Electrophoresis of the Second Kind

If a particle is able to sustain a super-limiting current, then such flows can cause it to move by electrophoresis of the second kind, as first noted by S.S. Dukhin in the 1980s. As shown in Fig. 5, second-kind electrophoresis has been observed experimentally for large (>10 pm) particles composed of cation-selective porous materials, and the flow structure has been studied in detail [8]. Due to the complexity of the phenomenon, however, the theory has mainly been limited to scaling arguments and heuristic boundary-layer approximations [18], but there is hope that the rigorous mathematical study of second-kind flows [7] could soon be extended to second-kind electrophoresis. Effects of walls, multiple particles, and broken symmetries should also eventually be studied. 

Electrophoresis of the second kind refers to the nonlinear electrokinetic motion of a conducting particle passing a superlimiting current due to electroosmotic flow of the second kind. 

Electrokinetic Motion of Polarizable Particles, Figure 5 Experiments on electrophoresis of the second kind for cationite KU-2-8 particles in 10 MNaCI. (a) Velocity versus time for particles diameters 0.42 mm (1), 0.33 mm (2), and 0.21 mm (3) with sketches of the observed flow fields, (b) Scaling of velocity with applied field for diameters 0.31 mm (1), 0.28 mm (2), and 0.26 mm (3) [8]... 

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