Giant Fluctuations Induced by Thermal Diffusion in Complex Liquids



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Vailati, Alberto and Ortiz de Zárate Leira, José María and otros, ... (2020) Giant Fluctuations Induced by Thermal Diffusion in Complex Liquids. Microgravity science and technology . ISSN 0938-0108

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The GRADFLEX experiment of ESA has shown that under microgravity conditions a stationary thermodiffusion process is accompanied by giant non-equilibrium fluctuations with size as large as the size of the sample. In the presence of small concentration gradients, the features of the non-equilibrium fluctuations can be described by means of linearized hydrodynamics. However, the linear models are not suitable to describe most cases of applicative interest, such as fluctuations induced by large gradients and under non-stationary conditions. Moreover, presently the investigation of non-equilibrium fluctuations has mainly involved single component fluids and binary mixtures, but recently transport processes in ternary mixtures have attracted increasing interest due to the experiments performed on the International Space Station in the framework of the DCMIX project of ESA. The Giant Fluctuations (NEUF-DIX) project of ESA will investigate non-equilibrium fluctuations during diffusive processes occurring in complex multi-component mixtures, where one of the components is a macromolecule, such as a polymer, a colloid or a protein. Important objectives will be the exploration of the features of the fluctuations under non-ideal conditions, such as large gradients, transient processes, and concentrated samples, and the understanding of how the fluctuations affect the interactions between macromolecules. The project involves the development of a dedicated facility, consisting of an array of shadowgraph optical instruments working in parallel, each one equipped with a thermal gradient cell. Here we outline the design concept of the facility and the results of performance tests performed on a breadboard to evaluate the suitability of the designed instrument to carry out scientific measurements of non-equilibrium concentration fluctuations in space.

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Artículo firmado por 23 autores. We acknowledge support from the European Space Agency (ESA). FC, HB, and LGF acknowledge support from the French Centre Nationale d’Etudes Spatiales (CNES) and from Excellence Initiative of University of Pau and Countries of Adour – I-Site E2S, a French “Investissements d’Avenir” programme. WK and DZ acknowledge support from the Deutsches Zentrum für Luft- und Raumfahrt (DLR grant 50WM1850). Funding Information Open access funding provided by Università degli Studi di Milano within the CRUI-CARE Agreement.

Uncontrolled Keywords:Nonequilibrium fluctuations; Mixtures; Thermodiffusion; Polystyrene; Semidilute; Schlieren; Soret
Subjects:Sciences > Physics > Thermodynamics
ID Code:62201
Deposited On:09 Oct 2020 11:11
Last Modified:09 Oct 2020 11:11

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