Arlt, Jochen; Martinez, Vincent; Dawson, Angela; Pilizota, Teuta; Poon, Wilson CK. (2019). Dynamics-dependent density distribution in active suspensions, 2015-2018 [dataset]. University of Edinburgh. School of Physics & Astronomy. Institute for Condensed Matter and Complex Systems. https://doi.org/10.7488/ds/2550
Dataset for the manuscript entitled 'Dynamics-dependent density distribution in active suspensions': Self-propelled colloids constitute an important class of intrinsically non-equilibrium matter. Typically, such a particle moves ballistically at short times, but eventually changes its orientation, and displays random-walk behaviour in the long-time limit. Theory predicts that if the velocity of non-interacting swimmers varies spatially in 1D, v(x), then their density ρ(x) satisﬁes ρ(x) = ρ(0)v(0)/v(x), where x = 0 is an arbitrary reference point. Such a dependence of steady-state ρ(x) on the particle dynamics, which was the qualitative basis of recent work demonstrating how to ‘paint’ with bacteria, is forbidden in thermal equilibrium. We verify this prediction quantitatively by constructing bacteria that swim with an intensity-dependent speed when illuminated and implementing spatially-resolved diﬀerential dynamic microscopy (sDDM) for quantitative analysis over ∼ mm length-scales. A spatial light pattern therefore creates a speed proﬁle, along which we ﬁnd that, indeed, ρ(x)v(x) = constant, provided that steady state is reached.
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