Micron-sized Spherical Particles Research Articles

Epoxy resin gel particles with adjustable stickiness and deformability for pesticide delivery

It is essential to develop a pesticide delivery system with a simple preparation process and strong leaf retention capability. In this study, epoxy resin (ER) was modified with alcohols with different carbon chain lengths through a one-step reaction to synthesize modified prepolymers (ModER). Among these, the ER modified by dodecanol (ER/Dodecanol) exhibited high flexibility, exceptional stickiness and the highest surface free energy. Subsequently, the organic phase containing emamectin benzoate (EB) and ModER was directly mixed with the aqueous phase containing sodium lignosulfonate (SL) to instantaneously obtain pesticide-loaded epoxy resin gel particles (ModERMP) through self-emulsification and electrostatic interaction. ER/Dodecanol loaded with EB (EB@ER/Dodecanol) had excellent flexibility. The particles underwent significant flattening, transitioning from micron-sized spherical particles to “biscuit-type” particles with nanoscale thickness. EB@ER/Dodecanol exhibited outstanding stickiness, enabling it to adhere to the mouthparts and legs of insects, thereby impacting their feeding behavior. Compared with that of the control, the leaf feeding rate for the experimental group was decreased by 9.36%. EB@ER/Dodecanol also had affinity for foliar micro/nanostructures while displaying excellent washout resistance. Following washing, the residue rate increased by 33.7% compared to that of the emulsifiable concentrate (EC). Furthermore, EB@ER/Dodecanol had excellent insecticidal activity both before and after washout. ModERMP represents a simple preparation process with robust washout resistance, thereby enhancing pesticide utilization rates.

Inhalable porous particles as dual micro-nano carriers demonstrating efficient lung drug delivery for treatment of tuberculosis

Inhalation therapy treating severe infectious disease is among the more complex and emerging topics in controlled drug release. Micron-sized carriers are needed to deposit drugs into the lower airways, while nano-sized carriers are of preference for cell targeting. Here, we present a novel and versatile strategy using micron-sized spherical particles with an excellent aerodynamic profile that dissolve in the lung fluid to ultimately generate nanoparticles enabling to enhance both extra- and intra-cellular drug delivery (i.e., dual micro-nano inhalation strategy). The spherical particles are synthesised through the condensation of nano-sized amorphous silicon dioxide resulting in high surface area, disordered mesoporous silica particles (MSPs) with monodispersed size of 2.43 μm. Clofazimine (CLZ), a drug shown to be effective against multidrug-resistant tuberculosis, was encapsulated in the MSPs obtaining a dry powder formulation with high respirable fraction (F.P.F. <5 μm of 50%) without the need of additional excipients. DSC, XRPD, and Nitrogen adsorption-desorption indicate that the drug was fully amorphous when confined in the nano-sized pores (9–10 nm) of the MSPs (shelf-life of 20 months at 4 °C). Once deposited in the lung, the CLZ-MSPs exhibited a dual action. Firstly, the nanoconfinement within the MSPs enabled a drastic dissolution enhancement of CLZ in simulated lung fluid (i.e., 16-fold higher than the free drug), increasing mycobacterial killing than CLZ alone (p = 0.0262) and reaching concentrations above the minimum bactericidal concentration (MBC) against biofilms of M. tuberculosis (i.e., targeting extracellular bacteria). The released CLZ permeated but was highly retained in a Calu-3 respiratory epithelium model, suggesting a high local drug concentration within the lung tissue minimizing risk for systemic side effects. Secondly, the micron-sized drug carriers spontaneously dissolve in simulated lung fluid into nano-sized drug carriers (shown by Nano-FTIR), delivering high CLZ cargo inside macrophages and drastically decreasing the mycobacterial burden inside macrophages (i.e., targeting intracellular bacteria). Safety studies showed neither measurable toxicity on macrophages nor Calu-3 cells, nor impaired epithelial integrity. The dissolved MSPs also did not show haemolytic effect on human erythrocytes. In a nutshell, this study presents a low-cost, stable and non-invasive dried powder formulation based on a dual micro-nano carrier to efficiently deliver drug to the lungs overcoming technological and practical challenges for global healthcare.

Modeling of Solidification Process and Investigation of Heat Transfer Mechanisms in Micron-Sized Spherical Cu Particles

Modeling of Solidification Process and Investigation of Heat Transfer Mechanisms in Micron-Sized Spherical Cu Particles

Measurement of fragments generated by hypervelocity impacts of micron-sized iron particles at grazing incidents

• Fragments of hypervelocity dust impacts are measured using a Delay Line Detector. • Majority of fragments created at grazing incidences are composed of dust projectile. • Fragmentation of projectiles increase with impact speed for grazing incidences. • The fragment speeds are distributed around 80% of the projectile impact speed. In this study, we present results from hypervelocity impacts of iron particles onto smooth surfaces under shallow incidence. For the first time, the submicron fragments of the projectiles were measured using a delay-line detector combined with a multichannel plate. Micron-sized spherical iron particles with speeds between 4–40 km/s are fired by a dust accelerator facility and impact on an optical mirror target at grazing angles of 2 ° , 4 ° , and 6 ° from the horizontal. Individual fragments generated in each impact event have been measured and analyzed including their speeds, masses, and trajectories. The total mass and momentum of fragments are comparable to their parent projectile. It is observed that most fragments have speeds exceeding 80 % of pre-impact velocities. Fragments generated at incident angle of 2 ° leave the target surface with even lower elevation angles of around 1 ° . The majority of impact fragments generated under incident angles of 4 ° and 6 ° form a spatial distribution centered an axis of 5 ° elevation, which increases with increasing impact speed. Furthermore, azimuthal scattering occurs with a distribution concentrated within ± 10 ° .

Polymerizable precursor method vs solid state reaction for the synthesis of Ni3(PO4)2 yellow hue pigment with advanced characteristics

In view of the rapid development of printing and electrophoretic display technologies, there is a high demand for pigments with pre-defined physical properties and pure colouration of one of the three subtractive CMY primaries (cyan, magenta or yellow). This contribution focuses on the development of an appropriate synthesis method of the yellow-hue Ni3(PO4)2 inorganic phosphate with the purpose to enable its application in advanced light reflective technologies. Polymerizable precursor method (PPM) and solid state reaction (SSR) were utilized for the synthesis and the results were evaluated with regards to phase composition, crystallinity, particle morphology and size distribution, surface area, porosity, density, optical reflectance and colour parameters of the product. Accordingly, PPM provides a number of advantages in comparison to SSR and to literature data reporting other inorganic yellow-shade pigments. Ni3(PO4)2 obtained by PPM fulfils two main demands as a subtractive primary pigment: ideal yellow shade and uniform spherical micron-sized particles morphology. Moreover, the product shows darker and saturated colouration, especially when taking into account the low particle size distribution which typically reduces colour saturation and increases lightness of the product. The obtained pigment with bright yellow colouration, that represents one of the CMY primaries, has a high potential for application in printing technologies and, after appropriate modification, in electrophoretic displays.

Analytical method using SEM-EDS for metal elements present in particulate matter generated from stainless steel flux-cored arc welding process

Welding fumes (WFs) can cause occupational pneumonoconiosis and other diseases in workers. WFs have complex chemical composition and morphology depending on the welding conditions. The WF surface is a key factor affecting those diseases. The objective of this study was to establish an analytical method focused on characterizing individual WFs and welding slags (WSs) formed during CO2 arc welding processes for knowledge acquisition of risk assessment. Especially, the characterization was focused on the elemental distributions near the surfaces obtained using fluxing agents and size of the WFs. WFs were collected using personal samplers. After welding, WS was also collected. The fluxing elemental distribution (e.g., Bi) near the surfaces WS and WFs were analyzed through scanning electron microscopy and energy-dispersive X-ray spectroscopy. As a result, some of the micron-sized spherical particles (SPs) grew by incorporating nanosized primary particles composed of other metal species. The fluxing agents formed elemental distribution patterns on the SP surface. Bi were dotted in an agglomerate. Mn amount in WS depends on Mn amount in the WFs. These results obtained through the analysis of both the WS and WF surface as well as the particle sizes will facilitate the establishment of exposure assessment models.

A review on multivesicular liposomes for pharmaceutical applications: preparation, characterization, and translational challenges.

Multivesicular liposomes (MVLs) are non-concentric, lipid-based micron-sized spherical particles. The usage of MVL for sustained drug delivery has seen progression over the last decade due to successful clinical and commercial applications. It provides attractive characteristics, such as high encapsulation efficiency, variety of sizes, structural stability, and different choices for the route of administration. Drug molecules are encapsulated in internal aqueous compartments of MVL, separated by lipid bilayer septa to form polyhedral structures. The integrity of these entrapped small molecules, peptides, or proteins is maintained throughout the therapy, thus providing sustained drug release on non-vascular administration. Despite the frequent use of unilamellar liposomes, characterization of MVLs is critical due to different puzzling problems, such as real-time size evaluation, initial burst, and in vivo performance. Moreover, available regulatory guidelines on liposomal drug product development are insufficient to assure ample in vitro-in vivo behavior of MVL. This review hereby highlights the innovations pertaining to development and manufacturing procedures, drug release mechanisms, and characterization techniques. The review also summarizes the applications, challenges, and future perspectives for successfully translating the research concept to a clinically accepted delivery system. Despite the intricacies involved in the development of MVL, establishing steadfast characterization techniques and regulatory paths could pave the way to its extensive clinical use.

Effect of process factors of microwave hydrothermal method on the preparation of micron-sized spherical α-Al2O3 particles

Spherical α-Al2O3 particles with the size of 1–2 μm were obtained by microwave hydrothermal(M-H) method and subsequent microwave calcination. In the synthesis, Al2(SO4)3·18H2O was used as the aluminum sources, and CH4N2O was used as the precipitant. The effects of M-H temperature, heating preservation time and pressure in the reactor on the morphology, phase composition, particle size and surface area of the particles were studied. The results show that amorphous precursors with high sphericity and good dispersion can be rapidly (30 min) produced by M-H method at low temperature (100 °C). Increasing the temperature or extending the holding time will destroy the spherical morphology of the precursor, while transforming its phase from amorphous to γ-AlOOH. Pressure in the reactor does not change the phase composition of the precursor, but affects its dispersion and homogeneity. The precursor retains its spherical morphology after microwave calcination at 1100 °C for 90 min. The resulting powders were hot pressed and sintered at 1650 °C for 30 min to obtain a high-performance ceramic plate with a thermal conductivity of 27.1 W/(m·K) and a Vickers hardness of 21.4 GPa.

Computational analysis of optical trapping of transparent and reflecting micron-sized spherical particles

In the ray-optics regime, we calculated the radial and axial force field on a micron-sized spherical particle in an optical levitation trap. The momentum change in the photon-stream path of tightly focused incident laser beam causes the calculated force field in the optical trap. The computational results for the force field are compared with the literature and a good agreement is obtained. Utilizing the benchmarked force field, the optical trapping dynamics of (i) a transparent spherical particle with continuous-wave 〖TEM〗_00 Gaussian beam and (ii) a reflecting spherical particle with continuous-wave 〖TEM〗_01^* Laguerre-Gaussian beam under various conditions are simulated in Matlab.

Lattice–Boltzmann simulations for analysing the detachment of micron-sized spherical particles from surfaces with large-scale roughness structures

Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice–Boltzmann method. The aim is to investigate the influence of surface roughness on the detachment of fine drug particles from larger carrier particles for transporting fine drug particles in a DPI (dry powder inhaler). Often the carrier surface is modified by mechanical treatments for modifying the surface roughness in order to reduce the adhesion force of drug particles. Therefore, drug particle removal from the carrier surface is equivalent to the detachment of a sphere from a rough plane surface. Here a sphere with a diameter of 5 μm at a particle Reynolds number of 1.0, 3.5 and 10 are considered. The surface roughness is described as regularly spaced semi-cylindrical asperities (with the axes oriented normal to the flow direction) on a smooth surface. The influence of asperity distance and size ratio (i.e. the radius of the semi-cylinder to the particle radius, Rc/Rd) on particle adhesion and detachment are studied. The asperity distance is varied in the range 1.2 <L/Rd < 2 and the semi-cylinder radius between 0.5 <Rc/Rd < 0.75. The required particle resolution and domain size are appropriately selected based on numerical studies, and a parametric analysis is performed to investigate the relationship between the contact distance (i.e. half the distance between the particle contact points on two neighbouring semi-cylinders), the asperity distance, the size ratio, and the height of the particle centroid from the plane wall. The drag, lift and torque acting on the spherical particle are measured for different particle Reynolds numbers, asperity distances and sizes or diameters. The detachment of particles from rough surfaces can occur through lift-off, sliding and rolling, and the corresponding detachment models are constructed for the case of rough surfaces. These studies will be the basis for developing Lagrangian detachment models that eventually should allow the optimisation of dry powder inhaler performance through computational fluid dynamics.

Electrocautery-induced molten metal particle generation from total joint replacements: Morphology and chemistry.

Electrosurgical techniques are used during surgery to cauterize, and their damaging effects have primarily been documented in terms of tissue necrosis, charring, and localized heat accumulation. Metallic implants as well as the surgical blade can experience incidental electrosurgical current arcing that results in the generation and transfer of melted metallic particles. This work examines the composition, particle size distribution, and chemical state of the melted alloy surfaces and particles produced in vitro. Using scanning electron microscopy and energy dispersive spectroscopy, a flash-melting particle generation phenomenon between source 304 SSL blades and polished cobalt-chromium-molybdenum (CoCrMo) and titanium-6-aluminum-4-vandaium (Ti6Al4V) surfaces was documented where 304 SSL mixed heterogeneously with the CoCrMo and Ti6Al4V ejecting "splatter" particles from the cautery site. The spherical micron-sized particles were embedded with sub-micron-sized particles with 42% of the total sample population measuring between 0.25 and 0.35 μm in diameter. CoCrMo-304 SSL particles were principally made of high concentrations of iron, oxygen, and nickel with embedded sub-micron-sized particles containing oxygen, chromium, and cobalt with lower concentrations of iron and molybdenum. Ti6Al4V-304 SSL interactions resulted in similar micron-sized particles made up of high concentrations of iron, nickel, and chromium with embedded sub-micron-sized particles containing titanium, oxygen, and small amounts of aluminum. X-ray photoelectron spectroscopy of damaged CoCrMo surfaces confirmed the presence of chromium (VI) following dry electrocautery contact in coagulation mode. The structural effects of electrocautery-induced damage are becoming visible in retrieval analysis, but the long-term physiological implications during the lifetime of the implant from this damage mode have yet to be defined.

Formation of mesoporous silica particles with hierarchical morphology

The transformation of mesoporous silica morphology from monoliths to spherical particles was investigated at room temperature in Pluronic F127/TEOS system as a function of HCl acid catalyst concentration to understand and control the mechanism. It is shown that the specific surface area and the size of mesoporous spherical silica particles can simply be adjusted by the catalyst concentration without using any additives or post-treatment. Above 3 M acid concentration, novel monodisperse micron sized spherical silica with hierarchical order of two levels was obtained. These silica spheres were formed of densely packed distorted hexagonal platelets of 20–30 nm in diameter. Within these platelets mesoporous channels were oriented along a single direction, however the platelets were randomly oriented in the spherical particles. Controlling the agglomeration of mesoporous silica primary particles by the concentration of the acid catalyst to obtain micron-sized spherical particles is novel. This approach allows the synthesis of particles whose sizes can be controlled in the range of ~1–4 μm and specific surface area in the range of ~200–500 m2/g. The morphology of the particles transforms from spherical shape to mesoporous monoliths at acid concentrations below 1 M due to slow hydrolysis and condensation. These results are important in understanding the role of catalyst concentration on the formation mechanism of different morphologies of mesoporous silica.

Packings of micron-sized spherical particles – Insights from bulk density determination, X-ray microtomography and discrete element simulations

The quantitative description of packing behaviour of particulate systems under consideration of realistic particle size distributions and material properties poses one challenging problem in powder technology, with impacts on a broad range of technological areas. Here we investigate the packing characteristics of micrometer to millimeter-sized, polydisperse spherical particle systems of glass, zirconia and copper by means of experimental measurements of the bulk density, X-ray microtomography (CT) and numerical simulations of the granular packings using a 3d discrete element method (DEM). The applied DEM method takes realistic material properties into account and considers the experimentally obtained particle size distributions as well as attractive inter-particle forces including adhesion (Johnson, Kendall, Roberts (JKR)) and non-bonded van der Waals (vdW) interactions. Good agreement of the packing densities predicted by DEM and observed in the experiments (bulk density determination & CT) is found. Moreover, we show that a simple mathematical expression for the packing fraction as a function of average particle size of the polydisperse powder system describes well our experimental and simulation results for all investigated materials, with only two fitting parameters. From the DEM simulations, the mean (first) coordination number in the respective polydisperse packing is extracted and discussed with respect to the experimentally obtained direct neighborhood detection from X-ray tomography and in context of previous works. The mean coordination number shows a rather broad variance due to the polydispersity of the samples considered. It also shows a remarkable dependency on the definition of particle contact. Therefore, caution is advised when evaluating coordination numbers with this quantity being highly dependent on the instrumental resolution.

Cellulose Acetate and Supercritical Carbon Dioxide: Membranes, Nanoparticles, Microparticles and Nanostructured Filaments.

Cellulose acetate (CA) is a very versatile biocompatible polymer used in various industrial sectors. Therefore, depending on the application, different morphologies are required. Different processes at industrial scale are commonly employed to obtain CA micro or nanoparticles (discontinuous structures) or CA membranes (continuous structures with discontinuities). In this work, two supercritical carbon dioxide (scCO2) based techniques, such as the semi-continuous supercritical antisolvent process (SAS) and the supercritical fluid phase inversion process, in which scCO2 plays the role of antisolvent, were employed. Varying the kind of organic solvent used to prepare the polymeric solution, the polymer concentration, and operating pressure and temperature, it was possible to tune the characteristics of the obtained material. In particular, using acetone as the organic solvent, filaments constituted by nanoparticles, expanded microparticles, nanoparticles with a mean diameter lower than 80 nm, and microporous membranes were obtained, varying the operating conditions. The attainment of spherical micron-sized particles was instead achieved using a mixture of acetone and DMSO as the organic solvent. Therefore, the versatility of the supercritical carbon dioxide-based techniques has been confirmed, and it was possible to obtain, using a single experimental plant, various morphologies of cellulose acetate (with controllable particles’ or pores’ diameters) by varying the operating conditions.

Photophoresis of aerosol particles with nonuniform gas–surface accommodation in the free molecular regime

The problem of calculating the photophoretic force acting on an aerosol particle, with nonuniform distributions of accommodation coefficients over the particle's surface in a rarified equilibrium gas medium in the free molecular regime, is considered within the framework of perturbation theory, using the assumption that the variations of accommodation coefficients are sufficiently small. In general, the expression for the force acting on a convex particle involves four contributions. The energy accommodation coefficient and the radiometric accommodation coefficient for normal momentum are used.The formulae for calculating all four contributions to the photophoretic force are presented for a uniform spherical particle with finite thermal conductivity and a nonuniform axisymmetric distribution of accommodation coefficients over its surface. According to our estimates, the photophoretic force is defined with good accuracy by only two contributions: the “delta-alpha” force and “delta-T” force. The other contributions are small corrections to these two prevailing forces of order 1% or less.The ratio between the “delta-alpha” and “delta-T” forces depends on the particle size, Knudsen number, and the differences in the accommodation coefficients. For micron-sized spherical particles, the photophoretic “delta-alpha” force exceeds the “delta-T” force, and also exceeds gravity if the variation in the radiometric accommodation coefficient over the particle's surface is more than 0.055. Thus, levitation of particles in the Earth's stratosphere is possible due to gravito-photophoresis. For centimetre-sized particles, the “delta-T” force is a few orders of magnitude larger than the “delta-alpha” force due to the influence of IR radiation on the particles' temperature.

Multiple particle tracking in time-lapse synchrotron X-ray images using discriminative appearance and neighbouring topology learning

Recent research has introduced a novel method of directly monitoring the effects of potential therapies for Cystic Fibrosis (CF) airway disease by quantifying mucociliary transit (MCT). In this method, micron-sized spherical particles are deposited into rodent airways, and synchrotron X-ray images are obtained to quantify the motion of the particles. However, the accurate tracking of these particles is challenging due to low contrast, image noise, and the presence of overlapping particles. Therefore, this paper proposes a novel method for detecting and tracking circular particles and measuring their dynamics. Accurate particle detection is achieved by applying a convolutional neural network (CNN). For robust multi-object tracking, this paper proposes a confidence model utilizing appearance and neighbouring topology learned by linear discriminant analysis. We also propose a detection recovery method using multi-frame association to restore the missed particles due to overlapping. The proposed method is tested with several different datasets and shows high levels of detection and tracking accuracy. Finally, by offering visual tracking analyses that display merging and splitting events, the proposed method can provide a better understanding of airway MCT behaviour.

Excellent electrochemical performances of high-voltage LiNi0.5Mn1.5O4 hollow microspheres synthesized by a static co-precipitation method

High-voltage LiNi0.5Mn1.5O4 hollow microspheres are synthesized through a static co-precipitation method. The LiNi0.5Mn1.5O4 microspheres are composed of the spherical micron-sized particles with hollow core, and it has a cubic spinel structure with a space group of Fd3m. Electrochemical results demonstrate that the prepared LiNi0.5Mn1.5O4 exhibit excellent cycle stability and rate capability. The LiNi0.5Mn1.5O4 materials with hollow microsphere structure and excellent electrochemical properties are expected to be used in high energy density lithium-ion batteries.

Effect of Carbon Nanotube Admixture on Anthracene Coking

The anthracene coking process has been investigated in the temperature range of 400–600°C. It has been shown that intermolecular interaction of two anthracene molecules resulting in the elimination of hydrogen and the formation of a C–C bond between the middle rings begins at a temperature of 450°C. Increasing the coking temperature to 500–600°C leads to the formation of poorly crystallized graphite. In the case of pure anthracene, the formation of micron-sized spherical carbon particles occurs. The addition of carbon nanotubes to anthracene leads to the formation of the carbon “coat” covering their surface. The thickness of the carbon “coat” depends on the temperature of coking. An amorphous carbon layer observed on the surface of carbon nanotubes has a thickness of 1–2 nm in the case of coking temperature of 450°C or 10–15 nm in the case of coking at 600°C.

Characteristics of tire wear particles generated in a laboratory simulation of tire/road contact conditions

An experimental study of the non-exhaust emission characteristics of tire wear particulate matter (PM) was performed using a tire wear simulator. Building upon previous studies of PM emissions from non-exhaust sources, the total amount of tire wear particles (TWPs) was measured and their morphological and elemental characteristics were investigated. The peak size of TWPs generated at a constant speed of 80 km/h was around 2 µm. Under harsh friction conditions, the mean diameter increased and the size distribution broadened. In addition, the number concentration of ultrafine particles increased significantly. Based on morphological study, we divided TWPs into five categories: sausage-like particles, micron-sized spherical particles, torn debris, ultrafine particles, and aggregates of ultrafine particles. The results of energy dispersive spectroscopy analysis showed that ultrafine particles from tire tread were composed of carbon, silica, and sulfur.

Comparative DEM-CFD study of binary interaction and acoustic agglomeration of aerosol microparticles at low frequencies

The paper concerns the problem of acoustic agglomeration due to the acoustic wake in diluted aerosols and addresses the development of the time-accurate discrete element method (DEM) simulation technique. The case of weak entrainment of heavier mono-sized microparticles at low-frequency sound waves is considered. The agglomerative motion of two identical micron-sized spherical particles is simulated numerically, and contribution of the particles boundary layer in transition from the diluted to the dense phase is investigated. A comparative study of the DEM approach against more accurate computational fluid dynamics (CFD) computations is performed. The 3D incompressible viscous flow of aerosol medium described by Navier–Stokes equations is considered regarding the fine scale of particles. The numerical results regarding the agglomeration rate, drag coefficient, and perturbation velocities are discussed. Moreover, the correction to the fluid–particle interaction force is proposed to increase the accuracy of the DEM model.