Siyoung Q. Choi 교수

High internal phase emulsions have been widely used as templates for various porous materials, but special strategies are required to form, in particular, particle-covered ones that have been more difficult to obtain. Here, we report a versatile strategy to produce a stable high internal phase Pickering emulsion by exploiting a depletion interaction between an emulsion droplet and a particle using water-soluble polymers as a depletant. This attractive interaction facilitating the adsorption of p

Two-dimensional films of surface-active agents-from phospholipids and proteins to nanoparticles and colloids-stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we pres

In vanadium redox flow batteries (VRFBs), a perfluorinated sulfonic acid (PFSA) ionomer membrane plays a crucial role in transporting ions through hydrophilic channels. However, its randomly interconnected channels with relatively large size in a hydrated state cause low proton/vanadium ion selectivity, imposing a limitation in enhancing performance of VRFB. Herein, we develop an ultrathin PFSA membrane of highly aligned ion channels with reduced size, by molecular arrangement on the air/water i

Versatile methods are described for the fabrication of micrometer-scale particles with defined shape, ferro- or paramagnetic properties, and amphiphilic Janus surface chemistry. Examples of their utility include measuring the rheological properties of complex, two-dimensional fluid interfaces and reversible, directed self-assembly at fluid interfaces. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edite

Double emulsions, the simplest form of multiple emulsion, have been intensively utilized in various industries as well as in fundamental research. A variety of strategies to effectively form double emulsions have been developed, but no simple yet controlled and scalable technique has been achieved yet. Herein, we examine the mechanism of the entire process of double emulsion formation by phase inversion, and we propose a universal one-step strategy for the formation of an oil/water/oil double em

High internal phase emulsions (HIPEs) and foams are ubiquitous in our daily lives. They are considered fluid composites with an extremely high-volume fraction of fluid fillers. As all other composite materials do, HIPEs and foams exhibit enhanced properties compared with the simple base fluids without liquid/gas fillers. They can disperse a huge amount of immiscible fluids in other fluids, and fluid fillers remarkably change their physicochemical properties, especially their rheological properti

A new fabrication method for an ultrathin (500 nm thick) pressure-sensitive adhesive (PSA) was demonstrated by utilizing a series of in situ cross-linked viscoelastic copolymer films. Viscoelastic films composed of poly(2-hydroxyethyl acrylate- co-2-ethylhexyl acrylate) were synthesized successfully in a one-step manner by an initiated chemical vapor deposition (iCVD) process, where free-radical polymerization is triggered in the vapor phase either by heat or UV, or a combination of both. In par

Heat dissipation materials in which fillers are dispersed in a polymer matrix typically do not exhibit both high thermal conductivity (<i>k</i>) and processability due to a trade-off. In this paper, we fabricate heat dissipation composites which overcome the trade-off using liquid metal (LM). By exceeding the conventional filler limit, ten times higher <i>k</i> is achieved for a 90 vol% LM composite compared with <i>k</i> of 50 vol% LM composite. Further, an even higher <i>k</i> is achieved by i

Adding small fractions of cholesterol decreases the interfacial viscosity of dipalmitoylphosphatidylcholine (DPPC) monolayers by an order of magnitude per wt %. Grazing incidence X-ray diffraction shows that cholesterol at these small fractions does not mix ideally with DPPC but rather induces nanophase separated structures of an ordered, primarily DPPC phase bordered by a line-active, disordered, mixed DPPC-cholesterol phase. We propose that the free area in the classic Cohen and Turnbull model

Capillary rise is important in many aspects of physical phenomena from transport in porous media to biotechnology. It is typically described by the Lucas-Washburn-Rideal equation (LWRE), but discrepancy between some experiments and the model still remains elusive. In this paper, we show that the discrepancy is simply from the contact angle change during the capillary rise with no help of any specific models, such as dynamic contact angle (DCA) models. To demonstrate this, we directly measure the

Pyrolysis is an environmental technology for the proper treatment of electronic waste (e-waste) for the production of fuel. However, the presence of brominated compounds in pyrolysis oil makes its commercialization difficult. In this study, various types of zeolites, HY (30), HZSM-5 (30), HZSM-5 (50), HZSM-5 (280), and basic metal oxides (MgO and CaO) were used for the pyrolysis of flexible printed circuit boards (FPCBs) for the first time to produce bromine-free oil. A higher production efficie

A sustainable nanofabrication approach is developed for isolating hybrid nanocelluloses (Hy-NCs) comprised of both long flexible fibers (CNFs) and needle-like crystals (CNCs) from a hardwood wet pulp (WP) using electron-beam irradiation (EBI). The method was applied to prepare spray-dried powders that could be transparently redispersed. As a result, the disassociated wet pulps had increased carboxylate contents of 0.04–0.12 mmol g–1 compared to the initial wet pulps and the corresponding dried p