Research ArticleBIOPHYSICS

Light-induced self-assembly of active rectification devices

Science Advances  01 Apr 2016:
Vol. 2, no. 4, e1501850
DOI: 10.1126/sciadv.1501850

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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.

Keywords
  • active matter
  • active Brownian particles
  • colloids
  • self-assembly
  • soft matter
  • biophysics
  • motile bacteria
  • computer simulation
  • Brownian dynamics
  • statistical thermodynamics

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

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