title: Soluto-inertial phenomena: Designing long-range, long-lasting, surface-specific interactions in suspensions.
abstract: Equilibrium interactions between particles in aqueous suspensions are limited to distances less than 1 μm. Here, we describe a versatile concept to design and engineer nonequilibrium interactions whose magnitude and direction depends on the surface chemistry of the suspended particles, and whose range may extend over hundreds of microns and last thousands of seconds. The mechanism described here relies on diffusiophoresis, in which suspended particles migrate in response to gradients in solution. Three ingredients are involved: a soluto-inertial "beacon" designed to emit a steady flux of solute over long time scales; suspended particles that migrate in response to the solute flux; and the solute itself, which mediates the interaction. We demonstrate soluto-inertial interactions that extend for nearly half a millimeter and last for tens of minutes, and which are attractive or repulsive, depending on the surface chemistry of the suspended particles. Experiments agree quantitatively with scaling arguments and numerical computations, confirming the basic phenomenon, revealing design strategies, and suggesting a broad set of new possibilities for the manipulation and control of suspended particles.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
authors.forename: Anirudha
authors.initials: A
authors.lastname: Banerjee
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
authors.forename: Ian
authors.initials: I
authors.lastname: Williams
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
authors.forename: Rodrigo Nery
authors.initials: RN
authors.lastname: Azevedo
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
authors.forename: Matthew E
authors.identifier: 0000-0001-9384-4023
authors.initials: ME
authors.lastname: Helgeson
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106 squires@engineering.ucsb.edu.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Squires
mesh_terms: D000465:Algorithms; D055598:Chemical Phenomena; D007700:Kinetics; D008956:Models, Chemical; D009038:Motion; D010316:Particle Size; D012996:Solutions / Q000737:chemistry*; D013499:Surface Properties; D013535:Suspensions / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012996:Solutions; D013535:Suspensions
keywords: colloid; diffusiophoresis; long-range interactions; soluto-inertial; suspensions