Ceramic fibers are used in many different fields of engineering. These fibers may become airborne during manifacturing, maintenance or dismantling of ovens, e. g. Because respirable fibers may cause serious health hazard, depending on their size, there is large interest in development of online fiber detectors being able to classify fibers according to their size. A promising detection concept is based on Fraunhofer theory for estimating the fiber size utilizing laser light scattered by a fiber. Because there are differences of Fraunhofer diffraction patterns compared to the actual scattering patterns, reference calculations with an exact light scattering method are presented.

In this paper, the Discrete Sources Method has been extended to describe the influence of the geometry asymmetry of a core-shell particle accounting for the effect of spatial dispersion inside the plasmonic metal shell. We found that varying the plasmonic shell thickness has more influence on the near field intensity distribution then on the average enhancement factor. Besides, we demonstrates that the effect of spatial dispersion can decrease the near field intensity up to 60% of its value and it provides a small blue shift.

Global rainbow refractometry (GRR) is an important technique for temperature measurements of droplets and has been applied to a wide field of technical sprays. In this work, the application of GRR to sprays with droplets as small as 1 - 30 mu m in diameter is investigated by means of Lorenz-Mie theory to evaluate the influence of varying droplet size distributions (DSD) and varying refractive indexes on the global rainbow. DSDs were found by fitting a Rosin-Rammler-Sperling-Bennett distribution to experimental data. Different DSDs, that are typical for flame spray pyrolysis applications were evaluated systematically with varying widths and mean diameters. A study of the angular rainbow maxima position with varying widths of DSDs shows a strong non-linearity. It is concluded that GRR experiments in polydisperse applications should be accompanied with an accurate sizing technique. Furthermore, possible droplet size-dependent distributions of refractive indexes within the samples may influence the results.

Nanometer to micrometer scale colloidal particles are regularly found in applications in which surface forces dominate behavior. Consequently, a wide range of surface force measurement tools have been developed to probe interactions as a function of physiochemical properties. One tool, Total Internal Reflection Microscopy (TIRM), is an exceptionally sensitive probe of both conservative and non-conservative surface forces. A recent variant of TIRM called Scattering Morphology Resolved (SMR) TIRM utilizes the morphology of scattered light in concert with the integrated intensity to measure the position and orientation of a colloidal particle. Although the target of SMR-TIRM is the field of non-spherical “anisotropic” particles, spherical particles have been found to scatter evanescent waves with surprising morphology. Herein, we present experiments and simulations of the scattering morphology of a spherical particle. The morphology was probed as a function of particle size, incident beam polarization, and particle separation distance. We found that spherical particles scattered light with a noncircular morphology. Moreover, we found the morphology depended upon both the scaled particle size with respect to the incident beam wavelength and the incident beam polarization. Although the scattering morphology from the sphere was surprisingly complex, we did not find that these effects would alter the interpretation of scattering as a function of particle separation distance.

Noble metals are commonly used as plasmon materials because of their high density of free electrons, but semiconductor materials are also becoming of interesting in this field because its electron density can be varied by doping. Metal nitrides can be an alternative to noble metals because of their low absorption loss and high electron density. Among others, TiN and ZrN seem to be most suitable as alternative plasmonic materials because their optical properties are dominated by conduction electrons near the plasmon frequency. There is the flame spray pyrolysis process, which is currently developed to produce such kind of nanoparticles. In this paper, based on an extension of the discrete sources method, the effect of the hydrodynamic Drude model of the quantum nonlocal effect on the optical characteristics of semiconductor nanoparticles is analyzed. The influence of accounting for the nonlocal effect (NLE) on the optical properties under spherical particles deformation has been investigated. It has been shown that accounting for the NLE leads to a plasmon resonance blue shift and a damping similar to noble metals. It was found that smaller particles demonstrate larger NLE influence than larger ones. Besides, the influence of polarization on the local and nonlocal responses of 3D nonspherical semiconductor particles has been investigated as well. Using simulation accounting for the nonlocal effect, it is shown that the extinction of a nonspherical ZrN particles exceeds that of a gold particle.

Using the modified discrete sources method, the problem of calculating plasmon spectra of the characteristic energy loss of electrons during the interaction with silver nanoparticles from 2 to 8 nm in size is solved. The calculated spectra are compared with the experimental data confirming the significant spatial dispersion effect. The importance of the consideration of this factor when analyzing the properties of plasmonic nanoparticles for applications in biosensorics and biomedicine is discussed.

The microexplosion and nanoparticle formation of single isolated burning droplets using titanium tetraisopropoxide (TTIP) as nanoparticle precursor are investigated experimentally. Spherical along with fine agglomerated titanium dioxide (TiO2) nanoparticles are obtained from the single droplet combustion of TTIP dissolved in pure xylene, pure ethanol and the mixture of xylene and ethanol. Strong, global, and continuous microexplosions are observed during the combustion of TTIP/xylene droplet and TTIP/xylene–ethanol droplet. We proposed a hypothesis of droplet microexplosions as follows: hydrolysis of TTIP at or in the droplet surface leads to formation of TiO2 nanoparticles, which together with the low volatility component near the droplet surface creates an impermeable shell for the high volatility component. The high volatility component in the interior is superheated to induce heterogeneous nucleation of bubbles beneath the shell, which increases the pressure inside the shell until microexplosion occurs. These insights are very important mechanisms for the well-established flame spray pyrolysis (FSP) process.

A camera-based light scattering approach coupled with a viscoelasticity-induced cell migration technique has been used to characterize the morphological properties of erythrocytes in microfluidic flows. We have obtained the light scattering profiles (LSPs) of individual living cells in microfluidic flows over a wide angular range and matched them with scattering simulations to characterize their morphological properties. The viscoelasticity-induced 3D cell alignment in microfluidic flows has been investigated by bright-field and holographic microscopy tracking, where the latter technique has been used to obtain precise cell alignment profiles in-flow. Such information allows variable cell probability control in microfluidic flows at very low viscoelastic polymer concentrations, obtaining cell measurements that are almost physiological. Our results confirm the possibility of precise, label-free analysis of individual living erythrocytes in microfluidic flows.

We investigate the plasmonic response of gold nanospheres calculated using discrete dipole approximation validated against the results from other discretization methods, namely the finite-difference time-domain method and the finite-element methods. Comparisons are also made with calculations from analytical methods such as the Mie solution and the null-field method with discrete sources. We consider the nanoparticle interacting with the incident field both in free space and sitting on a planar substrate. In the latter case, discrete dipole approximation with surface interaction is used; this includes the interaction with the 'image dipoles' using Sommerfeld integration.

A modified scheme of the discrete sources method has been applied to investigate the strong interaction between proximal noble metal nanoparticles. The new scheme enables calculation of a near-field enhancement of several orders with a high degree of accuracy. The total field enhancement in between two spheroidal particles and the scattering cross-section have been analyzed in the frequency domain depending on the separation distance, spheroid aspect ratio, equivolume diameter, and material. In particular, it has been found that spheroids of smaller size can produce larger field enhancement than larger ones. Simulation results demonstrate that it is possible to achieve localized surface plasmon resonance at any desired exciting wavelength by using an appropriate geometrical configuration and material of the coupled spheroids.

An efficient forward scattering model, based on the Method of Auxiliary Sources, is formulated for perfectly electrically conducting (PEC) and penetrable nanowires on dielectric substrates.The accuracy of the model is investigated parametrically, with emphasis on future application in an inverse scattering scheme.The model is tested on families of PEC and silver nanowires on silicon substrate.

This paper describes the generation of small water dro- plets in the size range down to a few microns. Commer- cially available inkjet printing devices are not suitable for producing such droplets since they produce satellite droplets. Furthermore, standard drop-on-demand de- vices are normally restricted to the generation of dro- plets with the same size as the orifice diameter. Using a new and more sophisticated computer-based signal gen- eration system, smaller-sized droplets can be generated from the same orifice. A key feature of the design is the generation of freely definable pulses. This enables the generation of acoustic modes within the fluid of the dro- plet generator, which leads to the generation of droplets without satellites. Only very few pulse forms enable the generation of suitable acoustic modes. Therefore, it is necessary to look for the specific pulse corresponding to the chosen droplet generator. Flexible pulse form gen- eration appears to be more suitable than simple pulse forms for the generation of such droplets.

Since its invention in the mid of eighties [1] Total Internal Reflection Microscopy (TIRM) has proven to be an effective technique to measure weak interactions between spherical colloidal particles and surfaces with a resolution of a few femtonewton. It is a single particle evanescent light scattering technique. In an experimental setup a laser beam is coupled into a prism and hits the glass-water interface with an angle slightly above the critical angle of total internal reflection. This generates an evanescent field near the interface that decays in the lower refractive index medium (water) with a characteristic penetration depth which depends on the angle of incidence. A colloidal particle that is dispersed in the medium will scatter light from the evanescent wave if it is in the vicinity of the surface. By registering a scattered intensity it is possible to deduce the particle-substrate distance. Compared to other methods for measure particle wall interactions like the surface force apparatus or the atomic force microscopy where a colloidal particle is attached to the tip, TIRM is the most sensitive technique because thermal fluctuations where limit the other methods in their resolution are exploited to determine the interaction potential. In this way forces in the order of a few femtonewton can be detected. TIRM has proven to be a valuable tool for the precise measurement of weak colloidal interactions as double layer forces, van der Waals forces, magnetic interactions and depletion forces. Review on TIRM can be found for example in [2,3].To compare experimental results with results of mathematical modeling an effective light scattering method is needed. For this purpose the Discrete Sources Method (DSM) has been chosen. The DSM is a well-known method for light scattering analysis, which has recently been applied for evanescent wave scattering [4].

We present the light scattering response of gold and silver particles on or near surfaces consisting of different materials. A comparison is made between a particle near a perfectly conducting surface and near a gold surface. The resulting scattering diagrams are found to be different. Beyond this, an approximation with a mirror particle shows little aggrement with a particle near a metal surface. Furthermore, we compare the spectral response of a combination of gold and silver materials for particles at different heights.

In practical applications a precise and fast detection of the shape of a single erythrocyte from its scattering characteristics is needed. For this reason detailed investigations of light scattering properties of erythrocyte and their relation to shape is of great interest in recent years. In this paper we analyze light scattering behavior of different shape models of erythrocyte using the discrete sources method. For this we compare scattering results for oblate spheroid, disk-sphere, Cassini-based shape and a shape for a real strainless erythrocyte introduced by Skalak. Numerical results for the scattering indicatrix and the differential cross section by different shape models and its orientations are presented.

The discrete sources method (DSM) is applied to calculate light scattering by a half-spherical bubble in water on a substrate. For the first time an algorithm which allows the near-field calculation on the base of DSM is presented. Such investigations are important in immersion lithography, as the presence of bubbles on a resist surface decreases image quality. On the base of DSM the numerical algorithm of the near-field calculation is realized. Numerical results for the near-field inside the resist for different depths under the surface are presented.

In this paper we investigate the capabilities of different light scattering programs for light scattering simulation of the single human red blood cell, also known as erythrocyte. Knowledge of the scattering properties can help to solve the inverse problem of classifying erythrocytes according to size and shape using measured scattering diagrams. We compare the different programs by presenting the corresponding scattering diagrams. Then we give an overview of computation times and point out the different characteristics of the methods.

In this paper the discrete source method (DSM) is applied to analyse light scattering from nano-particles on a prism surface. Results of a comparison of an approximate Mie model and the rigorous DSM model, which accounts for the light scattering interaction of the particle with the prism surface, are presented. It is shown that taking into account the particle-prism interaction plays a significant role for a correct interpretation of spectroscopic measurements.

The discrete sources method has been extended to analyze scattering spectra of axially symmetrical nonspherical nanoparticles deposited near a plane interface surface. It was found that increasing the lateral size of noble metal particles leads to a red shift of the scattering maximum value.