<< From starling aberrations to self-turbulent fluids, 'active systems' encompass a wide family of phenomena in which individual objects propel themselves forward, allowing them to display intriguing collective behaviors. (..) these objects collectively spend most of their time in one of two states, between which some intriguing behaviors can emerge. (..) these collective behaviors are determined by the ability of the self-propelling objects to swim upwards against the gravitational force, and their degrees of bottom-heaviness. For lower values of these quantities, groups of swimmers will sink to the bottom of their container just like inactive dust grains; but higher values will instead collect at the top. In between these states, smaller clusters of swimmers group at the bottom, which are fed by plumes of sinking particles. Also, porous clusters of swimmers can form, which allow individual particles to escape. >>
'Bottom-heavy squirmers' adopt characteristic group behaviours. Springer. May 28, 2020.
Ruhle F., Stark H. Emergent collective dynamics of bottom-heavy squirmers under gravity. Eur. Phys. J. E 43, 26 (2020). doi: 10.1140/epje/ i2020-11949-8. May 25, 2020.
