SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Wetting, Droplets and Microfluidics I (joint session DY/CPP)

CPP 34.6: Talk

Wednesday, March 29, 2023, 11:15–11:30, ZEU 148

Optically controlled micro-transport with reduced heating impact — •Antonio Minopoli, Elena Erben, Susan Wagner, and Moritz Kreysing — Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany

Recently it was demonstrated that thermoviscous flows can be used to move the cytoplasm of cells and developing embryos. These laser-induced intracellular flows (aka FLUCS), reach velocities comparable with those occurring during early stages of embryogenesis. As a side effect, the laser scanning may also cause temperature gradients across the sample (1-3 Kelvins) that could give rise to out-of-equilibrium phenomena. Here, we demonstrate that exploiting symmetry relations during the laser scan, we disentangle heating and flows. Specifically, since the flow speeds depend on the repetition frequency rather than on the beam velocity, it is possible to accelerate the scanning of the primary scan pattern, effectively compressing the scan signal to occupy only a fraction of the original period, and allowing to complement the flow stimuli by flow-invariant heat stimuli. We introduce strategies to complement even complex primary scan patterns by secondary heating stimuli thereby yielding a near isothermal temperature distribution and still generating significant net flows. As we experimentally show, the resulting temperature distributions are near homogenous across the sample (standard deviations 5-10 times lower than those measured with standard FLUCS) and can therefore be better compensated for by ambient cooling. In the next future, ISO-FLUCS may become the new standard for optofluidic manipulations within biological systems.