Flow-induced concentration gradients in shear-banding of branched wormlike micellar solutions
| Autor: | Vincenzo Guida, Carla Caiazza, Stefano Guido, Valentina Preziosi, Giovanna Tomaiuolo, D. O'Sullivan |
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| Přispěvatelé: | Caiazza, C., Preziosi, V., Tomaiuolo, G., O'Sullivan, Patrick, Guida, V., Guido, S. |
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Microfluidics Phase separation Video microscopy 02 engineering and technology 010402 general chemistry 01 natural sciences Biomaterials Shear-induced structuring Colloid and Surface Chemistry Surfactant Wormlike micelle Microchannel Conductance Velocimetry 021001 nanoscience & nanotechnology 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Microfluidic Shear (geology) Chemical physics Micellar solutions 0210 nano-technology Concentration gradient Shear banding |
| Zdroj: | Journal of Colloid and Interface Science. 534:695-703 |
| ISSN: | 0021-9797 |
| DOI: | 10.1016/j.jcis.2018.09.060 |
| Popis: | Hypothesis Shear-banding of branched wormlike solutions is a topic of active investigation which has not been fully elucidated. Here, we surmise that flow-induced microstructuring in the shear banding regime is associated with spatial concentration gradients. Experiments The experiments focus on the flow-induced behavior of a CTAB/NaSal wormlike micellar system. A unique approach based on a microfluidic-spitter geometry, combined with particle-image velocimetry and high-speed video microscopy, is used to separate the streams flowing out from the core and the near wall zones of the microchannel. Findings Here, we present the first direct experimental evidence of the correlation between phase separation and shear banding. By increasing the pressure-drop across a microcapillary, the onset of a grainy texture close to the wall, showing a flow-induced demixing effect, is observed. We use a splitter to measure effluent streams from the center and the near-wall zones in terms of viscosity, conductance and dry mass. We observe that phase-separation induced by the flow correlates with chemical concentration gradients. This confirms our hypothesis that shear-induced local de-mixing of the system is strongly related to chemical concentration gradients. |
| Databáze: | OpenAIRE |
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