The colocalization of density modulations and particle polarization is a characteristic emergent feature motile active matter in activity gradients. We employ the active-Brownian-particle model to derive precise analytical expressions for profiles single Janus-type swimmer vicinity an abrupt step. Our analysis allows optional (but not necessary) orientation-dependent propulsion speed, as often ...

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...