Complex fluids and active matter

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

It is common to the 2 PhyMV and SoftMat courses.

Present a modern introduction to the classical fields of complex fluid rheology and their applications, as well as to the emerging field of active matter: self-propelled fluids with collective behavior, found at different scales in living or physico-chemical systems: bird flights, schools of fish, crowds...

- Hydrodynamics

Recommended prerequisites : 

- Surfaces, Interfaces, Colloids,

- Statistical Physics

- Physics Biology

Integral Continuous Control

A) Complex fluids :

Introduction to non-Newtonian fluids: rheofludient, rheo-thickening, viscoelastic, thixotropic.

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

Phenomenological models of non-Newtonian fluids: Maxwell's model, Voigt's model (visco-plastic solid), Bingham's model (threshold fluid).

Measurement methods: different types of rheometers and different types of tests. One-point and two-point micro-rheology.

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

B) Active ingredient :

Examples of active matter, flights, shoals, hordes, crowds, bacterial colonies, mechanical examples (vibrators), physico-chemical examples, actin gel, SPV, partition system byABS.

The Vicsek model, simulations and phenomenology.

Hydrodynamic description, conservation laws, symmetries, slow variables.

Dry" active ingredient

• Polar: Toner & Tu model, study of model properties: phase transition, 2D order, giant fluctuations, "sound" waves, etc.
• Nématique: Model by Ramaswamy, Simha & Toner.

Wet" active ingredient. Hydrodynamics of active gels.

Optional examples to choose from:

- Janus particles

- Active growth. Active sedimentation.

- Active membrane fluctuation spectra.

- The parABS system, equations, equilibrium, quasi-static limit, oscillations, stability, travelling waves.

- Self Propelled Voronoi model.