Smectic Liquid Crystal Defects for Self‐Assembling of Building Blocks and Their Lithographic Applications

Abstract

crystal (LC) fi lm containing an ordered, periodic array of smectic LC defects. [ 9,10 ] Unlike previously reported self-assembling materials, which have been geared toward defect-free systems of the ordered structures, these approaches rely on the order of artifi cially made defects as building blocks to create templates. The proposed approaches based on LC defects have signifi cant advantages over existing methods to micro/nanopatterning applications, including easy fabrication, the creation of long-range surface ordering, very rapid formation of periodic arrays, and the ability to generate various featured sizes ranging from the micrometer to the sub-micrometer scale. Furthermore, the ordered array of LC defects occurs rapidly due to reversible and non-covalent interactions between the LC molecules and can easily be generated by controlling surface anchoring, which is a very simple and costeffective mechanism that is well suited to mass production. In addition, this process should not be limited to specifi c rodlike LC materials and it should be applicable to other smectic LC systems forming similar defect structures. Accordingly, such defect orders of LC materials can be very strong candidates for the periodic templates, compared to other soft-building blocks such as block copolymers, colloids, and surfactants.To introduce this new type of building block based on LC defect order, fi rstly we will describe various types of LC phases and their versatile defect structures. In particular, focal conic domains (FCDs), which are typical defect structures of the smectic phase, will be demonstrated in Section 2, since FCDs were fi rstly used to create defect orders. Next, we deal with defect arrays from three different FCDs including toric FCD (TFCD), parabolic FCD (PFCD), and cylindrical oily streak (OS). The TFCDs, which are generated in an antagonistic surface anchoring condition, will be described in detail. Then, the mechanism of TFCD formation is described in terms of surface anchoring, direct internal structure observation, and energetics in Section 3. In Section 4, the template-assisted self-assembling approaches, including some manipulating methods for the domain size, arrangement, and selective patterning of TFCDs, are demonstrated. Finally, we discuss their applications in soft lithographic templates, superhydrophobic surfaces, microlens arrays, organic photomasks, and trapping templates for colloidal particles based on large-area TFCD-array patterning in Section 5.As the fi eld of information displays is maturing, LC materials research is undergoing a modern-day renaissance. Devices Smectic Liquid Crystal Defects for Self-Assembling of Building Blocks and Their Lithographic ApplicationsRecently, it has been reported that liquid crystal (LC) defects can be used to create highly periodic templates by controlling the surface anchoring and the elastic properties of LC molecules. The self-assembled defect ordering of the LC materials takes advantage of the ability to achieve fast stabilization of molecular orde...

Transport of particles in liquid crystals

“…A rough estimate of the order of magnitude of the elastic energy associated with the director distortions around a strongly anchored micron-size particle placed in an otherwise uniform nematic cell, is 56 . Forces of the same nature are also responsible for attraction of colloidal particles to (particle-free) distortions and defects in the director field in nematics 47,57,58 , smectics [59][60][61] and blue phases 62 , for trapping and ordering of particles at the LC surfaces [63][64][65][66] , and even for symmetry-breaking that enables transport phenomena such as nonlinear electrophoresis in LCs 45,67 . As discussed in the next…”

Towards tunable defect arrangements in smectic liquid crystal shells utilizing the nematic–smectic transition in hybrid-aligned geometries

“…An interesting recent development, very different from display applications where defects must be avoided at any price, is the research on well-controlled defect configurations and ways of applying them. [1][2][3][4][5][6][7][8][9][10][11][12] A fascinating special case is given by LC droplets 13,14 and shells 15,16 since the spherical topology in combination with planar alignment (director n in the plane of the drop/shell surface) ensures specific configurations of topo- logical defects (disclinations) on the surface, 17 always with a net sum s = 2. The parameter s is the winding number that specifies how many full turns the director (or its projection on the surface) rotates around a defect.…”

Bifunctional ITO layer with a high resolution, surface nano-pattern for alignment and switching of LCs in device applications

“…The cells were inspected by using a POM (LV-100POL, Nikon Korea, Seoul, Korea) equipped with a rotational stage in the plane perpendicular to the direction of light propagation. 16 Figures 3a and b show wide-view POM images of the ECB cell, in which both substrates possess ITO patterns with a 20-nm line width, 100 nm height and 500-nm period in a 5Â5 mm area (see Supplementary Information, Supplementary Figure S2a). The differences that exist in optical textures between areas with and without the topographic pattern in the ITO layer are easily recognized.…”