(27g) Understanding and Engineering Diffusiophoretic Suspensions

The long history of diffusiophoresis owes much to Dennis Prieve and co-workers, who developed elegant theoretical expressions, membrane deposition experiments that supported these theories, and enabled quantitative prediction of diffusiophoretic phenomena for various purposes. Our lab has developed a microfluidic technique to design and control compositional gradients across suspensions, and to directly measure the diffusiophoretic migration that results from these gradients. This technique has revealed both quantitative agreement for existing theories, and qualitative surprises in new systems. We will describe diffusiophoretic migration under some unorthodox gradients - including solvents, ionic surfactants, zwitterions, and reacting solutes. We will present a generalized theory that reproduces Prieve & Anderson’s original expressions for diffusiophoresis, but also reveals connections to other phoretic migrations, and which explain some of the surprises we have observed in our experiments. Finally, we will describe our efforts to engineer ‘soluto-inertial’ interactions in suspensions, in which we engineer “beacon” particles that emit long-lived, long-ranged chemical fluxes, driving neighboring particles into diffusiophoretic migration. Building on Prieve’s fundamental insights about diffusiophoresis in this way, we envision versatile new capabilities for `smart suspensions’.