Abstract
Active particles are known to exhibit collective behavior and induce structure in a variety of soft-matter systems. However, many naturally occurring complex fluids are mixtures of active and passive components. The authors examine how activity induces organization in such multi-component systems. Mixtures of passive colloids and colloidal micromotors are investigated and it is observed that even a small fraction of active particles induces reorganization of the passive components in an intriguing series of phenomena. Experimental observations are combined with large-scale simulations that explicitly resolve the near- and far-field effects of the hydrodynamic flow and simultaneously accurately treat the fluid–colloid interfaces. It is demonstrated that neither conventional molecular dynamics simulations nor the reduction of hydrodynamic effects to phoretic attractions can explain the observed phenomena, which originate from the flow field that is generated by the active colloids and subsequently modified by the aggregating passive units. These findings not only offer insight into the organization of biological or synthetic active–passive mixtures, but also open avenues to controlling the behavior of passive building blocks by means of small amounts of active particles.
| Original language | English (US) |
|---|---|
| Article number | 2107023 |
| Journal | Small |
| Volume | 18 |
| Issue number | 21 |
| DOIs | |
| State | Published - May 26 2022 |
Funding
This work was supported by the Center for Bio‐Inspired Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), under Award DE‐SC0000989. The authors thank R. Yamamoto and J. Molina for kind assistance with the KAPSEL software that implements the SPM, specifically in aiding us to modify the software for the purposes of this manuscript. The authors thank the Quest high‐performance computing facility at Northwestern University for computational resources. J.S. acknowledges Freigeist grant number 91619 from the Volkswagen Foundation and the Fulbright–Cottrell Foundation. L.W. acknowledges financial support from the China Scholarship Council. The authors thank T. Gemming for access to electron microscopy and S. Heckel for taking images of active–passive mixtures.
Keywords
- Janus micromotors
- active particles
- aggregation
- colloids
- hydrodynamics
- simulations
ASJC Scopus subject areas
- Biotechnology
- General Chemistry
- Biomaterials
- General Materials Science
- Engineering (miscellaneous)