Abstract: Understanding the individual and the macroscopic transport properties of motile micro-organisms like bacteria is a timely question relevant to many technological applications. This is for example crucial in a medical context where the contamination via physiological conducts or the penetration of mucus barriers, is responsible for the outbreak of serious diseases. It is also relevant to the development of novel drug delivery technologies or environmental remediation strategies suited to fight oil spills or heavy metal pollutions.
Moreover, at the fundamental level, this question is also receiving a lot of attention. Fluids loaded with swimming micro-organisms has become a rich domain of applications for the statistical physics of “active matter” where the existence of microscopic sources of energy borne in the motile character of the particles leads to numerous original effects.
In this presentation, I will review several example we address experimentally in the lab and which lead us to revisit standard concepts of the physics of suspensions like Brownian motion, hydrodynamics dispersion or rheological response. I will also present new experiments showing how the motility of the bacteria can be controlled such as to extract work macroscopically.