Ferrofluid spin-up flow is studiedwithin a sphere subjected to a uniform rotatingmagnetic field from two surrounding spherical coils carrying sinusoidally varying currents at right angles and 901 phase difference. Ultrasound velocimetry measurements in a full sphere of ferrofluid shows no measureable flow. There is significant bulk flow in a partially filled sphere (1–14 mm/s) of ferrofluid or ...

We describe a convective instability of a stratified ferrofluid subject to a magnetic field. The ferrofluid is described as binary mixture featuring two important dimensionless numbers the barometric one B and the magnetic barometric one Bm. At the field strength, where the latter exceeds the former, instability sets in. We discuss the growth rate of linear perturbations and the amplitude of no...

The effect of magnetic anisotropy-axis alignment on the superparamagnetic (SPM) and superspin glass (SSG) states in a frozen ferrofluid has been investigated. The ferrofluid studied here consists of maghemite nanoparticles (γ-Fe2O3, mean diameter = 8.6 nm) dispersed in glycerine at a volume fraction of ~15%. In the high temperature SPM state, the magnetization of aligned ferrofluid increased by...

2014 We have observed the surface instability of the interface between a highly concentrated ferrofluid and a weakly concentrated one. Our experimental data clearly show the first order character of the transition between a flat interface and the observed regular pattern of peaks. A large hysteresis effect is observed because of the high value of the relative permeability (03BC ~ 40) of our con...

The viscosity n of Fe,O, ferrofluid at volume concentrations in the range t = 0.0-0.013 are measured. The corresponding range of values of q is 1.6-1.8 cp. A linear relationship exists between the relative viscosity and the concentration of the fluid. Measurements of relative resistivity of Fe,O, ferrofluid at various concentrations (E = 0.00526-0.0526) are also reported. The relative resistivi...

A novel micromixer which utilizes chaotic mixing induced by ferrofluid actuation is developed. The micromixer is fabricated by a polydimethylsiloxane micromolding technique. The micromixer consists of a T-shaped main mixing channel and two parallel sub-channels that intersect the main channel. Oscillation of a couple of ferrofluid slugs in the sub-channels, induced by external permanent magnet ...

We present a new method for the determination of the magnetic moment distribution ρ(μ) of ferrofluid particles from the magnetization curve measured on diluted ferrofluid samples in the liquid state. The method employs the solution of the standard integral equation describing the magnetization of a non-interacting particle system in the given external field as a convolution of the Langevin func...

Magnetic manipulation is a promising technique for lab-on-a-chip platforms. The magnetic approach can avoid problems associated with heat, surface charge, ionic concentration and pH level. The present paper investigates the migration of diamagnetic particles in a ferrofluid core stream that is sandwiched between two diamagnetic streams in a uniform magnetic field. The three-layer flow is expand...

A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commerc...

Concerns dealing with the application of superparamagnetic ferrofluid as a drug carrier are studied both experimentally and theoretically. A dynamically controlled electromagnet experiment was designed to focus a stable ferrofluid trap at a specified distance. A theoretical magnetic driving force equation has been compared to experimental results for verification; verification was not achieved....