Complex fluids and active matter

This course provides an introduction to the field of complex fluids and active matter, with applications in both soft matter physics and chemistry and the physics of living organisms and biological objects.

It is common to both the PhyMV and SoftMat courses.

Provide a modern introduction to the classic fields of complex fluid rheology and its applications, as well as to the emerging field of active matter: self-propelled fluids with collective behaviors, found at different scales in living or physicochemical systems: flocks of birds, schools of fish, crowds, etc.

- Hydrodynamics

Recommended prerequisites: 

- Surfaces, Interfaces, Colloids,

- Statistical Physics

- Physics Biology

Continuous Integral Control

A) Complex fluids:

Presentation of non-Newtonian fluids: rheofluidifiers, rheothickeners, viscoelastic fluids, thixotropic fluids.

Examples of practical systems: colloidal suspensions, polymers, biological fluids (blood, mucus, etc.), liquid crystals, pastes, giant micelles, transient networks, biological applications.

Phenomenological models of non-Newtonian fluids: Maxwell model, Voigt model (viscoplastic solid), Bingham model (threshold fluid).

Measurement methods: different types of rheometers and different types of tests. Single-point and two-point microrheology.

Microfluidics: microfluidic flows and rheology, capillary flows, stagnant and contracting flows. Instabilities (Saffman-Taylor, etc.)

B) Active Ingredient:

Examples of active matter, flights, banks, swarms, crowds, bacterial colonies, mechanical examples (vibrators), physical chemistry examples, actin gel, SPV, ABS partitioning system.

Vicsek's model, simulations, and phenomenology.

Hydrodynamic description, conservation laws, symmetries, slow variables.

"Dry" active ingredient

• Fleece: Toner & Tu model, study of the model's properties: phase transition, 2D order, giant fluctuations, "sound" waves...
• Nematic: Ramaswamy, Simha & Toner model.

Wet active material. Hydrodynamics of active gels.

Optional, examples to choose from:

- Janus particles

- Active growth. Active sedimentation.

- Active membrane fluctuation spectra.

- The system using ABS, equations, equilibrium, quasi-static limit, oscillations, stability, traveling waves.

- Self-Propelled Voronoï model.