Question

Recent advances in magnetorheology of ferrofluids (magnetic nanofluids)—a critical review

Answer 1

Ferrofluids, suspensions of nanometer sized magnetic particles in a suitable carrier fluid, have been extensively used in a variety of applications (leak free seals, lubricants, density separation, ink jet printers, electronics cooling, clutches, tunable dampers, tunable heat transfer fluids, optical filters, optical grating, defect sensors, biosensors, cell separation, magnetic resonance imaging based drug targeting, diagnostics in medicine, hyperthermia agents, etc.). Their ability to alter physical properties in a controlled fashion in response to an external magnetic field is exploited in various applications. Under the influence of an external magnetic field, the optical, thermal and rheological properties of ferrofluids can be precisely tuned and hence are categorized as 'smart' fluids. Over the years, ferrofluid has emerged as a reliable material in solving several complex engineering problems. Applications demand ferrofluids with tunable rheological properties and a knowledge of the quantities such as viscosity, yield stress and hysteresis of ferrofluids. This review provides an overview of studies on the magnetorheology of ferrofluids till date. Special emphasis is paid to the understanding of the nature of field induced microstructure in ferrofluids, their applications and various factors affecting the magnetorheological behavior of ferrofluids along with a brief overview on MR fluids. The background information is provided for beginners for better understanding of the subject.