Active matter: swimming and motility

Amoeboid swimming :


A prevailing dogma in biology is that cells of the immune system (leukocytes) use the adhesion machinery (combined with actin-myosin dynamics) on a substrate in order to crawl towards infections. While crawling is an essential process for leukocytes motion along the endothelium, before they transmigrate towards underlying tissues, expression of adhesion molecules like integrins are not required for the motion of these cells, thus calling the crawling paradigm into question.
We have made several recent studies on amoeswimming that reproduce real motions encountered in nature:

Simple models of swimmers:


Several studies are performed using simple swimmers like “three beads microswimmers”

 We have, for example, shown that this swimmer can perform steering; for example by adjusting phase shifts between springs, the swimmer can describe an arbitrary trajectory cnes:

 

Leukocyte use protein-paddling to move: crawling in a fluid:


We have shown experimentally and theoretically that T-Lymphocytes can move in a fluid thanks to transmembrane proteins, and that shape change is inefficient, despite apparent ample and frequent shape changes:

We have developed a model including acto-myosin dynamics and have shown that there is a spontaneous symmetry-breaking bifurcation leading to autonomous motion in a fluid:

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