Charlotte de Blois – Canopy elastic turbulence:Spontaneous formation of waves in beds of slender microposts

Institut des Matériaux Poreux de Paris (IMAP), UMR 8004 CNRS, Ecole Normale Supérieure de Paris, Ecole Supérieure de Physique et de Chimie Industrielles de Paris, PSL Université, 75005, Paris, France
ESPCI Paris, PSL Research University, MIE-CBI, CNRS UMR 8231, 10, Rue Vauquelin, F-75231 Paris Cedex 05, France

How the beating of cellular cilia in a surrounding fluid gives rise to fluid transport and coordinated cilia motions is a 70-year-old problem, but it remains an open question due to the complexity and the diversity in the length scale of the phenomenon involved. Theoretical studies [1] suggest a role for non-Newtonian hydrodynamic coupling between cilia. To better understand how a viscoelastic flow may interact with a bed of cilia, we build a microfluidic canopy, a large array of soft and flexible structures with micrometric scale (d = 2 um, h=50 um).

Under a viscoelastic flow, we observed the spontaneous emergence of waves in the form of propagating regions of low flow velocity compared to the surrounding flow. The occurrence of the wave is chaotic and shows characteristics of elastic turbulence. We systematically study the coupling between the low-velocity wave and the microfluidic canopy by combining flow velocimetry experiments and high-speed tracking of the pillars.
Furthermore, I intend to use the second part of this seminar as an opportunity to introduce a project proposal for an application to the LPS. This proposal can serve as a foundation for future discussions.

[1] C Brennen, and, and H Winet, Annual Review of Fluid Mechanics 9, 1 (1977)
[2] J. Fischer and M. Wegener, Laser Photonics Rev. 7, 1 (2013).
[3] J. Gottmann, M. Hermans, J. Ortmann, Phys. Procedia 534, 39 (2012).
[4] C de Blois, S. J. Haward, A. Q. Shen, PRF 8, 023301 (2023)