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Description
Soft porous media consisting of assemblies of biological objects are common in many industrial and natural situations. They are often confined, as in the case of yeast clogs trapped in a filtration membrane, or human tumor cells in the case of e.g. bone cancer. Whereas this confinement and the possible friction induced at the boundaries of the porous media are not addressed by the well-known poromechanics theory [1], some recent experimental results tend to prove their importance [2].
For this presentation, we have studied the mechanical properties of a clog of living particles based on observations at the microscale in a model configuration: we used the baker's yeast Saccharomyces cerevisiae, with known mechanical and biological properties, to form clogs that were observed in a quasi-2D microfluidic device with well-controlled dimensions to ensure a high degree of confinement [3]. After the formation of a clog, compression and decompression cycles were applied (see Figure), both in a flow-driven configuration and in an impermeable piston-driven one. The results show that the stress-displacement relationship deviates from the predictions of poromechanics theory and conventional interpretations in the literature, revealing a strong hysteresis. This is the signature of energy loss during the compression-decompression cycle. In addition, complementary experiments show that stress is stored during decompression.
A continuous model is proposed, which takes into account the coupling between the fluid flow, the deformation of the clog, and the friction against the device's walls. This reveals that the friction magnitude is dictated by a single dimensionless number, which is proportional to the friction coefficient multiplied by the aspect ratio of the device. This model reproduces all the observations remarkably well. Taken together, these results provide a first theoretical framework for the study of bioclogging on small scales and show that friction can have non-trivial effects on the mechanics of confined deformable porous media.
| References | [1] C.W. MacMinn, E.R Dufresne, J.S. Wettlaufer, Physical Review Applied, 2016, 5, 4. [2] T. Lutz, PhD Dissertation, 2021, Yale Graduate School of Arts and Sciences, New Haven, USA. [3] T. Desclaux et al., Physical Review Fluids, 2024, 9, 3, 034202. |
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| Country | France |
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