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    Enhanced oil-in-water droplet generation in a T-junction microchannel using water-based nanofluids with shear-thinning behavior: A numerical study

    , Article Physics of Fluids ; Volume 33, Issue 1 , 2021 ; 10706631 (ISSN) Besanjideh, M ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
    American Institute of Physics Inc  2021
    Nanofluids are widely used as the continuous phase during droplet formation in microsystems due to their impressive features such as excellent thermal, magnetic, and interfacial properties. Although it is well-known that nanofluids are susceptible to exhibit non-Newtonian behavior even at a low concentration of nanoparticles, effects of non-Newtonian behavior of nanofluids have not been studied on droplet formation thus far. In this study, oil-in-water droplet formation with a relatively high viscosity ratio of the immiscible phases was studied numerically in a T-junction microchannel. To inspect the non-Newtonian effects of aqueous nanofluids on droplet formation, empirical data on the... 

    Ferrofluid droplet breakup process and neck evolution under steady and pulse-width modulated magnetic fields

    , Article Journal of Molecular Liquids ; Volume 343 , 2021 ; 01677322 (ISSN) Bijarchi, M.A ; Favakeh, A ; Mohammadi, K ; Akbari, A ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2021
    Numerous applications in engineering and biotechnology have attracted the attention of many researchers to the analysis of underlying physical phenomena during the droplet pinch-off. In this study, the neck evolution during the formation of a ferrofluid droplet from a capillary is investigated under two types of magnetic field for a drop-on-demand system. The two types are steady and Pulse-Width Modulated (PWM) magnetic fields. First, under steady magnetic field, the necking process is studied for different values of magnetic Bond number and various angles between magnetic coil centerline and gravity. Subsequently, self-similar behavior in the vicinity of the detachment moment is observed.... 

    Experimental investigation of on-demand ferrofluid droplet generation in microfluidics using a Pulse-Width Modulation magnetic field with proposed correlation

    , Article Sensors and Actuators, B: Chemical ; Volume 329 , 2021 ; 09254005 (ISSN) Bijarchi, M. A ; Favakeh, A ; Alborzi, S ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2021
    Micro-magnetofluidics offers a promising tool to regulate the drop formation process with versatile applications in engineering and biomedicine. In the present study, on-demand ferrofluid drop generation at a T-junction is investigated utilizing a magnetic pulse. Also, a novel method for ferrofluid droplet formation is introduced using a non-uniform Pulse-Width Modulation (PWM) magnetic field. A novel mechanism of drop generation named “beating regime” was seen for the first time in which the ferrofluid moves back and forth before the breakup. The effect of the magnetic induction, continuous phase flow rate, duty cycle, and applied frequency on the generation frequency and drop diameter was... 

    Flow regime mapping for a two-phase system of aqueous alginate and water droplets in T-junction geometry

    , Article Physics of Fluids ; Volume 33, Issue 7 , 2021 ; 10706631 (ISSN) Mehraji, S ; Saadatmand, M ; Sharif University of Technology
    American Institute of Physics Inc  2021
    Microfluidic systems are an interesting topic for investigation due to their wide-spreading applications. Nowadays, polymeric solutions are used mainly for the generation of microparticles in biomedical engineering, food, and pharmaceutical industries. Droplet-based microfluidic devices have proposed an extensive interest in many applications such as chemical/biological/nanomaterial preparation to understand deeply the droplet size and formation in microchannels. However, numerous experimental and numerical studies have been done for oil-water combination, polymeric solutions behavior in the presence of oil has not been investigated widely. Therefore, it is important to understand the... 

    Electrowetting induced droplet generation in T-junctions

    , Article Journal of Heat Transfer ; Volume 143, Issue 5 , 2021 ; 00221481 (ISSN) Merdasi, A ; Moosavi, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2021
    In this study, droplet generation in a T-junction fluidic channel device was studied by using electrowetting actuation with the consideration of different droplet forming regimes. For this purpose, the finite element method (FEM) was used to solve the unsteady Naiver-Stokes equation. In addition, the level set method was applied to capture the interface between two phases. It was shown that there was a good agreement between obtained data and other work during the process of droplet generation in the absence of electrowetting actuation which results in the decrease in the size of the droplet with increasing the velocity ratios. In the shearing regime, the effectiveness of electrowetting on... 

    Shear-thinning droplet formation inside a microfluidic T-junction under an electric field

    , Article Acta Mechanica ; Volume 232, Issue 7 , 2021 , Pages 2535-2554 ; 00015970 (ISSN) Amiri, N ; Honarmand, M ; Dizani, M ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
    Springer  2021
    Researchers usually simplify their simulations by considering the Newtonian fluid assumption in microfluidic devices. However, it is essential to study the behavior of real non-Newtonian fluids in such systems. Moreover, using the external electric or magnetic fields in these systems can be very beneficial for manipulating the droplet size. This study considers the simulation of the process of non-Newtonian droplets’ formation under the influence of an external electric field. The novelty of this study is the use of a shear-thinning fluid as the droplet phase in this process, which has been less studied despite its numerous applications. The effects of an external electric field on this... 

    A plasmonic gold nanofilm-based microfluidic chip for rapid and inexpensive droplet-based photonic PCR

    , Article Scientific Reports ; Volume 11, Issue 1 , December , 2021 ; 20452322 (ISSN) Jalili, A ; Bagheri, M ; Shamloo, A ; Kazemipour Ashkezari, A. H ; Sharif University of Technology
    Nature Research  2021
    Polymerase chain reaction (PCR) is a powerful tool for nucleic acid amplification and quantification. However, long thermocycling time is a major limitation of the commercial PCR devices in the point-of-care (POC). Herein, we have developed a rapid droplet-based photonic PCR (dpPCR) system, including a gold (Au) nanofilm-based microfluidic chip and a plasmonic photothermal cycler. The chip is fabricated by adding mineral oil to uncured polydimethylsiloxane (PDMS) to suppress droplet evaporation in PDMS microfluidic chips during PCR thermocycling. A PDMS to gold bonding technique using a double-sided adhesive tape is applied to enhance the bonding strength between the oil-added PDMS and the... 

    The effect of a non-uniform pulse-width modulated magnetic field with different angles on the swinging ferrofluid droplet formation

    , Article Journal of Industrial and Engineering Chemistry ; Volume 84 , 2020 , Pages 106-119 Bijarchi, M. A ; Favakeh, A ; Shafii, M. B ; Sharif University of Technology
    Korean Society of Industrial Engineering Chemistry  2020
    In this study, ferrofluid droplet formation from a nozzle in the presence of a non-uniform Pulse-Width Modulated (PWM) magnetic field with different angles was studied experimentally. A Drop-on-Demand platform was introduced and three different regimes of droplet formation were observed. The regime map of the droplet formation was presented. A new type of droplet formation evolution was observed in which the droplet is formed while it is swinging around the nozzle, and the satellite droplet is not generated in this regime. The effects of five important parameters including magnetic flux density, applied magnetic frequency, duty cycle, distance between the nozzle and the center of the upper... 

    Ferrofluid droplet manipulation using an adjustable alternating magnetic field

    , Article Sensors and Actuators, A: Physical ; Volume 301 , 2020 Bijarchi, M. A ; Favakeh, A ; Sedighi, E ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2020
    Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes... 

    Numerical study on NOx reduction in a large-scale heavy fuel oil-fired boiler using suitable burner adjustments

    , Article Energy ; Volume 199 , 2020 Darbandi, M ; Fatin, A ; Bordbar, H ; Sharif University of Technology
    Elsevier Ltd  2020
    A numerical framework was carefully developed to simulate the combustion of heavy-fuel-oil (HFO) in a large-scale boiler. The present numerical solutions were compared with the measured data of a laboratory benchmark test and on-site operational data of the chosen HFO-fired boiler. Next, the developed framework was used to perform sensitivity analyses aiming to reduce the NO emission from the HFO-fired boiler without any adverse effect on its combustion performance. Practically, this study focused on re-adjustments of 24 working burners, which could control combustion in the HFO-fired boiler. The early outcome showed that the boiler NO emission and its combustion performance could be... 

    Ferrofluid droplet formation from a nozzle using alternating magnetic field with different magnetic coil positions

    , Article Journal of Magnetism and Magnetic Materials ; Volume 498 , 2020 Favakeh, A ; Bijarchi, M. A ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2020
    Ferrofluid has been used in many fields, such as microfluidics, droplet formation, and heat transfer, due to its potential to be attracted in the presence of a magnetic field. Droplet formation, itself, has many applications such as emulsions, 3D micro-printers, MEMS, and electro-sprays. In this study, the mechanism of ferrofluid droplet formation from the nozzle in the presence of an alternating magnetic field was investigated. The magnetic coil was fixed at different angles with respect to gravity and the effect of the alternating magnetic field and the angle of the magnetic coil axis with respect to gravity on the produced droplet volume, satellite droplet, and droplet formation frequency... 

    Swirl intensity as a control mechanism for methane purification in supersonic gas separators

    , Article Journal of Natural Gas Science and Engineering ; Volume 83 , 2020 Ghorbanian, K ; Amini Magham, M ; Sharif University of Technology
    Elsevier B.V  2020
    Supersonic gas separator is proposed for methane purification. One-dimensional analysis is performed to examine the design aspects associated with the converging-diverging nozzle and the liquid separation chamber. The results indicate that at low swirl intensities, the separation chamber length is about 100 times of the nozzle throat. Increasing the swirl intensity would lower this length sharply and it will be less than 10 for swirl intensity of unity which is equivalent to a swirl angle of 45°. In addition, a sensitivity analysis of the separator performance to the inlet conditions like the temperature, pressure, and composition of the mixture is carried out. It is observed that increasing... 

    CFD modeling of immiscible liquids turbulent dispersion in Kenics static mixers: Focusing on droplet behavior

    , Article Chinese Journal of Chemical Engineering ; Volume 28, Issue 2 , 2020 , Pages 348-361 Haddadi, M. M ; Hosseini, S. H ; Rashtchian, D ; Ahmadi, G ; Sharif University of Technology
    Chemical Industry Press  2020
    The present study is concerned with the computational fluid dynamics (CFD) simulation of turbulent dispersion of immiscible liquids, namely, water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software. To study the droplet size distribution (DSD), the Eulerian formulation incorporating a population balance model (PBM) was employed. For the Eulerian–Lagrangian approach, a discrete phase model (DPM) in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution (RTD) of droplets. In both approaches, a shear stress transport (SST)... 

    Effects of salinity, ion type, and aging time on the crude oil-brine interfacial properties under gravity condition

    , Article Journal of Petroleum Science and Engineering ; Volume 195 , December , 2020 Khajepour, H ; Akhlaghi Amiri, H. A ; Ayatollahi, S ; Sharif University of Technology
    Elsevier B.V  2020
    In this study, the impacts of salinity, ion type, and aging process were investigated on coalescence and spreading of crude oil interfaces (including an oil droplet and an oil film) under gravity, through drop rest time measurement techniques, aided by an image analysis system. Three different salt solutions of NaCl, Na2SO4, and MgCl2 were studied at different ionic strengths, ranged from 1% to 150% of Persian Gulf seawater ionic strength. According to the results, aging the oil droplet in the brine increased the interfacial rigidity. Addition of a gas phase - by thinning the surface oil film - almost doubled both rest time and spreading time values. In the aged mode, the presence of salt in... 

    Axis-switching and breakup of rectangular liquid jets

    , Article International Journal of Multiphase Flow ; Volume 126 , May , 2020 Morad, M. R ; Nasiri, M ; Amini, G ; Sharif University of Technology
    Elsevier Ltd  2020
    The behavior of low-speed liquid jets emerging from rectangular orifices into a quiescent air is studied numerically. After ejection, the rectangular cross-section transforms into an elliptical form along the jet and while axis-switching includes elliptical cross-sections only, the rectangular shape never establishes again. The optimum wavenumber, corresponding to the most dominant wave, is found to be greater in orifices with higher aspect ratios and, as a result, breakup length of the jet will be shorter. The breakup length decreases exponentially with the initial amplitude of disturbances. Moreover, it is observed that the form of final breakup leads to elimination of the satellite... 

    Numerical modeling of instability and breakup of elliptical liquid jets

    , Article AIAA Journal ; Volume 58, Issue 6 , June , 2020 , Pages 2442-2449 Morad, M. R ; Nasiri, M ; Amini, G ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2020
    Numerical simulations are performed to provide an in-depth insight into the effect of instabilities on liquid jets discharging from elliptical orifices. The axis-switching phenomenon and breakup are simulated and characterized under the effect of disturbances imposed at the nozzle exit. The simulations are based on the volume of fluid approach and an adaptive meshing. A range of orifice aspect ratios from 1 to 4 at the Rayleigh breakup regime is considered. The evolution of the jet cross section and axis switching under the influence of disturbances is compared with that of nonperturbed elliptical jets. It is found that the axis-switching repetition and breakup length exponentially decrease... 

    Fluidic barriers in droplet-based centrifugal microfluidics: Generation of multiple emulsions and microspheres

    , Article Sensors and Actuators, B: Chemical ; Volume 311 , May , 2020 Madadelahi, M ; Madou, M. J ; Dorri Nokoorani, Y ; Shamloo, A ; Martinez Chapa, S. O ; Sharif University of Technology
    Elsevier B. V  2020
    Droplet generation is very important in biochemical processes such as cell encapsulation, digital PCR (Polymerase Chain Reaction), and drug delivery. In the present paper, a density-based method called “fluidic barrier” is introduced to produce multiple emulsions on a centrifugal microfluidic platform or Lab-on-a-CD (LOCD). We show that the density and the viscosity of the fluids involved are important parameters for predicting the characteristics of the droplets generated with this method. Moreover, we broadened this concept by using the fluidic barriers to separate reactive chemicals. As a proof of concept, alginate and CaCl2 solutions are separated by an oil barrier to control the... 

    Parametric study of droplet formation and characteristics within microfluidic devices - A case study

    , Article International Journal of Applied Mechanics ; Volume 12, Issue 7 , 2020 Salehi, S. S ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
    World Scientific  2020
    Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a... 

    Microfluidic technologies to engineer mesenchymal stem cell aggregates—applications and benefits

    , Article Biophysical Reviews ; Volume 12, Issue 1 , 2020 , Pages 123-133 Salehi, S. S ; Shamloo, A ; Kazemzadeh Hannani, S. K ; Sharif University of Technology
    Springer  2020
    Three-dimensional cell culture and the forming multicellular aggregates are superior over traditional monolayer approaches due to better mimicking of in vivo conditions and hence functions of a tissue. A considerable amount of attention has been devoted to devising efficient methods for the rapid formation of uniform-sized multicellular aggregates. Microfluidic technology describes a platform of techniques comprising microchannels to manipulate the small number of reagents with unique properties and capabilities suitable for biological studies. The focus of this review is to highlight recent studies of using microfluidics, especially droplet-based types for the formation, culture, and... 

    Investigating the effect of reagent parameters on the efficiency of cell lysis within droplets

    , Article Physics of Fluids ; Volume 32, Issue 6 , 2020 Shamloo, A ; Hassani Gangaraj, M ; Sharif University of Technology
    American Institute of Physics Inc  2020
    Cell lysis is an essential primary step in cell assays. In the process of cell lysis, the cell membrane is destroyed and the substances inside the cell are extracted. By utilizing a droplet-based microfluidic platform for cell lysis, the mixer unit that is required for mixing lysis reagents with the cells can be excluded, and thus, the complexity of the fabrication process is reduced. In addition, lysing the cells within the droplets will prevent the cells from exposure to the channel walls, and as a result, cleanliness of the samples and the device is maintained. In this study, cell lysis within the droplets and the parameters affecting the efficiency of this process are investigated using...