title: Structure and dynamics of a layer of sedimented particles.
abstract: We investigate experimentally and theoretically thin layers of colloid particles held adjacent to a solid substrate by gravity. Epifluorescence, confocal, and holographic microscopy, combined with Monte Carlo and hydrodynamic simulations, are applied to infer the height distribution function of particles above the surface, and their diffusion coefficient parallel to it. As the particle area fraction is increased, the height distribution becomes bimodal, indicating the formation of a distinct second layer. In our theory, we treat the suspension as a series of weakly coupled quasi-two-dimensional layers in equilibrium with respect to particle exchange. We experimentally, numerically, and theoretically study the changing occupancies of the layers as the area fraction is increased. The decrease of the particle diffusion coefficient with concentration is found to be weakened by the layering. We demonstrate that particle polydispersity strongly affects the properties of the sedimented layer, because of particle size segregation due to gravity.
authors: Raymond and Beverly Sackler School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel.
authors: Adar
authors: A
authors: Sonn-Segev
authors: Department of Mechanical Engineering, Texas Tech University, 7th and Boston, Lubbock, Texas 79409, USA.
authors: Jerzy
authors: J
authors: Bławzdziewicz
authors: Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5B, Warsaw 02-106, Poland.
authors: Eligiusz
authors: E
authors: Wajnryb
authors: Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5B, Warsaw 02-106, Poland.
authors: Maria L
authors: ML
authors: Ekiel-Jeżewska
authors: Raymond and Beverly Sackler School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel.
authors: Haim
authors: H
authors: Diamant
authors: Raymond and Beverly Sackler School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel.
authors: Yael
authors: Y
authors: Roichman