Emergence of isoperichoric focusing in multicomponent colloidal particle dispersion at sedimentation equilibrium

Abstract

It has been demonstrated experimentally that the focusing effect can appear in a multicomponent (polydisperse in size) colloidal particle dispersion at sedimentation equilibrium. Consequently, an equilibrium concentration distribution of sedimenting colloidal particles of different sizes cannot be a simple convolution (or superposition) of the corresponding distributions of uniform size components of the dispersion. Although an extensive theoretical approach considering the microscopic scale interactions of the molecules or colloidal particles of the complex, gradient forming, liquid is needed to elucidate the macroscopically observed phenomena, the experimental results, reproduced several times, prove incontrovertibly the emergence of isoperichoric focusing (which is the more accurate term, compared with isopycnic focusing, describing the observed phenomena).