Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

Ody, T.; Panth, Mohan; Sommers, Andrew D.; Eid, Khalid

doi:10.1021/acs.langmuir.6b01030

Cited by 57 publications

(42 citation statements)

References 37 publications

(80 reference statements)

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“…Moreover, the magnetic force has been employed for ferrofluid droplet manipulation in digital-magnetofluidics, in which droplets move on an open surface. , Bulteau et al investigated the balance between magnetic force and gravitational force to control the motion of ferrofluid droplets on a superhydrophobic surface. Also, implementing a magnetic force to change the contact angle of ferrofluid droplets (magnetowetting), which causes the droplet to move, has been the subject of many studies so far. − …”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Dynamics of On-Demand Ferrofluid Drop Formation under a Pulse-Width-Modulated Nonuniform Magnetic Field

Bijarchi

2020

Langmuir

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Drop formation has been the focus of many studies because of its vast application in biomedicine and engineering, as well as its rich underlying physics. Applying a magnetic force on ferrofluids can provide more control over the formation process of the droplet. In this study, a time-dependent, nonuniform magnetic field was used for the formation of ferrofluid droplets using a nozzle. A pulse-width-modulation signal (PWM) was utilized to induce the time-dependent magnetic field, and a drop-on-demand system was designed using the capability of the PWM magnetic field. Three kinds of drop formation regimes under the PWM magnetic field were seen. Also, a new droplet generation regime was observed in which the drop is formed while it bounces back to the nozzle during the off-time period of the magnetic excitation. As compared to other techniques, the main advantage of droplet formation in this regime is that there will be no satellite droplet during the pinch-off. The regime map of drop formation based on the magnetic Bond number and the dimensionless induced frequency was obtained. Also, the effect of the duty cycle, the induced frequency, the magnetic induction, and the vertical interval between the coil's top surface and the nozzle on the drop formation evolution, the equivalent diameter of the droplets, the frequency of droplet formation, and the pulses that are necessary to form a drop was studied. Additionally, it was illustrated that by prolonging the duty cycle, the magnetic induction, or by decreasing the induced frequency, the equivalent diameter of the drop and the pulses that are necessary to form a drop reduce, while the frequency of drop formation increases. Eventually, a correlation for predicting the nondimensionalized diameter of the droplet, based on dimensionless variables, was presented with a maximum relative error of 8.1% and an average relative error equal to 2.2%.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Dynamics of On-Demand Ferrofluid Drop Formation under a Pulse-Width-Modulated Nonuniform Magnetic Field

Bijarchi

2020

Langmuir

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“…Stamatopoulos et al reported a radial gradient surface that could achieve horizontal self-transport distances up to 65 times the droplet diameter and even in uphill motion against gravity. Furthermore, wedged microgroove substrates, , bionic microgrooves, and chemical gradient coating surfaces could also be used to realize the self-actuation of droplets. A suitable wetting gradient could make the liquid droplet move spontaneously due to surface tension heterogeneity, inspiring a variety of exciting applications such as inkjet printing, water/oil separation, water harvesting, , antifogging, and microfluidic control …”

Section: Introductionmentioning

confidence: 99%

Regular Self-Actuation of Liquid Metal Nanodroplets in Radial Texture Gradient Surfaces

Song

et al. 2021

Langmuir

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Liquid metal movement in microfluidic devices generally requires an external stimulus to achieve its motion, which results in many difficulties to precisely manipulate its motion at a nanoscale. Therefore, there is an attempt to control the motion of a liquid metal droplet without the input of an external force. In this paper, we report an approach to achieve the self-actuation of a gallium nanodroplet in radial texture gradients on substrates. The results have proved the validity of this method. It is suggested that there are four stages in the self-motion of the droplet and that the precursor film forming on the second stage plays a pivotal role in the motion. Furthermore, how the impact velocity affects the self-actuation of the nanodroplet on the gradient surface is also studied. We find that the moderate impacting velocity hinders the self-actuation of the gallium nanodroplet. This study is very helpful to regulate the self-actuation on patterned substrates and facilitate their applications in the fields of microfluidics devices, soft robots, and liquid sensors.

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“…Moving liquid droplets in desired directions can be facilitated by the gravitational force [7,8] and unbalanced interfacial forces attributable to the wettability difference between regions of different surface energies [9]. A large number of studies have been committed to devise wettability gradient surface.…”

Section: Introductionmentioning

confidence: 99%

Laser pattern-induced unidirectional lubricant flow for lubrication track replenishment

et al. 2021

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Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation. Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades. This paper proposes the use of surface effect, wettability gradient, to achieve the goal. This method is simple and can be nicely implemented using femtosecond laser ablation. A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied. Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution, thereby escalating oil replenishment to the lubrication track. The effect is due to the unbalanced interfacial force created by the surface pattern. The influence of the shape and the pitch of teeth, which are the two governing factors, on oil transport is also reported. The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply. These results are promising, demonstrating the reduction in bearing friction and the increase in lubricating film thickness.

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Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

Cited by 57 publications

References 37 publications

Experimental Investigation on the Dynamics of On-Demand Ferrofluid Drop Formation under a Pulse-Width-Modulated Nonuniform Magnetic Field

Experimental Investigation on the Dynamics of On-Demand Ferrofluid Drop Formation under a Pulse-Width-Modulated Nonuniform Magnetic Field

Regular Self-Actuation of Liquid Metal Nanodroplets in Radial Texture Gradient Surfaces

Laser pattern-induced unidirectional lubricant flow for lubrication track replenishment

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