Diffusiophoresis is a nanoscale mechanism that induces particle transport whenever solute concentration gradients are present: depending on the sign of the diffusiophoretic coefficient $D_{dp}$, the particles may move towards the salt if $D_{dp}>0$ (salt-attracting configuration), or be repelled by the salt otherwise. Abécassis et al. (Nature mat., 2008) show that in a $\Psi$-shaped channel diffusiophoresis behaves like diffusion, with a positive or negative coefficient much larger than the real diffusion coefficient of the particle.
We study the case when particles and salt are realeased together in a mixing flow, with mixing efficiency delayed in the salt-attracting configuration, and enhanced in the salt-repelling case. We show that diffusiophoresis is not diffusion-like but rather a purely compressible mechanism. Using analytical and theoretical considerations together with numerical simulation, we study the case of different mixing flows, from a poorly efficient linear strain (stagnation point) to the case of chaotic advection. We explain why and how the coupled effects of mixing and diffusiophoresis can be measured through an effective Péclet number.