Ellipsoidal Particles Research Articles

Elongated Particles Show a Preferential Uptake in Invasive Cancer Cells

Mechanically driven cellular preference for drug carriers can enhance selectivity in cancer therapy, underscoring the importance of understanding the physical aspects of particle uptake. In this study, it was hypothesized that elongated particles might be preferentially taken up by deformable, aggressive cancer cells compared to normal cells. Two film-stretching methods were tested for 0.8–2.4 μm polystyrene (PS) particles: one based on solubility in organic solvents and the other on heat-induced softening. The heat-induced method produced more homogenous particle batches, with a standard deviation in the particle aspect ratio of 0.42 compared to 0.91 in the solvent-based method. The ability of cells to engulf elongated PS particles versus spherical particles was assessed in two subsets of human melanoma A375 cells. In the more aggressive cancer cell subset (A375+), uptake of elongated PS particles increased by 10% compared to spherical particles. In contrast, the less aggressive subset (A375−) showed a 25% decrease in uptake of elongated particles. This resulted in an uptake ratio between A375+ and A375− that was 1.5 times higher for elongated PS particles than for spherical ones. To further demonstrate relevance to drug delivery, elongated paclitaxel-loaded biodegradable, slow-releasing poly(lactic-co-glycolic) acid (PLGA) particles were synthesized. No significant difference in cytotoxic effect was observed between A375+ and A375− cells treated with spherical drug-loaded particles. However, treatment with ellipsoidal particles led to a significantly enhanced cytotoxic effect in aggressive cells compared to less aggressive cells. These findings present promising directions for tailored cancer drug delivery and demonstrate the importance of particle physical properties in cellular uptake and drug delivery mechanisms.

Simple Models of Directly Measured Energy Landscapes for Different Shaped Particles in Nonuniform AC Electric Fields.

We report direct measurements of potential energy landscapes for different shaped colloidal particles interacting with nonuniform AC electric fields. Epoxy particle shapes investigated include disks, ellipses, squares, rectangles, and rhombuses, which are all part of the superelliptical prism shape class and are chosen to systematically vary particle anisotropy and corner features. The measurement configuration consists of noninteracting single particles sedimented onto microscope slides within electric fields between parallel coplanar electrodes. Thermally sampled positions and orientations of single particles in nonuniform fields are tracked in an optical microscope, and measured potential energy landscapes are obtained via Boltzmann inversions. We develop a new analytically simple model that captures all measured energy landscapes for superelliptical prism shaped colloidal particles with electrostatic double layers. The model recovers known validated potentials for spherical and ellipsoidal particles, and therefore captures energy landscapes for a variety of different colloidal particle sizes, shapes, and materials reported in prior studies.

Controlling the orientation of ellipsoidal nanoparticles using fractional vector beams

In the field of nanotechnology, achieving precise manipulation of ellipsoidal nanoparticles presents a significant challenge because it requires controlling five degrees of freedom, including three spatial dimensions (position in 3D space) and two angular dimensions (polar and azimuthal angles). In this work, we investigate both the optical forces and trapping potentials on an ellipsoidal nanoparticle produced by tightly focused fractional vector beams (FVBs). Unlike the integer vector beams (IVBs), which manipulate only three spatial dimensions of ellipsoidal particles, FVB with an initial phase not only provides spatial position control but also enables precise manipulation of spatial orientation. Moreover, by adjusting the topological index and initial phase of the incident FVBs, arbitrary orientations in the 3D space of ellipsoidal nanoparticles can be achieved. Our results may find interesting applications in microfluidics, biomedical engineering, and nanotechnology.

The Effect of Ellipsoidal Particle Surface Roughness on Drag and Heat Transfer Coefficients Using Particle-Resolved Direct Numerical Simulation

The purpose of this study is to estimate the effect of roughness layer thickness on the heat transfer and drag coefficients of ellipsoidal particles. Using an OpenFOAM-based particle-resolved direct numerical simulation (PR-DNS) method, we calculated the drag coefficient and Nusselt number for an isolated axisymmetric nonspherical particle with a rough surface in a uniform flow. The PR-DNS results indicate that the drag coefficient varies linearly with the effective roughness Sef at different angles, which can be expressed as CD=kSef−1+CD0. The changes in k are consistent with the Happel and Brenner equation. Furthermore, the influence of roughness on the heat transfer efficiency factor can be represented by Ef=Sef−65. The models for the drag coefficient and Nusselt number are valid within the ranges 1.25≤Ar≤2.5,1≤Sef≤2, and 10≤Rep≤200, thereby extending the applicability of the equations developed for smooth particles. These newly developed correlations for the drag coefficient and Nusselt number can be utilized for non-isothermal flows of particle mixtures containing materials with various rough-surfaced ellipsoids.

Mass distribution impacts on particle translation and orientation dynamics in dilute flows

We present a novel model for tracking particles (based on Lagrangian particle tracking) with inhomogeneous mass distribution. Without loss of generality, the presented approach captures inhomogeneity by assuming an offset spherical inclusion in an elongated ellipsoidal particle matrix. The model is first validated on simplified flow configurations such as particles settling in vacuum or air as well as suspended in simple shear and laminar pipe flow, where we achieved an excellent agreement with the available reference results. Furthermore, we investigate the impact of the inclusion parameters on the particle motion. Finally, the deposition of inhomogeneous particles in a simplified bifurcation is analyzed. We conclude that the consideration of inhomogeneity significantly alters the translational and orientational dynamics of the particles. Consequently, we advocate for the consideration of more realistic mass distributions to increase the accuracy of modeling and predicting the motion of inhomogeneous particles in flows for real-world applications.

Modeling method of random collision of ellipsoidal particles in mechanical simulation for high energy solid propellant

Abstract It is based on the molecular dynamics algorithm of elliptical optimization to establish a mesostructure model of oval particles of high-energy solid propellant considering gradation and controllable filling rate according to the mesostructure characteristics of high-energy solid propellant. The bilinear cohesion model was applied to describe the interface damage behavior and carry out the high-energy propellant tensile test at three rates. The rationality of the elliptical particle model has been verified between the comparison of the calculated results with the experimental results established to describe the micromechanical behavior of high-energy propellants, which is to reveal the mesoscopic damage law of high-energy solid propellant under different tensile rates in this paper.

Float-Cast Microsieves with Elliptical Pores.

Polymeric microsieves bearing elliptical pores were successfully prepared via float-casting: a dispersion comprising nonvolatile acrylate monomers and ellipsoidal polystyrene particles was spread onto a water surface. The resulting self-organized monolayer was laterally compressed, and the monomer was photopolymerized, giving rise to a membrane comprising ellipsoidal particles laterally embedded in a 0.5 μm thin polymer membrane. The particles were dissolved, leaving behind elliptical pores. These pores had an average length of the major axis of 0.87 ± 0.1 μm and of the minor axis of 0.42 ± 0.07 μm and an aspect ratio of approximately 2. The microsieve bearing these submicrometric elliptical pores was transferred to a hierarchical structure made out of microsieves bearing circular pores of 6 μm diameter on top of a microsieve with 70 μm diameter pores. The resulting hierarchically structured microsieve had a porosity of 0.13. At a pressure difference of typically 103 Pa (Reynolds number aprox. 0.002), the volumetric permeance for water was Pe = /A/Δp = 0.5·10-6 m/s/Pa, the product viscosity·permeance is η·/A/Δp = 0.5·10-9 m. This value is lower than the corresponding values of microsieves with circular pores of similar diameter produced by the same technique. The beneficial effects of higher permeance per pore caused by the elliptical shape are countered by lower porosity caused by less efficient packing of the ellipsoidal particles.

Elasto-inertial focusing and rotating characteristics of ellipsoidal particles in a square channel flow of Oldroyd-B viscoelastic fluids

The elasto-inertial focusing and rotating characteristics of spheroids in a square channel flow of Oldroyd-B viscoelastic fluids are studied by the direct forcing/fictitious domain method. The rotational behaviours, changes in the equilibrium positions and travel distances are explored to analyse the mechanisms of spheroid migration in viscoelastic fluids. Within the present simulated parameters (1 ≤ Re ≤ 100, 0 ≤ Wi ≤ 2, 0.4 ≤ α ≤3), the results show that there are four kinds of equilibrium positions and six (five) kinds of rotational behaviours for the elasto-inertial migration of prolate (oblate) spheroids. We are the first to identify a new rotational mode for the migration of prolate spheroids. Only when the particles are initially located at a corner and wall bisector, some special initial orientations of the spheroids have an impact on the final equilibrium position and rotational mode. In other general initial positions, the initial orientation of the spheroid has a negligible effect. A higher Weissenberg number means the faster the particles migrate to the equilibrium position. The spheroid gradually changes from the corner (CO), channel centreline (CC), diagonal line (DL) and cross-section midline (CSM) equilibrium positions as the elastic number decreases, depending on the aspect ratio, initial orientation and rotational behaviour of the particles and the elastic number of the fluid. When the elastic number is less than the critical value, the types of rotational modes of the spheroids are reduced. By controlling the elastic number near the critical value, spheroids with different aspect ratios can be efficiently separated.

Ionic current blockade in a nanopore due to an ellipsoidal particle.

Nanopores in solid-state membranes have been used to detect, identify, filter, and characterize nanoparticles and biological molecules. In this work, we simulate an ionic flow through a nanopore while an ellipsoidal nanoparticle translocates through a pore. We numerically solve the Poisson-Nernst-Planck equations to obtain the ionic current values for different aspect ratios, sizes, and orientations of a translocating particle. By extending the existing theoretical model for the ionic current in the nanopore to the particles of ellipsoidal shape, we propose semiempirical fitting formulas which describe our computed data within 5% accuracy. We also demonstrate how the derived formulas can be used to identify the dimensions of nanoparticles from the available experimental data which may have useful applications in bionanotechnology.

A novel pseudo-rigid body approach to the non-linear dynamics of soft micro-particles in dilute viscous flow

We propose a novel, demonstrably effective, utmost versatile and computationally highly efficient pseudo-rigid body approach for tracking the barycenter and shape dynamics of soft, i.e. non-linearly deformable micro-particles dilutely suspended in viscous flow. Pseudo-rigid bodies are characterized by affine deformation and thus represent a first-order extension to the kinematics of rigid bodies. Soft particles in viscous flow are ubiquitous in nature and sciences, prominent examples, among others, are cells, vesicles or bacteria. Typically, soft particles deform severely due to the mechanical loads exerted by the fluid flow. Since the shape dynamics of a soft particle - a terminology that shall here also include its orientation dynamics - also affects its barycenter dynamics, the resulting particle trajectory as a consequence is markedly altered as compared to a rigid particle. Here, we consider soft micro-particles of initially spherical shape that affinely deform into an ellipsoidal shape. These kinematic conditions are commensurate with i) the affine deformation assumption inherent to a pseudo-rigid body and ii) the celebrated Jeffery-Roscoe model for the traction exerted on an ellipsoidal particle due to creeping flow conditions around the particle. Without loss of generality, we here focus on non-linear hyperelastic particles for the sake of demonstration. Our novel numerical approach proves to accurately capture the particular deformation pattern of soft particles in viscous flow, such as for example tank-treading, thereby being completely general regarding the flow conditions at the macro-scale and, as an option, the constitutive behavior of the particle. Moreover, our computational method is highly efficient and allows straightforward integration into established Lagrangian tracking algorithms as employed for the point-particle approach to track rigid particles in dilute viscous flow.

Analysis of heat transfer of ellipsoidal particles mixed composite with bounded domains

Analysis of heat transfer of ellipsoidal particles mixed composite with bounded domains

Elucidating the impact of non-spherical morphology on kinetic behavior of graphite using single-particle microelectrode

The precise assessment of the kinetic properties of graphite is crucial for the design of the material and the development of electrochemical models for lithium-ion batteries. However, conventional evaluation methods using composite electrodes fall short in excluding the influence of its porous structure and evaluating the influence of particle shape on kinetic behavior. In this work, we elucidate the impact of non-spherical morphology on kinetic behavior of single artificial graphite particle, employing the single-particle microelectrode technique. Three single artificial graphite particles with different sizes are pre-cycled and exhibit outstanding rate capability, maintaining a maximum capacity retention of 78.1 % at 200 C. Further, exchange current density and diffusion coefficients are determined through Tafel plots and the potentiostatic intermittent titration technique (PITT), respectively. It is found that the particle with a higher exposure of edge planes present elevated exchange current density and diffusion coefficients. Considering that the graphite particles typically feature an ellipsoidal rather than spherical shape, we propose an approach based on an ellipsoidal diffusion model for extracting diffusion coefficients. This model takes into account the non-spherical morphology of graphite, addressing the limitations inherent in the geometric assumptions of previous methods. The average relative error between the diffusion coefficients derived from the ellipsoidal diffusion model and the previous method using spherical assumptions is 215 %, indicating that accurately depicting the shape of ellipsoidal graphite particles in the model is crucial for obtaining correct estimates of kinetic parameters. This study offers direct experimental evidence of superior kinetic behavior of edge planes over basal planes. To leverage this characteristic, it is recommended to employ an out-of-plane aligned architecture for composite electrodes using novel techniques, e.g., 3D printing or magnetic alignment techniques.

Effect of Ellipsoidal Particle Shape on Tribological Properties of Lubricants Containing Nanoparticles

Adding nanoparticles can significantly improve the tribological properties of lubricants. However, there is a lack of understanding regarding the influence of nanoparticle shape on lubrication performance. In this work, the influence of diamond nanoparticles (DNPs) on the tribological properties of lubricants is investigated through friction experiments. Additionally, the friction characteristics of lubricants regarding ellipsoidal particle shape are investigated using molecular dynamics (MD) simulations. The results show that DNPs can drastically lower the lubricant's friction coefficient μ from 0.21 to 0.117. The shearing process reveals that as the aspect ratio (α) of the nanoparticles approaches 1.0, the friction performance improves, and wear on the wall diminishes. At the same time, the shape of the nanoparticles tends to be spherical. When 0.85 ≤ α ≤ 1.0, rolling is ellipsoidal particles' main form of motion, and the friction force changes according to a periodic sinusoidal law. In the range of 0.80 ≤ α < 0.85, ellipsoidal particles primarily exhibit sliding as the dominant movement mode. As α decreases within this range, the friction force progressively increases. The friction coefficient μ calculated through MD simulation is 0.128, which is consistent with the experimental data.

Precursor effect on the hydrothermal synthesis of pure ZnO nanostructures and enhanced photocatalytic performance for norfloxacin degradation

The indiscriminate production and use of antibiotics have caused an environmental imbalance. Therefore, advanced oxidative processes such as photocatalysis have been proposed to eliminate the presence of such emerging pollutants. On the other hand, the use of photocatalytic processes requires the development of highly efficient photocatalysts. This paper introduces photocatalysts based on ZnO nanostructures with different morphologies and grown by low-temperature hydrothermal synthesis. The choice of zinc precursor resulted in significant variations in both the morphology and size of the ZnO particles. Morphologies, such as, dumbbell-like structures, nanogranules, and ellipsoidal particles were obtained by altering the zinc precursor in a slightly alkaline medium, and parameters such as photocatalyst dosage, initial concentration of antibiotic Norfloxacin (NOR), and pH in photocatalysis were thoroughly investigated. The reactive species responsible for NOR degradation were photogenerated holes, superoxide radicals, and hydroxyl radicals, with the latter showing a greater contribution. Degradation pathways are also proposed, and intermediate products were identified by LC-MS. Thirteen degradation products, of which six were reported for the first time, were detected. Among the synthesized morphologies, nanogranules exhibited superior photocatalytic activity, achieving 100% NOR degradation after 70 min under UV-C light and excellent reusability after three cycles (97%). The results surpass those from previous studies, since the simple and efficient photocatalysts employed led to shorter degradation times.

Diffusion dynamics of an overdamped active ellipsoidal Brownian particle in two dimensions

Shape asymmetry is the most abundant in nature and has attracted considerable interest in recent research. The phenomenon is widely recognized: a free ellipsoidal Brownian particle displays anisotropic diffusion during short time intervals, which subsequently transitions to an isotropic diffusion pattern over longer timescales. We have further expanded this concept to incorporate active ellipsoidal particles characterized by an initial self-propelled velocity. This paper provides analytical and simulation results of diffusion dynamics of an active ellipsoidal particle. The active ellipsoidal particle manifests three distinct regimes in its diffusion dynamics over time. In the transient regime, it displays diffusive behavior followed by a super-diffusive phase, and in the longer time duration, it transitions to purely diffusive dynamics. We investigated the diffusion dynamics of a free particle as well as a particle in a harmonic trap, and a particle subject to a constant field force. Moreover, we have studied the rotational diffusion dynamics and torque production resulting from an external constant force field. Furthermore, our investigation extends to the examination of the scaled average velocity of an ellipsoidal active particle, considering both a constant force field and a one-dimensional ratchet.

Evolution of the Microstructure, Phase Composition and Thermomechanical Properties of the CuZnIn Alloys, Achieved by Thermally Controlled Phase Transitions

Ternary alloys with CuZnIn compositions based on the binary CuZn diagram and the modeled ternary system solidus projection were investigated. The as-cast alloys, hot-rolled sheets, and samples annealed at low temperature were examined. It was found that the α-CuZn solution phase, with minor indium additions (1–2% at.), was the primary phase crystallizing during casting and remained stable at low temperatures. The ternary phase with an approximate composition of Cu8(In,Zn)4.5 and a structure analogous to the high-temperature γ-Cu9In4 phase crystallized from the liquid state and remained stable at low temperatures. This behavior results from the stabilization against peritectoidal decomposition by the Zn atoms when substituting In in the structure. A new phase γ*-Cu9(In,Zn)4 with a modified structure was identified, characterized by a reduced unit cell and an altered electronic structure. The hot-rolling process preserves the phase composition and forms a composite-like structure, with the matrix composition of γ* and large ellipsoidal α-CuZn solution particles. On a microscale, the γ* matrix exhibited a specific structure resulting from segregation processes and was composed of micrometer-sized α-CuZn(In) solution particles and nano-sized β-CuZn phase precipitates. Low-temperature annealing intensifies the γ* matrix decomposition through binary phase precipitation.

Collective dynamics and pair-distribution function of active Brownian ellipsoids in two spatial dimensions

While the collective dynamics of spherical active Brownian particles is relatively well understood by now, the much more complex dynamics of nonspherical active particles still raises interesting open questions. Previous work has shown that the dynamics of rod-like or ellipsoidal active particles can differ significantly from that of spherical ones. Here, we obtain the full state diagram of active Brownian ellipsoids in two spatial dimensions without hydrodynamic interactions depending on the Péclet number and packing density via computer simulations. The system is found to exhibit a rich state behavior that includes cluster formation, local polar order, polar flocks, and disordered states. Moreover, we obtain numerical results and an analytical representation for the pair-distribution function of active ellipsoids. This function provides useful quantitative insights into the collective behavior of active particles with lower symmetry and has potential applications in the development of predictive theoretical models.

High-Resolution Two-Phase Velocimetry Of Aspherical Particles Using Wavelet-Based Optical Flow Velocimetry (WOFV) Benchmarked With Fully Resolved Direct Numerical Simulations

Several techniques exist to measure the carrier and dispersed phases in multi-phase flows. Particle image velocimetry (PIV) analyzes the carrier phase by cross-correlating particle images, but its resolution is limited by the size of the interrogation window, making it difficult to resolve fine-scale turbulent structures. Particle tracking algorithms capture translational motion of dispersed particles well, but struggle with rotational motion, especially for irregular and aspherical particles. Currently, there is no method that universally measures both the carrier phase velocity field and the translational and rotational motions of dispersed particles. This study evaluates wavelet-based optical flow velocimetry (wOFV) for motion estimation in multi-phase flows, focusing on dispersed ellipsoidal particles and their surrounding turbulent carrier flow using synthetic image data. The research proceeds in two phases: first, the rigid motion of ellipses, including translational and rotational components, is analyzed using wOFV-generated dense motion fields. The results highlight the critical role of the regularization weighting parameter λ. Higher λ values improve translational motion estimation, while an optimal λ avoids under-regularization and non-physical structures in rotational motion. wOFV maintains accuracy in combined motion scenarios with optimal λ values. In the second phase, wOFV captures the turbulent carrier flow around an aspherical particle, benchmarked against DNS data and compared to PIV. wOFV outperforms PIV in resolving finer structures near the particle surface and in accurately representing the wake region. Error analyses confirm wOFV’s superior performance, with optimal results within a specific λ range. In conclusion, wOFV is a highly effective tool for the analysis of multi-phase flow dynamics, providing greater resolution and accuracy than PIV, especially in complex scenarios involving aspherical particles.

Exploring the influence of pore shape on conductance and permeation

There are increasing numbers of ion channel structures featuring heteromeric subunit assembly, exemplified by synaptic α1βB glycine and α4β2 nicotinic receptors. These structures exhibit inherent pore asymmetry, but the relevance of this to function is unknown. Furthermore, molecular dynamics simulations performed on symmetrical homomeric channels often lead to thermal distortion whereby conformations of the resulting ensemble are also asymmetrical. When functionally annotating ion channels, researchers often rely on minimal constrictions determined via radius-profile calculations performed with computer programs, such as HOLE or CHAP, coupled with an assessment of pore hydrophobicity. However, such tools typically employ spherical probe particles, limiting their ability to accurately capture pore asymmetry. Here, we introduce an algorithm that employs ellipsoidal probe particles, enabling a more comprehensive representation of the pore geometry. Our analysis reveals that the use of nonspherical ellipsoids for pore characterization provides a more accurate and easily interpretable depiction of conductance. To quantify the implications of pore asymmetry on conductance, we systematically investigated carbon nanotubes with varying degrees of pore asymmetry as model systems. The conductance through these channels shows surprising effects that would otherwise not be predicted with spherical probes. The results have broad implications not only for the functional annotation of biological ion channels but also for the design of synthetic channel systems for use in areas such as water filtration. Furthermore, we make use of the more accurate characterization of channel pores to refine a physical conductance model to obtain a heuristic estimate for single-channel conductance. The code is freely available, obtainable as pip-installable python package and provided as a web service.

The Paradoxical Behavior of Rough Colloids at Fluid Interfaces.

Colloidal particles adsorb and remain trapped at immiscible fluid interfaces due to strong interfacial adsorption energy with a contact angle defined by the chemistry of the particle and fluid phases. An undulated contact line may appear due to either particle surface roughness or shape anisotropy, which results in a quadrupolar interfacial deformation and strong long-range capillary interaction between neighboring particles. While each effect has been observed separately, here we report the paradoxical impact of surface roughness on spherical and anisotropic ellipsoidal polymer colloids. Using a seeded emulsion polymerization technique, we synthesize spherical and ellipsoidal particles with controlled roughness magnitudes and topography (convex/concave). Via in situ measurement of the interfacial deformation around colloids at an air-water interface, we find that while surface roughness strengthens the quadrupolar deformation in spheres as expected by theory, in stark contrast, it weakens the same in ellipsoids. As roughness increases, particles of both shapes become more hydrophilic, and their apparent contact angle decreases. Using numerical predictions, we show that this partially explains the decreased interfacial deformation and capillary interactions between the ellipsoids. Therefore, particle surface engineering has the potential to decrease the capillary deformation by asymmetric particles via changing their capillary pinning, as well as wetting behavior at fluid interfaces.