Dispersed Microspheres Research Articles

Acoustic Assembly and Scanning of Superlens Arrays for High-Resolution and Large Field-of-View Bioimaging.

High-resolution and dynamic bioimaging is essential in life sciences and biomedical applications. In recent years, microspheres combined with optical microscopes have offered a low cost but promising solution for super-resolution imaging, by breaking the diffraction barrier. However, challenges still exist in precisely and parallelly superlens controlling using a noncontact manner, to meet the demands of large-area scanning imaging for desired targets. This study proposes an acoustic wavefield-based strategy for assembling and manipulating micrometer-scale superlens arrays, in addition to achieving on-demand scanning imaging through phase modulation. In experiments, acoustic pressure nodes are designed to be comparable in size to microspheres, allowing spatially dispersed microspheres to be arranged into arrays with one unit per node. Droplet microlenses with various diameters can be adapted in the array, allowing for a wide range of spacing periods by applying different frequencies. In addition, through the continuous phase shifting in the x and y directions, this acoustic superlens array achieves on-demand moving for the parallel high-resolution virtual image capturing and scanning of nanostructures and biological cell samples. As a comparison, this noncontact and cost-effective acoustic manner can obtain more than ∼100 times the acquisition efficiency of a single lens, holding promise in advancing super-resolution microscopy and subcellular-level bioimaging.

Denoising deep brain stimulation pacemaker signals with novel polymer-based nanocomposites: Porous biomaterials for sound absorption

<p>Deep brain stimulation (DBS) pacemakers are sophisticated medical devices that deliver electrical signals to targeted areas of the brain via implanted electrodes, effectively regulating abnormal brain activity and relieving symptoms of treatment-resistant neurological disorders. However, proximity to other electromagnetic equipment may introduce additional noise, which can be disruptive to individuals. To mitigate this issue, we propose a novel polymer-based nanocomposite for pacemakers for signal denoising. This research focused on the development and analysis of nanocomposites comprising polypropylene (PP) combined with montmorillonite nanoclay and graphene nanosheets (GNs). The nanocomposites were created by blending them through melting, using varying ratios of clay to GNs, with a total loading of 4 wt.%. This study focused on enhancing the signal-to-noise ratio for brain pacemakers by using nanocomposites. It investigated the noise reduction properties of PP nanocomposites, specifically in the outlet gate of the pacemaker. This research aimed to find the ideal ratio of clay to GNs in the PP matrix. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were conducted to analyze the crystalline structure and filler dispersion, as well as thermal behavior and filler–matrix interactions in the material. Scanning electron microscopy was employed to observe the dispersion of the nanofillers in the PP, and sound tube testing was conducted to evaluate the noise levels of the composites. The findings indicated that a porous structure of the nanocomposite with dispersed microspheres within the PP matrix and a long pathway facilitated increased dissipation of acoustic waves, making it suitable for denoising in brain pacemakers. Furthermore, the nanocomposite containing 2.75 wt.% of nanoclay and 1.25 wt.% of graphene components within the polypropylene matrix demonstrated a favorable signal-to-noise ratio compared to other evaluated nanocomposites.</p>

Synthesis of zeolite materials based on dispersed microspheres from fly ash from coal combustion and their sorption properties in relation to Pb(II) and Cd(II)

The influence of the composition of two narrow fractions of dispersed microspheres from fly ash from coal combustion and synthesis conditions on the production of microspherical monozeolite materials of a certain structural type was studied. The possibility of using synthesis products as Pb2+ and Cd2+ sorbents was assessed. It has been established that zeolitization products based on microspheres with a high content of glass phase (more than 90 wt. %) are monolithic solid materials of the geopolymer type, consisting of agglomerated microsphere residues and zeolite phases and, depending on the synthesis temperature, contain mainly one zeolite phase – NaX (FAU), NaP1 (GIS) or analcime (ANA). A simultaneous increase in the alkali concentration and the temperature of hydrothermal treatment led to a deeper transformation of glass microspheres and partial agglomeration of product particles with the formation of granules up to 100 microns in size. The product of alkaline activation of microspheres with a lower glass phase content (~65 wt. %) is a dispersed material based on unreacted microspheres, zeolite phases, mullite and quartz. Most zeolite products in the low Pb2+ and Cd2+ concentration range (not higher than 20 mg/l) were characterized by high solution purification parameters – KD up to 105 ml/g, the degree of extraction was up to 99%, while the most effective were sorbents based on zeolite phases NaP1 and analcime. Sorption isotherms of Pb2+ and Cd2 were approximated using the Langmuir, Freundlich, and Dubinin-Radushkevich models. It has been established that the sorption of heavy metals from dilute solutions is best described by the Freundlich and Dubinin-Radushkevich models. It has been shown that Pb2+/Cd2+ exchange forms of zeolite materials as a result of thermal exposure at 1000 оC undergo a phase transformation with the formation of mineral-like feldspar phases including lead (PbAl2Si2O8) or cadmium (CdAl2Si2O8).

Characterization and Magnetic Properties of Sintered Glass-Ceramics from Dispersed Fly Ash Microspheres

The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM10. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye’elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM10 to minimize solid waste pollution.

Wet spinning of strong cellulosic fibres with incorporation of phase change material capsules stabilized by cellulose nanocrystals

Incorporating a phase change material (PCM) into fibres allows the fabrication of smart textiles with thermo-regulating properties. Previously, such fibres have been made from thermoplastic polymers, usually petroleum-based and non-biodegradable, or from regenerated cellulose, such as viscose. Herein, strong fibres are developed from aqueous dispersions of nano-cellulose and dispersed microspheres with phase changing characteristics using a wet spinning technique employing a pH shift approach. Good distribution of the microspheres and proper compatibility with the cellulosic matrix was demonstrated by formulating the wax as a Pickering emulsion using cellulose nanocrystals (CNC) as stabilizing particles. The wax was subsequently incorporated into a dispersion of cellulose nanofibrils, the latter being responsible for the mechanical strength of the spun fibres. It was possible to produce fibres highly loaded with the microspheres (40 wt%) with a tenacity of 13 cN tex−1 (135 MPa). The fibres possessed good thermo-regulating features by absorbing and releasing heat without undergoing structural changes, while maintaining the PCM domain sizes intact. Finally, good washing fastness and PCM leak resistance were demonstrated, making the fibres suitable for thermo-regulative applications. Continuous fabrication of bio-based fibres with entrapped PCMs may find applications as reinforcements in composites or hybrid filaments.

Co3O4 anchored on ionic liquid modified PAN as anode materials for flexible lithium-ion batteries

Transition metal oxide Co3O4 is a candidate anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity and easy preparation. However, unmodified Co3O4 suffers from distinctly inferior rate capability and poor cycling stability. Here, we design and fabricate a three-dimensional (3D) island bridge structure (IBS) Co3O4 anchored into IL [BMIm][N(CN)2] modified PAN (Co3O4-PAN-IL) composite. The Co3O4 is uniformly dispersed microspheres, and IL modified PAN constitute a conductive network, which together form an IBS. The structure can effectively promote electron transfer, improve the specific surface area of the material, and alleviate the volume effect of cobalt oxide. More importantly, IL modified PAN has been considered as a highly conductive N-doping matrix after annealing. By virtue of these merits, the Co3O4-PAN-IL electrode demonstrates a high reversible capacity of 1499 mA h g−1 at 0.5C. After 800 cycles, the capacity of 1239 mA h g−1 was maintained, and the attenuation rate of each cycle was 0.022%. Compared with pure Co3O4, the electrochemical performance was significantly improved. The excellent electrochemical performance was due to the synergistic effect of nitrogen doping carbon network and uniformly dispersed Co3O4 particles. Furthermore, flexible pouch cells based on the cathode are further fabricated and demonstrate excellent electrochemical properties, highlighting the practical application of our deliberately designed electrode in flexible wearable electronics.

Removal of highly dispersive microspheres from wastewater using modified spirulina hetero-coagulation and their application in flame retardancy

There is an urgent demand to find an effective solution to microplastic pollution in water.

Self-adaptive preferential flow control using displacing fluid with dispersed polymers in heterogeneous porous media

Abstract

A cell-free approach with a supporting biomaterial in the form of dispersed microspheres induces hyaline cartilage formation in a rabbit knee model.

The objective of this study was to test a regenerative medicine strategy for the regeneration of articular cartilage. This approach combines microfracture of the subchondral bone with the implant at the site of the cartilage defect of a supporting biomaterial in the form of microspheres aimed at creating an adequate biomechanical environment for the differentiation of the mesenchymal stem cells that migrate from the bone marrow. The possible inflammatory response to these biomaterials was previously studied by means of the culture of RAW264.7 macrophages. The microspheres were implanted in a 3 mm-diameter defect in the trochlea of the femoral condyle of New Zealand rabbits, covering them with a poly(l-lactic acid) (PLLA) membrane manufactured by electrospinning. Experimental groups included a group where exclusively PLLA microspheres were implanted, another group where a mixture of 50/50 microspheres of PLLA (hydrophobic and rigid) and others of chitosan (a hydrogel) were used, and a third group used as a control where no material was used and only the membrane was covering the defect. The histological characteristics of the regenerated tissue have been evaluated 3 months after the operation. We found that during the regeneration process the microspheres, and the membrane covering them, are displaced by the neoformed tissue in the regeneration space toward the subchondral bone region, leaving room for the formation of a tissue with the characteristics of hyaline cartilage.

The application of the supported liquid membrane and molecularly imprinted polymers as solid acceptor phase for selective extraction of biochanin A from urine

An efficient sample clean-up and preconcentration procedure for phytoestrogens analysis in urine has been developed. It was based on a combination of solid phase extraction with hollow-fiber supported liquid membrane and molecularly imprinted beads (MIPs-HF-SLM-SPE). The molecularly imprinted polymers (MIPs) were synthesized by precipitation polymerization technique with biochanin A (BCA) as a template, giving narrowly dispersed microspheres with a regular shape. As the functional monomer, (dimethylamino)ethyl methacrylate (-DEM) turned out to be better than methacrylic acid (MAA) to get the best-imprinted effects. The MIPs used as sorbents in the MIPs-HF-SLM-SPE extraction process exhibited excellent binding selectivity for BCA, in comparison to non-imprinted polymers as well as its structural analogs (genistein and daidzein). Finally, the developed method was used to detect BCA in urine. Under optimal extraction conditions, the recovery of BCA in urine samples (using 4.5 mL sample spiked with 10 μg L−1) was over 41%, with a coefficient of variation (CV) < 6.6% (n = 5). The detection limit (LOD) and quantification limit (LOQ) for BCA analysis in urine were 0.41 and 1.36 μg L−1, respectively.

Controlling the shear thickening behavior of suspensions by changing the surface properties of dispersed microspheres.

To investigate the effect of the surface properties of dispersed particles on the shear thickening behavior of their corresponding suspensions and further control this characteristic, three kinds of suspensions were prepared by mixing SiO2, SiO2–NH2, and SiO2–COOH microspheres with a poly(ethylene glycol) fluid medium, and their rheological behavior was analyzed carefully. Compared to the SiO2 microsphere suspension, the SiO2–NH2 and SiO2–COOH microsphere suspensions show a weaker thickening behavior and a greater critical shear rate due to the aggregation tendency caused primarily by the organic chains. Moreover, the rheological behavior of the three suspensions display different dependencies on the pH value, which is comprehensively determined by the interaction between the microspheres and the medium. Moreover, the critical shear stress of suspensions with different pH values could be predicted by the Wagner model, which basically proves that the interaction between the particles significantly influences the beginning of thickening. The thickening degree could be interpreted by friction theory. The critical volume fraction corresponding to the onset of discontinuous shear thickening is determined by the friction coefficient between the particles, which is greatly affected by the pH value.

Liquid-liquid extraction intensification by micro-droplet rotation in a hydrocyclone

The previous literature reports that using a hydrocyclone as an extractor intensifies the mass transfer and largely reduces the consumption of extractant from 1800–2000 kg h−1 to 30–90 kg h−1. However, the intensification mechanism has not been clear. This paper presents experimental and numerical methods to study the multi-scale motion of particles in hydrocyclones. In addition to the usually considered translational behavior, the high-speed rotation of dispersed micro-spheres caused by the anisotropic swirling shear flow is determined. The rotation speeds of the tested micro-spheres are above 1000 rad s−1, which are much larger than the instantaneous rotation speed in isotropic turbulence. Due to the conical structure of a hydrocyclone, the rotation speed maintains stability along the axial direction. Numerical results show that the particle Reynolds number of micro-droplets in a hydrocyclone is equal to that in conventional extractors, but the particles have high rotation speeds of up to 10,000 rad s−1 and long mixing lengths of more than 1000 mm. Both the rotation of micro-droplets along the spiral trajectories and the intense eddy diffusion in a hydrocyclone contribute to the extraction intensification.

A microsphere suspension model of metamaterial fluids

Drawing an analogy to the liquid phase of natural materials, we theoretically propose a microsphere suspension model to realize a metamaterial fluid with artificial electromagnetic indexes. By immersing high-ε, micrometer-sized dielectric spheres in a low-ε insulating oil, the structured fluid exhibits liquid-like properties from dispersing phase as well as the isotropic negative electromagnetic parameters caused by Mie resonances from dispersed microspheres. The work presented here will benefit the development of structured fluids toward metamaterials.

Gadolinium fluoride mesoporous microspheres: controllable synthesis, materials and biological properties.

In this study, uniform gadolinium fluoride microspheres with controllable phases and structures have been synthesized for the first time by a facile ion exchange process using Gd(OH)CO3 solid microspheres as precursors. It is found that the as-synthesized NaxGdyFx+3y samples, including orthorhombic GdF3, cubic Na5Gd9F32 and hexagonal NaGdF4, all consist of well dispersed microspheres with mesopores. After the conversion process, the products mainly inherit the size and shape of the precursors. Moreover, the used ethylene glycol (EG) plays a key role in the phase and structure of the final NaxGdyFx+3y mesoporous spheres by impacting the etching and ion exchange process. Based on the time-dependent experiments of gadolinium fluorides, the possible formation mechanism is discussed in detail. Under 273 nm UV excitation, NaxGdyFx+3y:2% Eu3+ shows bright red emissions due to efficient energy transfer from Gd3+ to Eu3+. NaxGdyFx+3y:17% Yb3+/3% Er3+ exhibits the characteristic up-conversion (UC) emissions of Er3+. It is noted that the highest DC and UC emission intensities of NaGdF4:Ln should be due to the hexagonal phase. The fluorescent NaxGdyFx+3y mesoporous microspheres show obvious drug (doxorubicin hydrochloride, DOX) storage/release properties and good biocompatibility, suggesting their potential application in biomedical fields.

The effects of suspension particle size on the performance of air-jet, ultrasonic and vibrating-mesh nebulisers

Using latex microspheres as model suspensions, the influence of suspension particle size (1, 4.5 and 10 μm) on the properties of aerosols produced using Pari LC Sprint (air-jet), Polygreen (ultrasonic), Aeroneb Pro (actively vibrating-mesh) and Omron MicroAir NE-U22 (passively vibrating-mesh) nebulisers was investigated. The performance of the Pari nebuliser was independent of latex spheres particle size. For both Polygreen and Aeroneb Pro nebulizers, total aerosol output increased when the size of latex spheres increased, with highest fine particle fraction (FPF) values being recorded. However, following nebulisation of 1 or 4.5 μm suspensions with the Polygreen device, no particles were detected in the aerosols deposited in a two-stage impinger, suggesting that the aerosols generated from this device consisted mainly of the continuous phase while the dispersed microspheres were excluded and remained in the nebuliser. The Omron nebuliser efficiently nebulised the 1 μm latex spheres, with high output rate and no particle aggregation. However, this device functioned inefficiently when delivering 4.5 or 10 μm suspensions, which was attributed to the mild vibrations of its mesh and/or the blockage of the mesh apertures by the microspheres. The Aeroneb Pro fragmented latex spheres into smaller particles, but uncontrolled aggregation occurred upon nebulisation. This study has shown that the design of the nebuliser influenced the aerosol properties using latex spheres as model suspensions. Moreover, for the recently marketed mesh nebulisers, the performance of the Aeroneb Pro device was less dependent on particle size of the suspension compared with the Omron MicroAir nebuliser.

Facile Synthesis of Hierarchical Architecture FePO&lt;sub&gt;4&lt;/sub&gt;/C Composite Microspheres

Carbon coated micro/nanostructure FePO4composite materials were synthesized by hydrothermal methode, in which citric acid was used as both complexant and carbon resource. The dependence of synthesis process and complexant on the structure and morphology of composite materials were investigated by X ray diffraction (XRD) and scanning electronmicroscopy (SEM). The results showed that the sample consisted of dispersive microspheres with a quite uniform size distribution of 10μm through hydrothermal reaction at 130°C for 24h, when solution concetration was 0.03mol/L and pH value was nearly 2. After calcinated at 550°C for 3h, the microspheres were comprised of nanosticks, and their specific surface area can reach nearly 14 m2/g. Due to their micro/nanomicrosphere structure, the composite materials will benefit to the increase of lithium diffusion rate meanwhile preserve high tap density.

Dielectric analysis of CMPS-supported ionic liquids (ILs) microspheres in model gasoline by means of dielectric relaxation spectroscopy

Real-time monitoring of dielectric behaviors of CMPS-supported imidazolium ionic liquids (ILs) microspheres in model gasoline was performed by dielectric relaxation spectroscopy (DRS) from 40Hz to 110MHz. One dielectric relaxation in MHz frequency range is obviously observed for all systems and determined to be closely related to the interfacial polarization. The interfacial polarization is attributed from the different conductivities between dispersed microspheres and model gasoline since imidazolium-based ionic liquids have been immobilized on the surfaces of dispersed microspheres in the form of optimized spatial configurations. Meanwhile, dielectric parameters (ɛl, κl, ɛh, κh and f0) for all the systems are obtained by fitting Cole–Cole equation to the dielectric data. From the dielectric parameters, Hanai equations are employed to calculate phase parameters (ϕ, κm, ɛp and κp), which is used to characterize the electrical and structural properties of constituent phases of suspensions of conducting particles in non-conducting medium. The time-dependences of dielectric parameters and phase parameters are investigated in detail, and interfacial electrokinetic model for suspension of dense particles has been employed for interpreting these time-dependences. Here, we found that possible π–complexation bond and π–π interaction between imidazole rings of ILs and thiophene are responsible for time-dependences of all parameters. Furthermore, the time-dependences of parameters indicate that the electron density (polarization strength) on surfaces of dispersed microspheres decreases with the increment of extraction time.

Covalently bonded polystyrene/SiO2 microspheres via emulsion polymerisation stabilised solely by surface active Pickering stabiliser

Covalently bonded polystyrene/SiO2 microspheres were synthesised via Pickering emulsion polymerisation using methacryloxypropyltrimethoxysilane modified SiO2 as a sole stabiliser. The effect of polymerisation condition on morphologies of composites was investigated, and a formation mechanism of microspheres with different morphologies was proposed. Three strategies, increasing amount of stabiliser, adding inhibitor in continuous phase and employing cross-linking agent, were employed to regulate the morphology of products. It was concluded that suppression of nucleation in continuous phase was critical for the formation of dispersive microspheres with high sphericity and smooth surface.

Preparation of polystyrene/SiO2 microsphere via Pickering emulsion polymerization: Synergistic effect of SiO2 concentrations and initiator sorts

In this paper, polystyrene (PS)/SiO2 microspheres were successfully prepared via Pickering emulsion polymerization stabilized solely by ethacryloxypropyltrimethoxysilane (MPTMS) modified SiO2 nanoparticles. The formation mechanisms of PS/SiO2 microspheres with different morphology were investigated under various Pickering emulsion polymerization conditions. The results showed that SiO2 concentrations and initiator sorts would synergistically impact on the morphology of products corresponding to distinct formation mechanisms. When SiO2 concentrations was low and water-solute initiator potassium persulfate (KPS) was used, aqueous nucleation was dominant, which was deduced to the formation of dispersive microspheres sparsely anchored by SiO2 particles. When SiO2 concentrations was increased and oil-solute initiator azobisisobutyronitrile (AIBN) was applied, nucleation in oil phase prevailed which lead to the formation of microspheres densely packed by SiO2 particles.

Mild method for the agglomeration of dispersed polycaprolactone microspheres via a genipin‐crosslinked gelatin hydrogel

AbstractMicrosphere systems have been used to deliver drugs, proteins, and cells. However, dispersed microspheres can induce harmful effects after they are introduced into the body. To agglomerate these dispersed microspheres, an in situ forming system was developed to fabricate microsphere/hydrogel composites. Polycaprolactone microspheres with a porous surface and hollow core were physically incorporated into a genipin‐crosslinked gelatin hydrogel. The incorporation of microspheres reduced the swelling capacities and weakened the unexpected volume expansion, which is not favorable for in vivo implants. Additionally, the reacted genipin ratio increased with increasing gelatin concentration. The degradation of the composite was also determined, and it was proposed that the degradation mechanism of the composite was bulk collapse, whereas that for the pure hydrogel was surface erosion. The obtained microsphere/hydrogel composite might have a great potential application as an injectable system for tissue regeneration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013