Omnidirectional transport and navigation of Janus particles through a nematic liquid crystal film

TL;DR

This paper demonstrates how Janus colloids can be actively controlled to move omnidirectionally within a nematic liquid crystal film using electric fields, enabling precise navigation and potential applications in assembly and collective behavior.

Contribution

It introduces a method to control Janus particle trajectories in nematic liquid crystals via electric fields, with a detailed theoretical model explaining the motion mechanisms.

Findings

Controlled omnidirectional transport of Janus particles achieved.

Electric field parameters precisely steer particle trajectories.

Theoretical model explains dielectric-forward and pusher motion.

Abstract

We create controllable active particles in the form of metal-dielectric Janus colloids which acquire motility through a nematic liquid crystal film by transducing the energy of an imposed perpendicular AC electric field. We achieve complete command over trajectories by varying field amplitude and frequency, piloting the colloids at will in the plane spanned by the axes of the particle and the nematic. The underlying mechanism exploits the sensitivity of electro-osmotic flow to the asymmetries of the particle surface and the liquid-crystal defect structure. We present a calculation of the dipolar force density produced by the interplay of the electric field with director anchoring and the contrasting electrostatic boundary conditions on the two hemispheres, that accounts for the dielectric-forward (metal-forward) motion of the colloids due to induced puller (pusher) force dipoles. These findings open unexplored directions for the use of colloids and liquid crystals in controlled transport, assembly and collective dynamics.