Magnetic fluids have a unique combination of magnetic properties, fluidity and colloidal stability, which has allowed them to find applications in a variety of technical
devices, such as shock absorbers and sensors. One of the features of this smart material is the ability to control its physical properties using various combinations of magnetic influences. In
this work, the dynamics of a magnetic fluid volume levitating in an uniform magnetic field of an electromagnet undergoing oscillatory shear is investigated. The samples with different
physical parameters were considered, the dependence of magnetoviscous effect was investigated. It is shown that the microstructure of the sample and the presence of large magnetic
particles have the greatest influence on the dynamics of the magnetic fluid undergoing oscillatory shear and magnetoviscous effect. The results of the work can be used to develop a method
for express testing of magnetic fluid samples, as well as to develop acceleration and vibration sensors based on magnetic fluids [1].
The dependences of the viscosity for samples MF-1 – MF-4 are plotted, shown in Figure 1. The obtained dependences of the viscosity show an increase in its value by a factor of 5 for the
MF-1 sample, with an increase in the field to 1000 kA/m, which can be explained by interparticle interactions and the formation of weakly bound aggregates in the near-wall layer in a
more concentrated initial MF-1 sample. In a more diluted sample MF-2, such an increase in viscosity is not observed. The images MF-3, MF-4 are characterized by the presence of an
excess free surfactant, which negatively affects the magnetoviscous effect.
The work was carried out the part of the implementation of the program of strategic academic leadership "Priority-2030" (Agreements No. 075-15-2021-1155 and No. 075 -15-2021-1213)
and as part of the implementation of the state task (No 0851-2020-0035).<br>


**References:** 1. Ryapolov P. A., Polunin V. M., Shel'deshova E. V, JMMM 496, 165924 (2020).<br>

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/0830bf9692a5653321593e7b0a3af1e2.png)

Dynamics of magnetic fluids and bidisperse magnetic systems undergoing oscillatory shear

In previous works, we presented the results of the dynamics of the air-magnetic fluid interface under the influence of a non-uniform magnetic field of the moving ring magnet [1, 2]. A distinctive feature of the used magnetic systems is the presence of the magnetic levitation area, with the help of which it becomes possible to control the dynamics of non-magnetic inclusions in the magnetic fluid. This work presents the results of further studies, in which the experiments were performed in microchannels of various configurations with injection of a non-magnetic phase using the syringe pump. In addition to the dynamics of gas inclusions in a magnetic fluid in an inhomogeneous magnetic field, the behavior of non-magnetic droplets of various liquids is presented. The influence of the parameters of the magnetic field and the properties of a magnetic fluid on the dynamics of non-magnetic inclusions and the size of detached bubbles and drops is investigated. It was found that the feed rate of non-magnetic inclusions and external hydrostatic pressure do not affect the size of gas bubbles and non-magnetic drops detached from the levitating main volume. The ability to control the size of non-magnetic inclusions is shown using an external magnetic field and concentration of the magnetic fluid. The results presented in the work can be used to develop microfluidic counters and controlled dispensers of non-magnetic inclusions. The investigation was carried out with the support of part of the implementation of the state task for 2020 (No 0851-2020-0035).

![](https://assets.underline.io/uploads/markdown_image/1/image/bbf4b3226914678eaa7b1eb99bd0c3c3.jpg)

Data of video recording of the position of the interphase boundary of the volume of a nonmagnetic fluid in a magnetic fluid before, at and after the detachment of a nonmagnetic drop from it in an inhomogeneous magnetic field of a ring magnet

Dynamics of nonmagnetic inclusions in a microchannel with a magnetic fluid in an inhomogeneous magnetic field

**Please click on the poster to see the abstract or leave your comment to the author.**<br>
**Session Chair:** Norman Wereley, *University of Maryland*

QPB: Manipulation of Magnetic Fluids

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Evgeniiy Sokolov

2

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Dynamics of magnetic fluids and bidisperse magnetic systems undergoing oscillatory shear

Dynamics of nonmagnetic inclusions in a microchannel with a magnetic fluid in an inhomogeneous magnetic field

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