Open Positions

Master 2 internship (PMMH, ESPCI Paris)
Flows of suspensions of deformable particles

Philippe Bourrianne, Anke Lindner
PMMH, ESPCI Paris
philippe.bourrianne@espci.fr – anke.lindner@espci.fr

Flows of dry and wet granular suspensions have long been studied, from the regular discharge of sand in hourglasses or silos to the clogging of particles under confinement. While most of experimental studies have used rigid particles, particles in pratical applications often exhibit deformable features. In particular, the flow of red blood cells in the human body is known to be dramatically affected by diseases such as malaria, which increase cell stiffness and impair passage through narrow capillaries. Here, we have designed a model 2D microfluidic system to print particles of controlled shape, size and deformability [1]. By using stop-flow lithography, we are able to generate suspensions of 2D particles into a microfluidic channel and to study various flow geometries. With such system, we have studied microfluidic hopper flows of hard monodisperse disk-shaped particles, that exhibit similar behavior than the well-established laws in dry granular flows [1]. By designing ring particles, we perform experiments with packing composed of particle of controlled deformability to provide novel experimental measurements on the role played by deformability on clogging.

[1] L. Kool, J. Tampier, P. Bourrianne and A. Lindner, Hopper flows of dense suspensions: a 2D microfluidic model
system. Flow (2025).

Master 2 internship (PMMH, ESPCI Paris)
Liquid-solid composites

Philippe Bourrianne, Alice Pelosse
PMMH, ESPCI Paris
philippe.bourrianne@espci.fr – alice.pelosse@espci.fr

Composite materials combining architected soft solids and complex fluids offer a versatile platform to engineer mechanical properties through fluid-structure coupling. In such materials, a complex fluid is infused within a porous or cellular soft solid, whose geometry can be tailored to control the overall mechanical response. These composites can exhibit enhanced stiffness, energy absorption and impact resistance while retaining the tunability of architected materials [1]. This interplay is particularly
rich under dynamic loading, as deformation of the architecture modifies local flow conditions and, in turn, the mechanical response of the fluid. Shear-thickening suspensions are a striking example, exhibiting a rapid and reversible increase in viscosity under shear [2] due to the formation of frictional contacts between particles, enabling spectacular phenomena such as running across a bath of cornstarch suspension. When infused into 3D-printed soft solid foams, these suspensions couple shear-induced solidification with the architecture, strongly reinforcing the composite upon impact. By varying the fluid rheology and solid geometry, we aim to design adaptive materials with tunable stiffness and energy absorption, while elucidating the transient mechanisms governing their mechanical response.

[1] S.M. Livermore, A. Pelosse, M. van der Naald, H. Kim, S. Atis and H.M. Jaeger, Shear thickening inside elastic
open-cell foams under dynamic compression. Soft Matter (2025).
[2] P. Bourrianne, V. Niggel, G. Polly, T. Divoux and G.H. McKinley, Tuning the shear thickening of suspensions
through surface roughness and physico-chemical interactions. Physical Review Research (2022).