PMMA Particles Research Articles

Effect of capillary action and gravitational force on resistive pulse sensing with nanopipettes

In Resistive Pulse Sensing, nanoparticles dispersed in solution are individually detected and characterized during their translocation through a narrow pore or channel. Electrophoretic force and fluid flow can be precisely adjusted to direct nanoparticles toward the sensing zone. The impact of various factors on nanoparticle translocation dynamics, including solution ionic strength, pH, applied potential difference, and pipette tip geometry, has been extensively investigated. In this work, we focus on the role of pipette filling height, an experimental parameter often overlooked despite its significant impact on the overall pressure gradient and the resulting flow through the pipette tip. We used a solution of NaCl 150 mM plus 0.1 % v/v Triton X-100 at pH 7.2, a pipette with radius of approximately 200 nm and a voltage of ± 200 mV. Our findings reveal that the pipette filling height emerges as the critical factor dictating the translocation direction of negatively charged 160 nm PMMA particles and surpassing the combined effect of electrokinetic forces. Ultimately, our results indicate that considering the pipette filling level could enhance the accurate interpretation of experimental results, offering an additional parameter for fine-tuning nanoparticles dynamics, thus providing a valuable tool to researchers in this field.

Synthesis of Raspberry-like PMMA Particles In a Ternary Solvent Mixture with Binary Initiators.

There is continuing interest in the synthesis of raspberry-like polymer particles, among which most of the reports have tended to focus on polymer composite particles, while there are relatively few examples of polymer particles with a single component. In this study, raspberry-like poly(methyl methacrylate)(PMMA) particles were synthesized by a one-step method in a ternary solvent mixture with binary initiators. The effects of different polymerization parameters, including the solvent composition, the initiator composition, the stabilizer component, the polymerization temperature, the stirring rate, and the nature of the monomer, on the morphology and size of the resulting particles were studied. A plausible mechanism for raspberry-like particle formation was suggested based on the monitoring data of the polymerization kinetics. The raspberry-like PMMA particles have a high dispersion stability in a salty aqueous environment.

Tuning Thin Film Thickness and Porosity with Layer‐by‐Layer Submicronic Particles Assembly

AbstractPorous NiO films were prepared using Layer‐by‐Layer assembly of submicronic β‐Ni(OH)2 nanoplatelets and size‐controlled poly(methyl methacrylate) (PMMA) particles. β‐Ni(OH)2/PMMA thin films were elaborated using different PMMA particle sizes and concentrations. The elaborated films were then heated at a temperature of 325 °C in air for one hour to form porous NiO films by calcining β‐Ni(OH)2 nanoplatelets. PMMA polymeric particles were also calcined during this process, leading to film porosity. Thermal treatment experiments clearly showed a relationship between PMMA particle size and film properties i. e., porosity and thickness. NiO films exhibited huge pores, around 1 μm, and matter loss after calcination when PMMA particles with a diameter of 190±43 nm were employed. Partial collapsing of the films was also denoted. Experiments were then carried out by decreasing PMMA particle size (100±19 nm) leading to cohesive NiO films. Finally, the specific surface area (SSA) of the NiO films prepared with PMMA particles of 100 nm was determined by adsorption‐desorption of nitrogen gas using the BET (Brunauer–Emmet–Teller) method. This showed an increase in SSA with PMMA particle concentration.

PMMA light channels facilitate the additive manufacturing of complex-structured SiC reflector mirrors

The rapid manufacturing of lightweight SiC reflector mirrors has always posed a formidable challenge. We have successfully solved the problem of SiC slurry’s difficulty in vat photopolymerization by using highly transparent organic particles to construct the light channels for the first time. Through the integration of digital light processing with reaction sintering, we manufactured complex-structured SiC/Si reflector mirrors. Utilizing the light channels constructed with PMMA, ultraviolet light can effectively penetrate SiC slurry, thereby significantly enhancing the curing depth. During subsequent reaction sintering, PMMA particles induce the formation of numerous spherical silicon through dissolution-precipitation mechanism, alleviating stress concentration in the matrix and enhancing the flexural strength of SiC/Si ceramics. The method achieves significantly higher curing depth for SiC slurry and greater flexural strength for ceramic compared to similar materials. Extending the success above further, we have demonstrated their potential as high-quality products for practical applications.

Influence of particle parameters on deposition onto healthy and damaged human hair.

This research investigates how particle parameters, such as zeta potential, size, functional group, material composition, and hydrophobicity affect their affinity and deposition of particles onto hair. Streaming potential was used as the technique for analysis. The streaming potential data obtained was then converted to surface coverage data. Scanning electron microscopy (SEM) was also done to visualize particle localization on the hair surface. This study found stronger particle affinity on healthy than on damaged (oxidatively bleached) hair, due to diminished interaction sites from the removal of the hair shaft's external lipid layer. SEM imaging supported these findings and offered insights into particle localization. Hydrophilic silica particles accumulated along the exposed hydrophilic cuticle edges of healthy hair, due to hydrogen bonding with the exposed endocuticle. This localization is hypothesized to be due to the limited hydrophilic binding sites on the hydrophobic healthy hair cuticle surface. In damaged hair, an abundance of hydrophilic sites across the cuticle surface results in more dispersed binding. Hydrogen bonding and electrostatic attraction were shown to be the predominant forces influencing deposition, with hydrophobic interactions playing a less influential role. The affinity studies also proved that electrostatic attractions work over a longer range and are more effective at lower particle conditions compared with hydrogen bonding which only start to play a bigger role at higher particle concentrations. Steric hindrance of bulky side groups acted as a significant repulsive force. Results also revealed that larger particles deposit poorly on both healthy and damaged hair compared with smaller ones. Compared with neutrally charged silica nanoparticles (SN-2), positively charged PMMA particles (PN+16) have a stronger affinity to healthy hair, with highly charged particles (PN+49) depositing most rapidly. This study provides a fundamental understanding of how particle-surface parameters influence their affinity to hair and how damaging hair affects deposition.

Evaluation of bacteriophages for the alleviation of potential bacterial contamination risks in developmental engineering.

This research aimed to address the potential bacterial contamination risks in developmental engineering (DE) using bacteriophages. To compare and contrast the exemplar Escherichia coli T4 and M13 bacteriophages, human dermal fibroblasts cultivated on culture plates, natural cellulosic scaffolds, and poly(methyl methacrylate) (PMMA) particles were utilized as two-dimensional (2D) cell, three-dimensional (3D) tissue, and modular tissue culture models, respectively. When directly introduced into these distinct culture systems, both phages survived, exhibited no significant effects on the cultured cells or tissues, yet displayed their potentials to alleviate the infections caused by corresponding bacterial host cells. Apart from direct addition into the culture medium, both phages were also coated on PMMA, polystyrene, poly(lactic acid) particles with different diameters (5, 10, 30, and 100 µm) and cellulosic scaffolds. The coated phages endured the coating processes and demonstrated their viabilities in plaque assays. Further testing indicated that the phages coated on the PMMA particles tolerated multiple deliberate rinses and centrifugations, but not thermal treatment at 60-80°C. In summary, T4 and M13 bacteriophages not only manifested their antibacterial functions in diverse 2D cell, 3D tissue, and modular tissue culture systems, but also demonstrated their potentials of coating modular scaffolds to alleviate the bacterial contamination risks in DE.

Solvent‐Free Synthesis of PMMA Particles using Tandem Acoustic Emulsification

AbstractPoly(methyl methacrylate) (PMMA) colloidal particles are nowadays extensively used in several applications and more specifically in nanotechnology. Challenges are focused on the green synthesis process leading to size‐controlled particles. In the present work, PMMA particles were successfully synthesized using tandem acoustic emulsification in water without organic solvent, and cross‐linkers. 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (AIBA) or ammonium persulfate (APS), were used as initiators. Parameters leading to size control were clearly identified. Consequently, the cooling rate of the solution after polymerization time appears dominating. Particle size distribution was monodispersed for both initiators. A nonionic surfactant, Tween 20, was also added, leading to a decrease in size particle and an increase in synthesis yield. Depending on the chemical groups provided by the initiator, PMMA particles appear negatively or positively charged. These charges located on the particle surface led to stable particle dispersion by limiting aggregation phenomena. Tunable surface charge was confirmed across the elaboration of coatings only made of PMMA particles, using conventional techniques wherein charged species are needed (Layer‐by‐Layer assembly and electrophoretic deposition). PMMA particles were also labelled using fluorescent dyes. Fluorescein and Nile Blue A were loaded during the polymerization process to ensure a homogeneous distribution of the dyes within the particles.

Coalescence-Induced Self-Propelled Particle Transport with Asymmetry Arrangement.

We experimentally investigated the coalescence-induced droplet-particle jumping phenomenon on a submillimeter scale in symmetric and asymmetric particle arrangements with poly(methyl methacrylate) (PMMA) particles and stainless steel (SS) particles. Coalescence-induced droplet-particle jumping exhibited excellent capability and interesting behavior for both droplet jumping enhancement and particle transport. The particle increased the normalized droplet jumping velocity from 0.250 for no particle case to 0.315 and 0.320 for symmetric and asymmetric particle cases. Compared with similar-sized macrostructures fixed between droplets, better jumping performance with particles may be attributed to avoiding the work of adhesion during droplet-macrostructure separation. Besides, all particles always sunk at the bottom in the symmetric cases, while the stick mode for PMMA particles and sink, wander, and jet modes for SS particles appeared in the asymmetry cases. We revealed that the asymmetric particle arrangement induces an unbalanced surface tension force, which may provide a driving force in the vertical direction. Additionally, a small enough resistive force caused by hydrophobic particles is another necessary condition for the wonder and jet mode. Finally, we realized a significantly superior particle transport in the asymmetric SS particle cases with maximum particle height reaching ∼2.1 mm, ∼12.4 times the particle radius, the most significant vertical self-propelled transport distance currently.

Polarity switch of PMMA powder transported through a PMMA duct

During pneumatic conveying, powder electrifies rapidly due to the high flow velocities. In our experiments, the particles even charge if the conveying duct is made of the same material, which might be caused by triboelectrification between two asymmetric contact surfaces. Surprisingly, we found the airflow rate to determine the polarity of the overall powder charge. This study investigates the charging of microscale PMMA particles in turbulent flows passing through a square PMMA duct. The particles are spherical and monodisperse. A Faraday at the duct outlet measured the total charge of the particles. At low flow velocities, the particles charged negatively after passing through the duct. However, the powder’s overall charge switched to a positive polarity when increasing the flow velocity.

Structure and short-time diffusion of concentrated suspensions consisting of silicone-stabilised PMMA particles: a quantitative analysis taking polydispersity effects into account.

We characterise structure and dynamics of concentrated suspensions of silicone-stabilised PMMA particles immersed in index-matching decalin-tetralin mixtures by means of static and quasielastic light scattering experiments. These particles can reproducibly be prepared via a comparatively easy route and are thus promising model systems with hard-sphere interaction. We demonstrate the hard-sphere behaviour of dense suspensions of these systems rigorously taking polydispersity effects into account. Structure factors S(Q) can in the entire range of volume fractions with liquid-like structure quantitatively be modelled using a multi-component Percus-Yevick ansatz regarding the particle size distribution and the form factor assuming a core-shell model with a scattering length density gradient in the PMMA core. Herewith, hydrodynamic functions H(Q) are in the whole accessible Q-range beyond the second maximum of H(Q) quantitatively modelled using a rescaled δγ-approach for all investigated volume fractions. With these data, previously provided characterisation of dilute systems is extended: the excellent agreement of structural and dynamic properties with theoretical predictions for hard spheres demonstrates the suitability of these particles as a model system for hard spheres.

Granular aqueous suspensions with controlled interparticular friction and adhesion.

We present a simple route to obtain large quantities of suspensions of non-Brownian particles with stimuli-responsive surface properties to study the relation between their flow and interparticle interactions. We perform an alkaline hydrolysis reaction on poly(methyl methacrylate) (PMMA) particles to obtain poly(sodium methacrylate) (PMAA-Na) particles. We characterize the quasi-static macroscopic frictional response of their aqueous suspensions using a rotating drum. The suspensions are frictionless when the particles are dispersed in pure water. We relate this state to the presence of electrosteric repulsion between the charged surfaces of the ionized PMAA-Na particles in water. Then we add monovalent and multivalent ions (Na+, Ca2+, La3+) and we observe that the suspensions become frictional whatever the valency. For divalent and trivalent ions, the quasi-static avalanche angle θc at large ionic strength is greater than that of frictional PMMA particles in water, suggesting the presence of adhesion. Finally, a decrease in the pH of the suspending solution leads to a transition between a frictionless plateau and a frictional one. We perform atomic force microscopy (AFM) to relate our macroscopic observations to the surface features of the particles. In particular, we show that the increase in friction in the presence of multivalent ions or under acidic conditions is driven by a nanoscopic phase separation and the bundling of polyelectrolyte chains at the surface of the particle. Our results highlight the importance of surface interactions in the rheology of granular suspensions. Our particles provide a simple, yet flexible platform to study frictional suspension flows.

Autonomous and intelligent optical tweezers for improving the reliability and throughput of single particle analysis

Optical tweezers are an interesting tool to enable single cell analysis, especially when coupled with optical sensing and advanced computational methods. Nevertheless, such approaches are still hindered by system operation variability, and reduced amount of data, resulting in performance degradation when addressing new data sets. In this manuscript, we describe the deployment of an automatic and intelligent optical tweezers setup, capable of trapping, manipulating, and analyzing the physical properties of individual microscopic particles in an automatic and autonomous manner, at a rate of 4 particle per min, without user intervention. Reproducibility of particle identification with the help of machine learning algorithms is tested both for manual and automatic operation. The forward scattered signal of the trapped PMMA and PS particles was acquired over two days and used to train and test models based on the random forest classifier. With manual operation the system could initially distinguish between PMMA and PS with 90% accuracy. However, when using test datasets acquired on a different day it suffered a loss of accuracy around 24%. On the other hand, the automatic system could classify four types of particles with 79% accuracy maintaining performance (around 1% variation) even when tested with different datasets. Overall, the automated system shows an increased reproducibility and stability of the acquired signals allowing for the confirmation of the proportionality relationship expected between the particle size and its friction coefficient. These results demonstrate that this approach may support the development of future systems with increased throughput and reliability, for biosciences applications.

Suspension Photopolymerization of Methyl Methacrylate and ATRP Grafting of Thermo‐Responsive Polymers Using a Perylediimide Derivative Photoinitiator

AbstractThe first aim of this study is to develop a photo‐ATRP process using methyl methacrylate (MMA) by employing a novel perylenediimide derivative (PDI) as photoinitiator. The analysis of the MMA photopolymerization process kinetics is performed in solution and in bulk, demonstrating control over the reaction progress even if the polymerizations display a slow initiation step. The photo‐ATRP process for MMA in suspension is also developed and the obtained PMMA particles are further used to reinitiate the ATRP polymerization of thermoresponsive polymers (different molecular weights poly(ethylene glycol) methyl ether methacrylate and poly(N‐isopropylacrylamide)) (PNIPAM) in solution and surface‐initiated processes. The synthesized polymers by surface‐initiated process display a bimodal molecular weight distribution with a clear modification of the signal areas ratio depending on the grafted monomer and on the reaction conditions. The grafting process can take place on the surface of the polymer particles (Mn2), or it can also involve polymer chains located further at the interior of the polymer particles (Mn1). The lower critical solution temperature (LCST) transition is demonstrated for the PNIPAM functionalized polymer particles.

Moisture-electric foam based on dendritic colloids and polypyrrole-modified graphene oxide prepared by template method

Constructing a porous structure in moisture-electric generators (MEGs) is an effective strategy to increase the output power. However, the rapid and large-scale preparation of foam-based MEGs with controllable structures still faces challenges. Here, a moisture-electric (PGO@PVA) foam based on polypyrrole (PPy)-modified GO (PGO) and polyvinyl alcohol dendritic colloids were prepared by turbulent shear precipitation and template method. Consequently, the size and amount of PMMA particles were adjusted to control the porosity and pore size of PGO@PVA foam. With the mass ratio (PPy: GO = 2:1) of PPy/GO, PMMA size of 200 mesh, and the ratio between PMMA particles and PVA dendritic colloids of 10:1, the PGO@PVA foam illustrates 0.73 V of Uoc, 64 μA of Isc, 9.34 μW cm−2 of power density and 12.98 μWh·cm−2 of energy density. This work provides a novel strategy for efficient and large-scale preparation of high-performance MEGs with a tunable pore structure.

Influence of PMMA particle size control on the transmittance of PMMA/tempo-oxidized cellulose composites

Cellulose is a class of biopolymers that prominently contributes to developing lightweight, eco-friendly, and biodegradable plastics. Among them, nanofibrillated cellulose (NFC) is one of the most interesting due to its mechanical behavior. Mixing it with synthetic plastic such as poly(methyl methacrylate) (PMMA) reduces synthetic polymer usage, agro-industrial residue and develops fiber-reinforced composites. NFC was prepared from residual biomass and oxidized with TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical). Herein, NFC was incorporated (25, 50 and 75 wt%) in a colloidal emulsion of PMMA, with PMMA particle size control (50 and 175 nm). The investigation of this system on the PMMA/NFC transparency was addressed here. FTIR and SEM demonstrated effective incorporation of NFC and interaction with the PMMA. The increment of NFC increased the water contact angle and improved film transparency. Paired with PMMA particle size control, particularly at 50 nm, this favored composite transparency, becoming close to or even greater than pure NFC.Graphical abstract

3D‐printed alumina‐based ceramics with spatially resolved porosity

AbstractThe interest on porous ceramics has increased in the last years with the developments in additive manufacturing methods, enabling design of components with complex geometries for membranes, filters, catalytic converters, or biostructures. In this study, porous alumina samples were produced by using different concentrations of poly(methyl methacrylate) (PMMA) as pore‐forming agent (PFA) in a photocurable slurry via vat photopolymerization (VPP). The effect of layer thickness, PMMA particle size, and sintering temperature on the mechanical properties and microstructural features of the samples was investigated as a function of PMMA concentration. It is shown that the mechanical properties of 3D‐printed porous alumina are comparable with those fabricated by conventional processes. The Young modulus, fracture toughness as well as the biaxial strength decreased with increasing weight concentration of PFA (resulting in an increased total porosity). Specially using smaller PMMA particles has a positive effect, resulting in higher Young's modulus as well as fracture toughness. The feasibility of VPP for fabricating novel parts with more complex porosity regions is explored by printing multi‐material samples and porosity‐graded architectures. The counterbalance effect between porosity and mechanical properties may be optimized by tailoring material composition and processing parameters.

Determination of refractive index increments of PMMA particles dispersed in liquid phase

The refractive index increments of poly(methyl methacrylate) (PMMA) particles with sizes ranging from submicron to several microns were determined by measuring different concentrations of the solution and using a refractometer and microbalance calibrated by accurate traceability source. Conventionally, it was common to measure only the difference in refractive index between solvent and solution using a Bryce-type cell system, but it is difficult to perform traceable calibration since there is no reference material for refractive index increment. In this paper, we accurately quantify the refractive index increment by making individual measurements of the solvent and solution refractive indices, respectively, using Abbe-type refractometer. In addition, an uncertainty analysis was performed, and the results clarified the main factor of the variance in the refractive index increment measurements. The most important factor of variation of refractive index increment measurement is the measured apparent values at dilute concentration region including fluctuation of the system. This method was able to be applied to the determination of water content existing in particles. The percentage of the water content was determined using two different solvents, and the water content values were in good agreement within their uncertainties.

Digestion of preserved and unpreserved fish intestines for microplastic analysis with emphasis on quality assurance

BACKGROUND, Different preservation media used on fish samples may influence the digestion of organic matter for microplastic (MP) particle detection. Comparison of fresh and conserved fish is thereby problematic. OBJECTIVE, For quality assurance purposes and comparability of MP research, a method for digestion of preserved tissue like intestine with little impact on most MP particles was implemented. METHODS, Conserved fish samples were digested using SDS, KOH and Fenton’s reagents. The effect of the different chemicals used on different MP particles was then analyzed using Raman hit quality. Therefore, different filter materials were investigated using PMMA particles. RESULTS, Moist grided nitrocellulose filter was found best suited for this study. The effects of this digestion protocol on different polymer particles differed among polymers. Two of the used polymer particles dissolved during SDS + KOH treatment. PVC hard showed the highest loss of Raman hit quality (29.5 %). Some fish showed residues of sand or chitin from insects depending on their feeding strategy which could not be digested using this protocol. CONCLUSION, Not every polymer could be detected reliably using this protocol. For residues like sand or chitin, a density separation and enzymatic chitin degradation using chitinase may be needed, which could be implemented into this protocol.

Suspension of a single sphere in a stirred tank with transitional flow

AbstractThe lift‐off characteristics of a single spherical particle in a stirred tank with transitional flow generated by a Rushton impeller have been explored in detail by using image capturing and processing techniques. We found three kinds of typical particle suspension motions, namely, the lightest PMMA particle first moves upward from the bottom center of the tank to a certain height and then spirals up to the impeller, the heavier POM particle rises to a certain height vertically and then it spirals down to the tank bottom, the still heavier PTFE and glass particles jump at random when they are rolling irregularly on the tank bottom. The single‐phase flow field of the stirred tank was measured by using 2D‐PIV technique to address the mechanism of the particle lift‐off. The random distribution of the regions with larger liquid velocity closely above the tank bottom might be the reason why the PTFE and glass particles were lifted off randomly. As for the PMMA and POM particles being lifted from the bottom center and then stagnating at a certain height, the bulk flow dominates the particle suspension.

Evaluation of Polymeric Particles for Modular Tissue Cultures in Developmental Engineering.

Developmental engineering (DE) aims to culture mammalian cells on corresponding modular scaffolds (scale: micron to millimeter), then assemble these into functional tissues imitating natural developmental biology processes. This research intended to investigate the influences of polymeric particles on modular tissue cultures. When poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA) and polystyrene (PS) particles (diameter: 5-100 µm) were fabricated and submerged in culture medium in tissue culture plastics (TCPs) for modular tissue cultures, the majority of adjacent PMMA, some PLA but no PS particles aggregated. Human dermal fibroblasts (HDFs) could be directly seeded onto large (diameter: 30-100 µm) PMMA particles, but not small (diameter: 5-20 µm) PMMA, nor all the PLA and PS particles. During tissue cultures, HDFs migrated from the TCPs surfaces onto all the particles, while the clustered PMMA or PLA particles were colonized by HDFs into modular tissues with varying sizes. Further comparisons revealed that HDFs utilized the same cell bridging and stacking strategies to colonize single or clustered polymeric particles, and the finely controlled open pores, corners and gaps on 3D-printed PLA discs. These observed cell-scaffold interactions, which were then used to evaluate the adaptation of microcarrier-based cell expansion technologies for modular tissue manufacturing in DE.