Yunho Kim

Photonic microcapsules with onion-like topology are microfluidically designed to have cholesteric liquid crystals with opposite handedness in their core and shell. The microcapsules exhibit structural colors caused by dual photonic bandgaps, resulting in a rich variety of color on the optical palette. Moreover, the microcapsules can switch the colors from either core or shell depending on the selection of light-handedness.

Robust photonic microcapsules are created by microfluidic encapsulation of cholesteric liquid crystals with a hydrogel membrane. The membrane encloses the cholesteric core without leakage in water and the core exhibits pronounced structural colors. The photonic ink capsules, which have a precisely controlled bandgap position and size, provide new opportunities in colorimetric micro-thermometers and optoelectric applications. As a service to our authors and readers, this journal provides supporti

The biological activity of some proteins is known to be sensitive to oxidative damage caused by a variety of oxidants. The model protein staphylococcal nuclease was used to explore the effect on protein structural stability of oxidizing methionine to the sulfoxide form. These effects were compared with the effects of substituting methionines with isoleucine and leucine, a potential strategy for stabilizing proteins against oxidative damage. Wild-type nuclease and various mutants were oxidized wi

Abstract Recently, 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 ordering and structure due to the reversible and non‐covalent interactions of the LC molecules. In this Featre Article, the defect structures of liquid crystalline mater

Droplet-based microreactors are used for the continuous production of Pd nanocrystals. Specifically, commercially available polytetrafluoroethylene (PTFE) tube and silica capillaries are utilized to fabricate a fluidic device capable of generating water-in-oil droplets. In addition to the feasibility of using such droplets as microreactors for conducting a synthesis, the ability to control the composition and concentration of reagents by adjusting the flow rates is demonstrated; reagents are mix

Highly ordered organic semiconductor micropatterns of the liquid-crystalline small molecule 2,7-didecylbenzothienobenzothiophene (C10 -BTBT) are fabricated using a simple method based on template-assisted self-assembly (TASA). The liquid crystallinity of C10 -BTBT allows solvent-free fabrication of high-performance printed organic field-effect transistors (OFETs).

A photomask that combines two imaging elements (microlens arrays and clear windows) in one structure has been developed by using toric focal conic domain (TFCD) micro arrays of smectic liquid crystals. Their application as optically selective photomasks by simply adjusting (i) the illumination dose, (ii) the size of TFCD array mask, and (iii) the tone of photoresist (PR) is demonstrated (see figure).

Mechanically stable photonic micro particles based on polymerized cholesteric liquid crystals (CLCs) and its self-assembled patterns for anti-forgery applications.

Aromatic soluble polyimides (PIs) have been widely used in organic field-effect transistors (OFETs) as gate dielectric layers due to their promising features such as outstanding chemical resistance, thermal stability, low-temperature processability, and mechanical flexibility. However, the molecular structures of soluble PIs on the electrical characteristics of OFETs are not yet fully understood. In this work, the material, dielectric, and electrical properties are evaluated to systematically in

A self-assembly fabrication method was developed for the preparation of microlens arrays (MLAs). The procedure used the focal conic structures of semi-fluorinated smectic liquid crystals (LCs), the periodic toric focal conic domains (TFCDs), which were prepared on a surface-modified substrate. This LC-based MLA system focuses light via the intrinsic molecular orientations of the TFCDs, leading to a highly efficient MLA with good optical properties. The thickness of the smectic LC film could be u

We have developed highly periodic patterns with sub-micrometer features over large-areas using toric focal conic domains (TFCDs) originated from smectic liquid crystal (LC) as a new self-assembling building block. TFCDs are accomplished by precisely controlling the surface and interfacial properties of smectic LC. In order to apply the smectic liquid crystal defect arrays in soft lithography, the hexagonal arrays of domain patterns are used as molds for ultraviolet (UV) curable polymers, thereby

Abstract A novel fabrication method is developed for the preparation of superhydrophobic surfaces. The procedure uses focal conic structures of semi‐fluorinated smectic liquid crystals (LCs) whose periodic toric focal conic domains (TFCDs) are prepared on a surface modified substrate. Reactive ion etching (RIE) on the periodic TFCD surface leads to a superhydrophobic surface with a water contact angle of ∼160° and a sliding angle of ∼2° for a 10 µL water droplet. The results show that this pheno

Laser-induced graphene (LIG) has been utilized as a nonmetallic conductor for the development of various electronics due to its facile, direct, and scalable synthesis process. Here, the graphitization degree of LIG is simply controlled by adjusting the lasing conditions to encode different electronic functionalities such as resistance and capacitance on commercially available papers. The effect of lasing conditions including the number of lasing scans and the lasing power on the graphitization d