Related Experiment Video
Updated: Jun 19, 2026

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Phase separation of 2D meso-scale Coulombic crystals from meso-scale polarizable "solvent"
George K Kaufman1, Samuel W Thomas, Meital Reches
1Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge MA, 02138, USA.
Abstract:
This paper describes the phase separation of millimetre-scale spheres based on electrostatic charge. Initially, polymeric (Teflon, T; Nylon-6,6, N) and metallic (gold-coated Nylon-6,6, Au(N)) spheres are uniformly mixed in a two-dimensional (2D) monolayer on a gold-coated plate. Oscillating the plate vertically caused the spheres to charge by contact electrification (tribocharging). Positively charged N and negatively charged T spheres attracted each other more strongly than they attracted the capacitively charged, Au(N) spheres. The T and N spheres formed 2D Coulombic crystals, and these crystals separated from the Au(N) spheres. The extent and rate of separation increased with increasing amplitude of agitation during tribocharging, and with decreasing density of spheres on the surface. At high surface density, the T and N spheres did not separate from the Au(N) spheres. This system models the 2D nucleation of an ionic crystal from a polarizable liquid.
Related Concept Videos
Capillary Electrophoresis: Applications
Capillary zone electrophoresis (CZE) separates ionic components based on their electrophoretic mobility. It has been used to separate proteins, amino acids,...
Electrochemical Systems
Molecular Shape and Polarity
Size-Exclusion Chromatography
Silica particles offer advantages such as rigidity,...
Recrystallization: Solid–Solution Equilibria
Phase Transitions: Melting and Freezing

