Ferrofluid Mass Research Articles

The Theoretical and Experimental Study of a Ferrofluid Inertial Sensor

In this paper, an inertial sensor exploiting the self-levitation of a magnetic object immersed in ferrofluids is presented. The ferrofluid absorbed on the magnetic object produces an unusual buoyant force that resists gravity and serves as an elastic force. When the magnetic object moves under an external perturbation, the elastic force tries to return the magnetic object to its initial position. Therefore, the analysis of the buoyant force is the key to ensuring that the inertial sensor can achieve the excellent static performance. A series of simulations and experiments are used to optimize the buoyant force. Furthermore, the stable levitation height of the magnetic object is determined, and the influence of the ferrofluid mass on the buoyant force is studied. The comparison between numerical calculations and experimental measurements shows a good agreement. The satisfactory linearity and high sensitivity indicate the feasibility of the ferrofluid inertial sensor.

Influence of local particle concentration gradient forces on the flow-mediated mass transport in a numerical model of magnetic drug targeting

Magnetic nanoparticles have been widely applied in the nanomedicine field: therapies based on magnetic drug targeting have shown promising results towards the improvement of the current state of the art of medical treatments. Particles interaction with their carrying flow or the surrounding tissues still needs to be completely understood, as well as the mechanisms underlying interparticle interactions. These interactions can potentially promote particles aggregation in the fluid doman and therefore influence the therapy outcome. This study presents a numerical model to describe particles magnetohydrodynamics in a realistic setup for magnetic drug targeting. The focus is a quantitative analysis of the contribution of the local ferrofluid concentration gradients to the magnetic fluid volume force, as well as an investigation on the dependence of the magnetic fluid volume force on particles diameter and ferrofluid concentration. The results show that the main contribution to the magnetic fluid volume force is the magnetic field gradients term. However, the concentration gradients term ranges in the same order of magnitude and therefore cannot be neglected in the force formulation. In addition, the molar concentration distribution has been found to change with different force formulations and with different values of the molar influx too. The model outlines that the magnetic fluid volume force increases with the particle diameter and the ferrofluid concentration. However, both relationships are not linear, but more complex. The described approach proves to be versatile and further applicable to more complex geometries and scenarios. In addition, the outcome and the achievements of the presented numerical model provide for the first time insights into the role of the local ferrofluid concentration gradients in the determination of the magnetic fluid volume force and represent a starting point for further investigations of the mechanisms underlying the flow-mediated ferrofluid mass transport.

Ferrofluid appendages: Ferrofluid vortex container - A numerical investigation of free surface shape and vortex flow in ferrofluids for different relative densities

The use of ferrofluids as shapeable external appendage to a submerged body and as a mean of vortex flow induction is studied in this paper. Ansys-CFX numerical results are validated against analytical problems and used to analyze the ferrofluid free surface shape affected by gravity, different magnets and different densities of the surrounding non-magnetic fluids. It is demonstrated that the height, width, and curvature of ferrofluid can be controlled by magnet size and strength. It is also observed that ferrofluid mass loss may occur due to gravity which should be addressed in designing a fluid appendage. Subsequently, vortex production inside the ferrofluid is investigated via a shear flow on the magnet. It is shown that ferrofluid can contain complex vortices while being shaped by the magnetic field, gravity, and the vortices. It is also observed that vortices inside the ferrofluid affect the flow of the surrounding fluid. Additionally, the effects of surface tension and viscosity are briefly analyzed to roughly show the importance of these parameters for further works. Overall, it is concluded that using ferrofluids as appendages for shaping and controlling fluid flow around submerged bodies seem to be practical and needs further attention.

Investigations into a Planar Inductive Readout Strategy for the Monitoring of Ferrofluid Carriers

Ferrofluids can be conveniently used in magnetic immune-assay techniques, such as magnetic labeling, magnetic drug targeting, hyperthermia, contrast enhancement for magnetic resonance imaging, and magnetic separation of cells. A main issue of immune-assay techniques, often adopted in lab-on-chip systems, is the transitions of the biotarget from one site to another site. This is mandatory to expose the biotarget linked to the carrier to the chemical/physical processes occurring in different sites of the system. In this paper, a strategy to control and to monitor the position of a ferrofluid mass, which can assume the role of carrier, along a predefined path is presented together with some experimental results. The behavior of the sensing readout strategy for different masses of ferrofluid, the selected path, and the time of residence of the ferrofluid carrier in each site has been investigated. A minimum residence time of 740 ms has been estimated for the LabScale prototype developed, which confirms the suitability of the proposed control and sensing strategy. Moreover, the possibility to detect the direction of the ferrofluid mass movement has been demonstrated.

A ferrofluid inclinometer with a Time Domain Readout strategy

In this paper a tilt sensor exploiting the effect of the imposed tilt on a mass of ferrofluid free to slide along a glass channel is presented. The proposed inclinometer consists of a 10mm diameter pipe containing a 0.25ml of ferrofluid, an actuation coil to control the ferrofluid mass movement and two sensing coils to monitor its position. The actuation and the sensing coils are wound around the pipe and the length of the actuation/sensing system is 78mm.The novelty of this device, as respect to solutions already presented in the literature, consists in the conversion of the device tilt into the time elapsed between transitions of the ferrofluid mass in two fixed positions inside the channel. This Time Domain Readout strategy allows to implement a device with a frequency output which can be intended as the main advantage of the solution proposed.

A Ferrofluid Inclinometer with a Time Domain Readout Strategy

In this paper a tilt sensor exploiting the effect of the imposed tilt on a ferrofluid drop free to move inside a glass channel is presented. The proposed inclinometer consists of a 10 mm diameter pipe containing a 0.25 ml of ferrofluid, an actuation coil to control the ferrofluid mass movement and two sensing coils to monitor the mass position. The actuation and the sensing coils are wound around the pipe and the length of the actuation/sensing system is 78 mm. The novelty of this device, as respect to solutions already presented in the literature, consists in the conversion of the device tilt into the time elapsed between transitions of the ferrofluid mass in two fixed positions inside the channel. This time domain readout strategy allows to implement a digital form of the device output which can be intended as the main advantage of the solution proposed.

Can ferrohydrodynamic instabilities be useful in transducers? [Instrumentation Notes

Magnetic fluids are formed when magnetic particles are dispersed in a carrier liquid and suitably coated [1], [2]. Coating the particles provides an elastic shield which avoids particle friction, and it can be also used to implement bio-assay strategies. There are two types of magnetic fluids: magneto-rheological fluids and ferrofluids. The size of the dispersed particles is what distinguishes the two types of magnetic fluids: magnetorheological fluids containing magnetic particles with a diameter on the order of microns and the fluids change from a liquid to a solid in response to a high magnetic field while ferrofluids are colloidal suspensions of magnetic nanoparticles that maintain their liquid state in the presence of a strong magnetic field. In the case of ferrofluids, the higher the magnetization strength, the greater the magnetic pressure exerted by the fluid [3]. Magnetic fields applied to a ferrofluidic volume and the consequent magnetic force causes the alignment of the ferrofluidic particles in the direction of the field and modifies the viscosity and the control of the ferrofluid mass position. Interest in ferrofluids and magnetic particles exists because of the possibility of efficiently converting valuable elastic energy into mechanical energy in many applications. In this column, we describe some of the uses of ferrofluids and highlight ways to exploit its ferrohydrodynamic instabilities.

A Ferrofluidic Inertial Sensor Exploiting the Rosensweig Effect

In this paper, a novel device for sensing perturbations imposed to liquid media contained in a disposable housing is addressed. The device consists of a glass beaker filled with deionized water surrounding a small volume of ferrofluid; a permanent magnet is used to fix the position of the ferrofluidic mass in a compliant position and to generate spikes due to the Rosensweig effect. The effect of external stimuli on the beaker can be estimated by measuring the perturbation produced on the ferrofluidic mass. The latter strategy allows reducing drawbacks related to static friction of conventional inertial devices. The ferrofluid perturbations are monitored by two external planar coils in a differential configuration. The main features of the proposed strategy are structural decoupling between the electric read-out system and beaker housing, which allows both implementing noninvasive measurement in liquid media and making the architecture partially disposable, of low cost, and suitable for real applications.

A Ferrofluidic Inclinometer in the Resonant Configuration

In this paper, an innovative inclinometer exploiting ferrofluids is presented. The device consists of a glass pipe filled with deionized water and a drop of ferrofluid, a coil generating a retaining force on the ferrofluidic drop, a couple of sensing coils detecting the ferrofluidic mass position, and two exciter coils moving the ferrofluidic drop back and forth inside the water at the resonance frequency of the whole system. The device exhibits an intrinsic robustness against inertial shocks. The resonant operation mode represents the main novelty with respect to previous realizations of the ferrofluidic inclinometer presented by the authors. This strategy allows for improving the performances of the inclinometer also in terms of mechanical sensitivity. This paper will focus on the design and experimental characterization of the resonant inclinometer, showing improvements achieved by the resonant configuration with respect to the previous ?static implementation? without the exciter coils.

Behavior Analysis of a Ferrofluidic Gyroscope Performances

In this work a gyroscope using a ferrofluidic mass as inertial mass is presented. The device consists of a glass plate filled with deionized water with an injected ferrofluidic drop, a electromagnetic driving system to move the ferrofluidic mass back and forward along the actuation axis and a differential inductive readout system to sense the motion of the ferrofluidic sphere. An angular rate imposed to the device produces a deviation of the ferrofluidic mass trajectory which is measured by the differential readout system. Experimental surveys have been performed to characterize both the driving system and the behavior of the device.

A bio-inspired device to detect equilibrium variations using IPMCs and ferrofluids

This work describes a device designed and built to detect the inclination of a body, based on two emerging smart materials: ionic polymer–metal composites (IPMCs) and ferrofluids. The system is bio-inspired and simulates the behavior of the vestibular labyrinth, a biological component of living beings, situated in the inner ear and devoted to perception of the angular acceleration the head is subjected to. In the same way the proposed system is able to reveal its inclination by detecting the position of a ferrofluid mass inside a circular tube. The detection is performed by using the sensing properties of IPMCs, cut into opportunely sized strips, acting as ciliate cells in the tube. The system, details of which are given in the text, is totally new and combines two innovative technologies, IPMCs and ferrofluids, that allow good performance to be obtained at a low cost. The experimental setup is presented and several results are shown and discussed.

A Novel Ferrofluidic Inclinometer

Inertial transducers based on the use of ferrofluids as inertial mass can be of great interest due to their peculiarities and due to the advantages that they show when compared to traditional devices. Ferrofluids are special solutions of magnetic particles in a carrier liquid whose density and other physical features can be controlled by an external magnetic field. In this paper, the development of a ferrofluidic inclinometer, which exhibits a tunable operating range and a valuable metrological feature and an intrinsic robustness against inertial shocks, is presented. The device consists of one excitation coil and two sensing coils wound around a glass pipe where a drop of ferrofluid is contained in a water environment. The magnetic force, which is induced by the excitation coil, attracts the ferrofluidic mass in a position that depends on the device inclination. The voltage at the output of the two sensing coils is related to the ferrofluidic mass displacement and thus reflects the tilt to be measured. Analytical models, simulations, and experimental results are presented to demonstrate the suitability of the proposed approach.