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A numerical simulation through computational fluid dynamics is presented on the fluid flow mixing in a flow-focusing microfluidic device with three inlet channels confluence angles of 45, 67.5, and 90°. The effect of various parameters such as aspect ratio (0.5, 1, and 1.5), mixing channel length (1–4 mm), and Reynolds number (1–20) on the mixing efficiency, and the pressure drop are evaluated. The results demonstrate that the increase in mixing efficiency results from an increase in the Reynolds number and aspect ratio for all the angles. In addition, an increase in the pressure drop due to an increase in the Reynolds number and a decrease in the aspect ratio is observed. A longer length of the mixing channel indicates a higher mixing efficiency. The mixing efficiency is more suitable at an angle of 45° among the applied angles in terms of the operational and geometric parameters due to an increase in the contact surface of the flows at the inlet channels junction since the mixing index range is between 0.54 and 1 by varying the mentioned parameters.

The present study shows a facile route for producing doxorubicin (DOX)-loaded polycaprolactone (PCL) nanoparticles using a microfluidic device with a flow-focusing platform in a single step. Indeed, the evaluation of the performance of the flow-focusing microfluidic device for the preparation of DOX-loaded PCL (DOX/PCL) nanoparticles with a uniform size distribution and high encapsulation efficiency (EE) by applying the liquid non-solvent precipitation process is very important. Accordingly, the physicochemical characteristics of the DOX/PCL nanoparticles such as their mean size, polydispersity index (PDI), and EE were investigated by studying different parameters such as the flow rate ratio (FRR) and DOX concentration. Also, the release study was carried out at two pH of 5.5 and 7.4. The mean size of DOX/PCL nanoparticles achieved was in the range of 120-320 nm with a PDI ≤ 0.29 and EE between 48% and 87%. Moreover, the release profile of DOX/PCL nanoparticles was sustained for 10 days (≤66%) at pH 7.4. This means that the production process can result in a high EE and low release of the DOX drug.

In the present study, a double flow-focusing platform is applied to evaluate the application of microfluidic devices for the synthesis of liposomes with a uniform size distribution. The size, polydispersity index (PDI), and size distribution of liposomes are measured by varying different factors such as flow rate ratio (FRR), total flow rate (TFR), total lipid concentration, lipid/cholesterol molar ratio, and various lipid formulations. A comparison is made between the performance of double flow-focusing and single flow-focusing devices. The liposomes in the size range of 50–200 nm are produced with low PDIs of 0.1–0.37. The results show that the smallest particles are synthesized at the highest FRR and TFR, the lowest total concentration, a lipid/cholesterol molar ratio of 60:40, and single-lipid formulation. Also, the double flow-focusing device has the ability to apply higher TFR values than the single flow-focusing device, which leads to a higher productivity rate and smaller liposomes.

This study presents a novel and facile route to produce the methotrexate (MTX) loaded liposomal particles using the double flow focusing microfluidic (double-MHFF) device in a single step process. The double-MHFF design, due to the intensification of the mass diffusion by increasing the diffusion surface area of both phases can be a good candidate to produce the drug-loaded PEGylated liposomes. The physicochemical characteristics of the prepared MTX-liposome (MTX-L) and MTX-PEGylated liposome (MTX-PLL) such as particle size, polydispersity (PDI), and encapsulation efficiency are optimized by adjusting the operational and formulation parameters, like flow rate ratio (FRR), total flow rate (TFR), total lipid concentration and MTX concentration. Also, the release study is performed for MTX-L and MTX-PLL particles. The range of average size of the MTX-L and MTX-PLL nanoparticles are within 90–230 nm and 118–258 nm with PDI ≤ 0.32 and PDI ≤ 0.23, respectively. The double-MHFF device has the ability for achieving high encapsulation efficiency (≥ 60 %), especially for MTX-PLL. Also, the MTX-PLL nanoparticles have a sustained release and long-term fashion up to 72 h (≤ 48 %). This means that the high encapsulation efficiency and low release of MTX result from the production process.

This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases.

In this paper, a theoretical and experimental study of the energy and exergy efficiencies of cascade solar still is presented. By writing energy and exergy conservation equations for glass cover, brine, and absorber plate; correlations among climatic parameters, energy efficiency, exergy efficiency, and irreversibilities were provided. A computer simulation package was developed to analyze the energy and exergy effects. Effects of various parameters such as inlet brine flow rate, water thickness over the absorber plate, solar radiation intensity, ambient temperature, and inlet brine temperature on the energy and exergy efficiencies were investigated. The simulation results are in good agreement with the experimental data. Data analysis revealed that the maximum energy and exergy efficiencies which are 83.3% and 10.5% respectively are met when inlet brine flow rate reaches its minimum at 0.065 kg/min. Moreover, a comparison between exergy and energy efficiencies in terms of computational and experimental data for minimum and maximum input brine flow rates yielded RMSD of 7.34% and 3.8% for exergy efficiency and 6.11% and 4.25% for energy efficiency. Also, the analysis of irreversibility for different parts of the still in a specific day revealed that 84.17% of the entire system irreversibility was produced by the absorber plate.