Giant Fluctuations Induced by Thermal Diffusion in Complex Liquids

Alberto Vailati, Philipp Baaske, Henri Bataller, Serena Bolis, Marco Braibanti, Marina Carpineti, Roberto Cerbino, Fabrizio Croccolo, Jean Luc Dewandel, Aleksandar Donev, Loreto García-Fernández, Fabio Giavazzi, Robert Haslinger, Steven Hens, Maria Knauer, Werner Köhler, Ewald Kufner, José M. Ortiz de Zárate, Jeroen Peeters, Christian J. SchwarzInese Silkina, Shenghua Xu, Daniel Zapf

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)873-887
Number of pages15
JournalMicrogravity Science and Technology
Issue number5
StatePublished - Oct 1 2020


  • Microgravity
  • Non-equilibrium fluctuations
  • Shadowgraph
  • Thermodiffusion
  • Transport properties

ASJC Scopus subject areas

  • Modeling and Simulation
  • General Engineering
  • General Physics and Astronomy
  • Applied Mathematics


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