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Exotic structures with interesting physical and chemical properties can be achieved by self-organizing engineered building blocks. The central aim for self-assembly is to precisely control the position and orientation of individual building blocks. In this work, we use topological defects (disclinations) in nematic liquid crystals as templates to direct the self-assembly of colloidal particles into designable 3D structures. By photopatterning preprogrammed molecular orientations at two confining surfaces, we created pre-designable disclination networks and characterized their interactions with spherical colloidal particles. We find that colloidal particles are attracted to different disclinations depending on the orientation of the point defect (elastic dipole) around the colloids. We demonstrate that the positions, network structures, and orientation of the elastic dipoles of the colloidal chains can be pre-designed and reconfigured with remote illumination of polarized light. 

Disclinations in nematic liquid crystals are of great interest both theoretically and practically. The ability to create and reconfigure disclinations connecting predetermined points on substrates could enable novel applications such as directed self-assembly of micro/nanoparticles and molecules. In this study, we present a novel approach to design and create disclination interconnects that connect predetermined positions on substrates. We demonstrate that these interconnects can be switched between different states by re-writing photoalignment materials with linearly polarized light, and can be switched between degenerate states using electric fields. The demonstrated strategy allows for creation of multi-scale designer disclination networks and promises potential applications in directed assembly of colloidal micro-/nano-particles, command of active matter, and liquid crystal microfluidics 

Abstract Linear defect‐disclinations are of fundamental interest in understanding complex structures explored by soft matter physics, elementary particles physics, cosmology, and various branches of mathematics. These defects are also of practical importance in materials applications, such as programmable origami, directed colloidal assembly, and command of active matter. Here an effective engineering approach is demonstrated to pattern molecular orientations at two flat confining surfaces that produce complex yet designable networks of singular disclinations of strength 1/2. Depending on the predesigned director patterns at the bounding plates, the produced disclinations are either surface‐anchored, connecting desired sites at the boundaries, or freely suspended in bulk, forming ordered arrays of polygons and wavy lines. The capability is shown to control the radius of curvature, size, and shape of disclinations by varying uniform alignment orientation on one of these confining plates. The capabilities to precisely design and create highly complex 3D disclination networks promise intriguing applications in stimuli‐responsive reconfigurable materials, directed self‐assembly of molecules, micro‐ and nanoparticles, and transport and sorting in microfluidic applications. 

Abstract Shaping the intensity profile of a laser beam is desired by various industrial applications. In this paper, a new approach is presented to design and fabricate liquid crystal (LC) micro‐optical elements (MOEs) with engineered Pancharatnam–Berry (PB) phases for beam shaping. By generalizing the Snell's law for spatially variant PB phases, molecular orientation patterns are designed for the liquid crystal MOEs to shape a Gaussian laser beam into flattop intensity profiles with circular and square cross‐sections, with the β parameter varied from 4 to 42. It is demonstrated that such liquid crystal beam shaping MOEs can be fabricated with high throughput and high resolution by using a photopatterning technique based on plasmonic metamasks and that they produce excellent beam quality, no zero‐order light leakage with a beam size from 10 to 600 µm. As the plasmonic metamasks allow for encoding arbitrary molecular orientations, i.e., arbitrary geometric phase profiles, the approaches presented here are widely applicable to large‐scale manufacturing of liquid crystal MOEs for any beam shapes. 

Abstract Microlenses are desired by a wide range of industrial applications while it is always challenging to make them with diffraction‐limited quality. Here, it is shown that high‐quality microlenses based on Pancharatnam–Berry (PB) phases can be made with liquid crystal polymers by using a plasmonic photopatterning technique. Based on the generalized Snell's law for the PB phases, PB microlenses with a range of focal lengths andf‐numbers are designed and fabricated and their point‐spread functions and ability to image micrometer‐sized particles are carefully characterized. The results show that these PB microlenses withf‐number down to 2 are all diffraction‐limited. The capability of arraying these PB microlenses with 100% filling factor with a step‐and‐flash approach is further demonstrated. 

Abstract Recent developments of utilizing plasmonic metasurfaces in photopatterning of designer molecular orientations have facilitated numerous new applications of liquid crystals; while the optical efficiency of the metamasks remains a critical issue, especially in the UV region. Here a new design of plasmonic metasurfaces made of parallelepiped arrays is presented which yield very high and broadband transmission in the UV–vis wavelength range. It is shown that this plasmonic metamask exhibits two polarization peaks originated from a cavity mode and lattice resonance respectively and demonstrated that complex designer molecular orientations can be photopatterned by using this metamask with significantly reduced exposure time. This type of high‐efficiency broadband plasmonic metasurfaces is not only important for high resolution photopatterning of molecular orientation but also tailorable for various other flat optics applications in the UV and near UV regions.