title: Light-induced self-assembly of active rectification devices.
abstract: Self-propelled colloidal objects, such as motile bacteria or synthetic microswimmers, have microscopically irreversible individual dynamics-a feature they share with all living systems. The incoherent behavior of individual swimmers can be harnessed (or "rectified") by microfluidic devices that create systematic motions that are impossible in equilibrium. We present a computational proof-of-concept study showing that such active rectification devices could be created directly from an unstructured "primordial soup" of light-controlled motile particles, solely by using spatially modulated illumination to control their local propulsion speed. Alongside both microscopic irreversibility and speed modulation, our mechanism requires spatial symmetry breaking, such as a chevron light pattern, and strong interactions between particles, such as volume exclusion, which cause a collisional slowdown at high density. Together, we show how these four factors create a novel, many-body rectification mechanism. Our work suggests that standard spatial light modulator technology might allow the programmable, light-induced self-assembly of active rectification devices from an unstructured particle bath.
authors.affiliation: Division of Physical Chemistry, Lund University, 221 00 Lund, Sweden.
authors.forename: Joakim
authors.identifier: 0000-0002-7543-5549
authors.initials: J
authors.lastname: Stenhammar
authors.affiliation: Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Raphael
authors.initials: R
authors.lastname: Wittkowski
authors.affiliation: Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, UK.
authors.forename: Davide
authors.initials: D
authors.lastname: Marenduzzo
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, UK.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Cates
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D056656:Lab-On-A-Chip Devices; D008027:Light; D009038:Motion; D055585:Physical Phenomena
chemical_list: D003102:Colloids
keywords: Active Brownian particles; Active matter; Brownian dynamics; Colloids; Computer simulation; Motile bacteria; Statistical thermodynamics; biophysics; self-assembly; soft matter