Suspensions electrokinetic phenomena

Observation of this electrokinetic phenomenon involves the application of a spatially nonhomoge-neous electric field to the suspension this provoking the migration (or dielectrophoresis) of the polarized particles [48,49]. The particles will move toward the high-field region if they are more polarizable than the dispersion medium, or will be repelled toward the low-field region otherwise. 

Let us mention that dielectrophoresis has also found wide application in manipulation and sorting of particles and biological cells. Together with standard electrophoresis, it is perhaps the most often used electrokinetic phenomenon with practical applications in mind. Even particle separation can be achieved by using microelectrode arrays [55]. Based on the dielectrophoresis phenomenon, a new technique has recently become available for particle or cell separation, namely the dielectrophoresis/gravitational field-flow fractionation (DEP/G-FFF). In DEP/ G-FFF, the relative positions and velocities of unequal particles or cells are controlled by the dielectric properties of the colloid and the frequency of the applied field. The method has been applied to model polystyrene beads, but, most interestingly, to suspensions of different biological cells [56]. 

Marian von Smoluchowski (1872-1917). .. was a Polish physicist whose research on discrete state matter is still highly valued in modem science. He is particularly acknowledged for his theory on Brownian motion, which he developed independently of Einstein and which laid the foundation for the theory of stochastic processes. A similar rank is deserved by his discovery of density fluctuations in liquids and gases and their relevance for macroscopic scattering— most prominently explained by the phenomenon of critical opalescence. Both works proved veiy influential for the understanding of colloidal suspensions. Furthermore, he did pioneering work on the quantification of particle aggregation as well as in the field of electrokinetic phenomena. 

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