The role of channel height and actuation method on particle manipulation in surface acoustic wave (SAW)-driven microfluidic devices

Surface acoustic wave (SAW) micromanipulation offers modularity, easy integration into microfluidic devices and a high degree of flexibility. A major challenge for acoustic manipulation, however, is the existence of a lower limit on the minimum particle size that can be manipulated. As particle size reduces, the drag force resulting from acoustic streaming dominates over acoustic radiation forces; reducing this threshold is key to manipulating smaller specimens. To address this, we investigate a novel excitation configuration based on diffractive-acoustic SAW (DASAW) actuation and demonstrate a reduction in the critical minimum particle size which can be manipulated. DASAW exploits the inherent diffractive effects arising from a limited transducer area in a microchannel, requiring only a travelling SAW (TSAW) to generate time-averaged pressure gradients. We show that these acoustic fields focus particles at the channel walls, and further compare this excitation mode with more typical standing SAW (SSAW) actuation. Compared to SSAW, DASAW reduces acoustic streaming effects whilst generating a comparable pressure field. The result of these factors is a critical particle size with DASAW (1 $$\upmu$$ μ m) that is significantly smaller than that for SSAW actuation (1.85 $$\upmu$$ μ m), for polystyrene particles and a given $$\lambda _{\text {SAW}}$$ λ SAW = 200 $$\upmu$$ μ m. We further find that streaming magnitude can be tuned in a DASAW system by changing the channel height, noting optimum channel heights for particle collection as a function of the fluid wavelength at which streaming velocities are minimised in both DASAW and SSAW devices.

EFFECT OF THE ORDER OF APPLICATION OF COPPER AND ZINC COMPOUNDS ON CATALYTIC ACTIVITY IN CO-OXIDATION REACTION

На основе алюмохромового носителя экстракционно-пиролитическим методом (ЭПМ) синтезирована серия медь-цинк-содержащих катализаторов, проанализировано влияние порядка внесения активных компонентов (меди и цинка) на качественный и количественный состав формирующихся фаз, а также глубину размещения в гранулах носителя, структурно-прочностные и каталитические свойства образцов в процессе окисления СО кислородом воздуха.Рассчитанные значения энергии активации и предэкспоненциального множителя показали, что порядок внесения активных компонентов оказывает влияние на кинетические параметры: наилучшие результаты наблюдаются в образцах, полученных совместной пропиткой алюмохромового носителя. Константы скорости реакции окисления СО (k), рассчитанные во всем температурном диапазоне более, чем в 2 раза выше, чем при совместном внесении компонентов.С помощью электронно-зондового микроанализа изучена текстура поверхности катализаторов ЭПМ, установлено, что не смотря на порядок внесения, технология ЭПМ позволяет получать однородную текстуру - поверхность катализаторов характеризуется слоистостью с частицами чешуйчатой структуры с минимальным размером частиц во всех случаях 0,4 мкм, максимальным 3-4 мкм. Совместное внесение Zn и Cu обеспечивает равномерное распределение компонентов по сечению гранул катализаторов.Результаты работы могут быть применимы для построения технологии эффективных медь-цинковых катализаторов для процессов окисления. Область применения катализаторов – комплексная очистка многокомпонентных газовых смесей. A series of copper-zinc-containing catalysts was synthesized on the aluminum - chromium oxides base by the extraction -pyrolytic method (EPM), the effect of the order application active components (copper and zinc) on the qualitative and quantitative composition of the formed phases, as well as the depth of placement in the granules of the baser, structural strength and catalytic properties of samples during oxidation with air oxygen was analyzed.The calculated values of the activation energy and the pre-exponential multiplier showed that the order of application active components has an effect on the kinetic parameters: the best results are observed in samples obtained by joint impregnation of an alumochrome carrier. The rate constants oxidation CO (k) calculated over the entire temperature range are more than 2 times higher when the components added together.Using electron probe microanalysis, the surface texture of the EPM catalysts was studied, it was found that, despite the order of application, the EPM technology allows to obtain a homogeneous texture - the surface of the catalysts is characterized by layering with particles of a scaly structure with a minimum particle size of 0.4 microns in all cases, and maximum 3-4 microns. The joint application of Zn and Cu ensures an even distribution of the components over the cross section of the catalyst granules.The results of the work can be applied to build a technology of effective copper-zinc catalysts for oxidation processes. The scope of application of catalysts is complex purification of multicomponent gas mixtures.

Jaya Algorithm for Optimization of Cooling Slope Casting Process Parameters

This study proposed the Jaya algorithm to estimate an improved value of billet performance through the cooling casting process. Jaya algorithm is a recent evolution-based algorithm that simulates using stochastic behaviour. The algorithm concept is the solution obtained for a given problem should move towards the best solution and should avoid the worst solution. This algorithm requires only the common control parameters and does not require any algorithm specific control parameters. To the best our knowledge, Jaya algorithm is not yet been used computational approach for optimization practice, particularly in the Cooling casting process. Three Cooling slope parameters process that influences the billet performance measurements, a maximum degree of sphericity and minimum grain size are pouring temperature, slanting angle, and travelling distance. The results show that the Jaya algorithm gave a better optimal solution for the maximum degree of sphericity and minimum particle size than experimental data.

Production of Rosuvastatin Calcium Nanoparticles Using Gas Antisolvent Technique

The activity of pharmaceutical substances crucially depends on the bioavailability of the substances. The bioavailability of drugs in body and their rate of dissolution in the biological fluids are increased if the particle size is decreased. In the present paper, the Gas Anti-Solvent (GAS) method was used to lower the size of rosuvastatin particles. The effects of temperature (313–338 K), pressure (105–180 bar) and initial solute concentration (20–60 mg/ml) were evaluated by Response Surface Methodology (RSM). The optimum initial solute concentration, temperature and pressure were found to be 20 mg/ml, 313 K and 180 bar, respectively which resulted in the minimum particle size. Furthermore, the particles were characterized by Differential Scanning Calorimetry (DSC), Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-Ray Diffraction (XRD). The analyses showed that the rosuvastatin particles (60.3 nm) precipitated by GAS process become significantly smaller than the initial particles (45.8 µm).

Thermal and Mechanical Behavior of Elastomers Incorporated with Thermoregulating Microcapsules

Polyurethane (PU) is one of the principal polymers in the global plastic market thanks to its versatility and continuous improvement. In this work, PU elastomeric materials having thermoregulating properties through the incorporation of microcapsules (mSD-(LDPE·EVA-RT27)) from low-density polyethylene and vinyl acetate containing paraffin®RT27 as PCM were produced. Elastomers were synthesized while varying the molar ratio [NCO]/[OH] between 1.05 and 1.1 and the microcapsule (MC) content from 0.0 to 20.0 wt.%. The successful synthesis of the PUs was confirmed by IR analyses. All the synthesized elastomers presented a structure formed by a net of spherical microparticles and with a minimum particle size for those with 10 wt.% MC. The density and tensile strength decreased with the MC content, probably due to worse distribution into the matrix. Elastomer E-1.05 exhibited better structural and stability properties for MC contents up to 15 wt.%, whereas E-1.1, containing 20 wt.% MC, revealed mechanical and thermal synergy effects, demonstrating good structural stability and the largest latent heat. Hence, elastomers having a large latent heat (8.7 J/g) can be produced by using a molar ratio [NCO]/[OH] of 1.1 and containing 20 wt.% mSD-(LDPE·EVA-RT27).

Characteristics and Distribution of Microplastics in Shoreline Sediments of the Yangtze River, Main Tributaries and Lakes in China—From Upper Reaches to the Estuary

Microplastics (MPs) pervade the environment and increasingly threaten both natural ecosystems and human health. In this study, we investigated MP particle concentrations in sediment samples collected from 54 sites along the banks of the Yangtze River and its major tributaries and on lakeshores. The main polymer types found in the samples were polypropylene (PP), polystyrene (PS), and polyethylene (PE). MP particle abundance in the various types of locations was 35–51968 particles/kg dry weight (d.w.) on the banks of the main river, 52–1463 particles/kg (d.w.) on the banks of tributaries and 2574–23685 particles/kg (d.w.) on lakeshores. Correlation between MP abundance and mean annual runoff of each upstream tributary was significant, which suggests that increased runoff brings more microplastic waste to streambank sediments. The most common shape of MP particles in all upstream samples was flake and in downstream samples it was foam. Small microplastic particles (< 0.050 mm) were predominant at all sites in this study and the minimum particle size in samples from the Yangtze river banks was 0.065 mm. Average abundance of MP particles on the shores of the source lake was 9069 particles/kg around the inlet but only 866 particles/kg around the outlet; the difference was due to interception associated with sedimentation and precipitation in the lake. This study provides data and presents a theoretical basis for the analysis of the accumulation and distribution of MPs in sediment in the Yangtze River basin.

Optimal ultrasonication process time remains constant for a specific nanoemulsion size reduction system

This paper theorizes the existence of a constant optimum ultrasound process time for any size-reduction operation, independent of process parameters, and dependent on product parameters. We test the concept using the case of ‘ultrasonic preparation of oil-in-water nanoemulsions’ as model system. The system parameters during ultrasonication of a hempseed oil nanoemulsion was evaluated by a response surface methodology, comprising lecithin and poloxamer-188 as surfactants. Results revealed that the particle size and emulsion stability was affected significantly (p < 0.05) by all product parameters (content of hempseed oil-oil phase, lecithin and polaxamer-surfactants); but was not significantly (p > 0.05) affected by process parameter (‘ultrasonication process time’). Next, other process parameters (emulsion volume and ultrasonic amplitude) were tested using kinetic experiments. Magnitude of particle size reduction decreased with increasing ‘ultrasonication process time’ according to a first order relationship, until a minimum particle size was reached; beyond which ultrasonication no longer resulted in detectable decrease in particle size. It was found that the optimal ultrasonication process time (defined as time taken to achieve 99% of the ‘maximum possible size reduction’) was 10 min, and was roughly constant regardless of the process parameters (sample volume and ultrasonic amplitude). Finally, the existence of this constant optimal ultrasonication process time was proven for another emulsion system (olive oil and tween 80). Based on the results of these case studies, it could be theorized that a constant optimum ultrasonication process time exists for the ultrasonication-based size-reduction processes, dependent only on product parameters.

Desulfurization of Thar Lignite by Oxidative Alkali Leaching Under Pressure

Pakistan is the world largest lignite bearing country in the world due to the Thar coal reserves. Sulfur contained in this coal need to be removed prior to combustion. Oxidative alkali leaching in dissolved oxygen technique was used to remove the sulfur from Thar coal. This method removed enough all three types of sulfur; about 90% pyretic sulfur, 78% organic sulfur and 50% sulfate sulfur and more than 82S% of total sulfur removal was achieved. Effect of various reaction parameters were observed, it was investigated that reaction time and partial pressure of oxygen has positive effect on the desulfurization, higher the reaction time and oxygen partial pressure higher the degree of desulfurization, also the desulfurization increased with increase in reaction temperature and alkali concentration till some optimum value and then decreases with further increase in value of temperature and concentration of alkali, although desulfurization was observed maximum with minimum particle size. Coal was also characterized with Thermogravimetric Analysis (TGA) and Testo smoke number to investigate the combustion behavior of processed coal. It was observed that combustion properties of processed coal were improved and black smoke in processed coal was reduced.

Corylus avellana leaf extract-mediated green synthesis of antifungal silver nanoparticles using microwave irradiation and assessment of their properties

Due to high antimicrobial activity against numerous microorganisms, silver nanoparticles (AgNPs) are being utilized in various areas. Microwave-accelerated AgNPs synthesis using Corylus avellana leaf extract was evaluated. Based on randomly central composite design, 13 mixture solutions containing different amounts of the prepared extract (0.10–0.90 mL) and 1 mM silver nitrate solution (15–25 mL) were prepared and exposed to microwave irradiation for 180 s. Response surface methodology was utilized to evaluate the effects of the two independent variables on particle size and concentration of the synthesized AgNPs, as manifested in the place of broad emission peak (λ max) and its absorbance unit, respectively. Fourier transform infrared spectroscopy analysis indicated that the two hydroxyl and carboxylic acid functional groups with reducing activity existed in the prepared extract. Dynamic light scattering and transmission electron microscopy analyses revealed that the formed spherical AgNPs using optimum amounts of C. avellana leaf extract (0.9 mL) and 1 mM silver nitrate solution (25 mL) had minimum particle size (103.5 nm) and polydispersity index (PDI) (0.209), and maximum concentration (140 ppm) and zeta potential (−21.8 mV). Results indicated that the formed AgNPs had high fungicidal effects against the spoiled fungi of Colletotrichum coccodes and Penicillium digitatum.

Astaxanthin–garlic oil nanoemulsions preparation using spontaneous microemulsification technique: optimization and their physico–chemical properties

Garlic oil in water nanoemulsion was resulted through subcritical water method (temperature of 120 °C and pressure of 1.5 bar, for 2 h), using aponin, as emulsifier. Based on the prepared garlic oil nanoemulsion, astaxanthin–garlic oil nanoemulsions were prepared using spontaneous microemulsification technique. Response surface methodology was employed to evaluate the effects of independent variables namely, amount of garlic oil nanoemulsion (1–9 mL) and amount of provided astaxanthin powder (1–9 g) on particle size and polydispersity index (PDI) of the resulted nanoemulsions. Results of optimization indicated that well dispersed and spherical nanodroplets were formed in the nanoemulsions with minimum particle size (76 nm) and polydispersity index (PDI, 0.358) and maximum zeta potential value (−8.01 mV), using garlic oil nanoemulsion amount of 8.27 mL and 4.15 g of astaxanthin powder. Strong antioxidant activity (>100%) of the prepared astaxanthin–garlic oil nanoemulsion, using obtained optimum amounts of the components, could be related to the highest antioxidant activity of the colloidal astaxanthin (>100%) as compared to that of the garlic oil nanoemulsion (16.4%). However, higher bactericidal activity of the resulted nanoemulsion against Escherichia coli and Staphylococcus aureus, were related to the main sulfur bioactive components of the garlic oil in which their main functional groups were detected by Fourier transform-infrared spectroscopy.