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ISO-FLUCS: symmetrization of optofluidic manipulations in quasi-isothermal micro-environments

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Minopoli, A 
Wagner, S 
Erben, E 
Liao, W 
Stoev, ID 


jats:titleAbstract</jats:title>jats:pRecently, it has been demonstrated that thermoviscous flows can be used for a range of fine micromanipulations, such as moving the cytoplasm of cells and developing embryos, intracellular rheology, and femtonewton-range force measurements. These flows, also known as focused-light-induced cytoplasmic streaming (FLUCS), are induced by mid-infrared laser scanning of a temperature spot through the sample. However, localized laser scanning can inflict temperature perturbations of several Kelvins on the sample, potentially eliciting unspecific biological responses. In this study, we demonstrate how exploiting symmetry relations during laser scanning effectively disentangles laser heating and flow induction. We introduce flow-neutral scan sequences that use dynamic photothermal stimuli and spatiotemporal symmetry relations of scanning bridging up to three distinct time scales. We leverage further insights from a recently published analytical model of flow fields to present quasi-homogenous temperature distributions that leave flow lines and their local and directed character largely invariant. We present practical, intuitive solutions through predesigned sets of scan lines with near isothermal distributions and demonstrate that they are sufficient to generate and control flows in jats:italicCaenorhabditis elegans</jats:italic> embryos on a magnitude well in excess of endogenous flow velocities. Our results enable the separation of two previously tightly linked classes of physical stimuli, introduce a new, even less invasive standard for performing FLUCS perturbations, and pave the way for new unexplored avenues in the fields of soft matter and biomedicine.</jats:p> jats:pjats:boldGraphical Abstract</jats:bold></jats:p>


Acknowledgements: We thank Iain Patten for valuable discussions on the structure and layout of the manuscript, and Matthäus Mittasch, Anatol Fritsch and Matthias Loidolt for the construction of the microscope and early experiments. Moreover, we acknowledge the support of the Karlsruhe School of Optics & Photonics (KSOP) financed by the Ministry of Science, Research and the Arts of Baden-Wurttemberg as part of the sustainability financing of the projects of the Excellence Initiative II.


4012 Fluid Mechanics and Thermal Engineering, 40 Engineering, Bioengineering

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Springer Science and Business Media LLC
Volkswagen Foundation (92772)