Ferromagnetic Liquid Research Articles

Untethered & Stiffness-Tunable Ferromagnetic Liquid Robots for Cleaning Thrombus in Complex Blood Vessels.

Thrombosis is a significant threat to human health. However, the existing clinical treatment methods have limitations. Magnetic soft matter is used in the biomedical field for years, and ferromagnetic liquids exhibit tunable stiffness and on-demand movement advantages under magnetic fields. In this study, a ferromagnetic liquid robot (FMLR) is developed and applied it to thrombus removal in complex blood vessels. The FMLR consisted of Fe3O4 magnetic nanoparticles and dimethyl silicone oil. The FMLR can pass through a narrow complex maze through shape deformation by tailoring the intensity and direction of the external magnetic field. Finite element simulation analysis is used to validate the mechanism of controllable FMLR movements. Importantly, the storage modulus of FMLR can be tuned from 0.1 to 2018Pa by varying the external magnetic intensity, ensuring its effectiveness in removing rigid and stubborn thrombi present on the vascular walls. Toward medical robotic applications, FMLR can be used in telerobotic neurointerventional. Experiments demonstrating the capability of FMLR to remove thrombi in the ear veins of rabbits are conducted. This study introduces an efficient approach for thrombus elimination, broadening the utilization of FMLRs within the realm of clinical medicine.

Macroscopic dynamics of ferromagnetic smectic-A.

We derive the macroscopic dynamic equationsfor ferromagnetic smectic-A liquid crystals for which the spontaneous magnetization is parallel to the layer normal of the layering. As additional macroscopic variables when compared to simple fluids, we have the layer displacement u, familiar from smectic liquid crystals, and the magnetization density M. We find a number of reversible and dissipative cross-coupling terms to the additional macroscopic variables and discuss possible experiments to detect them. Among other effects, we point out that the velocity of first sound becomes anisotropic due to the influence of the modulus of the magnetization, while the magnitude of the velocity of second sound is modified. As for the static behavior, we find cross-coupling terms between the magnitude of the magnetization, on the one hand, and layer compression as well as osmotic pressure, on the other hand. In addition, we point out that as a dissipative effect, temperature gradients can induce gradients in the magnetization parallel to the layer normal, mediated by layer compressions.

Современные электронные датчики угла наклона: обзор основных физических принципов функционирования и перспективных разработок

Electronic tilt angle sensors, also called inclinometers, are devices that measure horizontal tilt and are widely used in many fields of science and technology. This paper considers not only the basic physical principles of the functioning of such sensors, but also provides examples of some promising developments in this field. Currently, tilt angle measuring devices based on electronic accelerometers are becoming increasingly common. At the same time, such devices have a significant disadvantage, which is expressed in the fact that the greater the measured angle of inclination, the lower the sensitivity of the device becomes. An important task is to develop specialized inclinometers with higher performance and lower power consumption. Such sensors use solid-state, liquid or gas free mass, which is driven by gravitational forces. Resistive, capacitive, inductive, magnetic, fiber-optic and optical methods are most often used to measure the reaction to gravity. Mercury or electrolyte is usually used as a conductive medium in liquid tilt sensors with an electric outlet, while devices with ferromagnetic liquid are also being developed. Optical inclinometers are immune to electromagnetic interference, which is suitable for extreme operating conditions and provides potentially high performance. Most of these devices are fiber sensors with a Bragg grid. In thermal inclinometers, the slope is analyzed by changing the resistance of the electrodes in the temperature field of the hot air flow in a sealed chamber. Capacitive inclinometers have a number of advantages, such as simplicity of design, non-contact measurement and the possibility of extended linear movement. It should be noted that in addition to tilt angle sensors, switches are being developed and successfully applied that open or close electrical contacts when a certain angle of inclination is reached.

Numerical Analysis of the Magnetic Dipole Effect on a Radiative Ferromagnetic Liquid Flowing over a Porous Stretched Sheet

Numerical Analysis of the Magnetic Dipole Effect on a Radiative Ferromagnetic Liquid Flowing over a Porous Stretched Sheet

Anisotropic Darcy–Brinkman Magnetic Fluid Convection under the Influence of a Time-Dependent Sinusoidal Magnetic Field

The impact of the sinusoidal mode of a magnetic field involving time fluctuations on the threshold of the ferromagnetic smart liquid convection in a saturated permeable medium is investigated using the regular perturbation technique. The Darcy–Brinkman model with anisotropic permeability is used to describe the flow through porous media. The thermal anisotropy is implemented in the energy equation. The problem might be useful in thermal engineering applications such as dynamic loudspeakers and computer hard discs and in medical applications like the treatment of tumor cells and the cell separation, to name a few. The regular perturbation technique is based on the minimum amplitude of a magnetic field modulation, and the onset criterion is dealt with in terms of a correction in the critical Rayleigh number and wavenumber. The thermal Rayleigh number correction depends on the magnetic field modulation frequency, magnetic force, anisotropies, porosity, and Prandtl number. At moderate values of the magnetic field modulation frequency, the impact of various physical factors is perceived to be noteworthy. The influences of the magnetic mechanism, Prandtl number, porosity parameter, and Brinkman number are shown to augment the destabilizing effect of the magnetic field modulation for moderate values of the frequency of a modulation. However, the destabilizing effect of the magnetic field modulation is diminished due to an increase in the values of the mechanical anisotropy parameter and thermal anisotropy parameter. The study reveals that the effect of the magnetic field modulation could be exploited to control the convective instability in an anisotropic porous medium saturated by a ferromagnetic fluid.

A Comprehensive Review of Ferromagnetic Liquid Dynamics and Nonlinear Thermal Buoyancy Effects

Ferromagnetic liquid is a unique class of fluids that exhibits strong magnetic properties when subjected to a magnetic field. This liquid has been extensively studied in various industrial and scientific applications due to its unique properties such as high thermal conductivity, heat capacity, and electrical conductivity. One of the key phenomena associated with this type of liquid is its nonlinear thermal buoyancy effect, which refers to the motion of the liquid due to variation in temperature caused by a non-uniform magnetic field. In recent years, there has been a growing interest in studying the nonlinear thermal buoyancy effect in ferromagnetic liquids, specifically in the context of heat transport processes.
 Non-Fourier heat flux is another crucial aspect of ferromagnetic liquids that has gained considerable attention among researchers. Non-Fourier heat flux is characterized by the deviation from the linear Fourier's law of heat conduction, where the rate of heat transfer is not proportional to the temperature gradient. In ferromagnetic liquids, this phenomenon is mainly attributed to the presence of magnetic fields, which influence the heat transfer processes within the liquid. This nonlinear heat flux behavior has significant implications in a wide range of applications, including heat dissipation, cooling, and thermal insulation.
 Radiated elastic surfaces are another key feature of ferromagnetic liquids that has recently emerged as a promising area of research. These surfaces are formed when a magnetic field is applied to a ferromagnetic liquid, resulting in the formation of elastic waves on the surface. These waves are created due to the interaction between the magnetic field and the elastic properties of the liquid. The formation of these surfaces has been observed to have a considerable impact on the heat transfer behavior of the liquid, where they act as efficient heat dissipators and significantly enhance the rate of heat exchange between the liquid and its surroundings.
 In summary, the interplay of nonlinear thermal buoyancy, non-Fourier heat flux, and radiated elastic surfaces in ferromagnetic liquids has attracted significant attention in recent years due to its potential for a wide range of practical applications. The understanding of these phenomena has the potential to significantly improve the design and efficiency of various heat transfer processes, making ferromagnetic liquids an important area of study in materials science and engineering. Future research in this field is expected to focus on developing more comprehensive models and experimental techniques to further explore the complex thermal and magnetic interactions in ferromagnetic liquids.

3D-Printed ferromagnetic Liquid Crystal Elastomer with Programmed Dual-Anisotropy And Multi-Responsiveness.

Liquid crystal elastomers (LCE) and magnetic soft materials are promising active materials in many emerging fields, such as soft robotics. Despite the high demand for developing active materials that combine the advantages of LCE and magnetic actuation, the lack of independent programming of the LCE nematic order and magnetization in a single material still hinders the desired multi-responsiveness. In this study, we developed a ferromagnetic LCE (magLCE) ink with nematic order and magnetization that can be independently programmed to be anisotropic, referred to as dual anisotropy, via a customized 3D printing platform. The magLCE ink was fabricated by dispersing ferromagnetic micro-particles in the LCE matrix, and a 3D printing platform was created by integrating a magnet with 3-DoF motion into an extrusion-based 3D printer. In addition to magnetic fields, magLCEs can also be actuated by heating sources (either environmental heating or photo-heating of the embedded ferromagnetic microparticles) with a high energy density and tunable actuation temperature. We demonstrated a programmed magLCE strip robot with enhanced adaptability to complex environments (different terrains, magnetic fields, and temperatures) using a multi-actuation strategy. The magLCE also has potential applications in mechanical memory, as demonstrated by the multi-stable mechanical metastructure array with remote writability and stable memory. This article is protected by copyright. All rights reserved.

Electric field-induced interfacial instability in a ferroelectric nematic liquid crystal

Studies of sessile droplets and fluid bridges of a ferroelectric nematic liquid crystal in externally applied electric fields are presented. It is found that above a threshold, the interface of the fluid with air undergoes a fingering instability or ramification, resembling to Rayleigh-type instability observed in charged droplets in electric fields or circular drop-type instabilities observed in ferromagnetic liquids in magnetic field. The frequency dependence of the threshold voltage was determined in various geometries. The nematic director and ferroelectric polarization direction was found to point along the tip of the fingers that appear to repel each other, indicating that the ferroelectric polarization is essentially parallel to the director. The results are interpreted in connection to the Rayleigh and circular drop-type instabilities.

Tuneable optical diffractive structures from liquid crystalline materials incorporated into periodic polymeric scaffolds

ABSTRACTDiffractive optical elements (DOEs) are micro-structured components used in various photonic devices to manipulate propagation direction and often also polarisation state of optical beams. The simplest type of DOEs are one-dimensional diffraction gratings. We perform theoretical investigation of electrical and magnetic tunability of such gratings composed as a periodic assembly of polymer and ferromagnetic nematic liquid crystal (LC) layers. We analyse how various grating parameters and boundary conditions influence the LC configuration in the assembly. For static response to external electric and/or magnetic fields, the distortion profile of the director field is determined numerically and analytically by minimisation of the Landau-de Gennes free energy, while for the dynamic response only numerical solutions are provided. The resulting optical diffraction properties are determined numerically via solving the Maxwell’s equations by using the rigorous coupled-wave analysis. We demonstrate that the described methodology provides an efficient tool for designing various new types of polarisation-sensitive LC-based DOEs, such as three-state polarisation switches for application in spectroscopic, optical communication, and remote sensing systems.

Magnetic induced terahertz modulation characteristics based on ferromagnetic nematic liquid crystals

In recent years, solid state terahertz (THz) modulators have obtained rapid progress with the widespread use of two-dimensional (2D) materials in the field of THz; however, challenges remain in preparing flexible THz modulators. In this study, flexible ferromagnetic nematic materials were prepared by doping thermotropic nematic liquid crystals 5CB into magnetic fluids, and the influence of water was reduced by a self-made cyclic olefin copolymer (COC) microfluidic chip. THz modulation characteristics of magnetic fluid and ferromagnetic nematic liquid crystal (FNLC) under the induction of external magnetic field were compared using a THz time domain spectroscopy system. Under the action of a 91 mT magnetic field, the magnetic fluid has a maximum modulation depth (MD) of 54%. Under the same magnetic field, the maximum MD of the FNLC materials increase to 78% because of the rearrangement of Fe3O4 nanoparticles induced by the topological defect of the liquid crystal. We demonstrate that the magneto-optical effect is significantly enhanced in the ferromagnetic nematic liquid crystal hybrid system. This strategy of doping thermotropic nematic liquid crystals to enhance the magneto-optical effect has great potential for THz filtering, modulation, and sensing applications.

Magnetic induced terahertz modulation characteristics based on ferromagnetic nematic liquid crystals

Magnetic induced terahertz modulation characteristics based on ferromagnetic nematic liquid crystals

Flow and Heat Transfer Analysis of a Thin Film Ferromagnetic Liquid over an Unsteady Stretching Sheet

A two-dimensional, unsteady flow of a thin layer of ferromagnetic liquid over a stretching sheet is considered. The flow is exposed to an external magnetic field in the direction of the stretching sheet. The boundary layer equations with the associated boundary conditions are transformed into ODEs using suitable similarity transformations. The resultant system of ODEs is numerically solved using the shooting technique by appropriately guessing the initial values and then correcting them by the Newton-Raphson scheme. The effects of the dimensionless parameters on the flow and heat exchange characteristics are graphically analyzed. It is found that the thickness of the film reduces with magnetization and unsteadiness parameters.

Assessment of the effect of ferromagnetic liquids on oil recovery of bituminous sands

In Azerbaijan, in addition to natural oil, there are large reserves of it in the form of bituminous rocks. The largest reserves are concentrated in the Balakhani part of the Kirmaki mountain, which are more than 50 million tons. In order to extract oil from bituminous rocks, various methods are used. Including such methods of extracting oil from bituminous rocks (BR): boiling BR with water without additives and with alkaline type additives; extraction method using various solvents; thermal cracking of BR; flotation method and supercritical fluid extraction. In addition to these, methods of influencing bituminous sands with various physical fields are also used, one of which is the use of ferromagnetic fluids (FMF). The use of alkali reactive reagent with iron nanoparticles is an improvement of the method for extracting heavy oil components from bituminous rocks and an environmentally friendly innovative technology. The study of the influence of the magnetic field with tension to 10 A/m on the process of oil extraction from bituminous rocks before and after the use of ferromagnetic fluid showed an increase in oil recovery by 7–8 % and 8–11 %, respectively. Further increase in the external magnetic field strength with the maximum tight bond of the magnetic moment with ferromagnetic particles of nanometer sizes can lead to the appearance of additional tangent stresses caused by the braking of the particle rotation field, the subsequent increase of the effective viscosity of the colloid solution. A numerical method for determining the threshold value of the magnetic field strength has been proposed to analyze this phenomenon, at which the value of the dynamic viscosity of the magnetic fluid is achieved, which is the limit for oil from the field corresponding to the extraction of oil from bituminous rocks.

Effect of Throughflow on Marangoni Convection in Ferromagnetic Liquids with Variable Viscosity

The effect of surface tension and vertical throughflow in magnetic field and temperature sensitive liquid of Newtonian ferromagnetic type is examined. Combining shooting and Galerkin techniques the stationary critical eigenvalues are computed. On the ferroconvection onset, M3, non-buoyancy magnetic parameter and Pr (>1), Prandtl number have no influence. For upward or downward directions dual effect of destabilizing or stabilizing the system is observed in the presence of vertical throughflow. Throughflow effect studied through Pe, Peclet number delays ferroconvection onset and is observed to be independent to flow direction. M1, the magnetic buoyancy number, and V, the variable viscosity parameters have destabilizing influences on the system. Ferrofluids being fascinating materials are used as constant agents for magnetic resonance imaging (MRI). The great variety of magnetic fluids are tailored for technological, biological, medical and material science applications. Key words: Ferroconvection, throughflow, surface tension, temperature dependent viscosity, magnetic field dependent viscosity.

Numerical investigation of ferromagnetic liquid film flow over an unsteady stretching surface in the presence of radiation and aligned magnetic field

AbstractAn investigation of the two‐dimensional unsteady flow of a thin layer of ferromagnetic liquid past a stretching sheet is performed. The flow is exposed to an external magnetic field in the axial direction along with the thermal radiation effect. Relevant Maxwell's equations are considered together with the conservation laws of fluid dynamics to model the problem. The mathematical model is constructed using a system of partial differential equations with relevant boundary conditions, which are transformed into two‐point boundary value problem (BVP) using similarity transformations. The resultant BVP is numerically solved by a shooting technique that involves Runge–Kutta–Fehlberg (RKF45) method to integrate the initial value problem and the Newton–Raphson method to refine the guessed initial values. The influence of the dimensionless parameters on the flow and heat exchange characteristics is graphically analyzed. It is found that the thickness of the film increases for higher values of the thermal radiation parameter. The thermal profile shows increasing behavior with the radiation parameter and reverse effect with the Prandtl number.

Ferromagnetic Lubricants in a Bearing with a Porous Coating of a Base Ring

Based on the flow equation of the ferromagnetic liquid lubricant for the “thin layer”, the continuity equation and the Darcy equation describing the flow of a lubricant in a porous body, the paper presents an accurate self-similar solution of the V-shaped sliding support with a porous coating of the base ring surface taking into account the rheological properties of the lubricant with ferromagnetic properties when the working gap is partially filled at the laminar flow mode. Analytical dependencies were obtained for the field of velocities and pressures in lubricating and porous layers. Besides, the main working characteristics of the studied friction pair are determined: bearing capacity and friction force. The paper provides the assessment of the influence of parameters characterizing ferromagnetic rheological properties, length of the loaded region of the Hartmann number and parameter characterizing the presence of electromagnetic field on the bearing capacity and friction force.

Effect of Stefan blowing and magnetic dipole on chemically reactive second-grade nanomaterial flow over stretching sheet

A numerical examination is executed to scrutinise the heat and mass transfer characteristics in a stagnation point flow of viscous ferromagnetic second-grade liquid over a stretching sheet. Moreover, features of chemical reaction, magnetic dipole and Stefan blowing aspects are presented in this novel attempt by employing Buongiorno model in the flow problem. Similarity transformations are used to convert the governing partial differential equations into ordinary differential form, which are then solved using classical Runge–Kutta (RK) process with shooting technique. The solutions for the flow, thermal, concentration, skin friction, rate of heat and mass transfer characteristics are attained numerically and presented graphically. The significant results of the current study are that the rising values of ferromagnetic interaction parameter declines the velocity. The improvement in values of Brownian motion and thermophoresis parameter augments the heat transfer. Furthermore, the rising values of thermophoresis parameters decline the heat and mass transfer rate.

Synthesis, structure and electromagnetic properties of FeCoAl/C nanocomposites

Magnetic nanoparticles play an important role in rapidly developing advanced branches of science and industry, e.g. fabrication of magnetic storage media, synthesis of ferromagnetic liquids, medicine and chemistry. One problem faced in the usage of magnetic nanoparticles is their high chemical activity leading to oxidation in air and agglomeration. The chemical activity of magnetic nanoparticles stems from the contribution of their large specific surface to volume ratio. Carbon coating of nanoparticles reduces the interaction between nanoparticles. FeCoAl/C metal-carbon nanocomposites have been synthesized using IR pyrolysis of polymer / metal salt precursors. The effect of synthesis temperature (IR heating) in the range from 500 to 700 °C on the structure and composition of the nanomaterials has been studied. We show that the forming particles are the FeCoAl ternary solid solution with a FeCo based bcc lattice. An increase in the synthesis temperature from 500 to 700 °C leads to an increase in the coherent scattering region of three-component nanoparticles from 5 to 19 nm. An increase in the aluminum content from 20 to 30 % relative to Fe and Co results in an increase in the size of the nanoparticles to 15 nm but this also entails the formation of a Co based solid solution having an fcc lattice. An increase in the nanocomposite synthesis temperature and a growth of the relative Al content as a result of a more complete carbonization and the structure-building effect of metals reduce the degree of amorphousness of the nanocomposite carbon matrix and lead to the formation of graphite-like phase crystallites having an ordered structure. The effect of synthesis temperature and relative content of metals on the electromagnetic properties (complex dielectric and magnetic permeability) of the synthesized nanocomposites has been studied. Synthesis conditions affect the radio absorption properties of the nanocomposites, e.g. reflection loss (RL) in the 3—13 GHz range.

Mathematical model of a ferromagnetic lubricant in the presence of a porous coating in the bearing structure

Based on the flow equation of a ferromagnetic liquid lubricant for a “thin layer”, the continuity equation and Darcy’s equation describing the flow of a lubricant in a porous body, an exact self-similar solution of wedge-shaped sliding support with a porous coating of the surface of the support ring is found, taking into account the dependence of the viscosity of the ferromagnetic lubricant and the permeability of the porous coating with the incomplete filling of the working gap. Analytical dependencies for the velocity and pressure fields in the lubricating and porous layer are obtained. Also, the main operating characteristics are determined load-bearing capacity and friction force. The numerical analysis of the theoretical results showed that the bearing capacity of the bearings can be increased by 8-12% in the range of the studied load-speed modes. At the same time, the coefficient of friction is reduced by 14-16%. To verify and confirm the effectiveness of the obtained theoretical models, an experimental study of a modified wedge-shaped sliding support on TP-22C, MS-20 oil and their mixture with various additives was carried out. As a result of theoretical and experimental studies, tribotechnical characteristics were determined that allow us to judge the presence of a long-term friction mode.

Synthesis, structure and electromagnetic properties of FeCoAl/C nanocomposites

Magnetic nanoparticles play an important role in rapidly developing advanced branches of science and industry, e.g. fabrication of magnetic storage media, synthesis of ferromagnetic liquids, medicine and chemistry. One problem faced in the usage of magnetic nanoparticles is their high chemical activity leading to oxidation in air and agglomeration. The chemical activity of magnetic nanoparticles stems from the contribution of their large specific surface to volume ratio. Carbon coating of nanoparticles reduces the interaction between nanoparticles. FeCoAl/C metal-carbon nanocomposites have been synthesized using IR pyrolysis of polymer/metal salt precursors. The effect of synthesis temperature (IR heating) in the range from 500 to 700 °C on the structure and composition of the nanomaterials has been studied. We show that the forming particles are the FeCoAl ternary solid solution with a FeCo based bcc lattice. An increase in the synthesis temperature from 500 to 700 °C leads to an increase in the coherent scattering region of three-component nanoparticles from 5 to 19 nm. An increase in the aluminum content from 20 to 30% relative to Fe and Co results in an increase in the size of the nanoparticles to 15 nm but this also entails the formation of a Co based solid solution having an fcc lattice. An increase in the nanocomposite synthesis temperature and a growth of the relative Al content as a result of a more complete carbonization and the structure-building effect of metals reduce the degree of amorphousness of the nanocomposite carbon matrix and lead to the formation of graphite-like phase crystallites having an ordered structure. The effect of synthesis temperature and relative content of metals on the electromagnetic properties (complex permittivity and permeability) of the synthesized nanocomposites has been studied. Synthesis conditions affect the radio absorption properties of the nanocomposites, e.g. reflection loss (RL) in the 3–13 GHz range.