How Activity Landscapes Polarize Microswimmers without Alignment Forces

Active-particle suspensions exhibit distinct polarization-density patterns in activity landscapes, even without anisotropic particle interactions. Such polarization alignment forces is at work motility-induced phase separation and betrays intrinsic microscopic to mesoscale observers. Using stable long-term confinement of a single thermophoretic microswimmer dedicated force-free trap, we examine the polarized interfacial layer motility step confirm that it does not exert pressure onto bulk. Our observations are quantitatively explained by an analytical theory can also guide analysis more complex geometries many-body effects.Received 12 January 2021Accepted 20 April 2021DOI:https://doi.org/10.1103/PhysRevLett.126.228001© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Physical SystemsActive brownian particlesSelf-propelled janus particlesTechniquesTheories collective dynamics & active matterPolymers Soft MatterStatistical Physics