Fig. 3. Elasticity-directed placement and assembly of tangentially anchored polystyrene spheres in regions with bend deformations of the patterned director.

(A) Director deformations around a tangentially anchored sphere in a uniform nematic are of quadrupolar symmetry, with two point defects, called boojums, at the poles. (B) Periodic splay-bend stripe pattern; the normalized bend energy density is labeled by colors according to the scale on the right-hand side. A sphere placed and released in the splay region using optical tweezers migrates toward the bend region. The dark red curve is the typical experimental trajectory of the sphere’s center. (C) Self-assembly of spheres into chains in the regions of maximum bend (bright-field microscope and unpolarized light). (D) Experimentally measured x(t) dependence for a sphere moving from y = l to y = l/2 and its theoretical fit by Eq. 9. (E) Experimentally measured y(t) of a sphere moving from y = l to y = l/2 and its theoretical fit by Eq. 10. All spheres have radius of R = 2.5 μm; periodicity of the director pattern is l = 80 μm. The LCs used are 5CB (C) and MLC6815 (D and E).