Rapid magnetofluidic mixing in a uniform magnetic field

Abstract

This paper reports the investigation of mixing phenomena caused by the interaction between a uniform magnetic field and a magnetic fluid in a microfluidic chamber. The flow system consists of a water-based ferrofluid and a mixture of DI water and glycerol. Under a uniform magnetic field, the mismatch in magnetization of the fluids leads to instability at the interface and subsequent rapid mixing. The mismatch of magnetization is determined by concentration of magnetic nanoparticles. Full mixing at a relatively low magnetic flux density up to 10 mT can be achieved. The paper discusses the impact of key parameters such as magnetic flux density, flow rate ratio and viscosity ratio on the mixing efficiency. Two main mixing regimes are observed. In the improved diffusive mixing regime under low field strength, magnetic particles of the ferrofluid migrate into the diamagnetic fluid. In the bulk transport regime under high field strength, the fluid system is mixed rapidly by magnetically induced secondary flow in the chamber. The mixing concept potentially provides a wireless solution for a lab-on-a-chip system that is low-cost, robust, free of induced heat and independent of pH level or ion concentration.

Magnetic particle mixing with magnetic micro-convection for microfluidics

“…Magnetic fluid, being a colloidal dispersion of magnetic particles, can be used as a model system for future applications. Several examples of magnetic and non-magnetic fluid mixing have already been demonstrated [3,4]. Here we evaluate the possible use of the magnetic micro-convection phenomenon for mixing applications, applying the knowledge obtained in previous theoretical and experimental studies [5,6].…”

Inception of vortical coherent structures from spinning magnetic nanoparticles in rotating magnetic fields – New nanofluid microscale mixing tool

“…In parallel, MNPs have also been studied for use as nanoscale devices to stimulate mixing in micro-scale when the whole system is subject to timevarying external magnetic fields [10][11][12][13][14]. The potential for mixing applications appears particularly remarkable for rotating magnetic fields (RMFs) although different magnetic fields have been considered [9][10][11][12][13][14].…”

“…However, while several studies used or investigated the effects of uniform magnetic fields on the physical behavior of MNP-laden fluids, interpretation of the resulting phenomenon usually has been made based on simulations or measurements performed indirectly or at a large scale [9,14,18]. In order to fine tune the development of a mixing technology based on spinning MNPs in rotating magnetic fields, a clearer picture of the ferrohydrodynamics at play is required.…”

“…Owing to this disposition, they have been involved in many applications where mixing at the micro-scale is a critical issue, e.g., catalytic reactions, separation, drug delivery and microfluidic devices [6][7][8][9]. In parallel, MNPs have also been studied for use as nanoscale devices to stimulate mixing in micro-scale when the whole system is subject to timevarying external magnetic fields [10][11][12][13][14].…”

Design and fabrication of magnetically functionalized flexible micropillar arrays for rapid and controllable microfluidic mixing

“…Magnetism-based approach has already been well utilized for mixing control in microfluidic systems, such as mixing in parylene microchip by integrated magnetic stir bar under a rotating magnetic field [28,29]. Ferrofluid was also reported as an efficient mixing medium inside the microfluidic chamber where full mixing could be obtained with a low magnetic flux density [30].…”