An active fluid denotes a suspension of agents (particles, macromolecules, bacteria, or cells) that are able to convert energy into individual propulsion (for bacteria or cells this is internal chemical energy). Such self-propelled agents generally exhibit collective behavior (swarming). This project will explore active motion and swarming in complex non-Newtonian fluids. Sofar no thorough study has been done to for example really understand the behavior of active bacterial fluids when the suspending fluid is non-Newtonian. From a practical point of view this has a tremendous importance as many biological fluids in the body are non-Newtonian and there is a growing medical interest in understanding how bacteria are transported in lumen (intestine or ureter) or may eventually cross mucus barriers and provoke serious diseases. Furthermore, bacteria are currently being explored as a potential medicament vectors in the perspective of personalized medicine , and more recently magnetotactic bacteria were used to directly search and destroy cancer cells .
The project is further relevant to understand bacterial contamination of food or cosmetics, contamination and decontamination soils and aquifers, which all involve confined bacterial motion in complex fluids. The project also connects to materials science and self-assembly of functional meso-scale structured materials. The research will involve studies of both living active matter (ESPCI) and synthetic non-living model systems of active matter (NTNU). Two main active fluid systems will be studied: bacterial suspensions including magnetotactic bacteria (ESPCI), and suspended electro-hydrodynamically driven colloidal rotors emulating collective behavior of bacterial swarms (NTNU). Different complex fluid environments will be tested, in particular colloidal clay fluids/gels (NTNU).