Suspension Of Microparticles Research Articles

Light therapies for acne.

Light therapies for acne.

Biosilicate as a dentin pretreatment for total-etch and self-etch adhesives: In vitro study

PurposeTo evaluate the effect of dentin pre-treatment using biosilicate microparticle suspension prior to the application of total-etch and self-etch adhesives on dentin microtensile bond strength. Material and methodsThe labial enamel of forty bovine central incisors was removed using 600-grit SiC disks to expose the flat dentin surface. Six bonding protocols were evaluated (n=10): Group 1 (etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2—Control group); Group 2 (10% biosilicate suspension prior to etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2); Group 3 (10% biosilicate suspension after etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2); Group 4 (self-etch adhesive Adper Easy One™—Control group); Group 5 (10% biosilicate suspension prior to the self-etch adhesive Adper Easy One™); Group 6 (10% biosilicate suspension after the self-etch adhesive Adper Easy One™). Composite build-ups were performed with Filtek™ Z350. The specimens were stored in distilled water for 24h at 37°C and sectioned into sticks with a 1.0mm2 cross-sectional area. Each stick was tested in a Universal testing machine (0.5mm/min), and the mean microtensile bond strength data (MPa) were analyzed by two-way ANOVA and Bonferroni׳s multiple comparisons test (α=0.05). Representative SEM micrographs were taken to compare the microstructure of different treatments of dentin. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS. ResultsGroup 3 (10% biosilicate suspension after acid etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2) showed the highest bonding values (p<0.05). Regarding the self-etch adhesive, there was no difference (p>0.05) between Group 5 and Group 6. SEM images demonstrated biosilicate microparticles in groups 2 and 4. EDS data analysis showed higher amounts of Ca and P ions in groups treated with biosilicate than control groups. ConclusionThe application of biosilicate microparticle suspension as dentin pre-treatment positively influenced the bond strength of the total-etch adhesive when used after acid etching; meanwhile, it does not interfere with the bonding ability of self-etch adhesive to dentin.

Spray‐dried microparticles composed of cinnamoyl poly(N‐isopropylacrylamide‐co‐hydroxyethylacrylate) and gold nanoparticle

ABSTRACTTemperature‐ and NIR irradiation‐responsive microparticles composed of cinnamoyl poly(N‐isopropylacrylamide‐co‐hydroxyethylacrylate) [CinP(NIPAM‐HEA)] and gold nanoparticle (GNP) were prepared by a spray‐drying method. According to the cloud points determined by an optical method, the HEA content in P(NIPAM‐HEA) had no marked effect on the lower critical solution temperature (LCST). However, the cinnamoyl group content in CinP(NIPAM‐HEA) had a significant effect on the LCST. The LCSTs determined by a calorimetric method was in agreement with those determined by an optical method. The hydrodynamic mean diameter of gold nanoparticle (GNP) prepared by reducing gold ions was about 30 nm and it seemed to be a nanosphere on TEM photo. Spray‐dried CinP(NIPAM‐HEA) microparticles containing GNP was 1.5 μm to 12 μm in diameter on SEM photo. Gold was detected on the energy‐dispersive X‐ray spectrum of the microparticles. The amount of FITC‐dextran released for 12 h from the microparticles was much higher at temperatures above the LCST (at 37 °C and 45 °C) than below the LCST (at 20 °C and 25 °C). The cumulative release amount in 12 h was only about 3% without NIR irradiation, whereas the value was about 26.5% when NIR was irradiated to the microparticle suspension. The photothermal energy generated by GNP was believed to render the thermosensitive copolymers de‐swollen and hydrophobic, allowing for the active release of dye from the microparticles. The NIR irradiation‐responsive GNP‐loaded microparticles could be applied to the development of NIR‐responsive drug carriers which release their contents in response to an external stimulus (i.e., NIR irradiation). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44141.

Coulomb fission of a dusty plasma

Experimental observations are presented of the splitting (fission) of a suspension of charged microparticles (dusty plasma) into two fragments when the plasma was suddenly turned off. The triggering mechanism for fissioning of the dust cloud is discussed in terms of a pinching instability driven by the ion drag force.

Numerical investigation of hard-gel microparticle suspension dynamics in microfluidic channels: Aggregation/fragmentation phenomena, and incipient clogging

The aggregation/fragmentation dynamics of hard-gel microparticles suspended in a Newtonian liquid flowing through a straight channel is studied by numerical simulations. A one-way Discrete Element Method is employed to simulate the motion and the adhesion of the particles. The formation and fragmentation of aggregates, and their deposition at the channel walls are investigated by varying the Reynolds number and the strength of the adhesive force. A non-periodic channel is considered to simulate the start-up phase of aggregate formation till a ‘pseudo steady-state’ condition. Results in terms of microstructures, particle velocity profiles, and spatial and temporal evolution of aggregates in 2D and cylindrical (3D) channels are presented and discussed.

Second Harmonic Generation in Microstructured Barium Titanate

We investigate the second harmonic generation under femtosecond pulse-periodic laser radiation in barium titanate in the form of ceramics, in pores of a globular photonic crystal, and in a water colloidal suspension. We measure the dependence of the second harmonic radiation intensity on the incident laser power. Excitation of the second harmonic was carried out by powerful (108 W) pulses of a solid-state Yb:KGW laser (wavelength, 1,026 nm) operating at 200 kHz. We estimate the efficiency of the second harmonic generation in various microstructured phases of barium titanate and show that the threshold of plasma formation in a suspension of barium titanate microparticles in water is substantially higher than in ceramics and in the ferroelectric photonic crystal. The second-harmonicgeneration power can be significantly increased in a water suspension of barium titanate microparticles.

Enhancement of laminar convective heat transfer using microparticle suspensions

This paper investigates the enhancement of convective heat transfer within a sub-millimetre diameter copper tube using Al2O3, Co3O4 and CuO microparticle suspensions. Experiments are conducted at different particle concentrations of 1.0, 2.0 and 5.0 wt% and at various flow rates ranging from 250 to 1000 µl/min. Both experimental measurements and numerical analyses are employed to obtain the convective heat transfer coefficient. The results indicate a significant enhancement in convective heat transfer coefficient due to the implementation of microparticle suspensions. For the case of Al2O3 microparticle suspension with 5.0 wt% concentration, a 20.3 % enhancement in convective heat transfer coefficient is obtained over deionised water. This is comparable to the case of Al2O3 nanofluid at the same concentration. Hence, there is a potential for the microparticle suspensions to be used for cooling of compact integrated systems.

Preparation of iron—polysiloxane vertically ordered microneedles from a suspension of iron microparticles in liquid silicone rubber

A simple method for the preparation of the vertically located flexible iron—polysiloxane magnetic needles up to 12 mm long by the self-organization of iron carbonyl microparticles in a solution of thermally cured polydimethylsiloxane rubber in a vertical magnetic field is proposed. The generated structures withstand heating to 300 °С with an appreciable loss of flexibility. Their properties are investigated by scanning electron, atomic force, and optical microscopy.

Preparation, characterization and pharmacokinetics of doxycycline hydrochloride and florfenicol polyvinylpyrroliddone microparticle entrapped with hydroxypropyl-β-cyclodextrin inclusion complexes suspension

In order to effectively control the bacterial pneumonia in pigs, doxycycline hydrochloride (DoxHcl) and florfenicol (FF) microparticle suspension together with inclusion complexes was prepared by using hydroxypropyl-β-cyclodextrin (HP-β-CD) as host molecules, polyvinylpyrroliddone (PVP) as polymer carriers and hydroxypropyl methyl cellulose (HPMC) as suspending agents. In vitro antibacterial activity, properties, stability and pharmacokinetics of the suspension were studied. The results demonstrated that DoxHcl and FF had a synergistic or additive antibacterial activity against Streptococcus suis, Actinobacillus pleuropneumoniae and Haemophilus parasuis. The size, polydispersity index and zeta potential of microparticles were 1.46±0.06μm, 0.30±0.02 and 1.53±0.04mV, respectively. The encapsulation efficiency (EE) of DoxHcl and FF was 45.28%±3.30% and 89.69%±2.71%, respectively. The re-dispersed time and sedimentation rate of the suspension were 1min and 1. The suspension went through the 9-gage needle smoothly with withdrawal volume of 9.12±0.87mL/min. The suspension showed good stability when stored away from light, no irritation at the injection site and sustained release in PBS buffer. After intramuscular administration to pig, DoxHcl and FF could maintain over 0.15μg/mL for 72h. Compared to the control injection, the suspension increased the elimination half-life (T½ke) as well as mean residence time (MRT) of DoxHcl from 5.73 to 9.77h and from 12.02 to 18.81h, and those of FF from 12.02 to 26.19h and from12.02 to 28.16h, respectively. The suspension increased the bioavailability of DoxHcl and FF by 1.74 and 1.13-fold, respectively. These results suggest that the compound suspension is a promising formulation for pig pneumonia therapy.

Organic photo sensors for multi-angle light scattering characterization of particle systems.

Organic Photo Sensor (OPS) technology allows printing on conformable plastic-like substrates complex-shaped, arbitrarily-sized and pre-aligned photosensitive elements. This article reports, to the best of our knowledge, the first investigation to implement this emerging technology for Multi-Angle Light Scattering (MALS) characterization of nano- and microparticle suspensions. Monte Carlo and Lorenz-Mie theory calculations as well as preliminary experimental results on latex suspensions clearly demonstrate the potential of the proposed approach.

Magnetorheology of Core–Shell Structured Carbonyl Iron/Polystyrene Foam Microparticles Suspension with Enhanced Stability

The sedimentation stability of a carbonyl iron (CI)-based magnetorheological (MR) fluid was improved by wrapping CI particles with a polystyrene (PS) foam layer. The PS layer on the CI particles was synthesized via conventional dispersion polymerization and was subsequently foamed using a supercritical carbon dioxide fluid to produce core–shell structured particles. The density of particles decreased after the PS-layer wrapping and subsequent PS-layer foaming. The surface morphology was observed by scanning electron microscope (SEM) and the specific surface areas were determined by Brunauer–Emmett–Teller (BET) adsorption measurements. Both modifications (PS-layer wrapping and foaming) increased the surface roughness of the particles, yet preserved particle’s spherical shape. The effect of the volume expansion after modification on the magnetorheological properties was investigated by using a vibrating sample magnetometer (VSM) and a rotational rheometer. All suspensions tested presented similar MR behavio...

CFD modelling of a mixing chamber for the realisation of functionally graded scaffolds

Biological tissues are characterised by spatially distributed gradients, intricately linked with functions. It is widely accepted that ideal tissue engineered scaffolds should exhibit similar functional gradients to promote successful tissue regeneration. Focusing on bone, in previous work we proposed simple methods to obtain osteochondral functionally graded scaffolds (FGSs), starting from homogeneous suspensions of hydroxyapatite (HA) particles in gelatin solutions. With the main aim of developing an automated device to fabricate FGSs, this work is focused on designing a stirred tank to obtain homogeneous HA–gelatin suspensions. The HA particles transport within the gelatin solution was investigated through computational fluid dynamics (CFD) modelling. First, the steady-state flow field was solved for the continuous phase only. Then, it was used as a starting point for solving the multi-phase transient simulation. CFD results showed that the proposed tank geometry and setup allow for obtaining a homogeneous suspension of HA micro-particles within the gelatin solution.

Multiplexed hydrogel microparticle suspension arrays for facile ribosomal RNA integrity assays

Reliable RNA integrity assay is important for a wide range of applications in genomics and diagnostics, yet the existing technologies have certain limitations such as large amount of sample required, high cost of equipment and/or long turnaround times. We report a simple assay method to analyze bacterial ribosomal RNA (rRNA) from complex total RNA samples utilizing shape-encoded and single-stranded DNA-conjugated hydrogel microparticle suspension arrays with no need for target amplification and under standard fluorescence imaging conditions. We show that our simple microparticle-based sensing scheme is reliable, sequence-specific and presents a responsive binding behavior to target RNA concentrations. Moreover, the relative stability of 16S and 23S rRNA can be assessed in a simple shape encoding-based multiplexed format. Combined, these findings represent a significant step toward cheap, fast, simple, and reliable assays for the analysis of rRNA and general RNA integrity.

High flux electrospun nanofiberous membrane: Preparation by statistical approach, characterization, and microfiltration assessment

Preparation, characterization and evaluation of new generation of micro-filters based on polyacrylonitrile electrospun nanofiberous membrane (ENM) were thoroughly investigated. First, quantitative relationships between average diameter, bead area density of nano-fibers and certain electrospinning parameters, i.e., concentration, voltage, spinning distance, and feed rate, were established by empirical modeling based on a central composite design. The analysis revealed that concentration, voltage and distance are the significant parameters. Also, adequacy checking indicated the appropriateness of fit for the models. Afterwards, bead-free ENMs with diameter of 100–500 nm were prepared and characterized in terms of porosity, pore size and mechanical properties. The results indicate that as the nano-fiber diameter increases from 100 nm to 500 nm, porosity decreases from 74% to 61%, pore radius increases from 0.48 µm to 1.40 µm and tensile properties slightly decrease. Moreover, pure water flux increased with increasing nano-fiber diameter and membrane compaction was observed with increasing applied pressure for each membrane. Finally, ENM with fiber diameter of 100 nm showed the highest rejection rate of 99% and steady permeate flux of 118 l/m2h using TiO2 micro-particles suspension. Such finding demonstrates that ENMs with proper fiber diameter and morphology are excellent choices for high flux microfiltration applications.

Thermal mechanisms of laser marking in transparent polymers with light-absorbing microparticles

Interaction of highly viscous polystyrene suspensions of light-absorbing microparticles with pulsed radiation of a Q-switched YAG:Nd3+ laser is investigated. Absorption of laser radiation by the suspended microparticles causes thermal decomposition (pyrolysis) of the polymer in the vicinity of the overheated particles. Laser-induced incandescence (LII) of light-absorbing microparticles under irradiation by a sequence of laser pulses is observed. The mechanism of laser marking includes formation of light-absorbing and scattering centers by accumulation of carbonaceous and gaseous products of pyrolysis.

Deposition of superhydrophobic coatings from lacquer suspension of iron microparticles in a magnetic field

Method is described for forming a superhydrophobic coating on the surface of aluminum by curing of a suspension of microparticles of carbonyl iron in an organofluorine lacquer in air in a permanent magnetic field.

Mechanism of immunoglobulin G adsorption on polystyrene microspheres

The adsorption of polyclonal immunoglobulin G (IgG) on negatively charged polystyrene microparticle suspension (latex) was studied by using the Laser Doppler Velocimetry (LDV) measurements. Using this technique, the dependence of the electrophoretic mobility of particles on the IgG concentration in the suspension was measured for various ionic strengths and pH 3.5. The increase in the electrophoretic mobility was quantitatively interpreted in terms of the 3D electrokinetic model. On the other hand, the maximum coverage of IgG on latex was determined using the depletion method based on AFM imaging. It was shown that IgG adsorption was irreversible and that its maximum coverage on the microspheres increased from 1.4mgm−2 for 0.001M NaCl to 2.0mgm−2 for 0.15M NaCl. This was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. The stability of IgG monolayers on the particles was confirmed in separate experiments where changes in its electrophoretic mobility were monitored over prolonged time periods. Additionally, the acid-base properties of the IgG monolayers on latex were determined in pH cycling experiments. The isoelectric point of the IgG monolayers on the microspheres was 4.8. The results obtained in this work indicate that basic physicochemical characteristics of IgG can be acquired via electrophoretic mobility measurements using microgram quantities of the protein.

Biodegradable fibre scaffolds incorporating water-soluble drugs and proteins.

A new type of biodegradable drug-loaded fibre scaffold has been successfully produced for the benefit of water-soluble drugs and proteins. Model drug loaded calcium carbonate (CaCO3) microparticles incorporated into poly(lactic acid-co-glycolic acid) (PLGA) fibres were manufactured by co-precipitation of CaCO3 and the drug molecules, followed by electrospinning of a suspension of such drug-loaded microparticles in a PLGA solution. Rhodamine 6G and bovine serum albumin were used as model drugs for our release study, representing small bioactive molecules and protein, respectively. A bead and string structure of fibres was achieved. The drug release was investigated with different drug loadings and in different pH release mediums. Results showed that a slow and sustained drug release was achieved in 40 days and the CaCO3 microparticles used as the second barrier restrained the initial burst release.

Energy Harvesting Through Optical Properties of TiO2 and C- TiO2 Nanofluid for Direct Absorption Solar Collectors

Nanofluids are tailored suspensions of nanoparticles in a suitable base fluid. The discovery of nanofluids by Stephen choi opened a new heat transfer mechanism. Since then several research has taken place to explore thermal, electrical and magnetic property of nanofluids. Nanofluids showed enhanced electrical and thermal conductivities. The nanofluids are also proved as a potential candidate for direct absorption solar collectors (DASC). The present work investigates the effect of nanoparticle volume fraction and the associated optical intensity attenuation with a semiconductor laser diode of wavelength 670 nm. Nanoparticles of Titanium dioxide (TiO 2 ) and Carbon doped Titanium dioxide (C-TiO 2 ) are prepared by sol gel and characterized by powder XRD, SEM and UV. Since carbon is a good absorption material, TiO 2 are doped with carbon (C-TiO 2 ) to increase the absorption of incident radiation. Nanoparticles of TiO 2 and C-TiO 2 with two weight fractions such as 0.04 and 0.08 are dispersed in water and ethylene glycol to obtain TiO 2 and C-TiO 2 nanofluids. The nanofluids are investigated for their sedimentation time. Stability of TiO 2 nanofluid is nine times more than C-TiO 2 nanofluid but C-TiO 2 nanofluid are found to be efficient absorbers than TiO 2 nanofluid. A low volume fraction of C-TiO 2 nanofluid can ensure high stability, low pumping power and good absorption for a DASC. Keywords- : Nanofluid, TiO 2 C-TiO 2, optical absorption, Laser.DASC 1. Introduction Increasing consumption and growing demands of electrical appliances across the globe have posed a threat on the non renewable energy resources and has made us exploit the maximum of renewable energy resources, in which solar energy is the ultimate choice. Solar energy has been investigated for photovoltaic and thermal applications (Duffie, 1980) [1]. A major thrust in materials development is to identify new materials in order to increase the efficiency of solar cells. Materials with ultra fine grain size and nanomaterials have provided an opportunity to tune the band gap and absorption of the existing solar energy. Conventional solar cells transfer the heat from the flat plate to the working fluid and it suffers from the large heat loss. The concept of direct absorption solar collectors in which working fluid acts as absorber and carrier of heat started replacing the conventional solar cells (Otanicar TP,2009) [2]. Since thermal conductivity of pure liquids are extremely less than solid particles, suspension of microparticles gained prominence. But micro-colloidal suspensions has drawbacks like abrasion and sedimentation. Nanofluids were substituted by Robert Taylor (2009) to overcome the above problems [3].The term Nanofluid was coined by Stephen Choi in 1995.[4] Nanofluids are suspensions of nanosized solid particles (1-100nm) in suitable base fluids. Since 1995, nanofluids have been explored as a heat transfer fluid and the best results have been reported by Eastman and Stephen Choi in ( 2001). In the past five years nanofluids have been also explored for their electrical (Suvankar Ganguly 2009)[5] and magnetic properties( John Philip,2009).[6] Nanofluids can be prepared by two ways, single step method (H Zhu 2004 )[7] or two step method (Eastman 1997) [8]. Single step method is based on simultaneous synthesis of nanoparticle and nanofluid and two step methods involve; the synthesis of nanoparticles in the first step followed by dispersion in a suitable base fluid in the second step. The success of nanofluid for DASC depends on suitable choice of base fluid and nanoparticles. The best nanofluids have high stability, high absorption of sun light and minimum abrasion. In the present work an attempt has been made to identify the best absorption nanofluid.

High-Throughput Contact Flow Lithography.

High-throughput fabrication of graphically encoded hydrogel microparticles is achieved by combining flow contact lithography in a multichannel microfluidic device and a high capacity 25 mm LED UV source. Production rates of chemically homogeneous particles are improved by two orders of magnitude. Additionally, the custom-built contact lithography instrument provides an affordable solution for patterning complex microstructures on surfaces.