Diffusiophoretic transport and dispersion of colloids across complex landscapes

Understanding the transport and dispersion of colloids in heterogeneous environments is essential for a wide range of phenomena, from drug delivery to subsurface energy storage and contaminant removal. The classical description of colloid transport relies on the balance between advection by the background flows and diffusion of particles. However, it is known that colloids can also move in the presence of solute gradients, a phenomenon known as diffusiophoresis. Recent studies have demonstrated the utility of diffusiophoresis in manipulating and steering colloids in simple microfluidic geometries. Yet, it remains a question whether diffusiophoresis could play an important role in more complex environments, where background fluid flows are often present. Here, combining experimental observations and numerical simulations of microfluidic channels patterned with obstacles, we study the competition between phoretic and convective migration of colloids and discuss the implications of the phoretic migration at the pore-scale on the transport and dispersion of colloids at the macroscopic scale.