Light Diffusion Research Articles

Preparation of cross-linked poly (methyl methacrylate) microspheres by post-crosslinking method and its application in light diffusers

Preparation of cross-linked poly (methyl methacrylate) microspheres by post-crosslinking method and its application in light diffusers

An IoT-based smart optical platform for colorimetric analyzing multiple samples of biomarkers

In this work, we have designed, implemented, and characterized an IoT-enabled optical platform that serves as a highly efficient colorimetric analyzer for disposable rapid diagnostic test kits. We have taken color images of the test chip using an external camera module connected to an IoT-enabled single-board mini-computer, which are then analyzed using an image processing algorithm. To prevent image burning and to reduce the impact of ambient lighting, we have proposed a unique light-diffusing model and have maintained a strategic distance within the white acrylic imaging enclosure of the platform. In order to ensure even and uniform distribution of light on the sample within the platform, we have carried out a study with the incorporation of a highly bright single LED, an LED array, and attaching a PDMS-made light diffuser on the LED array at varying light incident angles on custom-made single-channel test kits containing blood hematocrit. Finally, based on the optimized lighting conditions, we have successfully applied the proposed platform for the detection of blood hematocrit, β-hCG, and SARS-CoV-2 antigen, and were able to identify their different levels of concentration. Since the device is portable in size and cost-effective to implement, it can also be used for analyzing other biomarkers in resource-limited communities for point-of-care (POC) applications.

Mechanics and physics of the light-driven response of hydrogels

Hydrogels are versatile and environmentally sensitive materials having appealing and tunable physical-chemical-mechanical properties, similar to those encountered in natural living tissues, which enable their use in a wide range of applications, especially in the biomedical field. In the present study, we investigate the temperature-driven responsiveness of one class of elastomeric gels, namely poly-N-isopropylacrylamide (pNIPAm), that allows for temperature-controlled swelling. In particular, we consider the mechanical behavior of temperature-sensitive hydrogels in which the temperature variation is the result of light-thermal conversion enabled by nanoparticles embedded in the material. Relying on a theoretical multi-physics-based model describing light diffusion, heat generation and transfer, fluid absorption, and mechanics, the morphing response of hydrogel elements is investigated. The complex interplay between fluid uptake (swelling) and mechanical deformation taking place at different temperatures is investigated. In particular, the light-driven swelling response of hydrogel under a time-dependent light stimulus is studied. It is shown that the self-cooling of the material influences the material responsiveness. Accordingly, we demonstrate the interplay between the generated and the dispersed heat, which is a key aspect for an efficient design of tunable devices and materials.

Experimental Analysis of the Behavior of Mirror-like Objects in LiDAR-Based Robot Navigation

Mobile robots are equipped with various sensors to perform object detection, localization, and navigation. Among these sensors, LiDAR (light detection and ranging) is the most widely used sensor for environment map creation. However, LiDAR-based localization is challenging in modern environments containing specular surfaces, such as mirrors and glasses, that cause light reflection, penetration, or diffusion. These conditions make the obtained map inaccurate, unreliable, and noisy. This paper presents the effects of mirror-like objects in various indoor arrangements on 2D LiDAR-based maps. Experiments were conducted using a mobile robot equipped with LiDAR navigating in an environment with several mirrors. Experiments suggest that laser scans may be fully reflected off mirrors, causing no range or intensity data and creating a faulty map. Objects or boundaries within the range of LiDAR may be mapped behind the surface of the mirror, and robot self-detection may occur on the surface of the mirror. This situation exacerbates when more than one mirror is present in the environment. The results presented in this paper can aid the development of LiDAR-based indoor navigation to identify and remove inconsistencies created in LiDAR maps due to mirror-like objects.

Phase transition induced low temperature diffusion bonding of Zr-4 alloy using a pure Ti interlayer

In this paper, a low-temperature sealing of Zr-4 alloy induced by α→β phase transitions by using a pure Ti interlayer was reported. Both Ti and Zr compositions show smooth transition at the Ti/Zr interface when no phase transition happened. While a Ti, Zr elemental distribution plateau, corresponding to a light gray diffusion zone, was found at the Ti/Zr interface after a β-(Ti, Zr) phase transition happened. Results show that, to achieve the same shear strength of 294 MPa, the bonding temperature was reduced by 100 ℃ after using the pure Ti foil interlayer. Molecular dynamics (MD) simulation data show that the diffusion coefficients of Zr in β-(Ti, Zr) and α-(Ti, Zr) are 0.194 × 10−11 m2/s and 0.015 × 10−11 m2/s respectively, which further proves the β-(Ti, Zr) phase transition zone can indeed facilitate the diffusion of Zr-4/Zr-4 couples and lower the diffusion bonding temperature.

Numerical simulation and experimental study of gas diffusion in a ship engine room

Research on the engine room's natural gas leakage and diffusion has great significance for the LNG Powered ships' design, the fire risk assessment and explosion. In this paper, a model experiment system with a scale ratio of 1:10 was established. Helium gas was used instead of natural gas to study the evolution law of light gas concentration distribution in the model engine room over time. The CFD model of light gas diffusion in the indoor thermal environment is verified by experimental data and used to simulate the natural gas diffusion behavior in a full-size ship's engine room. The influence of leakage amount, cabin temperature, ventilation conditions, leakage location and other factors on the distribution of natural gas concentration was analyzed. The results show that the established CFD model has good predictive power for the diffusion behavior of light gas in the ship's engine room, and the numerical simulation results of the trend of leakage gas concentration with time are consistent with the experiment, and the maximum error is not more than 20%. The amount of leakage has a great influence on the concentration near the leakage location. The larger the initial volume flow and the higher the temperature of the leakage, the larger the dangerous area in the ship's engine room. Increasing ventilation flow is an effective way to reduce the diffusion area and control the concentration of natural gas in the engine room. When the ventilation flow is doubled, the diffusion area of natural gas reduces to 1/3. The leaked natural gas will gather at the location nearing the obstacles which block the jet flow and the upper layer of the engine room. The research results provide a basis for accurately predicting the spatial and temporal distribution model and method of gas diffusion concentration in the engine room environment.

Highly Transparent and Mechanically Robust Energy‐harvestable Piezocomposite with Embedded 1D P(VDF‐TrFE) Nanofibers and Single‐walled Carbon Nanotubes

AbstractHerein, highly transparent, flexible, and ultrathin piezocomposite, in which electrospun poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)] nanofibers (NFs) and aerosol‐synthesized single‐walled carbon nanotubes (SWCNTs) are embedded in elastomer matrix, is fabricated. The P(VDF‐TrFE) NF mat is exploited as a piezoelectric layer of the piezocomposite while the SWCNT film is applied as a transparent conductive electrode thereof. The use of these 1D nanomaterials allows the piezocomposite not only to be high transparency along with low diffusion of light (i.e., haze factor) but also to exhibit enhanced mechanical properties. In addition, the coupling effect of piezo‐ and flexoelectricity exhibited from the electrospun NFs and the acid‐doping effect conducted on the SWCNTs facilitates a significant improvement in kinetic energy‐harvesting performance, leading to a maximum output voltage of 26.8 V. Moreover, electrospinning and aerosol chemical vapor deposition methods employed here are facile, scalable, and cost‐effective, thus are expected to accelerate the development of industrially feasible next‐generation wearable electronics.

Early cancer detection using the fluorescent Ashwagandha chitosan nanoparticles combined with near-infrared light diffusion characterization: in vitro study

Early cancer diagnosis through characterizing light propagation and nanotechnology increases the survival rate. The present research is aimed at evaluating the consequence of using natural nanoparticles in cancer therapy and diagnosis. Colon cancer cells were differentiated from the normal cells via investigating light diffusion combined with the fluorescence effect of the Ashwagandha chitosan nanoparticles (Ash C NPs). Ionic gelation technique synthesized the Ash C NPs. High-resolution transmission electron microscope, dynamic light scattering, and zeta potential characterized Ash C NPs. Fourier transform infrared spectroscopy analyzed Ash C NPs, chitosan, and Ashwagandha root water extract. Moreover, the MTT assay evaluated the cytotoxicity of Ash C NPs under the action of near-infrared light (NIR) irradiation. The MTT assay outcomes were statistically analyzed by Bonferroni post hoc multiple two-group comparisons using one-way variance analysis (ANOVA). Based on the Monte-Carlo simulation technique, the spatially resolved steady-state diffusely reflected light from the cancerous and healthy cells is acquired. The diffuse equation reconstructed the optical fluence rate using the finite element technique. The fluorescent effect of the nanoparticles was observed when the cells were irradiated with NIR. The MTT assay revealed a decrease in the cell viability under the action of Ash C NPs with and without laser irradiation. Colon cancer and normal cells were differentiated based on the optical characterization after laser irradiation. The light diffusion equation was successfully resolved for the fluence rate on cells’ surfaces showing different normal and cancer cells values. Ash C NPs appeared its fluorescent effect in the presence of NIR laser.

Diffusion of light in turbid media with internal reflections

We relate the the Kubelka-Munk equations for the description of the intensity transfer of light in turbid media to a one-dimensional diffusion equation, which is obtained by averaging the three-dimensional diffusion equation over the lateral directions. This enables us to identify uniquely the Kubelka-Munk parameters and derive expressions for diffuse reflection and transmission coefficients including the effect of internal reflections. Without internal reflections we recover the Kubelka-Munk formulae for these coefficients. We show that the Kubelka-Munk equations are the proper radiative-transfer equations for the one-dimensional diffusion problem.

Multiphysics modelling of light-actuated liquid crystal elastomers

Liquid crystalline elastomers (LCEs) represent a promising class of responsive polymers whose physical properties are peculiar to both fluids and solids. Thanks to their microscale structure made of elongated rigid molecules (mesogens)—characterized by their capability to reversibly switch from an isotropic to an ordered state—LCEs exhibit a number of remarkable physical effects, such as self-deformation and mechanical actuation triggered by external stimuli. Efficient and physics-based modelling, aimed at designing and optimizing LCE-based devices (such as artificial muscles, deployable structures, soft actuators, etc.), is a fundamental tool to quantitatively describe their mechanical behaviour in real applications. In the present study, we illustrate the multi-physics modelling of light-driven deformation of LCEs, based on the photo-thermal energy conversion. The role played by the light diffusion and heat transfer within the medium is considered and their effect on the obtainable actuation is studied through numerical simulations based on the multi-physics theory developed.

Integral imaging-based tabletop light field 3D display with large viewing angle

Light field 3D display technology is considered a revolutionary technology to address the critical visual fatigue issues in the existing 3D displays. Tabletop light field 3D display provides a brand-new display form that satisfies multi-user shared viewing and collaborative works, and it is poised to become a potential alternative to the traditional wall and portable display forms. However, a large radial viewing angle and correct radial perspective and parallax are still out of reach for most current tabletop light field 3D displays due to the limited amount of spatial information. To address the viewing angle and perspective issues, a novel integral imaging-based tabletop light field 3D display with a simple flat-panel structure is proposed and developed by applying a compound lens array, two spliced 8K liquid crystal display panels, and a light shaping diffuser screen. The compound lens array is designed to be composed of multiple three-piece compound lens units by employing a reverse design scheme, which greatly extends the radial viewing angle in the case of a limited amount of spatial information and balances other important 3D display parameters. The proposed display has a radial viewing angle of 68.7° in a large display size of 43.5 inches, which is larger than the conventional tabletop light field 3D displays. The radial perspective and parallax are correct, and high-resolution 3D images can be reproduced in large radial viewing positions. We envision that this proposed display opens up possibility for redefining the display forms of consumer electronics.

Photothermal catalytic H2 production over hierarchical porous CaTiO3 with plasmonic gold nanoparticles

The synergistic promotion by photocatalysis and thermocatalysis is a promising approach for sustainable hydrogen (H2) production. Herein, we rationally design a perovskite-based catalyst with three-dimensionally ordered macroporous structure (3DOM CaTiO3-Au) for photothermal catalytic H2 production from different substrates. The hierarchical 3DOM structure facilitates light harvesting and mass diffusion of the substrates, while the gold nanoparticles (Au NPs) promote charge separation. The photogenerated and hot electrons are oriented accumulated on the surface of Au NPs. The non-metallic gold species [Au(I)] show more activity for H2 evolution. As a result, 3DOM CaTiO3-Au exhibits excellent activity for H2 production from glycerol and other substrates with hydroxyl groups. The present work demonstrates a feasible approach to improve sustainable H2 production by rationally designing and fabricating efficient photothermal catalysts.

A dialogue between matter and light

This article is a rather brief and theoretical synthesis of the composition criteria in the architectural space and of their affective significance through a dialogue between different matters in relation to light. This study presents three representative papers of whose authors are well-established personalities in the domain of architecture, who left, in their works, genuine cultural references of significant value across time. The authenticity of these papers transcends the vicissitude of time and offers them priority in the system of values that analyzes the use of the architectural space, that employs philosophical and sensitive language of communication with the malleable matter exclusively in relation with the transition of light through these. It is important to refer to these reference works in order to analyze the way to represent principles in the system of values in different cultures and then to validate these basics across time. Beyond these aspects, establishing certain references generates the premises for a study framework, as this article aims to do, as well as the context to deepen symbolical significances and the search of new references to complete their exploration. The specific difference of any creative approach is, obviously, its method of representation. The syntax selected to sustain the basic concept and the artist’s own vision differs through the surprising associations of matters in the light. Textures, colors and the level of light diffusion are the elements of this syntax. The conveyed message has its own way of being transmitted and it results in a particular emotion upon the viewer and a unique experience that ends up being shared within a community across many generations, crucial for the individual to develop his/her emotions.

Three-dimensional wide-field fluorescence microscopy for transcranial mapping of cortical microcirculation

Wide-field fluorescence imaging is an indispensable tool for studying large-scale biodynamics. Limited space-bandwidth product and strong light diffusion make conventional implementations incapable of high-resolution mapping of fluorescence biodistribution in three dimensions. We introduce a volumetric wide-field fluorescence microscopy based on optical astigmatism combined with fluorescence source localization, covering 5.6×5.6×0.6 mm3 imaging volume. Two alternative configurations are proposed exploiting multifocal illumination or sparse localization of point emitters, which are herein seamlessly integrated in one system. We demonstrate real-time volumetric mapping of the murine cortical microcirculation at capillary resolution without employing cranial windows, thus simultaneously delivering quantitative perfusion information across both brain hemispheres. Morphological and functional changes of cerebral vascular networks are further investigated after an acute ischemic stroke, enabling cortex-wide observation of concurrent collateral recruitment events occurring on a sub-second scale. The reported technique thus offers a wealth of unmatched possibilities for non- or minimally invasive imaging of biodynamics across scales.

A Nighttime and Daytime Single-Image Dehazing Method

In this study, the requirements for image dehazing methods have been put forward, such as a wider range of scenarios in which the methods can be used, faster processing speeds and higher image quality. Recent dehazing methods can only unilaterally process daytime or nighttime hazy images. However, we propose an effective single-image technique, dubbed MF Dehazer, in order to solve the problems associated with nighttime and daytime dehazing. This technique was developed following an in-depth analysis of the properties of nighttime hazy images. We also propose a mixed-filter method in order to estimate ambient illumination. It is possible to obtain the color and light direction when estimating ambient illumination. Usually, after dehazing, nighttime images will cause light source diffusion problems. Thus, we propose a method to compensate for the high-light area transmission in order to improve the transmission of the light source areas. Then, through regularization, the images obtain better contrast. The experimental results show that MF Dehazer outperforms the recent dehazing methods. Additionally, it can obtain images with higher contrast and clarity while retaining the original color of the image.

Effect of Water Storage and Bleaching on Light Transmission Properties and Translucency of Nanofilled Flowable Composite.

This study investigated the effect of water sorption and bleaching on light transmission properties (Straight-light transmission (G0), Light diffusion (DF) and Amount of transmitted light (AV)) and translucency parameters (TP) of nano-filled flowable composites. A total of 35 composite disks (0.5 mm thickness) were prepared using A2 shade of 5 nanofiller composites (n = 7/each); Beautifil Flow Plus X F03 (SHOFU INC), Clearfil Majesty ES Flow (Kuraray Noritake Dental), Estelite Universal Flow (EUF, Tokuyama Dental), Estelite Flow Quick (Tokuyama Dental) and Filtek Supreme Ultra Flowable Restorative (FSU, 3M ESPE). Then, they were cured by LEDs (VALO, Ultradent) on standard mood (1000 mW/cm2) for 20 s. Samples were tested for straight-line transmission (G0), diffusion (DF), the amount of transmitted light (AV) and (TP) immediately after 24 h (dry storage), after 1-week water storage and after each of the three cycles of in-office bleaching (HiLite, SHOFU INC). Result: G0, DF, AV and TP were significantly affected by different materials (p < 0.001). The AV of FSU increased significantly after the 1-week water storage, then after the second bleaching cycle (p < 0.001). The TP for EUF slightly decreased (p = 0.019) after 1-week water storage, then increased throughout bleaching. Conclusion: Ageing/bleaching conditions do not affect G0, DF, AV and TP. The compositional variation between nano-filler composites resulted in a significant difference between materials.

Determination of the shear viscosity and light quark diffusivity of QGP with two-particle correlation functions

We discuss measurements of general balance functions recently reported by the ALICE collaboration in the context of a two-stage quark production model and towards the determination of light quark diffusivity.

Nanopapers toward Green Photonic and Optical Applications

Nanopapers are known as thin sheets chiefly made of firmly crammed renewable nanomaterials including nanocellulose, nanochitin, and nanochitosan that endow much superior physicochemical merits in comparison to ordinary paper. The ever-augmenting popularity of employing nanopapers in copious applications is related to alluring and unrivalled characteristics comprising their innate renewability, biodegradability, nontoxicity, flexibility, and printability as easy-to-functionalize/administrate bioplatforms. Nanopapers have witnessed tremendous growth over the last decades in advanced optical applications ranging from (bio)sensors, optoelectronic devices, photovoltaic (PV) devices, electrochromic devices, organic light-emitting diodes (OLEDs), light diffusers, ultraviolet (UV)-blocking devices, phototransistors, photocatalysis, and anticounterfeiting substrates on account of their inherent natural features together with other optoelectronic properties, particularly their optical transparency, high flexibility, and mechanical properties. In the current review, while introducing different types of nanopapers, we intend to provide novel insights on how they have been tailored and employed in combination with other optical (nano)materials to fabricate nanopaper-based platforms for a wide variety of green photonic and optical applications. Building upon the extraordinarily features unveiled by nanopapers as promising bionanomaterials and significant progress in this area, we envisage that nanopaper-based platforms will provide ground-breaking prospects to develop efficient, affordable, and disposable optical devices in the near future.

Luminescent light diffuser for diffuse lighting applications.

The lighting industry currently accounts for a significant proportion of all energy demand. Luminescent white lighting is often impure, inefficient, expensive, and detrimentally emitsas a point source, meaning the light is emitted from a focused point. A luminescent light diffuser offers the potential to create a spatially broad lighting fixture. We developed a luminescent light diffuser consisting of three commercially available luminescent dye species (rhodamine 6G, fluorescein, 7-diethylamino-4-methylcoumarin) dispersed within a polymer matrix (polyvinyl alcohol), or commercial paint, and coated on a planar waveguide. A Light-emitting diode (LED) (385 nm) is directed into the waveguide which excites the luminescent species, coating the panel, creating a device that emits spatially broad pure white light. As the emission depends on escape cone emission from the waveguide, the device's emission was found to depend highly on the coating film quality and components. We present two systems: a small 40 mm × 40 mm prototype, made using standard water-soluble polymer (polyvinyl alcohol), to study the underlying operational principles, and a 100 mm 100 mm device with optimized efficiency fabricated with a clear commercial paint. By doping the polymer matrix with scattering silica microparticles we achieved a maximum photon outcoupling efficiency of 78%, whilst maintaining colour purity with an increased device size of more than 300 times (compared with the input LED). This work shows that it is possible to construct an inexpensive and spatially broad lighting source, whilst maintaining colour purity at a low cost.

Depth-Resolved Localization Microangiography in the NIR-II Window.

Detailed characterization of microvascular alterations requires high-resolution 3D imaging methods capable of providing both morphological and functional information. Existing optical microscopy tools are routinely used for microangiography, yet offer suboptimal trade-offs between the achievable field of view and spatial resolution with the intense light scattering in biological tissues further limiting the achievable penetration depth. Herein, a new approach for volumetric deep-tissue microangiography based on stereovision combined with super-resolution localization imaging is introduced that overcomes the spatial resolution limits imposed by light diffusion and optical diffraction in wide-field imaging configurations. The method capitalizes on localization and tracking of flowing fluorescent particles in the second near-infrared window (NIR-II, ≈1000-1700nm), with the third (depth) dimension added by triangulation and stereo-matching of images acquired with two short-wave infrared cameras operating in a dual-view mode. The 3D imaging capability enabled with the proposed method facilitates a detailed visualization of microvascular networks and an accurate blood flow quantification. Experiments performed in tissue-mimicking phantoms demonstrate that high resolution is preserved up to a depth of 4mm in a turbid medium. Transcranial microangiography of the entire murine cortex and penetrating vessels is further demonstrated at capillary level resolution.