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Core-Shell Modeling of Light Scattering by Vesicles: Effect of Size, Contents, and Lamellarity
摘要： Having a fast, reliable method for characterizing vesicles is vital for their use as model cell membranes in biophysics, synthetic biology, and origins of life studies. Instead of the traditionally used Rayleigh-Gans-Debye approximation, we use an exact extended Lorenz-Mie solution for how core-shell particles scatter light to model vesicle turbidity. This approach enables accurate interpretations of simple turbidimetric measurements and is able to accurately model highly scattering vesicles, such as larger vesicles, those with multiple layers, and those with encapsulated material. We uncover several surprising features, including that vesicle lamellarity has a larger effect on sample turbidity than vesicle size and that the technique can be used to measure the membrane thickness of vesicles. We also examine potential misinterpretations of turbidimetry and discuss when measurements are limited by forward and multiple scattering and by the geometry of the instrument.
关键词： Lorenz-Mie theory,turbidimetry,membrane thickness,vesicles,lamellarity,light scattering
更新于2025-11-19 16:56:35
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Scatter Enhanced Phase Contrast Microscopy for Discriminating Mechanisms of Active Nanoparticle Transport in Living Cells
摘要： Understanding the uptake and transport dynamics of engineered nanomaterials (ENMs) by mammalian cells is an important step in designing next-generation drug delivery systems. However, to track these materials and their cellular interactions, current studies often depend on surface-bound fluorescent labels which have the potential to alter native cellular recognition events. As a result, there is still a need to develop methods capable of monitoring ENM-cell interactions independent of surface modification. Addressing these concerns, here we show how Scatter Enhanced Phase Contrast (SEPC) microscopy can be extended to work as a generalized label-free approach for monitoring nanoparticle uptake and transport dynamics. To determine which materials can be studied using SEPC, we turn to Lorenz-Mie theory, predicting that individual particles down to ~35 nm can be observed. We confirm this experimentally, demonstrating that SEPC works for a variety of metal and metal oxides, including: Au, Ag, TiO2, CeO2, Al2O3, and Fe2O3 nanoparticles. We then demonstrate that SEPC microscopy can be used in a quantitative, time-dependent fashion to discriminate between distinct modes of active cellular transport, including intracellular transport and membrane assisted transport. Finally, we combine this technique with microcontact printing to normalize transport dynamics across multiple cells, allowing for a careful study of ensemble TiO2 nanoparticle uptake. This revealed three distinct regions of particle transport across the cell, indicating that membrane dynamics play an important role in regulating particle flow. By avoiding fluorescent labels, SEPC allows for a rational exploration of the surface properties of nanomaterials in their native state and their role in endocytosis and cellular transport.
关键词： Scatter Enhanced Phase Contrast,Lorenz-Mie Theory,Endocytosis,Nano-Bio Interface,Nanoparticle
更新于2025-09-23 15:23:52
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Photophoretic force measurement on microparticles in binary complex plasmas
摘要： This article presents a method to measure the photophoretic force on microparticles in complex plasmas. A laser heating setup is used to increase the kinetic temperatures of binary mixtures composed of melamine-formaldehyde (MF) and silica (SiO2) particles. The temperature gain of both particle species due to the additional thermal reservoir is compared to a laser force model. Contributions of radiation pressure and photophoretic forces are determined through a variation of neutral gas pressure and application of Lorenz-Mie theory. The photophoretic force is found to be significant for MF particles at typical conditions in complex plasma experiments.
关键词： photophoretic force,microparticles,radiation pressure,complex plasmas,Lorenz-Mie theory,binary mixtures,laser heating
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Scattering of a Conducting Sphere Covered with Chiral Metamaterials by a Plane Wave
摘要： Based on the Lorenz-Mie theory, the scattering characteristics of a conducting sphere covered with chiral metamaterials (CMMs) by a plane wave are numerically calculated. The relative permittivity and permeability of CMMs are negative. In the case of negative refractive index, the analytical expressions for the scattering of a multilayered CMMs sphere are briefly given. In this paper, the effects of the negative refractive and the thickness of CMMs on electromagnetic scattering of a conducting sphere are analyzed. The results show that the backscattering of the conducting sphere can be reduced by the CMMs coating, whereas the scattering is not necessarily reduced with the increasing of the coating thickness. Therefore, we can use the thinner CMMs to achieve the better stealth performance to some extent.
关键词： CMMs,Lorenz-Mie theory,Scattering
更新于2025-09-19 17:15:36
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GCforce: Decomposition of optical force into gradient and scattering parts
摘要： A MATLAB function GCforce is presented for the calculation of gradient and scattering parts of optical force (OF). The decomposition of OF into the gradient and scattering parts, or, equivalently, the conservative and nonconservative components, is of great importance to the physical understanding of optical micromanipulation. In this paper, we propose a formulation to decompose the OF acting on a spherical particle immersed in an arbitrary monochromatic optical field, based on the generalized Lorenz-Mie theory and the Cartesian multipole expansion approach. The expressions for the gradient and scattering forces are given explicitly in terms of the partial wave expansion coefficients of the optical field shining on the particle and the Mie coefficients of the particle. A MATLAB function GCforce.m is also presented for the calculation. The explicit and rigorous decomposition of the OF into conservative and non-conservative forces shed light on the understanding of light-matter interaction as well as contributes significantly to the designing of optical fields to achieve various optical micromanipulation.
关键词： Scattering force,Gradient force,Multipole expansion theory,Generalized Lorenz-Mie theory
更新于2025-09-09 09:28:46
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Methods to retrieve the complex refractive index of aquatic suspended particles: going beyond simple shapes
摘要： The scattering properties of aquatic suspended particles have many optical applications. Several data inversion methods have been proposed to estimate important features of particles, such as their size distribution or their refractive index. Most of the proposed methods are based on the Lorenz–Mie theory to solve Maxwell’s equations, where particles are considered homogeneous spheres. A generalization that allows consideration of more complex-shaped particles is the T -matrix method. Although this approach imposes some geometrical restrictions (particles must be rotationally symmetrical) it is applicable to many life forms of phytoplankton. In this paper, three different scenarios are considered in order to compare the performance of several inversion methods for retrieving refractive indices. The error associated with each method is discussed and analyzed. The results suggest that inverse methods using the T -matrix approach are useful to accurately retrieve the refractive indices of particles with complex shapes, such as for many phytoplankton organisms.
关键词： Lorenz–Mie theory,scattering properties,T-matrix method,refractive index,aquatic suspended particles,phytoplankton
更新于2025-09-09 09:28:46