Chemically-induced phoretic flow, or how to turn a curtain of light into virtual micro-fluidic boundaries

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With this project we would like to establish and rationalize an unique way for the manipulation of colloidal particles at interfaces in aqueous solution. Superficially, one may consider the concept of light-driven diffusioosmosis and the local (porous particles)-global (light intensity patterns) ansatz of creating almost arbitrary flow patterns as an implementation of virtual microfluidics – that is, colloids can be transported, confined and manipulated without external pumps or the presence of solid walls of microfluidic chambers and channels. The theoretical analysis will give us an in-depth characterization of the nature of the confining forces, and whether and how they may be represented as an effective solute potential. This is particularly important when thermal motion and colloidal particle Brownian diffusion are important. In the proposed research we intend to set up reference experiments whose results can be compared directly to the theoretical calculations and simulations. In addition to these fundamental questions, the whole phenomenology opens up a number of other “theory-compatible” questions, such as segregation dynamics in mixtures of particles or the motion of self-propelled particles in dynamically fluctuating confined geometries, all of which may be studied more closely during this research. In summary, our project offers an unusually close alignment of theory and experiment regarding an intriguing non-equilibrium system that touches upon many cutting-edge problems of phoretically-driven particle dynamics together with hydrodynamic interactions in a unique setting.