Electrically controlled topological micro cargo transportation.

We demonstrate electrically controlled linear translation and precision positioning of a colloidal particle in a soft matter device. The basis of transportation is the time dependent electric field reconfiguration and manipulation of a topological line defect between two distinct hybrid aligned nematic liquid crystal domains having opposing tilt orientations. Deliberately tuning an applied voltage relative to a low threshold value (5.7 V at 1 kHz) permits defect trapping of the colloidal particle and allows subsequent control over the particle's velocity and bidirectional linear movement over millimeter distances, without the need for externally imposed flow nor for lateral confining walls.

Flow-induced delayed Freedericksz transition.

We demonstrate that a compact manometer experiment allows direct observation of a delay to the classical electric-field-induced Freedericksz transition produced by flow in a highly dispersive nematic liquid crystal layer. The Ericksen-Leslie equations are used to show that a flow aligning torque generated in the nematic layer under Poiseuille flow competes with the orthogonal electric-field reorientation torque. This model fully reproduces the experimental results using only self-consistently determined viscosity values, and predicts a more generally applicable expression for the dependence of the delay E(c)∝sqrt[ζ/Δχ(e)] on the shear rate ζ and on the electric susceptibility anisotropy Δχ(e).