Field-dependent anisotropic microrheological and microstructural properties of dilute ferrofluids

Abstract

We have measured microrheological and microstructural properties of a superparamagnetic ferrofluid made of Mn0.75Zn0.25Fe2O4 (MZF) nanoparticles, using passive microrheology in a home-built inverted microscope. Thermal motion of a probe microsphere was measured for different values of an applied external magnetic field and analysed. The analysis shows anisotropy in magneto-viscous effect. Additional microrheological properties, such as storage modulus and loss modulus and their transition are also seen. We have also obtained microstructural properties such as elongational flow coefficient [Formula: see text] , relaxation time constant [Formula: see text] , coefficient of dissipative magnetization [Formula: see text] , etc., using the analysis given in Oliver Muller et al., J. Phys.: Condens. Matter 18, S2623, (2006) and Stefan Mahle et al., Phys. Rev. E 77, 016305 (2008) over our measured viscosity data. Our values for the above parameters are in agreement with earlier theoretical calculations and macro-rheological experimental measurements. These theoretical calculations consider an ideal situation of zero-shear limit, which is best approximated only in the passive microrheology technique described here and a first time measurement of all these parameters with passive microrheology.

Magnetically controllable fluids in their nanotechnological aspect

“…W ostatnich latach prowadzone są bardzo intensywne badania nad zastosowaniem cieczy sterowalnych [7÷9, 13,16,18], zwłaszcza że połącze-nie tej problematyki z odkryciami w dziedzinie nanotechnologii stwarza obiecujące perspektywy.…”

Application of ferrofluids

“…Analiza literatury dotyczącej wykorzystania ferrocieczy wskazuje na liczne problemy natury badań podstawowych i technologicznych, które wciąż nie zostały rozwiązane i mogą stanowić przedmiot dalszych prac [1,14,17,20]. Z kolei interesującymi zagadnieniami do rozwijania w najbliższym czasie są: kompozycja cieczy ferromagnetycznych, modelowanie i opis matematyczny zjawisk związanych z obecnością ferrocieczy, sterowanie ich zachowaniem i kolejne zastosowania FF w urządzeniach technicznych.…”

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

“…These dynamic properties, in turn, allow quantifying the viscoelastic and dielectric moduli of the structural evolution of the fluid toward their equilibrium states [34]. This approach may help to interpret recent experiments of passive microrheology [35,36] and Altern Current spectroscopic techniques that measure the viscoelastic dynamics and dielectric relaxation of colloidal magnetic fluids. It is expected these theoretical methods be extended to help to understand the corresponding experimental observations of similar dynamics in two-dimensional paramagnetic colloids [37] and under external fields.…”