Active fluids polarize the channel walls with topological defects

Categorías: IN2UB

In a recent publication in Nature Communications, researchers from the SOC&SAM group have demonstrated that active fluids made from an in-vitro reconstitution of filamentous proteins and molecular motors, both components of the cytoskeleton, behave in a surprising way when flowing inside microchannels.  In the presence of ATP, the cell fuel, these filaments develop self-sustained chaotic flows. As a result, the layer of aligned fibers, or nematic, is permeated by distortions, called topological defects. Just like ions in an aqueous solution, defects in a layer of ordered fibers exist in a balance between positive and negative distortions, a well-known fact in different areas of soft material science. Remarkably, when this active nematic is confined by microchannels, negative topological defects accumulate on the walls, while their positive counterparts are in excess in the bulk, a situation in striking analogy with the electrical double layer that forms near the surface of electrodes or of colloidal particles in suspensions.

Active boundary layers in confined active nematics. Jerôme Hardoüin, Claire Doré, Justine Laurent, Teresa Lopez-Leon, Jordi Ignés-Mullol & Francesc Sagués. Nature Communications volume 13, Article number: 6675 (2022)