  We present the diffusiophoresis of ellipsoidal particles induced by ionic
solute gradients. Contrary to the common expectation that diffusiophoresis is
shape independent, here we show experimentally that this assumption breaks down
when the thin Debye layer approximation is relaxed. By tracking the translation
and rotation of various ellipsoids, we find that the phoretic mobility of
ellipsoids is sensitive to the eccentricity and the orientation of the
ellipsoid relative to the imposed solute gradient, and can further lead to
nonmonotonic behavior under strong confinement. We show that such a shape- and
orientation-dependent diffusiophoresis of colloidal ellipsoids can be easily
captured by modifying theories for spheres.
