Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 4: New Methods: Experiments

O 4.2: Talk

Monday, March 18, 2024, 10:45–11:00, MA 005

how to stop motion of microparticles by using local light-driven diffusio-osmosis (l-LDDO) under external flow — •Daniela Vasquez, Fabian Rohne, Svetlana Santer, and Marek Bekir — University of Potsdam, Institute for Physic and Astronomy, Karl-Liebneckt str. 25, Haus 28, Potsdam, Germany

Liquid flow can be generated by external pressure (pumping) or by using different types of surface bound phenomena as diffusio-osmosis. For example, the latter requires solute concentration gradients with precise local control in a reversible way and at arbitrary surface. In this study, we use a local light-driven diffusion-osmosis (l-LDDO), where it is possible to manipulate the motion of micro particles reversibly and at any surface. The motor of the mechanism is a photosensitive azobenzene surfactant that present photo-isomerization between more hydrophobic trans and hydrophilic cis isomer. When porous microparticles are immersed in aqueous azobenzene surfactant solution, particle motion can be manipulated during light stimulation of appropriated wavelength.

Under external pumped fluid flow the local-LDDO motion is so strong that it provides a light induced velocity gain of porous particle along a streamline or it can be completely reversed by simply changing the wavelength into full motion stop of such particles against an external pumped fluid flow. Thus, with one stimulus we are able to manipulate the particle motion in both directions. Here we investigate stopping of the microparticles with studying the strength of local-light-driven diffusio-osmosis (l-LDDO) flow.

Keywords: azobenzene containing surfactant; photo-isomerization; light-driven diffusio-osmosis