On-demand ferrofluid droplet formation with non-linear magnetic permeability in the presence of high non-uniform magnetic fields

Bijarchi, Mohamad Ali; Yaghoobi, Mohammad Ali; Favakeh, Amirhossein

doi:10.1038/s41598-022-14624-w

Cited by 13 publications

(6 citation statements)

References 53 publications

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“…Several studies have been performed to investigate the droplet formation and the mixing within droplets using magnetic particles [ 28 ]. Some of these works evaluated the mixing efficiency and merging of microparticles into a magnetic platform [ 29 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Non-Uniform Magnetic Field on the Efficiency of Mixing in Droplet-Based Microfluidics: A Numerical Investigation

et al. 2022

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Achieving high efficiency and throughput in droplet-based mixing over a small characteristic length, such as microfluidic channels, is one of the crucial parameters in Lab-on-a-Chip (LOC) applications. One solution to achieve efficient mixing is to use active mixers in which an external power source is utilized to mix two fluids. One of these active methods is magnetic micromixers using ferrofluid. In this technique, magnetic nanoparticles are used to make one phase responsive to magnetic force, and then by applying a magnetic field, two fluid phases, one of which is magneto-responsive, will sufficiently mix. In this study, we investigated the effect of the magnetic field’s characteristics on the efficiency of the mixing process inside droplets. When different concentrations of ferrofluids are affected by a constant magnetic field, there is no significant change in mixing efficiency. As the magnetic field intensifies, the magnetic force makes the circulation flow inside the droplet asymmetric, leading to chaotic advection, which creates a flow that increases the mixing efficiency. The results show that the use of magnetic fields is an effective method to enhance the mixing efficiency within droplets, and the efficiency of mixing increases from 65.4 to 86.1% by increasing the magnetic field intensity from 0 to 90 mT. Besides that, the effect of ferrofluid’s concentration on the mixing efficiency is studied. It is shown that when the concentration of the ferrofluid changes from 0 to 0.6 mol/m3, the mixing efficiency increases considerably. It is also shown that by changing the intensity of the magnetic field, the mixing efficiency increases by about 11%.

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Section: Introductionmentioning

confidence: 99%

The Effect of Non-Uniform Magnetic Field on the Efficiency of Mixing in Droplet-Based Microfluidics: A Numerical Investigation

et al. 2022

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“…where B is the magnetic flux density (T), and M is the magnetization of the ferrofluid ( ) A m , which can be expressed by the Langevin function (eq 8). 46,55 Ä…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…Ferrofluid is a colloidal suspension of magneto-responsive particles in a fluidic medium , and has found many applications in microfluidics for its controllability with magnetic stimuli, for example, in droplet manipulation, − droplet formation, − droplet splitting, double emulsion generation, shape control, mixing, and pumping . Backholm et al studied the damped oscillations of ferrofluid sessile droplets immersed in oil and developed theoretical models to describe the oscillating system .…”

Section: Introductionmentioning

confidence: 99%

Vibration and Jumping of Ferrofluid Marbles under an Initial Magnetic Perturbation

et al. 2023

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Liquid marbles are being promoted as a replacement for conventional droplets in digital microfluidics. Liquid marbles can be remotely controlled by an external magnetic field if ferrofluid is utilized as their liquid cores. In this study, the vibration and jumping of a ferrofluid marble is experimentally and theoretically investigated. An external magnetic field is utilized to induce deformation in a liquid marble and an increase in its surface energy. As the magnetic field is switched off, the stored surface energy converts to gravitational potential and kinetic energies until it is dissipated. An equivalent linear mass-spring-damper system is used to study the vibration of the liquid marble, and the effect of its volume and initial magnetic stimulus on the vibrational characteristics, such as natural frequency, damping ratio, and deformation of the liquid marble, is experimentally examined. By analyzing these oscillations, the effective surface tension of the liquid marble is evaluated. Also, a novel theoretical model is proposed to obtain the damping ratio of the liquid marble, suggesting a new tool for the measurement of liquid viscosity. Interestingly, it is observed that the liquid marble jumps from the surface in the case of high initial deformation. Based on conservation law of energy, a theoretical model for predicting the liquid marbles jumping height and the boundary between jumping and non-jumping zones in terms of nondimensional numbers, namely, magnetic and gravitational Bond numbers and Ohnesorge number, is proposed with an acceptable error compared to experimental data.

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“…Ferrofluid, a stabilized suspension of magnetic nanoparticles in a fluidic media [ 27 , 28 ], has been found to have a myriad of applications in microfluidic systems thanks to its controllability by an external magnetic field [ 20 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. In the last decades, researchers have comprehensively studied the manipulation of ferrofluid droplets [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ].…”

Section: Introductionmentioning

confidence: 99%

Magnetically Driven Manipulation of Nonmagnetic Liquid Marbles: Billiards with Liquid Marbles

et al. 2022

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Liquid marbles are droplets encapsulated by a layer of hydrophobic nanoparticles and have been extensively employed in digital microfluidics and lab-on-a-chip systems in recent years. In this study, magnetic liquid marbles were used to manipulate nonmagnetic liquid marbles. To achieve this purpose, a ferrofluid liquid marble (FLM) was employed and attracted toward an electromagnet, resulting in an impulse to a water liquid marble (WLM) on its way to the electromagnet. It was observed that the manipulation of the WLM by the FLM was similar to the collision of billiard balls except that the liquid marbles exhibited an inelastic collision. Taking the FLM as the projectile ball and the WLM as the other target balls, one can adjust the displacement and direction of the WLM precisely, similar to an expert billiard player. Firstly, the WLM displacement can be adjusted by altering the liquid marble volumes, the initial distances from the electromagnet, and the coil current. Secondly, the WLM direction can be adjusted by changing the position of the WLM relative to the connecting line between the FLM center and the electromagnet. Results show that when the FLM or WLM volume increases by five times, the WLM shooting distance approximately increases by 200% and decreases by 75%, respectively.

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On-demand ferrofluid droplet formation with non-linear magnetic permeability in the presence of high non-uniform magnetic fields

Cited by 13 publications

References 53 publications

The Effect of Non-Uniform Magnetic Field on the Efficiency of Mixing in Droplet-Based Microfluidics: A Numerical Investigation

The Effect of Non-Uniform Magnetic Field on the Efficiency of Mixing in Droplet-Based Microfluidics: A Numerical Investigation

Vibration and Jumping of Ferrofluid Marbles under an Initial Magnetic Perturbation

Magnetically Driven Manipulation of Nonmagnetic Liquid Marbles: Billiards with Liquid Marbles

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