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.
Highlights
Rapid CommunicationsDinesh Kumar Sahu, Swapnil Kole, Sriram Ramaswamy ,2 and Surajit Dhara 1,* 1School of Physics, University of Hyderabad, Hyderabad 500 046, India
Electrophoresis, the use of electric fields to transport tiny particles through fluids, is an important technology for macromolecular sorting, colloidal assembly, and display devices and a challenging area of soft-matter research [1,2,3,4,5,6,7,8]
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, which accounts for the dielectric-forward motion of the colloids due to induced puller force dipoles
Summary
Dinesh Kumar Sahu, Swapnil Kole, Sriram Ramaswamy ,2 and Surajit Dhara 1,* 1School of Physics, University of Hyderabad, Hyderabad 500 046, India. 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, which 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. The nonlinear electro-osmotic flow resulting from an imposed electric field yields bidirectional transport of dipolar particles parallel to the local director, thanks to their broken fore-aft symmetry, an effect termed liquid-crystal-enabled electrophoresis [20,21,22,23,24].
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