: Particle tracking is a fundamental technique for investigating a variety of biophysical processes, from intracellular dynamics to the characterization of cell motility and migration. However, observing three-dimensional (3D) trajectories of particles is in general a challenging task in classical microscopy owing to the limited imaging depth of field of commercial optical microscopes, which represents a serious drawback for the analysis of time-lapse microscopy image data. Therefore, numerous automated particle-tracking approaches have been developed by many research groups around the world. Recently, digital holography (DH) in microscopy has rapidly gained credit as one of the elective techniques for these applications, mainly due to the uniqueness of the DH to provide a posteriori quantitative multiple refocusing capability and phase-contrast imaging. Starting from this paradigm, a huge amount of 3D holographic tracking approaches have been conceived and investigated for applications in various branches of science, including optofluids, microfluidics, biomedical microscopy, cell mechano-trasduction, and cell migration. Since a wider community of readers could be interested in such a review, i.e., not only scientists working in the fields of optics and photonics but also users of particle-tracking tools, it should be very beneficial to provide a complete review of state-of-the-art holographic 3D particle-tracking methods and their applications in bio-microfluidics.

Holographic imaging of unlabelled sperm cells for semen analysis: a review.

Abstract: Quantitative phase maps of living swimming spermatozoa. Male reproductive health in both humans and animals is an important research field in biological study. In order to characterize the morphology, the motility and the concentration of the sperm cells, which are the most important parameters to feature them, digital holography demonstrated to be an attractive technique. Indeed, it is a label-free, non-invasive and high-resolution method that enables the characterization of live specimen. The review is intended both for summarizing the state-of-art on the semen analysis and recent achievement obtained by means of digital holography and for exploring new possible applications of digital holography in this field.

Photopolymer-based volume holographic optical elements: design and possible applications

Abstract: In this paper, Volume Holographic Optical Elements (V-HOEs), such as holographic gratings and spherical lenses, are designed and fabricated by using a prototype of photopolymer. The recording process of V-HOEs and their appropriate characterization are described. Moreover, V-HOEs possible applications as solar concentrator are investigated and results are discussed. Finally, a system that allows passive solar tracking is proposed and preliminary results are reported.

Volume holographic gratings: fabrication and characterization

Abstract: Volume Holographic Gratings is designed and fabricated to obtain a simple, lightweight and cheap light deflector. The entire process, starting from the chemical preparation of the photosensitive material, to the recording of Volume Holographic Gratings and their appropriate characterization, is reported. The recording material was a new photopolymer sensitive to light at 532nm. Results showed that the recorded Volume Holographic Grating presents a very high value of the diffraction efficiency, up to 94%. In addition, a flexible material is used to write Volume Holographic Gratings.

Hydrodynamic self-focusing in a parallel microfluidic device through cross-filtration

Abstract: The flow focusing is a fundamental prior step in order to sort, analyze, and detect particles or cells. The standard hydrodynamic approach requires two fluids to be injected into the microfluidic device: one containing the sample and the other one, called the sheath fluid, allows squeezing the sample fluid into a narrow stream. The major drawback of this approach is the high complexity of the layout for microfluidic devices when parallel streams are required. In this work, we present a novel parallelized microfluidic device that enables hydrodynamic focusing in each microchannel using a single feed flow. At each of the parallel channels, a cross-filter region is present that allows removing fluid from the sample fluid. This fluid is used to create local sheath fluids that hydrodynamically pinch the sample fluid. The great advantage of the proposed device is that, since only one inlet is needed, multiple parallel micro-channels can be easily introduced into the design. In the paper, the design method is described and the numerical simulations performed to define the optimal design are summarized. Moreover, the operational functionality of devices tested by using both polystyrene beads and Acute Lymphoid Leukemia cells are shown.

Volume holographic gratings as optical sensor for heavy metal in bathing waters

Abstract: Sensor holograms utilize the diffraction principle of transmitting volume holographic grating (VHG) recorded within a photopolymer appositely functionalized to detect a specific stimulus or analyte. A change in the swelling or shrinking state or cross-linking density of the polymer can be caused by the hologram interaction with an analyte. This leads to a change in the recorded hologram sensor and thus, considering an incident monochromatic light and the VHG angular selectivity, to an angle shift of the diffracted maximum intensity. In this work, two new photopolymers based on a sol-gel matrix opportunely functionalized to be sensitive to transition metals or heavy metals were used as sensitive material to record VHGs. An interferometric set up with a laser source at 532nm was used to record VHGs and gratings of 1000 lines/mm were realized. When exposed to a solution of water and lead, an angle shift of about 3° of the first order diffraction of the grating was measured, demonstrating its capability to reveal the presence of heavy metal in water.

Trends, fads and ART!

Abstract: Morphological selection techniques of gametes and embryos are of current interest to clinical practice in ART. Although intracytoplasmic morphologically selected sperm injection (IMSI), time lapse imaging morphometry (TLIM) or quantification of chromosome numbers (PGS) are potentially useful in research, they have not been shown to be of statistically predictive value and, thus, have only limited clinical usefulness. We make the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome. Since previous attempts to identify metabolic markers for embryo quality have failed and there is no evidence that the intrinsic nature of gametes and embryos can be improved in the laboratory, embryologists can only minimize environmental or operator induced damage while these cells are manipulated ex vivo.

Analysis of phase patterns in photochromic polyurethanes by a holographic approach

Abstract: Photochromic polyurethanes based on diarylethene units show a large reversible modulation of refractive index in the Vis-NIR spectral region. The change of refractive index in the material is easily induced by visible laser illumination, without any optical or chemical post-process. In this paper, patterns at the micron scale range have been written by a suitable direct laser writing machine and characterized at 1550 nm by means of a digital holographic approach. The refractive index profile has been retrieved, its dependence on the film thickness and writing speed was shown. The writing process has also been modelled by means of a kinetic model, showing theoretically the dependence of the pattern width and profile with the writing condition. It is demonstrated how the photochromic films are suitable for developing a reconfigurable platform for complex phase patterns working in the NIR.

Analysis of bovine sperm cells by a combined holographic and Raman microscopy approach

Abstract: In this work, an approach based on digital holography (DH) combined with Raman spectroscopy (RS) is used for a complete label-free analysis of single bovine spermatozoa. DH allows to obtain high-resolution images of bovine sperm from the reconstruction of a single acquired hologram, highlighting in some cases morphological alterations. Quantitative 3D reconstructions of sperm head, both normal and anomalous, have been studied and an unexpected structure of the post-acrosomal region of the head has been detected. Raman imaging analysis have also confirmed such anomalies, suggesting the protein vibrations as associated Raman marker of the defect.

Spermatozoa quality assessment: a combined holographic and Raman microscopy approach

Abstract: Semen analysis is widely used as diagnostic tool for assessing male fertility, controlling and managing the animal reproduction. The most important parameters measured in a semen analysis are the morphology and biochemical alterations. For obtaining such information, non-invasive, label-free and non-destructive techniques have to be used. Digital Holography (DH) combined with Raman Spectroscopy (RS) could represent the perfect candidate for a rapid, non-destructive and high-sensitive morphological and biochemical sperm cell analysis. In this study, DH-RS combined approach is used for a complete analysis of single bovine spermatozoa. High-resolution images of bovine sperm have been obtained by DH microscopy from the reconstruction of a single acquired hologram, highlighting in some cases morphological alterations. Quantitative 3D reconstructions of sperm head, both normal and anomalous, have been studied and an unexpected structure of the post-acrosomal region of the head has been detected. Such anomalies have been also confirmed by Raman imaging analysis, suggesting the protein vibrations as associated Raman marker of the defect.

New perspectives in silicon micro and nanophotonics

Abstract: In the last two decades, there has been growing interest in silicon-based photonic devices for many optical applications: telecommunications, interconnects and biosensors. In this work, an advance overview of our results in this field is presented. Proposed devices allow overcoming silicon intrinsic drawbacks limiting its application as a photonic substrate. Taking advantages of both non-linear and linear effects, size reduction at nanometric scale and new two-dimensional emerging materials, we have obtained a progressive increase in device performance along the last years. In this work we show that a suitable design of a thin photonic crystal slab realized in silicon nitride can exhibit a very strong field enhancement. This result is very promising for all photonic silicon devices based on nonlinear phenomena. Moreover we report on the fabrication and characterization of silicon photodetectors working at near-infrared wavelengths based on the internal photoemission absorption in a Schottky junction. We show as an increase in device performance can be obtained by coupling light into both micro-resonant cavity and waveguiding structures. In addition, replacing metal with graphene in a Schottky junction, a further improve in PD performance can be achieved. Finally, silicon-based microarray for biomedical applications, are reported. Microarray of porous silicon Bragg reflectors on a crystalline silicon substrate have been realized using a technological process based on standard photolithography and electrochemical anodization of the silicon. Our insights show that silicon is a promising platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.

Schottky graphene/silicon photodetectors based on internal photoemission effect

Abstract: In this paper, the design of a graphene/silicon photodetector working at both 1.55 μm and room temperature is reported. The device is a Schottky diode and the absorption mechanism is based on the internal photoemission effect. In order to quantify the performance of the photodetector, quantum efficiency, bandwidth and dark current density are numerically calculated. Performance comparison between our proposed device and typical metal/silicon Schottky photodetectors is reported. Graphene/silicon devices show an efficiency as high as 39.5% at 1300 nm and 34.9% at 1550 nm but, unfortunately, a high dark current density of 0.8 nA/μm2. Finally, a bandwidth of about 7.6 GHz can be estimated.

A combined holographic and Raman microscopy approach for the assessment of spermatozoa

Abstract: In this study we suggest a combined approach for the sperm analysis in which DH and RS work together, providing complementary, label-free, non-destructive qualitative and quantitative information on bovine spermatozoa. DH and RS allows high resolution morphological analysis and chemical assessment of the highlighted morphological abnormalities, respectively. The same combined-approach has also been tested as assessing method for identifying X- and Y-bearing sperm cells, in order to show their suitability to control and preselect the sex of breeding animal offspring.

Photoluminescence of graphene oxide integrated with silicon substrates

Abstract: In this work we have investigated the photoluminescence signal emitted by graphene oxide (GO) nanosheets infiltrated in silanized porous silicon (PSi) matrix. We have demonstrated that a strong enhancement of the PL emitted from GO by a factor of almost 2.5 with respect to GO on crystalline silicon can be experimentally measured. This enhancement has been attributed to the high PSi specific area. In addition, we have observed a weak wavelength modulation of GO photoluminescence emission, this characteristic is very attractive and opens new perspectives for GO exploitation in innovative optoelectronic devices and high sensible fluorescent sensors.

A parallel microfluidic device for hydrodynamic focusing of acute lymphoid Leukemia cells

Abstract: A novel parallel-channel microfluidic device exploiting cross-filtering to perform hydrodynamic focusing has been designed and successfully tested with Leukemia cells. The proposed approach allows to overcome the main limits till now presented by previous devices, and represents a step forward the realization of an on-chip integrated cytofluorimeter.

Self-hydrodynamic focusing in a parallel microfluidic device

Abstract: Flow focusing is a fundamental prior step in order to sort, analyze and detect particles or cells. In traditional flow-cytometry flow focusing is achieved by hydrodynamic focusing. An additional sheath fluid is used in order to confine the sample one. The main drawback of the method is the need of at least two inlets, one for the sheath and one for the sample fluid. This adds a big limitation: it is difficult to realize a device with multiple parallel micro-channels, and therefore exploit one of the main advantages introduced by microfluidic technology. As a matter of fact, the possibility of having more channels working simultaneously helps with the clogging problems, and at the same time improves the throughput. In this work we propose a parallelized microfluidic device that allows getting hydrodynamic focusing by needing of only one inlet. This is achieved by introducing a cross-filter region at each micro-channel.

Inducing cell rotation in a microfluidic device by hydrodynamic forces

Abstract: The realization of a novel microfluidic device for inducing cell rotation is reported. It exploits the hydrodynamic forces acting on cells moving in a flow characterized by a parabolic velocity profile. The device operation was tested on yeast cells, since they have an asymmetrical shape due to a bud formation during the duplication phase. Image processing analysis of the experimental data allowed to precisely evaluate the cell angular orientation and rotation rate.