Electrically Driven Rotation and Nonreciprocal Motion of Microparticles in Nematic Liquid Crystals

Abstract

Dispersion of microparticles in nematic liquid crystals offers a novel means for controlling both their orientation and position through the combination of topology and external stimuli. Here, cuboidal and triangular prism shaped microparticles in parallel plate capacitor cells filled with a nematic liquid crystal are studied. Experimental observations are compared with numerical simulations to show that the optimal orientation of the particles is determined by their aspect rations, the relative separation gap of their containers and the applied voltage. It is observed that in systems that allow unrestricted particle rotation, the long axes of the particles are able to fully align themselves with the external electric field. However, when particle rotation is geometrically restricted, it is found that increasing the voltage past a critical value causes the short axis of the particle to realign with the electric field due to anchoring breaking. It is shown that symmetry of the particles then plays a key role in their dynamics following the removal of the electric field, allowing the triangular prisms to travel perpendicular to the applied electric field, whereas only rotation is possible for the cuboidal particles.

Emergence of Directional Rotation in an Optothermally Activated Colloidal System

“…In this context, two interrelated tasks have been pursued: first, a variety of colloidal matter has been realized and studied in the context of active systems. − Second, diverse methods including chemical, − electric, − magnetic, − and optical fields − have been innovated that can act as an environmental cue to translate and rotate soft systems.…”

Nematic Colloidal Micro‐Robots as Physically Intelligent Systems

“…For example, micro-robot shape and anchoring conditions can mold nematogen orientation and dictate the formation of topological defects; the ability to reposition the micro-robot allows this information to be embedded at arbitrary sites in the domain. Furthermore, in far-from-equilibrium systems, the energy landscape around micro-structures can be dynamically reconfigured to generate dynamic defect structures [37][38][39][40][41][42][43][44][45][46] by an interplay of the elasticity and external fields in these highly nonlinear fluids. Such reconfigurable energy landscapes provide exciting opportunities for exploitation in untethered micro-robotic systems.…”

Mechanochromic Responses of Cholesteric Liquid Crystal Droplets with Nanoscale Periodic Helical Structures Showing Reversible and Tunable Structural Color

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