19 Novembre – Thesis defense - Elizaveta Frants

12 h30 Russia

Non-equilibrium electrophoresis of ion-selective microparticle.

The work is devoted to the theoretical and numerical study of the motion of a spherical cation-selective particle in an electrolyte under the action of an external electric field of various strengths. The outer electrolyte region is not limited, so the problem is completely free from the possible influence of the walls.
The following main results were obtained in the work:
1. Asymptotic and numerical solution of the electrophoresis problem in a weak electric field.
2. In the limiting case of the weak electric field, the dependence of the electrophoretic velocity on the electric field strength is derived, which is a generalization of the Helmholtz-Smoluchowski formula for a dielectric particle (an equilibrium process) to the ion-selective particle (non-equilibrium process).
3. An analytical expansion of the problem is obtained for the limiting case of a strong electric field in each of the thin boundary layers (electric double layer, space charge region and diffusion layer).
4. The emergence of electrokinetic instability in the region of the incoming cations flux was found. A scenario of the flow transition from regular to chaotic is obtained.
Both the understanding of the dependence of the particle velocity on the electric field strength and the discovered phenomenon of electrokinetic instability of the space charge region are of practical importance. The electrokinetic instability can be used to create new microfluidic devices for mixing liquids on a micro-scale and for evaluating the efficiency of using electrokinetic instability in the creation of such devices.

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