Monodisperse Polystyrene Particles Research Articles

Particle removal from solid surfaces via an impinging gas jet pulse: Comparison between experimental and CFD-DEM modeling results

Computational and experimental studies are performed to investigate the influence of a gas jet pulse impinging perpendicularly onto a flat solid surface seeded with a monolayer of spherical particles. A numerical resuspension model is derived to predict particle release into the gas phase during jet impingement. To this end, discrete particles are immersed in a continuous gas phase modeled via Large Eddy Simulation to capture the effect of jet turbulence on the particle detachment process. Two-way coupling between particulate and gas phase is established via a near-wall particle drag model and a lift model. Direct particle–wall interactions are captured with adhesion, rolling friction and sliding friction models. To validate the overall modeling approach, numerical results are compared with resuspension experiments for monodisperse polystyrene particles placed on a glass slide. Simulations show that the particles preferentially mobilize by rolling, followed to a limited extend by lift off from the solid surface driven by aerodynamic forces and particle–particle collisions. Resuspension occurs in the first instants after jet impingement. Computational and experimental results for removal efficiency Γ are in good agreement in terms of the location of their r50 parameter, i.e., the radial position where 50% of the particles have been removed by the jet; both results show a linear dependence between the r50 value and the jet Reynolds number of the impinging jet. However, experimental Γ(r) curves generally have a smooth sigmoidal shape whereas numerical results predict a sharp transition. Some model shortcomings are identified which lead to an underprediction of particle lift-off and which explain the observed differences. Furthermore, the experimental Γ curves nearly collapse onto each other when plotted over the predicted local wall-shear stress.

Enhancing particle size characterization performance through proficiency testing program: result and insights from inter-laboratory comparison

The proficiency testing (PT) for particle size characterization by inter-laboratory comparison was organized by the dimensional metrology department of the National Institute of Metrology Thailand (NIMT). This program aims to enhance and to expand the efficiency and capability of testing laboratories in the field of particle size characterization using various techniques, including atomic force microscope (AFM), transmission electron microscope (TEM), scanning electron microscope (SEM), and dynamic light scattering (DLS). The measurement range covers nanometer to micrometer scale. These instruments are importance for research and development especially to nanotechnology related industries. The PT program was conducted in 2022 where five artifacts were used: monodispersed gold nanoparticle (diameter 20 nm), monodispersed polystyrene particle (diameter 100 nm, 500 nm, and 1500 nm) and monodispersed silica oxide particle (diameter 100 nm). The monodispersed polystyrene particles, diameter 100 nm and 1500 nm are certified reference materials (CRMs). These two artefacts were used as the reference to evaluate accuracy of participant laboratories. The other 3 artefacts are reference material under development. Hence, the assigned values were calculated from consensus among all participants. To evaluate the performance of participant laboratories, En values and z-scores were calculated for each artefact and each measuring technique. The assessment of participant performance through performance scores allows the participant to determine how accurate and how appropriate the measurement results and measurement uncertainties evaluation are. From the results, unsatisfied results can be categorized into three scenarios. First, the measurement uncertainties were not appropriately evaluated. Secondly, measurands obtained from all measuring techniques are not the same. Lastly, the magnification used in microscopy techniques plays a crucial role to resolution and accuracy of size determination.

Electrical and Thermal Properties of Surface-Modified Copper Nanowire/Polystyrene Nanocomposites through Latex Blending.

The incorporation of conductive nanofillers into an insulating polymer matrix commonly leads to nanocomposites with good electrical, thermal, and mechanical properties. In this study, copper nanowires (CuNWs) and polystyrene (PS) microspheres were synthesized along with the fabrication of CuNW/PS polymer nanocomposites. The electrical, thermal, mechanical, rheological, and morphological properties of the CuNW/PS nanocomposites were examined. The CuNWs were homogeneously dispersed in the PS matrix through latex blending. For the CuNW/PS nanocomposites, the storage modulus was higher than the loss modulus at all frequencies, indicating their elastic-dominant behavior. The electrical and thermal conductivities of the nanocomposites increased with an increasing CuNW content. Using a mixed dispersion of two monodisperse PS particles of 500 nm and 5 μm in diameter resulted in the highest electrical conductivity (ca. 10° S/m for 30 wt % nanofillers) among the nanocomposites. In addition, the introduction of silica- and polydopamine-coated CuNWs as nanofillers imparted insulation properties to the nanocomposites, with electrical conductivities to 10-10-10-8 S/m. When using 500 nm PS particles, the thermal conductivity of the surface-modified CuNW/PS nanocomposite at 30 wt % of CuNW was enhanced to 0.22 W/m·K compared to 0.17 W/m·K for its unmodified counterpart. We have achieved multiple innovative approaches, including the use of mixed particle sizes, surface modification of CuNW, and the exploration of elastic-dominant behavior. This enhanced thermal conductivity, coupled with the attainment of insulation properties, presents a distinct advantage for thermal interface material (TIM) applications.

Effect of Fabric Substrate and Introduction of Silk Fibroin on the Structural Color of Photonic Crystals.

Monodispersed polystyrene (PS) particles were prepared and deposited onto various kinds of textile fabrics using a gravity sedimentation method. The monodispersed PS particles were self-assembled on fabrics to form a photonic crystal, which has an iridescent structural color. The structural color of fabrics was determined by the bandgaps of photonic crystals. Moreover, the effect of the fabric substrate, including the raw materials, base color, and fabric weave, etc., on the structural color of the photonic crystals was studied. Scanning electron microscopy and UV-vis spectrometry were adopted to characterize the structure and optical performance of photonic crystals. The results indicate that the silk fabric with a black base color and satin weave contribute to a bright and pure textile structural color. In order to solve the problem of low color fastness of the structural color on the fabric surface, silk fibroin (SF) was introduced to the PS microsphere solution. Results show that the addition of SF slightly affects the brightness of the structural color, while it has a certain reinforcing effect on the structural color fastness to rubbing and washing.

Hollow particles synthesized by water-soluble and oil-soluble initiators and the mechanism of incorporating an oil-soluble initiator

Monodisperse polystyrene particles were first synthesized by soap-free emulsion polymerization to enhance the monodispersity of hollow particles. Thereafter, the polystyrene particles were immersed in an aqueous solution of 2,2′-azobis(2-methylbutyronitrile) (V-59) to allow the particles to absorb V-59 while maintaining their monodispersity. Thermogravimetric measurements using p-styrenesulfonic acid sodium salt revealed that this absorption occurred not through electrostatic interactions but through hydrophobic ones. Subsequently, the TEOS sol-gel reaction was performed on the polystyrene particle surface to create a silica shell with the help of N-vinyl acetoamide. Finally, the synthesized particles were heated to induce the decomposition reaction of V-59 (which emits nitrogen gas) in the particles, thereby creating a hollow structure as the gas stayed in the particle. These procedures enabled the synthesis of monodisperse hollow particles.

Correction to: Development of Monodispersed Polystyrene Particles as Thailand Reference Materials (TRM)

Correction to: Development of Monodispersed Polystyrene Particles as Thailand Reference Materials (TRM)

Development of Monodispersed Polystyrene Particles as Thailand Reference Materials (TRM)

The purpose of this study was to develop monodispersed polystyrene particles as certified reference materials in accordance with the ISO 17034: 2016 and the ISO Guide 35. It can play a significant role especially during the COVID-19 pandemic since several covering items such as filtering facepiece respirators or medical masks must be investigated for the quality of operation by various sizes of polystyrene. The polystyrene particles were prepared in-house by National Nanotechnology Center (NANOTEC) using polymerization of styrene. Each batch was preliminary check for distribution, aggregation and averaged size by using dynamic light scattering. Then polystyrene particles were prepared to 1% solid suspension in deionized water for homogeneity testing, stability assessment and characterization using transmission electron microscope with ImageJ software. The 100 nm polystyrene as an example has been successfully synthesized fulfilled the criteria of size deviation from nominal value less than ± 10 nm and polydispersity index less than 0.05. Then, the particle size of polystyrene was statistically analyzed for screening test with the results of the coefficient of variation less than 10%. Stability assessment consisting of short-term stability testing with three different temperatures and long-term stability testing within 6 months observed was carried out. The results of short-term and long-term stability were presented within the maximum acceptable. The homogeneity tests for within bottle standard deviation and between bottle standard deviation were performed with randomly sampling. The results of homogeneity tests satisfied the criteria and therefore assigned the value as the certify value. Consequently, the certify value of 105.5 ± 4.6 nm of monodispersed polystyrene particles has been successfully developed as Thailand reference materials which were similar level of quality and accuracy to the standard commercial products.

Fabrication and Characterization of Inverse-Opal Titania Films for Enhancement of Photocatalytic Activity

Novel materials with a periodic structure have recently been intensively studied for various photonic and photocatalytic applications due to an efficient light harvesting ability. Here, inverse opal titania (IOT) has been investigated for possible enhancement of photocatalytic activity. The IOT films were prepared on a glass support from silica and polystyrene (PS) opals by sandwich-vacuum-assisted infiltration and co-assembly methods, respectively. The reference sample was prepared by the same method (the latter) but with PS particles of different sizes, and thus without photonic feature. The modification of preparation conditions was performed to prepare the films with a high quality and different photonic properties, i.e., photonic bandgap (PBG) and slow photons’ wavelengths. The morphology and optical properties were characterized by scanning electron microscopy (SEM) and UV/vis spectroscopy, respectively. The photocatalytic activity was evaluated (also in dependence on the irradiation angle) for oxidative decomposition of acetaldehyde gas under irradiation with blue LED by measuring the rate of evolved carbon dioxide (CO2). It has been found that PBG wavelength depends on the size of particles forming opal, the void diameter of IOT, and irradiation angle, as expected from Bragg’s law. The highest activity (more than two-fold enhancement in the comparison to the reference) has been achieved for the IOT sample of 226-nm void diameter and PBG wavelengths at 403 nm, prepared from almost monodisperse PS particles of 252-nm diameter. Interestingly, significant decrease in activity (five times lower than reference) has been obtained for the IOT sample of also high quality but with 195-nm voids, and thus PBG at 375 nm (prohibited light). Accordingly, it has been proposed that the perfect tunning of photonic properties (here the blue-edge slow-photon effect) with bandgap energy of photocatalyst (e.g., absorption of anatase) results in the improved photocatalytic performance.

Design and experimental investigation of a novel spiral microfluidic chip to separate wide size range of micro-particles aimed at cell separation.

Isolation of microparticles and biological cells on microfluidic chips has received considerable attention due to their applications in numerous areas such as medical and engineering fields. Microparticles separation is of great importance in bioassays due to the need for smaller sample and device size and lower manufacturing costs. In this study, we first explain the concepts of separation and microfluidic science along with their applications in the medical sciences, and then, a conceptual design of a novel inertial microfluidic system is proposed and analyzed. The PDMS spiral microfluidic device was fabricated, and its effects on the separation of particles with sizes similar to biological particles were experimentally analyzed. This separation technique can be used to separate cancer cells from the normal ones in the blood samples. These components required for testing were selected, assembled, and finally, a very affordable microfluidic kit was provided. Different experiments were designed, and the results were analyzed using appropriate software and methods. Separator system tests with polydisperse hollow glass particles (diameter 2-20 µm), and monodisperse Polystyrene particles (diameter 5 & 15 µm), and the results exhibit an acceptable chip performance with 86% of efficiency for both monodisperse particles and polydisperse particles. The microchannel collects particles with an average diameter of 15.8, 9.4, and 5.9 μm at the proposed reservoirs. This chip can be integrated into a more extensive point-of-care diagnostic system to test blood samples.

Adjustable polystyrene nanoparticle templates for the production of mesoporous foams and ZnO inverse opals

The manifold applications of porous materials, such as in storage, separation, and catalysis, have led to an enormous interest in their cost-efficient preparation. A promising strategy to obtain porous materials with adjustable pore size and morphology is to use templates exhibiting the appropriate nanostructure. In this study, close-packed polystyrene (PS) nanoparticles, synthesized by emulsion polymerization, were used to produce porous PS and ZnO inverse opals. The size and distribution of the polystyrene nanoparticles, characterized by dynamic light scattering (DLS), small-angle neutron scattering (SANS), and scanning electron microscopy (SEM), were controlled via the concentration of sodium dodecyl sulfate (SDS). Systematic measurements of the water/styrene-interfacial tension show that the critical micelle concentration (CMC) of the ternary water–styrene–SDS system, which determines whether monodisperse or polydisperse PS particles are obtained, is considerably lower than that of the binary water–SDS system. The assemblies of close-packed PS nanoparticles obtained via drying were then studied by small-angle X-ray scattering (SAXS) and SEM. Both techniques prove that PS nanoparticles synthesized above the CMC result in a significantly unordered but denser packing of the particles. The polystyrene particles were subsequently used to produce porous polystyrene and ZnO inverse opals. While the former consists of micrometer-sized spherical pores surrounded by extended open-cellular regions of mesopores (Rpore ≈ 25 nm), the latter are made of ZnO-nanoparticles forming a structure of well-aligned interconnected pores.Graphical abstract

Monodisperse polystyrene microspheres containing quaternary ammonium salt groups by two-stage dispersion polymerization: effect of reaction parameters on particle size and size distribution

A facile approach to prepare monodisperse polystyrene (PS) particles containing quaternary ammonium salts with long alkyl chain was reported. The PS particles containing quaternary ammonium salts are prepared by two-stage dispersion polymerization in ethanol/water (80/20 w/w) mixture with polyvinylpyrrolidone (PVP) as a steric stabilizer and fatty alcohol polyoxyethylene ether (AEO-9) as a co-stabilizer. Polymerizations are conducted using N′-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide (QDMDB) as a comonomer added in the second stage. We identify reaction conditions where one can obtain the functional polystyrene microspheres with a size distribution less than 3%. The influence of the initiator concentration, the styrene monomer concentration, the stabilizer concentration, and QDMDB comonomer concentration on the average particle size and the efficient of variation are investigated comprehensively. The novel particles are examined using scanning electron microscopy (SEM), gel permeation chromatography (GPC), zeta potential, and nuclear magnetic resonance (1H NMR). QDMDB comonomer not only functionalized the polystyrene particles but also proved to be effective in controlling the particle size and size distribution. According to these results, we show that two-stage dispersion polymerization is an effective pathway for the structure design of the functional microspheres.

Real-Time Detection of Gas and Chemical Vapor Flows by Silica Inverse-Opals

A silica inverse-opal is fabricated through the co-assembly of silica precursors and mono-dispersed polystyrene particles with a diameter of 287 nm. Then, the polymer face-centered-cubic structure was removed by calcination procedure to obtain a silica inverse-opal offering sharp stop-band around 445 nm. Sensitivity of the sample for static refractive index detection was acquired by its immersion in different water/ethanol mixtures. Furthermore, an experimental setup was designed to evaluate the dynamic response of sample for diverse gas and water vapor flows. Fabricated sample is capable of offering high sensitivities as high as 415 nm/RIU and reversible responsivities as fast as 120 ms. Also, it has been shown that despite reduced sensitivity in dynamic measurements, fabricated silica inverse-opal is able to detect slight refractive index variations and thus very small alterations in gas and vapor flows. According to which, the proposed structure may find numerous applications in remote and non-destructive gas and vapor flow sensing.

A Facile Method for Preparation of Polymer Particles Having a “Cylindrical” Shape

AbstractA facile and novel approach to prepare monodisperse polystyrene (PS) particles having a “cylindrical” shape was discovered. Spherical PS particles prepared by dispersion polymerization were stirred in a polyvinylpyrrolidone (PVP) aqueous solution for several hours using a magnetic stirrer at room temperature. In the presence of PVP, the spherical PS particles deformed into cylindrical shapes following stirring; however, the particles did not deform in the absence of PVP. The deformation rate of the particles was affected by the molecular weight of the dissolved PVP. This stirring method is not only highly efficient and high yielding, but also applicable to other materials such as polymethyl methacrylate. Moreover, the cylindrical particles were successfully applied as particulate surfactants in a Pickering emulsion system, which exhibited excellent stability in comparison to a system using spherical particles as a surfactant. In the first case, the emulsion was left standing for more than 4 months.

A Facile Method for Preparation of Polymer Particles Having a "Cylindrical" Shape.

A facile and novel approach to prepare monodisperse polystyrene (PS) particles having a "cylindrical" shape was discovered. Spherical PS particles prepared by dispersion polymerization were stirred in a polyvinylpyrrolidone (PVP) aqueous solution for several hours using a magnetic stirrer at room temperature. In the presence of PVP, the spherical PS particles deformed into cylindrical shapes following stirring; however, the particles did not deform in the absence of PVP. The deformation rate of the particles was affected by the molecular weight of the dissolved PVP. This stirring method is not only highly efficient and high yielding, but also applicable to other materials such as polymethyl methacrylate. Moreover, the cylindrical particles were successfully applied as particulate surfactants in a Pickering emulsion system, which exhibited excellent stability in comparison to a system using spherical particles as a surfactant. In the first case, the emulsion was left standing for more than 4 months.

Formation of Liquid Marbles Using pH-Responsive Particles: Rolling vs Electrostatic Methods.

Aqueous dispersions of micrometer-sized, monodisperse polystyrene (PS) particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) colloidal stabilizer on their surfaces were dried under ambient conditions at pH 3.0 and 10.0. The resulting dried cake-like particulate materials were ground into powders and used as a stabilizer to fabricate liquid marbles (LMs) by rolling and electrostatic methods. The powder obtained from pH 3.0 aqueous dispersion consisted of polydisperse irregular-shaped colloidal crystal grains of densely packed colloids which had hydrophilic character. On the other hand, the powder obtained from pH 10.0 aqueous dispersion consisted of amorphous and disordered colloidal aggregate grains with random sizes and shapes, which had hydrophobic character. Reflecting the hydrophilic-hydrophobic balance of the dried PDEA-PS particle powders, stable LMs were fabricated with distilled water droplets by rolling on the powders prepared from pH 10.0, but the water droplets were adsorbed into the powders prepared from pH 3.0. In the electrostatic method, where an electric field assists transport of powders to a droplet surface, the PDEA-PS powders prepared from pH 3.0 jumped to an earthed pendant distilled water droplet to form a droplet of aqueous dispersion. Conversely the larger powder aggregates prepared from pH 10.0 did not jump due to cohesion between the hydrophobic PDEA chains on the PS particles, resulting in no LM formation.

Pulse Size Distributions in Tunable Resistive Pulse Sensing.

The use of resistive pulse sensors for submicron particle size measurements relies on a clear understanding of pulse size distributions. Here, broadening of such distributions has been studied and explained using conical pores and nominally monodisperse polystyrene particles 200-800 nm in diameter. The use of tunable resistive pulse sensing (TRPS) enabled continuous in situ control of the pore size during experiments. Pulse size distributions became broader when the pore size was increased and featured two distinct peaks. Similar distributions were generated using finite element simulations, which suggested that relatively large pulses are produced by particles with trajectories passing near to the edge of the pore. Other experiments determined that pulse size distributions are independent of applied voltage but broaden with increasing pressure applied across the membrane. The applied pressure could also be reversed in response to a pulse, which enabled repeated measurement of individual particles moving back and forth through the pore. Hydrodynamic and electrophoretic focusing each appear to affect particle trajectories under certain conditions.

Nanoparticle tracking analysis of particle size and concentration detection in suspensions of polymer and protein samples: Influence of experimental and data evaluation parameters

Nanoparticle Tracking Analysis (NTA) is an emerging technique for detecting simultaneously sub-micron particle size distributions and particle concentrations of a sample. This study deals with the performance evaluation for the detection and characterisation of various particles by NTA. Our investigation focusses on the NTA measurement parameter set-ups, as will be shown in this study, are very crucial parameters to correctly analyse and interpret the data. In order to achieve this, we used (i) polystyrene standard particles as well as (ii) protein particles.We show the highly precise and reproducible detection of particle size and concentration in monodisperse polystyrene particle systems, under specified and constant parameter settings. On the other hand, our results exemplify potential risks and errors while setting inadequate parameters with regards to the results and thus interpretation thereof. In particular changes of the parameters, camera level (CL) and detection threshold (DT), led to significant changes in the determined particle concentration. We propose defined and specified “optimal” camera levels for monodisperse particle suspension characterisations in the size range of 20–1000nm. We illustrate that the results of polydisperse polystyrene standard particle solution measurements, highly depend on the used parameter settings, which are rarely published with the data. Changes in these settings led to the “appearance” or “disappearance” of particle populations (”peaks”) for polydisperse systems. Thus, a correct evaluation of the particle size populations in the sample becomes very challenging.For the use of NTA in biopharmaceutical analysis, proteinaceous samples were investigated. We analysed protein particle suspensions and compared unstressed and stressed (formation of aggregates) protein samples similar to polystyrene particle analysis. We also studied these samples in two different measuring modes (general capture mode and live monitoring mode) that the commercially available analysis software is offering. Our results stated the live monitoring mode as more suitable for protein samples, as the results were more reproducible and less operator-depending.In conclusion, NTA is a potential technique and unique in quantitative evaluation of particle suspensions in the subvisible size range, especially for monodisperse suspensions. We strongly urge on not underestimating the influence of the measuring parameters on the obtained results, which should be presented with the data in order to better judge and interpret the NTA results.

Effect of spacer and crossflow velocity on the critical flux of bidisperse suspensions in microfiltration

Crossflow microfiltration is a popular application spanning various industries. Although the impacts on fouling of feed bidispersity, crossflow velocity (CFV) and spacer, all of which are present in practical operations, are known separately, the understanding of the interplay of these three factors on fouling is lacking. Accordingly, this study used the Direct Observation Through the Membrane (DOTM) technique to characterize the critical flux of monodisperse and bidisperse polystyrene particles in both the absence and presence of a spacer over a range of CFV values. The results indicate that (i) the combined effects of both bidispersity (dp=3µm and 10µm) and spacer gave the highest Jcrit values for the smaller particles throughout the CFV range investigated; (ii) bidispersity was more effective in enhancing Jcrit at a lower CFV, while the presence of a spacer was more effective at a higher CFV; (iii) a higher CFV diminished the enhancement induced by bidispersity more than that by the spacer; and (iv) comparisons between models and experimental data reveal that shear-induced diffusion models based on monodisperse particles are deficient for bidisperse mixtures, because they cannot allow for particle size segregation effects that occur in flowing mixed systems.

Encapsulation of Polymer Colloids in a Sol-Gel Matrix. Direct-Writing of Coassembling Organic-Inorganic Hybrid Photonic Crystals.

The spontaneous self-assembly of polymer colloids into ordered arrangements provides a facile strategy for the creation of photonic crystals. However, these structures often suffer from defects and insufficient cohesion, which result in flaking and delamination from the substrate. A coassembly process has been developed for convective assembly, resulting in large-area encapsulated colloidal crystals. However, to generate patterns or discrete deposits in designated places, convective assembly is not suitable. Here we experimentally develop conditions for direct-writing of coassembling monodisperse dye-doped polystyrene particles with a sol-gel precursor to form solid encapsulated photonic crystals. In a simple procedure the colloids are formulated in a sol-gel precursor solution, drop-cast on a flat substrate, and dried. We here establish the optimal parameters to form reproducible highly ordered photonic crystals with good optical performance. The obtained photonic crystals interact with light in the visible spectrum with a narrow optical stop-gap.

Visualization and evaluation of flow during water filtration: Parameterization and sensitivity analysis

This paper deals with visualization and evaluation of flow during filtration of water seeded by artificial microscopic particles. Planar laser induced fluorescence (PLIF) is a wide spread method for visualization and non-invasive characterization of flow. However the method uses fluorescent dyes or fluorescent particles in special cases. In this article the flow is seeded by non-fluorescent monodisperse polystyrene particles with the diameter smaller than one micrometer. The monodisperse sub-micron particles are very suitable for testing of textile filtration materials. Nevertheless non-fluorescent particles are not useful for PLIF method. A water filtration setup with an optical access to the place, were a tested filter is mounted, was built and used for the experiments. Concentration of particles in front of and behind the tested filter in a laser light sheet measured is and the local filtration efficiency expressed is. The article describes further progress in the measurement. It was carried out sensitivity analysis, parameterization and performance of the method during several simulations and experiments.