Assembly and control of 3D nematic dipolarcolloidal crystals

摘要

Topology has long been considered as an abstract mathematical discipline with little connectionto material science. Here we demonstrate that control over spatial and temporalpositioning of topological defects allows for the design and assembly of three-dimensionalnematic colloidal crystals, giving some unexpected material properties, such as giant electrostrictionand collective electro-rotation. Using laser tweezers, we have assembled threedimensionalcolloidal crystals made up of 4 mm microspheres in a bulk nematic liquid crystal,implementing a step-by-step protocol, dictated by the orientation of point defects. The threedimensionalcolloidal crystals have tetragonal symmetry with antiparallel topological dipolesand exhibit giant electrostriction, shrinking by 25–30% at 0.37Vmm1. An external electricfield induces a reversible and controllable electro-rotation of the crystal as a whole, with theangle of rotation being B30 at 0.14Vmm1, when using liquid crystal with negativedielectric anisotropy. This demonstrates a new class of electrically highly responsive softmaterials.