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The movement of colloidal particles in a fluid due to a gradient in the concentration of another species.

Schematic illustrating diffusiophoretic motion of a colloidal particle (blue) in a concentration gradient of a solute (red). Note that there is also a concentration gradient of the solvent (green). The particle is moving a diffusiophoretic velocity ${\displaystyle {\bf {v}}_{\text{dp}}}$, in a fluid that is stationary far from the particle. The fluid velocity decays from ${\displaystyle {\bf {v}}_{\text{dp}}}$ for fluid in contact with the surface of the particle, to near zero, within the interface at the particle's surface.