Particle encapsulation in aqueous ferrofluid drops and sorting of particle-encapsulating drops from empty drops using a magnetic field

Soft Matter ◽  
2021 ◽  
Author(s):  
Utsab Banerjee ◽  
Sachin Jain ◽  
Ashis Sen
Keyword(s):  
Magnetic Field ◽  
Continuous Phase ◽  
Biochemical Assays ◽  
Particle Encapsulation

Handling and manipulation of particle-encapsulating droplets (PED) have profound applications in biochemical assays. Herein we report encapsulation of microparticles in aqueous ferrofluid droplets in a primary continuous phase (CP) and...

Green Function Calculations of Properties for the Magnetocaloric Layered Structures Based Upon FeMnAsP

SPIN ◽  
2016 ◽  
Vol 06 (03) ◽  
pp. 1650010
Author(s):  
Osvaldo F. Schilling
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Green Function ◽  
Landau Theory ◽  
Random Phase ◽  
Layered Structures ◽  
Continuous Phase ◽  
Theoretical Treatment ◽  
Entropy Variation ◽  
Commercial Applications

The alternating Fe–Mn layered structures of the compounds FeMnAsxP[Formula: see text] display properties which have been demonstrated experimentally as very promising as far as commercial applications of the magnetocaloric effect are concerned. However, the theoretical literature on this and other families of magnetocaloric compounds still adopts simple molecular-field models in the description of important statistical mechanical properties like the entropy variation that accompanies applied isothermal magnetic field cycling, as well as the temperature variation following adiabatic magnetic field cycles. In the present paper, a random phase approximation Green function theoretical treatment is applied to such structures. The advantages of such approach are well known since the details of the crystal structure are easily incorporated in the model, as well as a precise description of correlations between neighbor spins can be obtained. We focus on a simple one-exchange parameter Heisenberg model, and the observed first-order phase transitions are reproduced by the introduction of a biquadratic term in the Hamiltonian whose origin is related both to the magnetoelastic coupling with the phonon spectrum in these compounds as well as with the values of spins in the Fe and Mn ions. The calculations are compared with experimental magnetocaloric data for the FeMnAsxP[Formula: see text] compounds. In particular, the magnetic field dependence for the entropy variation at the transition temperature predicted from the Landau theory of continuous phase transitions is reproduced even in the case of discontinuous transitions.

scholarly journals Weak Singularities of the Isothermal Entropy Change as the Smoking Gun Evidence of Phase Transitions of Mixed-Spin Ising Model on a Decorated Square Lattice in Transverse Field

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1533
Author(s):  
Jozef Strečka ◽  
Katarína Karl’ová
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Ising Model ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
Transverse Magnetic ◽  
Continuous Phase ◽  
Square Lattice ◽  
Mixed Spin ◽  
Weak Singularities

The magnetocaloric response of the mixed spin-1/2 and spin-S (S>1/2) Ising model on a decorated square lattice is thoroughly examined in presence of the transverse magnetic field within the generalized decoration-iteration transformation, which provides an exact mapping relation with an effective spin-1/2 Ising model on a square lattice in a zero magnetic field. Temperature dependencies of the entropy and isothermal entropy change exhibit an outstanding singular behavior in a close neighborhood of temperature-driven continuous phase transitions, which can be additionally tuned by the applied transverse magnetic field. While temperature variations of the entropy display in proximity of the critical temperature Tc a striking energy-type singularity (T−Tc)log|T−Tc|, two analogous weak singularities can be encountered in the temperature dependence of the isothermal entropy change. The basic magnetocaloric measurement of the isothermal entropy change may accordingly afford the smoking gun evidence of continuous phase transitions. It is shown that the investigated model predominantly displays the conventional magnetocaloric effect with exception of a small range of moderate temperatures, which contrarily promotes the inverse magnetocaloric effect. It turns out that the temperature range inherent to the inverse magnetocaloric effect is gradually suppressed upon increasing of the spin magnitude S.

DYNAMIC SIMULATION OF PRESSURE DRIVEN FLOW OF FLUIDS WITH SUSPENDED FERROUS PARTICLES IN A MICRO CHANNEL UNDER MAGNETIC FIELD

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4890-4897
Author(s):  
SINAN OZCAN ◽  
CAHIT A. EVRENSEL ◽  
MARK A. PINSKY ◽  
ALAN FUCHS
Keyword(s):  
Magnetic Field ◽  
Pressure Gradient ◽  
Uniform Magnetic Field ◽  
Computational Study ◽  
Fluid Phase ◽  
Continuous Phase ◽  
Micro Channel ◽  
Carrier Fluid ◽  
Discrete Phase ◽  
Pressure Driven Flow

This computational study focuses on the dynamics of individual ferrous particles and the flow of the incompressible Newtonian fluid under the effect of an externally applied magnetic field and pressure gradient in a two-dimensional micro channel with smooth walls. The particle dynamics is simulated as a discrete phase using MATLAB code and the fluid flow is solved as a continuous phase using Computational Fluid Dynamics Software FLUENT. Interaction between the particle and fluid phases are included as hydrodynamic forces predicated by the fluid phase simulation and updated particle locations determined by the particle phase solution under non-uniform magnetic field. Non-uniform magnetic field forces the particles to move to poles of the magnet, and results in their accumulation. This causes drastic change on the continuous phase flow and pressure distribution, which in turn influences the particle motion. Predicted dynamics of the suspended ferrous particles under magnetic field and flow of the carrier fluid with pressure gradient is in reasonably well agreement with previous work. The results show that non-uniform magnetic field generated by externally placed magnets can be used to control the locations of the particles and flow of the fluid in a micro channel.

scholarly journals Magnetic-field-controlled spin fluctuations and quantum critically in Sr3Ru2O7

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
C. Lester ◽  
S. Ramos ◽  
R. S. Perry ◽  
T. P. Croft ◽  
M. Laver ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Inelastic Neutron Scattering ◽  
Density Wave ◽  
Quantum Critical Point ◽  
Spin Density Wave ◽  
Continuous Phase ◽  
Spin Fluctuations ◽  
Electronic Heat Capacity ◽  
Electronic Heat

AbstractWhen the transition temperature of a continuous phase transition is tuned to absolute zero, new ordered phases and physical behaviour emerge in the vicinity of the resulting quantum critical point. Sr3Ru2O7 can be tuned through quantum criticality with magnetic field at low temperature. Near its critical field Bc it displays the hallmark T-linear resistivity and a $$T\,{{{{{{\mathrm{log}}}}}}}\,(1/T)$$ T log ( 1 / T ) electronic heat capacity behaviour of strange metals. However, these behaviours have not been related to any critical fluctuations. Here we use inelastic neutron scattering to reveal the presence of collective spin fluctuations whose relaxation time and strength show a nearly singular variation with magnetic field as Bc is approached. The large increase in the electronic heat capacity and entropy near Bc can be understood quantitatively in terms of the scattering of conduction electrons by these spin-fluctuations. On entering the spin-density-wave ordered phase present near Bc, the fluctuations become stronger suggesting that the order is stabilised through an “order-by-disorder” mechanism.

scholarly journals Diamagnetic Manipulation of Cell-Encapsulating Droplets

2021 ◽  
Author(s):  
Stephanie Buryk-Iggers
Keyword(s):  
Magnetic Field ◽  
Flow Rate ◽  
Continuous Phase ◽  
Phase Flow ◽  
Label Free ◽  
Flow Focusing ◽  
Precise Control ◽  
Prostate Cells ◽  
The Magnetic Field ◽  
Droplet Phase

In this thesis, a microfluidic method for label-free control of cell encapsulating droplets is developed using diamagnetic forces. To generate droplets in a microfluidic device, we use a symmetrical flow-focusing design, where two streams of a continuous phase shear a single stream of a droplet phase, resulting in droplet generation. First, it is shown that by adjusting only the droplet phase flow rate, precise control of empty droplets can be achieved. Human prostate cells are then introduced to the system and encapsulated by droplets. Control of the cell-encapsulated droplets and empty droplets is studied. It is shown that cell-encapsulated droplets and empty droplets deflect by different amounts when exposed to the magnetic field. By exploiting this difference, efficient sorting of empty droplets from cell-encapsulated droplets is achieved at a purity of 85% in a single pass. Following sorting, cells are analyzed and show 90% viability after a two-hour incubation period.

High-frequency magnetic field on crystal field diluted S = 1 Ising system: magnetic relaxation near continuous phase transition points

2018 ◽  
Vol 96 (12) ◽  
pp. 1321-1332 ◽  
Author(s):  
Gül Gülpınar ◽  
Rıza Erdem
Keyword(s):  
Magnetic Field ◽  
Crystal Field ◽  
High Frequency ◽  
Low Frequency ◽  
Continuous Phase ◽  
Irreversible Thermodynamics ◽  
Critical Temperatures ◽  
High Frequency Region ◽  
Magnetization Relaxation ◽  
Transition Points

Magnetization relaxation and the steady state response of the S = 1 Ising model with random crystal field to a time varying magnetic field with a frequency ω is modelled and studied here by a method that combines the statistical equilibrium theory with the theory of irreversible thermodynamics. The method offers information on the relaxation time (τ) of the system as well as the temperature (θ) and ω dependencies of the complex (AC or dynamical) susceptibility (i.e., χ(ω) = χ′(ω) − iχ″(ω)). The so-called low- and high-frequency regions are separated by τ because τ−1 → 0 as θ approaches the critical temperatures (θc). One can choose to keep the frequency ω fixed and observe the low-frequency behaviors followed by the high-frequency behaviors when θ → θc. It is shown that χ(ω) exhibits different behaviors in low- and high-frequency regimes that are separated by the quantity ωτ: χ′(ω) converges to static susceptibility and χ″(ω) → 0 for ωτ ≪ 1. However, in the high-frequency region where ωτ ≫ 1, χ′(ω) vanishes and χ″(ω) displays a peak at the critical temperature (θc). Besides the above, the logarithm of the susceptibility components versus log(ω) is also plotted. From these plots, one plateau (a step-like) region and a shifted peak with rising temperature is observed for the real and imaginary parts, respectively.

scholarly journals Diamagnetic Manipulation of Cell-Encapsulating Droplets

2021 ◽  
Author(s):  
Stephanie Buryk-Iggers
Keyword(s):  
Magnetic Field ◽  
Flow Rate ◽  
Continuous Phase ◽  
Phase Flow ◽  
Label Free ◽  
Flow Focusing ◽  
Precise Control ◽  
Prostate Cells ◽  
The Magnetic Field ◽  
Droplet Phase

In this thesis, a microfluidic method for label-free control of cell encapsulating droplets is developed using diamagnetic forces. To generate droplets in a microfluidic device, we use a symmetrical flow-focusing design, where two streams of a continuous phase shear a single stream of a droplet phase, resulting in droplet generation. First, it is shown that by adjusting only the droplet phase flow rate, precise control of empty droplets can be achieved. Human prostate cells are then introduced to the system and encapsulated by droplets. Control of the cell-encapsulated droplets and empty droplets is studied. It is shown that cell-encapsulated droplets and empty droplets deflect by different amounts when exposed to the magnetic field. By exploiting this difference, efficient sorting of empty droplets from cell-encapsulated droplets is achieved at a purity of 85% in a single pass. Following sorting, cells are analyzed and show 90% viability after a two-hour incubation period.

Non-Fermi liquid behavior below the Néel temperature in the frustrated heavy fermion magnet UAu2

2021 ◽  
Vol 118 (49) ◽  
pp. e2102687118
Author(s):  
Christopher D. O’Neill ◽  
Julian L. Schmehr ◽  
Harry D. J. Keen ◽  
Luke Pritchard Cairns ◽  
Dmitry A. Sokolov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Fermi Liquid ◽  
Continuous Phase ◽  
Metallic State ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Liquid Behavior ◽  
Charge Modulation ◽  
Fermi Liquid Behavior

The term Fermi liquid is almost synonymous with the metallic state. The association is known to break down at quantum critical points (QCPs), but these require precise values of tuning parameters, such as pressure and applied magnetic field, to exactly suppress a continuous phase transition temperature to the absolute zero. Three-dimensional non-Fermi liquid states, apart from superconductivity, that are unshackled from a QCP are much rarer and are not currently well understood. Here, we report that the triangular lattice system uranium diauride (UAu2) forms such a state with a non-Fermi liquid low-temperature heat capacity C/T∼log (1/T) and electrical resistivity ρ(T)−ρ(0)∝T1.35 far below its Néel temperature. The magnetic order itself has a novel structure and is accompanied by weak charge modulation that is not simply due to magnetostriction. The charge modulation continues to grow in amplitude with decreasing temperature, suggesting that charge degrees of freedom play an important role in the non-Fermi liquid behavior. In contrast with QCPs, the heat capacity and resistivity we find are unusually resilient in magnetic field. Our results suggest that a combination of magnetic frustration and Kondo physics may result in the emergence of this novel state.

scholarly journals Effects of Nano-Diamond on Magnetorheological Fluid Properties

NANO ◽  
2017 ◽  
Vol 12 (10) ◽  
pp. 1750119 ◽  
Author(s):  
Mingmei Zhao ◽  
Jinqiu Zhang ◽  
Jun Yao ◽  
Zhizhao Peng
Keyword(s):  
Magnetic Field ◽  
Yield Strength ◽  
Three Dimensional ◽  
Wear Test ◽  
Continuous Phase ◽  
Shear Yield ◽  
Fluid Properties ◽  
The Difference ◽  
Observation Method ◽  
The Magnetic Field

In order to analyze the effects of nano-diamond on the performance of magnetorheological fluids (MRFs), in this paper, the MRF-1 with a 2% mass fraction in nano-diamond and the MRF-2 without nano-diamond were prepared by the carbonyl iron powder as the dispersed phase and the synthetic mineral oil as the continuous phase. The viscosity and shear stress of MRFs under different magnetic fields were measured by the Anton-Paar rheometer (MCR 302). The MRF settling stability was studied by a standing observation method. A four-ball wear machine was utilized for the wear test at 0.1 T of magnetic field, whereas the magnetic field was provided by an external coil. Also, the three-dimensional white light interferometer was utilized to observe the surface of the ball wear spot, in order to determine the MRF friction properties. The results demonstrated that the nano-diamond had a significant increase in the surface wear. The shear yield strength and settling stability of the MRF could be highly enhanced. The higher the strength of the magnetic field was, the higher the difference in the shear yield strength was. These phenomena demonstrated that the physical properties of the nano-diamond could have a higher impact on MRF, which was of high significance to the preparation of MRFs with excellent performance.

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