Pinning dislocations in colloidal crystals with active particles that seek stacking faults. Issue 17 (14th April 2020)

• Record Type: Journal Article
• Authors: VanSaders, Bryan; Glotzer, Sharon C.
• Is Part Of: Soft matter. Volume 16:Issue 17(2020)
• Page Start: 4182
• Page End: 4191
• Publication Date: 2020-04-14
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c9sm02514f
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : By designing the shape of an active particle, its transport through a dense crystal can be tailored, as well as its interaction with dislocation defects present in the host crystal. Abstract : There is growing interest in functional, adaptive devices built from colloidal subunits of micron size or smaller. A colloidal material with dynamic mechanical properties could facilitate such microrobotic machines. Here we study via computer simulation how active interstitial particles in small quantities can be used to modify the bulk mechanical properties of a colloidal crystal. Passive interstitial particles are known to pin dislocations in metals, thereby increasing resistance to plastic deformation. We extend this tactic by employing anisotropic active interstitials that travel super-diffusively and bind strongly to stacking faults associated with partial dislocations. We find that: (1) interstitials that are effective at reducing plasticity compromise between strong binding to stacking faults and high mobility in the crystal bulk. (2) Reorientation of active interstitials in the crystal depends upon rotational transitions between high-symmetry crystal directions. (3) The addition of certain active interstitial shapes at concentrations as low as 60 per million host particles (0.006%) can create a shear threshold for dislocation migration. This work demonstrates how active materials in a dense matrix can locally sense their environment and lead to bulk property changes.