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4시 20분부터 제1과학관 31214 e+강의실에서 간단한 다과를 제공합니다.

아 래

Title: 연성물질 기반 위상학적 결함구조의 상전이와 응용

Speaker: 윤   동   기  교수님 (KAIST)

Date & Time: Nov. 8. (Wed.) 2017, 4:30 PM

Place: Natural Science 1,  Room No. 31214

Abstract: Topological defect structure is one of the most interesting topic in physics and material sciences. Especially, the topological defect transition was highlighted by Nobel prize in physics last year. But this topic is hard to understand and realize in the practical condition because the size and time-scale are huge in cosmos or so tiny in skyrmion system. So, we proposed to use liquid crystal (LC) materials to directly show this interesting topic, phase transition of topological defect [1].

In details, LCs are materials in widespread use as the basis of display technologies, have drawn much recent attention for their defects that draw together such concepts as topology, self-assembly, and micro-patterned materials. However, relatively little is known about the fate of the defects during a phase transition from one LC phase to another. Here, we examine defects in the in-situ thermal phase transition from nematic to smectic A in hybrid-aligned LC droplets on water substrates using experimental, theoretical and numerical analyses. The hybrid-aligned nematic droplet spontaneously generates boojum defects. During cooling, toric focal conic domains arise through a sequence of morphological transformations involving nematic stripes and locally aligned focal conic domains. This simple experiment reveals a surprisingly complex pathway by which very different types of defects may be related across the nematic-smectic A phase transition, and presents new possibilities for controlled deformation and patterning of LCs, which are useful in the patterning applications such as hydrophobic surface, illumination, and sensors [2-5].

References:

[1] Min-Jun Gim, et al, “Morphogenesis of liquid crystal topological defects during the nematic-smectic A phase transition” Nature Communications, 8, 15453 (20170

[2] Dae Seok Kim, et al, “Controlling Gaussian and mean curvatures at microscale by sublimation and condensation of smectic liquid crystals” Nature Communications, 7, 10236 (2016)

[3] Dae Seok Kim, et al, “Fabrication of Periodic Nanoparticle Clusters Using Soft Lithographic Template”, J. Mater. Chem. C, 3, 4598 (2015)

[4] Dae Seok Kim, et al, "Fast Fabrication of Sub-200-nm Nanogrooves using Liquid Crystal Material" ACS Applied Materials & Interfaces 8, 11851 (2016)

[5] Dae Seok Kim, et al, “Arrangement and SERS Applications of Nanoparticle Clusters Using Liquid Crystals” ACS Applied Materials & Interfaces, 9, 7787 (2017)