Colloid Journal最新文献

Micromixers represent microchannel devices that promote effective fluid integration within a constrained spatial domain and a specified flow pathway. The mechanism of induced-charge electroosmosis has garnered substantial attention from the microfluidics scholarly community over the past decade. In this study, an electroosmotically actuated micromixer amalgamates two disparate fluids that enter through individual inlets into a unified channel measuring 15 μm in width and 80 μm in length, respectively. A sinusoidal electric potential, with a peak value of 0.1 V at a frequency of 8 Hz, is applied across the electrodes. To enhance the operational efficacy of the micromixer, 45 uniform circular barriers are integrated within the microchannel. According to the simulation outcomes, the micromixer attains an exemplary mixing efficiency nearing 0.97 and exhibits promising potential applications across a diverse array of fields, including biochemistry and biomedical sciences.

Morphological characteristics of the nanolayers of amphiphilic tert-butylthiacalix[4]crown-4-ether in cone stereoisomeric form 1 and bolaamphiphilic nitrothiacalix[4]biscrown-5-ether in 1,3-alternate form 2 deposited onto quartz substrate at varying solvent, temperature, and concentration of compounds are analyzed. Quantum-chemical calculations of the considered calix[4]arenes reveal a favorable micellar aggregation (the packing factor p < 0.3). During AFM visualization of calixarene nanolayers prepared through evaporation of solvent on substrate, spherical associates that are 200–800 nm in size are detected for compound 1, which enlarge with a decrease in the concentration of compound and an increase in solvent polarity and environmental temperature. At the same time, the dispersity of the sizes of associates increases with a decrease in temperature, but has a mixed dependence on solvent and concentration. The most uniform size distribution of spherical particles is achieved upon Langmuir monolayer formation at the air–water interface upon deposition of the solution of compound 1 in 10^–5 M solution in chloroform onto water subphase and upon vertical transfer onto substrate. In the case of bolaamphiphile 2, spherical associates are formed at t = 23°C in 10^–5 М solution in toluene and at 4°С in 10^–4 М solution in chloroform, while under other combinations of conditions, the nanofilm is represented by thread-like structures (at 23°С) and tactoid aggregates (at 4°С). Dynamic light scattering study of the solutions of amphiphile 1 in chloroform allows to detect spherical aggregates (particle size is 202 ± 92 nm), which indicates the decisive role of solvent in the formation of spherical aggregates in nanolayers, while in other cases the supramolecular organization of calixarenes is presumably affected by the interaction with substrate.

The aim of this work is to find new ways to synthesize latexes (polymer suspensions) with a given size and surface structure of particles. The need for such latexes is not large-scale, but their development and production are extremely important for the development of high technologies. Monodisperse latexes are especially valuable in immunological diagnostics of a wide range of diseases. The article presents the results of studies of the nucleation of latex particles in a heterogeneous monomer−water system. The results of these studies made it possible to find conditions for the reproducible synthesis of monodisperse polystyrene latexes. In order to change the surface structure of latex particles, cetyl alcohol was dissolved in the initial monomer phase (styrene). The article presents the results of electron microscopic studies of the synthesized latexes. Nano crystals of this alcohol are clearly visible on the surface of the latex particles. It is suggested that, in deep monomer conversions, the process of crystallization of cetyl alcohol begins in polymer-monomer particles.

This work is devoted to studying the effect of an additional treatment of detonation nanodiamond (DND) powder of basic purification on the surface composition of DND particles, as well as their electrokinetic properties and aggregate stability in solutions of an indifferent electrolyte (NaCl) within a wide pH range. It has been found that an increase in the degree of purification and the number of protonated carboxyl groups on the surface of DND particles due to additional acidic and thermoammonia treatments leads to a shift in the position of the isoelectric point (IEP) from pH 7.0 for an initial sample to pH 6.3 and pH 6.0, respectively. It has been shown that the coagulation thresholds of the hydrosols at natural pH and the positions of stability zones in a 10^–3 M sodium chloride solution are in complete compliance with the IEP values. The highest thresholds values at pH 5.8 are observed for the initial DND, while, for the dispersion of DND particles subjected to the thermoammonia treatment, the fast coagulation occurs already at a concentration of 10^–4 M. It has also been found that the aggregate stability zones for additionally treated DND samples almost coincide with each other. For DND of basic purification, the stability zone expands in the region of positive zeta-potentials, while, in the region of negative values, no stability is observed, probably, due to the partial dissolution of surface impurities at high pH values and the transfer of their ionic forms to the solution, which causes coagulation of the DND particles.

The stabilization of bulk nanobubbles with a balance at their boundary of the Laplace pressure due to surface tension and electrostatic pressure due to Coulomb forces is considered. The presence of a hydrate layer of thickness ~1 nm with a tangential orientation of water dipoles around it is taken into account, the low permittivity of which, approximately equal to 3, increases the pressure at the boundary of the nanobubble. The dimensions and charge of a stable nanobubble are determined. It is shown that in salt water, the hydrate layer, regardless of the charge of the nanobubble, increases the pressure at its boundary by almost 30 times, and in fresh water—from 10 to 4 times.

This paper presents the results of a numerical simulation of an electrolyte solution behavior near a spherical dielectric microparticle covered with a homogeneous ion-selective shell under the influence of an external electric field. The particle is assumed to be stationary, and the electrolyte either stays still or is pumped externally with a constant velocity in absence of the electric field. The field, in turn, generates electroosmotic flow near the particle’s surface. It is shown that concentration polarization can occur near the particle, whereas electrokinetic instability only occurs near particles with a sufficiently thick shell. When the particle’s surface charge is opposite to the one of its shell, non-stationary regimes may be observed when the shell is thin enough.

Antibacterial coatings are used in the food, textile, and construction industries, as well as in biotechnology and medicine. This review considers the main types of coatings that prevent surfaces from fouling with biomacromolecules and microorganisms, i.e., anti-adhesive, contact-type, release-based, multifunctional, and intelligent (“smart”) coatings. For each type of the coatings, the most relevant and efficient active substances and their action mechanisms are described. Despite the wide use of anti-adhesive surfaces and contact-type coatings, they have many drawbacks that limit the scope of their application and reduce their activity and durability. Numerous studies have shown that multifunctional and intelligent coatings have a high potential for practical application and further studies of their modification aimed at producing universal and economically advantageous coatings. The main problem of the practical application of such surfaces is the imperfection of the methods used to assess the stability and antibacterial properties of the coatings under laboratory conditions.

A set of rheological equations based on structural-kinetic representations has been presented to describe viscous and elastic properties of structured liquids, namely, concentrated suspensions, emulsions, micellar solutions, and polymer solutions and melts. The structural model equations are valid for equilibrium stationary and equilibrium oscillating flows. The equations are suitable for approximating (tau (dot {gamma })), ({{N}_{1}}(dot {gamma })), (G{kern 1pt} ^{"}(omega )), and (G{kern 1pt} '(omega )) rheological curves in some intervals of shear rates or oscillation frequencies, with each interval corresponding to a certain state of a structure. The results of approximating shear viscosity curves for a polymer solution, a micellar solution, and an emulsion are presented as examples.

Porous crosslinked polyelectrolyte microspheres 1–5 μm in diameter have been synthesized on the basis of either p-styrene sulfonate used as a functional monomer or a mixture of p-styrene sulfonate and vinyl acetate. The content of sulfonate groups in the obtained polyelectrolyte microspheres is higher than 2 mmol/g. It has been shown that the incorporation of the hydrophobic comonomer significantly increases the swelling degree of the polyelectrolyte microspheres. The adsorption value of model compounds (fuchsine and methylene blue) has been found to significantly exceed the concentration of sulfonate groups. The morphology and structure of the surface layer of polyelectrolyte microspheres have been studied by optical and scanning electron microscopy and FTIR spectroscopy, while their specific surface area has been determined by the BET method.

The time dependences of the contact angles and the wetted surface spot diameters have been measured during the interaction between Co–Cu melts with copper contents of 20, 40, and 60 at % and graphite at temperatures of 1390, 1440, 1490, 1540, and 1590°C. Under these conditions, graphite is not wetted by the Co–Cu melts: the final contact angles for Co80–Cu20, Co60–Cu40, and Co40–Cu60 are 95, 110, and 100°, respectively. Therewith, the final diameters of the wetted surface spots somewhat increase. The metallographic analysis of the microstructure of the Co–Cu–C composite materials obtained by the contact alloying of Co–Cu melts with carbon has shown that the morphology of the structural components and the phase composition of the samples depend on the copper content. Composite materials (Co–27%C–10%Cu) + (Co–32%C–62%Cu) + C and (Co–19%C–15%Cu) + (Co–25%C–72%Cu) + C obtained by the interaction of the Co–Cu melts containing 20 and 40 at % copper with graphite have a macrohomogeneous structure.