Electromagnetophoretic Micro-convection around a Droplet in a Capillary

Abstract

The electromagnetophoretic behavior of organic droplets in an electrolyte solution was investigated in a silica capillary cell using a superconducting bulk magnet (3.5 T) and a magnetic circuit (2.7 T). The initially dispersed emulsion droplets of dodecane migrated to the wall of the capillary, responding to the direction of an electric current, and coalesced to form smaller and larger droplets after some repeated migrations. When the electric current was applied continuously, the larger droplets became arranged with regular intervals on the wall, and smaller droplets rotated around the larger droplets. These interesting behaviors were analyzed while taking into account the local electric current density determined by the flow velocity of the ionic current around a droplet, which was lowest on the electrode sides of the droplet. The difference in the local electric current density generated the Lorentz-force difference in the medium, which lead to local microconvection around the droplet, and also the alignment of larger droplets by a repelling effect between the adjacent microconvections.

Applications of magnetic and electromagnetic forces in micro-analytical systems

“…Funaki et al observed a curious micro-convection of smaller organic droplets around a larger organic droplet in a capillary electromagnetophoretic system. 241 When the electric current of 0.5 or 1.0 mA was applied at 3.5 T or 2.7 T, larger droplets became arranged at regular intervals on the capillary wall, and smaller droplets circulated around the larger droplets (Fig. 17).…”

“…The electromagnetophoretic buoyancy was shown to be useful for dynamic force measurement and manipulation of diamagnetic particles. 244 The local Lorentz force, which can be changed by the inhomogeneous current density around micro-subjects, 241,254 will be useful to fabricate micro-structured flow systems. In a Cu magnetoelectrodeposition surface, its chiral selectivity was observed.…”

Evaluating the Creaming of an Emulsion via Mass Spectrometry and UV–Vis Spectrophotometry

“…Recent analytical studies of emulsions include evaluations of collapse processes, , analysis of the interface of droplets, − and analysis of emulsion products . Turbidity measured by ultraviolet–visible spectrophotometry (UV–vis) has normally been used for the evaluation of emulsion stability. − For instance, the time profile of turbidity was studied to evaluate the coalescence and/or solubilization kinetics of oil in microemulsion droplets , and for determining the phase-inversion temperature. , However, when an incident light insufficiently passes through an emulsion with rather high turbidity, it is difficult to obtain reliable data.…”

Zeptomole Detection Scheme Based on Levitation Coordinate Measurements of a Single Microparticle in a Coupled Acoustic-Gravitational Field

“…Additionally, information on the reaction dynamics and thermodynamics can be deduced from the particle behavior in a physical field. Suwa and Watarai studied the magnetophoresis of various particles − and evaluated the interfacial adsorption of laurate complexes with dysprosium ions on fluorotoluene microdroplets from their magnetophoretic velocities . The surface complexation between laurate and the paramagnetic dysprosium ion largely modifies the magnetic property of the microdroplet and allows detection of the reaction that occurs on the droplet.…”