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Micromixers and Microvalves for Point-of-Care Diagnosis and Lab-on-a-Chip Applications
Published in Raju Khan, Chetna Dhand, S. K. Sanghi, Shabi Thankaraj Salammal, A. B. P. Mishra, Advanced Microfluidics-Based Point-of-Care Diagnostics, 2022
Aarathi Pradeep, T. G. Satheesh Babu
Rheological microvalves make use of the rheological properties of the fluid to bring about the valve action. Electrorheological fluids are widely used for developing lab-on-a-chip devices. These fluids are a type of colloidal suspension whose viscosity changes in response to an applied electrical field. They exhibit a solid-like behavior in an applied electric field of 1–2 kV/mm. Miyoshi et al. described the development of microvalves based on nematic liquid crystals whose viscosity is a function of the applied electric field (Miyoshi et al. 2016). Ferrofluids employ magnetic particles suspended in a carrier liquid to produce magnetic liquids that can respond to the localized magnetic field, thus providing easy actuation. Vinogradova et al. carried out numerical studies of a ferrofluid-based valve that responds to the magnetic field of an in-built current-carrying wire (Vinogradova et al. 2019).
Magnetizable Fluids
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Tom Black, J. David Carlson, Daniel E. Barber
Ferrofluid is a magnetically responsive liquid. Its magnetic properties arise from a stable suspension of magnetic particles in a liquid medium. Each particle is itself a permanent magnet. In order to achieve a stable suspension, the particles must remain far enough apart that their magnetic moments do not interact strongly. In this way the particles are not attracted to each other, but are free to respond to an external magnetic force. This separation is normally accomplished by coating the particles with a surfactant. Figure 43.1 represents the ferrofluid system schematically. Surfactant molecules are long polymer chains of a type that is compatible with the liquid medium. They are provided with a functional group at one end that binds to the particle. With a proper surfactant formulation, and given the right conditions, a particular particle species can be suspended in a particular liquid medium [2]. Surfactant chemistry and processing conditions are generally proprietary, and are specific to a given end use application. The following is a discussion of the nature of the particles and liquid media that are most commonly found in commercial ferrofluids.
Magnetic Nanofluids—A Novel Concept of Smart Fluids
Published in Mangey Ram, Mathematics in Engineering Sciences, 2019
The suspension of nanoparticles on conventional fluids sometimes enhanced the thermal conductivity of fluids even by 100 times than that of the carrier fluids. Many experimental investigations have been performed to demonstrate the enhancing and lowering of heat transfer behavior of MNF so that they can be utilized in improving the process performance of thermal devices. The study of the rheological behavior of magnetic nanosuspensions have numerous commercialized applications in engineering and applied sciences (physical and medical sciences), such as various industrial thermal devices, computer storage devices, magnetic sealing, energy conversion system, thermal power generating system, nuclear reactors, transportation, biomedicine, etc. These fluids are also used in lubrication process in dampers and bearings. In electronics, ferrofluids are greatly applied to several devices, for example, sensors, accelerometer, densimeters, pressure transducers, electromechanical, energy converters etc. One special application of MNFs is their use as magnetic ink for high-speed, inexpensive and silent printers. Due to the effect of the Curie’s law, these fluids become less magnetic at high temperature, and the heated fluid is replaced from its position with the cold fluid, attracted by the externally applied magnetic field. This property of ferrofluids manifests in its heat reducing capabilities, which finds its heat controller applications in electric motors, high rotating surface devices, and hi-fi loudspeakers.
Bioconvective Carreau nanofluid flow with magnetic dipole, viscous, and ohmic dissipation effects subject to Arrhenius activation energy
Published in Numerical Heat Transfer, Part A: Applications, 2023
Magnetohydrodynamics (MHD) is basically the study of flow that have magneto properties and electrically transmitted fluids. In conducting fluids, the magnetic field (MF) induce current those polarized fluids and itself changes the MF reciprocally. Some common examples of magneto-fluids are electrolytes, liquid metals, salt water, and plasma. Now, MHD has extensive range of implementations in astrophysics, geophysics, and in agricultural sciences. Also, very often in technical fields, MHD has a substantial interest because of its high-yielding utilization in industrial fields. For example, liquid metal flow control, nuclear reactor cooling, MHD power generators, petroleum industries, plasma studies such as high-temperature plasma, biological transportation, control of hypervelocity vehicles, and crystal growth, some related work can be seen in Refs. [5–9]. A liquid that strongly magnetized by applying magnetic field is known as ferrofluid or normally referred as ferromagnetic fluid. When magnetic nanoparticle are added to base fluid, formed a nanofluid subclass, as they frequently respond to applied magnetic field. Ferrofluid has numerous real life applications in industrial and scientific field such as targeting cancer cells or tumors, MRI, biomedical engineering, medicines, sensor and optical applications, hi-fi speakers, purification of molten metals, in electrical devices to heat controlling, magnetic based devices, lithographic designing, accelerometer, shock absorbers, ferrofluid lubrication of bearings, etc., are some common example of ferrofluids.
Dynamics of ferromagnetic due to nonlinear thermal buoyancy when Cattaneo–Christov heat flux and magnetic dipole whose magnetic scalars are significant
Published in Waves in Random and Complex Media, 2022
T.K. Sreelakshmi, Annamma Abraham, A.S. Chethan, Essam R. El-Zahar, C.S.K. Raju, B.T. Raju, Nehad Ali Shah
For such an implementation scenario, a ferromagnetic liquid seemed to be good. The candidate as the flow could be regulated through a magnetic field by external means. The analysis of the interaction of electromagnetic fields with fluids has begun to gain attention in recent years with the promise of implementations in areas such as chemical engineering, nuclear fusion, medicine and high-speed noise-free printing. Ferrofluids have nearly specific magnetic properties as a solid but act as a continuous liquid in particular ways. A peculiar mixture of magnetic and fluidic properties justifies the creation of many groundbreaking applications. A magnetic fluid is a stable and liquid two-phase matter and a three-component structure composed of magnetic particles, liquid carriers and surfactants. Particles are either positively or negatively charged in the former case. The fluid is called ferrofluid-ionic. In the above case, a suitable surfactant is coated with each particle and the resultant liquid is known as the surfaced fluid layer. On the other hand, in the presence of a magnetic field, the magnetic fluid should remain stable, i.e. there should be no agglomeration and phase separation. The authors [13–17] studied the flow properties by taking ferrofluid into account based on relevance.
Non-Uniform Magnetic Field Effect on Forced Convection Heat Transfer of Flattened Tubes Using Two-Phase Mixture Model
Published in Heat Transfer Engineering, 2021
Elnaz Yousefi, Hamid Reza Nazif, Hasan Najafi Khaboshan, Amiratabak Azarinia
Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid (oil, water, ethylene glycol, etc.). The nanoparticles used in nanofluids are typically made of metal oxides or carbon nanotubes which are suspended in the base fluid for increasing the thermal conductivity of fluid [15]. The existence of nanoparticles in the base fluid causes to improve the heat transfer rate as a result of this extensive thermal conductivity [16]. Najafi Khaboshan and Nazif [17] analyzed the improvement of heat transfer and entropy generation of Al2O3/water nanofluid in an alternating oval cross-section tube, numerically. They detected that the heat transfer rate of nanofluids increases with an increment in the volume fraction of nanoparticles. Also, they showed that the nanoparticles size has a reverse relationship with heat transfer and pressure loss. In recent years, the magnetic nanofluids have been also used for enhancing the heat transfer which have both properties of the fluid and magnetic [18, 19]. Ferrofluids are one of the magnetic nanofluids that are made of the ferromagnetic nanoparticles (such as Fe3O4) suspended in a fluid (such as water) [20]. In this research, the Fe3O4/water ferrofluids have been used as a working fluid.