Barriuso Gutiérrez, Carlos MiguelSerna, HoracioPagonabarraga, IgnacioValeriani, Chantal2026-02-032026-02-032025Soft Matter, 2025, 21, 20101744-684810.1039/d4sm01356ehttps://hdl.handle.net/20.500.14352/1314172025 Acuerdos transformativos CRUE C. V. acknowledges funding IHRC22/00002 and PID2022- 140407NB-C21 from MINECO. This project has received funding from the European Union’s Horizon research and innovation programme under the Marie Skłodowska-Curie grant agreement no 101108868 (BIOMICAR). I. P. acknowledges financial support from DURSI under Project No. 2021SGR673, Ministerio de Ciencia, Innovacio´n y Universidades MCIU/AEI/FEDER under grant agreement PID2021-126570NB100 AEI/FEDER-EU and Generalitat de Catalunya for financial support under Program Icrea Acade`mia. We acknowledge MARENOSTRUM-BSC (grant FI-2024-2-0044). C. M. B. G. acknowledges enriching discussions with Jose´ Martı´n-Roca, Juan Pablo Miranda Lo´pez and Rodrigo Fernandez-Quevedo.The effect of gravity on the collective motion of living microswimmers, such as bacteria and microalgae, is pivotal to unravel not only bio-convection patterns but also the settling of bacterial biofilms on solid surfaces. In this work, we investigate suspensions of microswimmers under the influence of a gravitational field and hydrodynamics, simulated via the dissipative particle dynamics (DPD) coarsegrained model. We first study the collective sedimentation of passive colloids and microswimmers of the puller and pusher types upon increasing the imposed gravitational field and compare them with previous results. Once sedimentation occurs, we observe that, as the gravitational field increases, the bottom layer undergoes a transition to an ordered state compatible with a hexagonal crystal. In comparison with passive colloids, both pullers and pushers easily rearrange at the bottom layer to anneal defects. Specifically, pullers are better than pushers in preserving the hexagonal order of the bottom mono-layer at high gravitational fields.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/journal articlehttps://doi.org/10.1039/D4SM01356Eopen access538.9Física de materiales22 Física2211 Física del Estado Sólido