A thermal gradient pushing thermophoretic particles against an interface can
induce a strong and long ranged attraction leading to the prompt formation of
stable, ordered structures. Such interactions are hydrodynamic in nature and
driven by Marangoni forces on particle surfaces. The movie shows seven 2 μm
silica beads in water. The interaction switches on when the ceiling of the
sample chamber is heated by laser absorption. Eventually the particles find the
closest packed cluster and stay there until laser heating is switched off and
the cluster disgregates.
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Colloidal attraction induced by a temperature gradient
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