Dresden 2017 – scientific program

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 47: Fluids and Interfaces I

CPP 47.7: Talk

Wednesday, March 22, 2017, 18:00–18:15, ZEU 255

Light-switchable molecules at planar fluid interfaces — •Josua Grawitter and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany

Surfactants are part of many self-assembled structures in soft matter, from biological membranes to liquid foams. Especially promising are surfactants which change shape under illumination, so-called photosensitive surfactants, because their isomer densities can locally be manipulated with light.

We study their dynamics at a planar fluid interface using a coarse-grained theory for a surfactant mixture, which follows previous research on surfactant-driven droplets [1, 2]. The theory takes into account light-switching, surfactant adsorption, diffusion, mean field interactions, and advection due to Marangoni flow, which is initiated by gradients in surface tension. We present an exact solution of the incompressible Stokes flow for two immiscible fluids with an arbitrary field of surface tension at a planar interface. Using our theory we calculate the dynamic profiles of photosensitive surfactants driven by spots of light with intensities either constant in time or oscillating.

[1] M. Schmitt and H. Stark, Europhys. Lett. 101, 44008 (2013).
M. Schmitt and H. Stark, Phys. Fluids 28, 012106 (2016).

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