Orientationally Glassy Crystals of Janus Spheres

Abstract

Colloidal Janus spheres in water (one hemisphere attractive and the other repulsive) assemble into two-dimensional hexagonal crystals with orientational order controlled by anisotropic interactions. We exploit the decoupled translational and rotational order to quantify the orientational dynamics. Via imaging experiments and Monte Carlo simulations we demonstrate that the correlations in the orientation of individual Janus spheres exhibit glass-like dynamics that can be controlled via the ionic strength. Thus, these colloidal building blocks provide a particularly suitable model glass system for elucidating non-trivial dynamics arising from directional interactions, not captured by the consideration of just translational order.

Orientational ordering of closely packed Janus particles

“…Most natural expectation would be that the relaxation of the system proceeds as a coarsening process [23] of the stripes. However an experimental study [17] has suggested some sort of glassy dynamics. A stripe is a train of tetramers with the same orientation σ.…”

“…However the nature of the orientational ordering have not been fully studied yet. While a theoretical study [18] predicts an orientationally ordered state for large enough patch sizes, an experiment [17] suggests an orientational glass phase. In the present work, we perform extensive Monte Carlo simulation to study both the static and dynamic aspects of the orientational configurations.…”

“…Indeed such set ups have been implemented and analyzed experimentally. [16,17]. However the nature of the orientational ordering have not been fully studied yet.…”

Natural selection in the colloid world: active chiral spirals

“…12 These examples raise interesting puzzles that go beyond simply observing the chirality of the trajectories, puzzles about the relationship between shape and motion, especially when the mounting interest in active material design must ultimately be grounded in coordinating the motion of body parts and the whole body. Regarding the experimental system, this study goes beyond this laboratory's traditional interest in single-component Janus particles [13][14][15] and considers instead the new dynamic structures which result when one mixes Janus particles with isotropic particles, both of them in an electric field. Building upon a preliminary study presented elsewhere 16 in which the Janus particles are repulsive to each other, here we consider particles that mutually attract to form active filaments.…”

Measuring rotational diffusion of colloidal spheres with confocal microscopy

“…However, for colloidal spheres, their rotational dynamics have hardly been explored with confocal microscopy yet. Rotational diffusion of colloidal spheres has been used to explore the decoupling of translational-rotational motion in concentrated colloidal systems [25,26] . In this communication, we demonstrate a quantitative method to concurrently measure the translational and rotational diffusion of colloidal spheres with confocal microscopy.…”