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

Bijarchi, Mohamad Ali; Favakeh, Amirhossein; Alborzi, Saeed; Shafii, Mohammad Behshad

doi:10.1016/j.snb.2020.129274

Cited by 36 publications

(17 citation statements)

References 50 publications

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“…Using the chain rule and assuming that the air as continuous phase is non-magnetic (𝜒 𝑐 = 0), the magnetic susceptibility gradient becomes ∇𝜒 = rearranging this equation, the magnetic susceptibility is calculated via Equation (13).…”

Section: Governing Equations and Numerical Discretization Methodsmentioning

confidence: 99%

“…Surfactants are coated around the nanoparticles to increase the stability of the suspension. Ferrofluids simultaneously have the magnetic properties of nanoparticles as well as the fluidity of carrier fluid and have found various applications such as heat transfer enhancement [10,11], mixing [12], droplet generation from the nozzles and microfluidics [13,14], droplet splitting [15,16], merging [17], and manipulation in magnetic digital microfluidics [18,19]. Mefford et al [20] showed the application of utilizing ferrofluid droplets for restorative treatment of retinal detachment by investigating the ferrofluid droplet movement in a viscous medium using a small magnet.…”

Section: Introductionmentioning

confidence: 99%

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On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

Bijarchi

Yaghoobi

Favakeh

2021

Preprint

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The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field achieved by the larger domain for the boundary condition. The Finite volume method and coupling of level-set and Volume of Fluid methods are used for solving equations. The droplet formation is simulated in a two-dimensional axisymmetric domain. The method of solving fluid and magnetic equations is validated using a benchmark. Then, ferrofluid droplet formation is investigated experimentally and the numerical results are in good agreement with the experimental data. The effect of 12 dimensionless parameters including the ratio of magnetic, gravitational, and surface tension forces, the ratio of the nozzle and magnetic coil dimensions, and ferrofluid to continuous-phase properties ratios are studied. The results showed that by increasing the magnetic Bond number, gravitational Bond number, Ohnesorge number, dimensionless saturation magnetization, initial magnetic susceptibility of ferrofluid, the generated droplet diameter reduces, whereas the formation frequency increases. The same results were observed when decreasing the ferrite core diameter to outer nozzle diameter, density, and viscosity ratios.

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Section: Governing Equations and Numerical Discretization Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

Bijarchi

Yaghoobi

Favakeh

2021

Preprint

Self Cite

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Section: Recently Developed Applicationsmentioning

confidence: 99%

“…The size and frequency of FF droplet generation at a T-junction can be controlled by a non-uniform time-dependent magnetic field, a suitable alternative for moving magnets or an array of micro-coils. 813,814 Nonuniform magnetic field induced ferrofluid droplet splitting presented above creates a large liquid surface area, a magnetically tunable, hydrophobic, liquid substrate. Functionalized by a fusion protein the ferrofluid interface is capable of capturing antibody molecules, which are released when the pH of the solution is decreased (Fig.…”

Section: Ferrofluid Droplet Technologymentioning

confidence: 99%

Ferrofluids and bio-ferrofluids: looking back and stepping forward

et al. 2022

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“…Prior knowledge of droplet size, shape, formation frequency or pressure drop are usually required for the work with devices based on droplet-based microfluidic. Several experimental studies have already investigated the mechanisms behind droplet generation in microfluidic channels [11][12][13][14][15]. Those measurements give an adequate information about the needs of a certain experimental setup; it is not possible however, to include the influence of all effective parameters on the system.…”

mentioning

confidence: 99%

Parameters influencing the droplet formation in a focusing microfluidic channel

et al. 2021

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In the present work a detailed numerical study of the parameters influencing the droplet formation in a flow-focusing microfluidic device are made. First, an extensive verification of the simulations with data from the literature is carried out. Influence of parameters like viscosity and inflow velocity are compared with the results from literature showing a good agreement. Some differences are attributed to the different numerical techniques used: in the present work a pure volume-of-fluid method is used, while in the reference study this method is combined with the level-set method. As a second step of the verification of the present model, a comparison with experimental data from the literature was carried out which shows a very good agreement. After the verification was completed, eight new simulations are carried out covering a wide range of velocities of the continuous phase uc. In these simulations the velocity of the discrete phase ud remains unchanged. The variation of the continuous phase velocity reveals that with increasing the value of uc, respectively the value of the capillary number Ca, the droplet length reaches a point of saturation, i.e. a point where the droplet length does not decrease any more. For the present setup this saturation occurs for Ca > 0,03. On the other hand, when the velocity of the continuous phase goes towards very low values (Ca < 0,01 for the present setup), the droplet size increases significantly. Further, it was found that for increasing capillary numbers Ca above a value around 0,015 for water/oil and above 0,025 for water + 40% glycerol / oil systems, a transmission from the dripping towards the jetting regimes of droplet formation occurs. It was shown that when the viscosity of the continuous phase increases, higher total pressure jumps in the droplet occur, also leading to the formation of smaller droplets.

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

Cited by 36 publications

References 50 publications

On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

Ferrofluids and bio-ferrofluids: looking back and stepping forward

Parameters influencing the droplet formation in a focusing microfluidic channel

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