Micron-sized Polystyrene Particles Research Articles

Concentration-polarization electroosmosis for particle fractionation.

Concentration-polarization electroosmosis (CPEO) refers to steady-state electroosmotic flows around charged dielectric micro-particles induced by low-frequency AC electric fields. Recently, these flows were shown to cause repulsion of colloidal particles from the wall of a microfluidic channel when an electric field is applied along the length of the channel. In this work, we exploit this mechanism to demonstrate fractionation of micron-sized polystyrene particles and bacteria in a flow-focusing device. The results are in agreement with predictions of the CPEO theory. The ease of implementation of CPEO-based fractionation in microfluidics makes it an ideal candidate for combining with current techniques commonly used to generate particle lift, such as inertial or viscoelastic focusing, requiring no extra fabrication steps other than inserting two electrodes.

Adsorptive removal of micron-sized polystyrene particles using magnetic iron oxide nanoparticles

Microplastics are able to pass through many filtration systems due to their small sizes, making it difficult to remove them from, for example, water. In this study, we evaluated the ability of using magnetic iron oxide (Fe3O4) nanoparticles to achieve the adsorptive removal of micron-sized polystyrene (microPS) particles. Application of a magnet for 3 min to an aqueous sample of microPS particles mixed with iron oxide nanoparticles for 1 min was able to effectively remove the microPS particles from the water. Transmission electron microscopy images of such samples showed the formation of Fe3O4-PS complexes due to the adsorption of PS particles onto iron oxide nanoparticles. This adsorption followed the pseudo-first order kinetic and Langmuir isotherm model. Hydrophobic interactions were concluded from our experiments to be the main interactions involved in the aggregation of iron oxide with PS particles. Ions present in an environmental freshwater sample inhibited the ability of iron oxide particles to become adsorbed PS particles, but the adsorption performance was improved by increasing the amount of iron oxide particles. The iron oxide particles could be recovered from the Fe3O4-PS complexes by desorption process. Our study showed the potential advantages of iron oxide particles for removing environmental pollutants of microplastics via highly efficient and environmental-friendly procedure.

Particle Size Characterization in Liquid–Solid Dispersion With Aggregates by Broadband Ultrasound Attenuation

Ultrasound attenuation methods for particle size characterization generally assume that the dispersed phases are uniformly dispersed in the continuous phase. However, the aggregation of particles in dispersions affects ultrasound attenuation, which limits the estimation accuracy of the attenuation model. A broadband ultrasound method is proposed, which utilizes a fractal approach to address the acoustic attenuation influence of particle aggregation. First, a chirp-based swept-frequency mode is designed to demodulate the ultrasonic attenuation at a low time cost to ensure the consistency of multifrequency attenuation. Next, considering the effect of particle aggregation on attenuation, the ultrasound attenuation model based on Faran scattering theory is modified by the fractal approach. Then, the inversion of particle size characterization is formulated as an optimization problem of nonlinear and nonconvex functions. An iterative optimization method is proposed to solve the ill-posed inverse problem, in which covariance matrix adaptive evolutionary strategy (CMA-ES) is developed as its inverse solver, and the fractal modified attenuation model is developed as its forward solver. Finally, the experiments were carried out with a mixture of micron-sized polystyrene particles and water. Experimental results indicate that the attenuation predicted by the proposed attenuation model is in good agreement with that measured in liquid–solid dispersion with particle aggregation, and the effectiveness of CMA-ES based on multiple distribution functions is verified for the inversion of particle size characterization.

Interaction of Cyanobacteria with Nanometer and Micron Sized Polystyrene Particles in Marine and Fresh Water

Microplastics and nanoplastics are emerging pollutants, widespread both in marine and in freshwater environments. Cyanobacteria are also ubiquitous in water and play a vital role in natural ecosystems, using photosynthesis to produce oxygen. Using photography, fluorescence microscopy and cryogenic and scanning electron microscopy (cryo-SEM, SEM) we investigated the physicochemical response of one of the most predominant seawater cyanobacteria (Synechococcus elongatus, PCC 7002) and freshwater cyanobacteria (S. elongatus Nageli PCC 7942) when exposed to 10 μm diameter polystyrene (microPS) and 100 nm diameter polystyrene (nanoPS) particles. Marine and freshwater cyanobacteria formed aggregates with the nanoPS, bound together by extracellular polymeric substances (EPS), and these aggregates sedimented. The aggregates were larger, and the sedimentation was more rapid for the marine system. Aggregate morphologies were qualitatively different for the microPS samples, with the bacteria linking up a small number of particles, all held together by EPS. There was no sedimentation in these samples. The cyanobacteria remained alive after exposure to the particles. The particle size- and salt concentration-dependent response of cyanobacteria to these anthropogenic stressors is an important factor to consider for a proper understanding of the fate of the particles as well as the bacteria.

Polystyrene microplastics impaired the feeding and swimming behavior of mysid shrimp Neomysis japonica.

Growing evidences revealed the deleterious impacts of microplastics (MPs) on marine organisms. However, the effects of MPs on the movement behavior of marine crustacean is poorly understood. Therefore, this study aims to evaluate the physiological and behavioral responses of mysid shrimp (Neomysis japonica) larvae to polystyrene (PS) and carboxylated polystyrene (PS-COOH). PS-COOH presented a greater physiological toxicity to shrimp larvae compared to PS, causing significant lethal and growth inhibition effect, owing to bioaccumulation of MPs inside stomach. Both two MPs decreased the feeding efficiency of larvae, showing weakened predation competence. Moreover, reduced hunting and/or explorative ability of shrimps caused by MPs was also identified, which was evidenced by an overall decrease in swimming activity, range and frequency after exposure. Our study firstly highlighted that micron-sized polystyrene particles had the negative effects on the movement behavior of mysid shrimp larvae, thus posing potential hazard to population dynamics and ecological function of marine crustacean.

On-Flow Immobilization of Polystyrene Microspheres on β-Cyclodextrin-Patterned Silica Surfaces through Supramolecular Host-Guest Interactions.

Species-specific isolation of microsized entities such as microplastics and resistant bacteria from waste streams is becoming a growing environmental challenge. By studying the on-flow immobilization of micron-sized polystyrene particles onto functionalized silica surfaces, we ascertain if supramolecular host–guest chemistry in aqueous solutions can provide an alternative technology for water purification. Polystyrene particles were modified with different degrees of adamantane (guest) molecules, and silica surfaces were patterned with β-cyclodextrin (β-CD, host) through microcontact printing (μCP). The latter was exposed to solutions of these particles flowing at different speeds, allowing us to study the effect of flow rate and multivalency on particle binding to the surface. The obtained binding profile was correlated with Comsol simulations. We also observed that particle binding is directly aligned with particle’s ability to form host–guest interactions with the β-CD-patterned surface, as particle binding to the functionalized glass surface increased with higher adamantane load on the polystyrene particle surface. Because of the noncovalent character of these interactions, immobilization is reversible and modified β-CD surfaces can be recycled, which provides a positive outlook for their incorporation in water purification systems.

Characteristics of non-spherical fluidized media in a fluidized bed–membrane reactor: Effect of particle sphericity on critical flux

Abstract The fluidization of millimeter-sized media to mitigate the membrane fouling by micron-sized particles has received increasing attention, but a question that remained unanswered is the effect of the sphericity of the fluidized media on the energy-efficiency of fouling mitigation, which motivated the current study. Four millimeter-sized fluidized media types, of which three had similar equivalent volume diameters, were investigated, with micron-sized polystyrene particles serving as the particulate foulant. The direct observation through the membrane (DOTM) technique was used to determine the local critical flux, while a high-speed video camera was used to capture the local fluidization hydrodynamics (namely, particle velocity, particle rotation velocity, particle contact area and particle momentum). The results indicate that (i) although smaller media mitigated fouling better among higher-sphericity media, the smallest, low-sphericity media here performed similarly or worse; (ii) lower-sphericity media gave lower particle rotation, greater contact area with the membrane, and lower particle momentum; (iii) in contrast to higher-sphericity media, the extent of local fouling mitigation decreased as the particle velocities increased and the local critical flux was not the most strongly correlated with particle momentum; (iv) lower-sphericity media generally gave lower overall critical flux for the same hydrodynamic characteristic; (v) particle sphericity is a negligible factor in the energy-efficiency of fouling mitigation by similar-sized fluidized media, but, between low-sphericity media, the larger media was more energy-efficient. The findings here highlight the non-negligible influence of the particle sphericity of the fluidized media, and are expected to be valuable in the optimization of the properties of the fluidized media towards more energy-efficient membrane fouling mitigation.

Metal scaffolds for acoustic trapping of polystyrene particles in water suspensions

The concept of ultrasonic 3D caging is based in wells designed to host three orthogonal half-wave acoustic resonances defined by its three dimensions generating a single-pressure-node in the center where particles collect to aggregate. A replacement of the planar shapes in these cavities by curved walls introduce changes in the pressure patterns, generating different effects on the particles exposed to the acoustic field. Here we present an experimental study of the acoustic behavior of aqueous suspensions of micron-sized polystyrene particles (Cv~1%) exposed to ultrasounds at a frequency f~1MHz in a metal scaffold made up of stainless steel wires crossed-linked orthogonally to form a mesh with a light of 1mm (something larger than λ/2). Once applied the acoustic field, the particles are rapidly attracted by the rods of the mesh distances much larger than their diameter (Φp = 6µm), where are trapped and remain adhered to the scaffold during the acoustic actuation and even later, providing stable aggregate...

Effect of bubble characteristics on critical flux in the microfiltration of particulate foulants

Fouling control by bubbling is widely implemented in membrane bioreactors (MBRs), but a mechanistic understanding of the relationship between the bubble characteristics and critical flux is missing. This study is targeted at bridging the gap. A microfiltration setup employing bubbling as a means of fouling mitigation was set up. The direct observation through the membrane (DOTM) technique was used to determine the critical flux of a feed containing micron-sized polystyrene particles, while a high-speed video camera was used to characterize the bubble behavior. The results indicate that (i) the local critical flux (Jc,local) values increased with height along the membrane and with gas flow rate, but was relatively invariant with liquid flow rate; (ii) with respect to height, the mean bubble velocity and mean bubble area per bubble increased, while the number of bubbles per unit membrane area decreased; (iii) bubble momentum and mean area per bubble had the most positive correlation with Jc,local,; and (iv) the overall critical flux (Jc,overall, which is the average of the local critical fluxes) increased linearly with respect to the ratio of gas to total flow rates, and steeply then more gradually with respect to power required. Finally, a comparison between the two two-phase flow systems employed for fouling mitigation (namely, bubbling and fluidized granular activated carbon (GAC)) was carried out.

Initial stage sintering of polymer particles – Experiments and modelling of size-, temperature- and time-dependent contacts

The early-stage sintering of thin layers of micron-sized polystyrene (PS) particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C), is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (r crit ~ 1 μm) below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than r crit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.

Interactions of Colloidal Particles and Droplets with Water-Oil Interfaces Measured by Total Internal Reflection Microscopy.

Total internal reflection microscopy (TIRM) is a well-known technique to measure weak forces between colloidal particles suspended in a liquid and a solid surface by using evanescent light scattering. In contrast to typical TIRM experiments, which are carried out at liquid-solid interfaces, here we extend this method to liquid-liquid interfaces. Exemplarily, we demonstrate this concept by investigating the interactions of micrometer-sized polystyrene particles and oil droplets near a flat water-oil interface for different concentrations of added salt and ionic surfactant (SDS). We find that the interaction is well described by the superposition of van der Waals and double layer forces. Interestingly, the interaction potentials are, within the SDS concentration range studied here, rather independent of the surfactant concentration, which suggests a delicate counter play of different interactions at the oil-water interface and provides interesting insights into the mechanisms relevant for the stability of emulsions.

Aqueous Foams Stabilized with Several Tens of Micrometer-sized Polymer Particles: Effects of Surface Hydrophilic–Hydrophobic Balance on Foamability and Foam Stability

40 micrometer-sized polystyrene particles coated by polymer shells with various hydrophilic–hydrophobic balances were synthesized by seeded dispersion polymerization and used as a foam stabilizer. ...

Templated Electrochemical Fabrication of Hollow Molybdenum Sulfide Microstructures and Nanostructures with Catalytic Properties for Hydrogen Production

MoS2 is known to possess promising catalytic properties toward the hydrogen evolution reaction (HER). However, current synthetic procedures of nanostructured MoS2-based materials with high-density active edge sites are tedious and require high temperatures, costly instrumentation, and often rather toxic solvents. The electrochemical deposition (ED) of molybdenum sulfide films from solution-based precursors represents a more-viable approach, which also enables the fabrication of micronanostructured films through solid template assistance. Here, we investigate the catalytic properties of different molybdenum sulfide films prepared via electrodeposition from aqueous and organic solution of the tetrathiomolybdate precursor. A template-assisted deposition was employed to prepare nanostructured porous films and hollow spherical microstructures, using submicrometer- and micrometer-sized polystyrene particles, respectively. All fabricated structures demonstrated catalytic performances with recorded overpotentials...

Fabrication of cage-like particles via unstable seeded dispersion polymerization: A new concept in the polymerization-induced self-assembly

ABSTRACTThe formation mechanism of hollow micron-sized polystyrene (PS) particles having numerous dents on the surface, so-called cage-like particles, obtained from seeded dispersion polymerization (SDP) of 2-ethylhexyl methacrylate (EHMA) with low molecular weight (MW) PS particles stabilized by poly(vinyl alcohol) (PVA) in the presence of hexadecane droplets was investigated. It was found that association of poly(2-ethylhexyl methacrylate) (PEHMA)/hexadecane phases which occurs due to the instability of the obtained composite particles followed by a diffusion of PS ellipsoidal particles into each other is the main process responsible for the production of such unique morphology. Time course monitoring of the SDP showed that diffusion of hexadecane and/or PS and/or PEHMA phase into PS/PEHMA/hexadecane composite particles through PS shell which happens based on Ostwald ripening is the main phenomenon which results in the formation of the dents on the surface of final particles. Moreover, the experimental results revealed that in this reaction system, the polymerization develops in a faster manner rather than the SDP employing seed particles having higher MWs. Furthermore, it was observed that particles with different surface morphologies can be produced by using different hydrocarbons. The elimination of small particles which are produced in addition to the cage-like ones via decreasing the concentration of the stabilizer was another interesting finding of this research. The acquired results showed that unstable SDP is expected to be a new concept in polymerization-induced self-assembly (PISA) which employs instability of a dispersion for self-assembly of polymeric particles, and therefore, production of polymeric unique objects.

Fabrication of unique cage-like polystyrene particles having lots of dents on the surface via unstable seeded dispersion polymerization

Unique, hollow, micron-sized polystyrene (PS) particles having lots of dents on the surface, so-called cage-like particles, were obtained by seeded dispersion polymerization of 2-ethylhexyl methacrylate with PS particles stabilized by poly(vinyl alcohol) in the presence of hexadecane droplets. The effect of main parameters (e.g., average molecular weight of seed particles, and stabilizer and initiator type) responsible for acquiring such particles was investigated. The experimental results revealed that cage-like shape is produced because of particle coagulation during polymerization. Moreover, it was observed that changing stabilizer and initiator type, and employing seed particles with low average molecular weight, which all of them contribute in coagulation of particles, result in the fabrication of cage-like shape.

Encapsulation of multiple large spherical silica nanoparticles in hollow spherical silica shells

Here we present the results of a stepwise synthesis of multiple large silica nanoparticles encapsulated in hollow, micron sized silica shells for future display applications. In the first step, 200-nm diameter silica nanoparticles were modified with 3-(trimethoxysilyl) propylmethacrylate (MPS) coupling agent. These nanoparticles were then embedded in micron-sized polystyrene particles synthesized through dispersion polymerization. To form silica shells on the polymer composite particles, tetraethylorthosilicate (TEOS) was added with cetyltrimethylammonium bromide (CTAB) surfactant. These three steps resulted in the formation of silica shell-covered solid polystyrene particles, each containing multiple silica nanoparticles. In the last step, polystyrene content was removed via calcination to achieve a multiple-silica-core-in-hollow-silica-shell composite structure. Dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM) confirmed the core/shell morphology of the composite structure.

Laboratory Scale Systems for the Plasma Treatment and Coating of Particles

We here report two reactor designs for the efficient and uniform plasma treatment of particles: 1) retrofitting an existing plasma reactor with a loudspeaker for agitation (LPR) and 2) adapting a rotary evaporator by adding custom electrodes (RPR). Both designs offer versatility, low building cost, convenience of use, flexibility, facile vacuum sealing and achieve effective agitation and coating of particles. The latter was exemplified by plasma polymerizing perfluorooctane (PFO) onto micron-sized polystyrene particles. The coated particles were evaluated by XPS, ToF-SIMS and water contact angle measurement to compare and contrast the resulting PFO plasma coatings (PFOpp) between the two reactor designs. The highest fluorine to carbon ratio (1.85, Teflon = 2) was achieved at a pressure of 100 mTorr in the RPR.

Morphing Metal–Polymer Janus Particles

The direct deformation and shape recovery of micron-sized polystyrene particles via nanoimprint lithography is reported. The recovery of the programmed PS particles can be utilized to create a range of smart Janus particles with contrasting properties in conductivity and topography, by use of metal-layer constrained recovery.

Micron-sized polystyrene particles by surfactant-free emulsion polymerization in air: Synthesis and mechanism

In this study, a novel, robust approach is presented to produce micrometer-scale-sized polystyrene particles with narrow size distribution in highly concentrated latexes. The approach could be easily employed by those not skilled in the art to produce large quantities of polymer particles for research applications. A recent hypothesis is corroborated for the mechanism of particle growth in surfactant-free emulsion polymerization, based on heterocoagulation of precursor particles onto mature ones.

Synthesis of Poly(3,4-ethylenedioxythiophene)–Palladium Nanocomposite-coated Polymer Particles by Chemical Oxidative Seeded Dispersion Polymerization

Abstract Poly(3,4-ethylenedioxythiophene)–palladium nanocomposite was deposited in situ from water-based solution onto micrometer-sized polystyrene particles. The resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, and chemical compositions.