Soft matter under stress (MMC)

We design model materials and study their mechanical response, plasticity, and fracture when subjected to extreme stresses.

Static properties of non-equilibrium systems

We develop dynamic DNA hydrogels that can reorganise themselves via associative strand exchange mechanisms. This approach endows the materials with exceptional resilience and unparalleled structural adaptability.

*Figure : The merging of two dynamic solid hydrogels at temperatures more than 40°C below their melting point is achieved through an associative strand exchange mechanism.*

We study colloidal glass transitions in microgravity using systems whose volume fraction can be adjusted by adding thermosensitive polymer dispersions. Introducing polymers into colloidal systems generally allows us to control interactions more finely and understand their properties better at various distances from equilibrium.

Precursors of failure and yielding transition

We observe the microscopic rearrangements that precede gel fracture. These measurements reveal the dynamic features that signal imminent macroscopic failure.

*Figure : The local dynamics of a biopolymer during creep, as revealed by the amplitude of displacements measured by light scattering. Tags: time to failure.*

From a rheological perspective, we characterize the transition between the solid and fluid states in colloidal suspensions. We analyze this transition by combining rheological measurements and time-resolved structural studies.

Figure : Unified state diagram for the fluidization transition. For small deformation amplitudes, soft systems such as mayonnaise and toothpaste exhibit solid-like dynamics (blue dots) with low fluidity. As the deformation amplitude increases, these systems undergo a fluidization transition (gray dots). This transition is characterized by the coexistence of two types of dynamics (solid and fluid). Ultimately, these systems are fluidized at very large deformations, at which point the microscopic dynamics resemble those of a liquid. (Copyright © 2023, authors under exclusive license from Springer Nature Limited).

Viscoelastic systems under extreme deformations

We study how droplets deform after impact in relation to the viscoelastic properties of their constituent fluids. By comparing deformations after impact on solid and liquid nitrogen surfaces, we have determined the relative contributions of different flow modes to dissipation.

_{Top-views of the liquid sheets after impact and reconstruction of the transverse section of the bead.}

We study the mechanisms involved when a drop crosses a liquid-liquid interface by combining numerical and experimental approaches. This involves designing an original experimental device to observe the passage at very high inertia (1000 g).