We explore the dynamics of topological point defects on surfaces of magnetically responsive colloidal microspheres in a uniformly aligned nematic liquid crystal host. We show that pinning of the liquid crystal directo...
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We explore the dynamics of topological point defects on surfaces of magnetically responsive colloidal microspheres in a uniformly aligned nematic liquid crystal host. We show that pinning of the liquid crystal director to a particle surface with random nanostructured morphology results in unexpected translational dynamics of both particles and topological point defects on their surfaces when subjected to rotating magnetic fields. We characterize and quantify the “stick-slip” motion of defects as a function of field rotation rates as well as temperature, demonstrating the roles played by the competition of elastic forces, surface anchoring, and magnetic torques on the sphere as well as random-surface-mediated pinning of the easy axis of the nematic director on colloidal microspheres. We analyze our findings through their comparison to similar dynamic processes in other branches of science.
作者：
Younghoon SongYunjin JeongTaehong KwonDaewon LeeDong Yoon OhTae-Joon ParkJunhoi KimJiyun KimSunghoon KwonInstitutes of Entrepreneurial BioConvergence
Seoul National University Seoul 151-742 Republic of Korea. skwon@snu.ac.kr and Department of Electrical and Computer Science Seoul National University Seoul 151-742 Republic of Korea. Institutes of Entrepreneurial BioConvergence
Seoul National University Seoul 151-742 Republic of Korea. skwon@snu.ac.kr and Interdisciplinary Program of Bioengineering Seoul National University Seoul 151-742 Republic of Korea. Nano Systems Institute
Seoul National University Seoul 151-742 Republic of Korea. Department of Materials Science and Engineering
Ulsan National Institute of Science and Technology Ulsan 44919 Republic of Korea. Institutes of Entrepreneurial BioConvergence
Seoul National University Seoul 151-742 Republic of Korea. skwon@snu.ac.kr and Department of Electrical and Computer Science Seoul National University Seoul 151-742 Republic of Korea and Interdisciplinary Program of Bioengineering Seoul National University Seoul 151-742 Republic of Korea and Nano Systems Institute Seoul National University Seoul 151-742 Republic of Korea and Seoul National University Hospital Biomedical Research Institute Seoul National University Hospital Seoul 151-742 Republic of Korea and Quantamatrix Inc. Seoul 151-742 Republic of Korea.
Correction for 'Liquid-capped encoded microcapsules for multiplex assays' by Younghoon Song et al., Lab Chip, 2017, DOI: .
Correction for 'Liquid-capped encoded microcapsules for multiplex assays' by Younghoon Song et al., Lab Chip, 2017, DOI: .
We have investigated experimentally the thermal conductivity of suspended twisted bilayer *** measurements were performed using the optothermal Raman *** was found that the thermal conductivity of the twisted bilayer ...
We have investigated experimentally the thermal conductivity of suspended twisted bilayer *** measurements were performed using the optothermal Raman *** was found that the thermal conductivity of the twisted bilayer graphene is lower than that of monolayer graphene and the reference Bernal stacked bilayer graphene in the entire examined temperature range(00 K–700 K).This finding indicates that
Hydroxyapatite (HAP) is a biocompatible bio-ceramic whose structure and composition is similar to bone. However, its lack of strength and toughness have seriously hampered its applications as a bone graft substitute m...
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The progress of realizing colloidal structures mimicking natural forms of organization in condensed matter is inherently limited by the availability of suitable colloidal building blocks. To enable new forms of crysta...
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The progress of realizing colloidal structures mimicking natural forms of organization in condensed matter is inherently limited by the availability of suitable colloidal building blocks. To enable new forms of crystalline and quasicrystalline self-organization of colloids, we develop truncated pyramidal particles that form nematic elastic dipoles with long-range electrostaticlike and geometry-guided low-symmetry short-range interactions. Using a combination of nonlinear optical imaging, laser tweezers, and video microscopy, we characterize colloidal pair interactions and demonstrate unusual forms of self-tiling of these particles into crystalline, quasicrystalline, and other arrays. Our findings are explained using an electrostatics analogy along with liquid crystal elasticity and symmetry breaking considerations, potentially expanding photonic and electro-optic applications of colloids.
One-dimensional crystals of fluorinated perylene diimides were achieved by the self-assembly of them via solvent-nonsolvent *** π-conjugated fluorinated perylene diimides were assembled into highly-ordered nanostruct...
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One-dimensional crystals of fluorinated perylene diimides were achieved by the self-assembly of them via solvent-nonsolvent *** π-conjugated fluorinated perylene diimides were assembled into highly-ordered nanostructures of well-defined morphologies in organic solvents due to the π-π interaction between the aromatic *** was found that with more introduced F atoms,perylene diimides showed remarkably improved solubility and thus were much easier to grow into crystals,due to the increased polarity induced by the strong electron-withdrawing F *** importantly,single crystal of N,N＇-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide（DPFPP）was obtained,and the unit cell-dimensions of triclinic structure were determined by the selected area electron diffraction（SAED） pattems to be a=0.712 nm,b=1.072 nm,c=2.914 nm,a=97.0°,β=89.6°,γ=93.4°.Owing to most of the longest c-axis orienting nearly vertically to the long axis of the needle crystal,the molecular planes are expected to be vertical to the needle axis.
Surface modification of halloysite nanotube（HNT） with in situ grown Fe304 nanoparticles and carbona- ceous layers introduced by a hydrotbermal carbonization process of glucose has been achieved. Structure and mor- p...
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Surface modification of halloysite nanotube（HNT） with in situ grown Fe304 nanoparticles and carbona- ceous layers introduced by a hydrotbermal carbonization process of glucose has been achieved. Structure and mor- phology investigations demonstrate that iron oxide nanoparticles are uniformly anchored on the halloysite and pre- vent the aggregations of halloysite and carbon, forming a protective layer that stabilizes and improves the property of HNT/Fe3OdC nanocomposite. Magnetism characterization proves the superparamagnetic behavior of HNT/Fe304/C hybrid at room temperature, which makes it easily separated from dye solution under an external magnetic field. Ex- ploration of adsorption ability demonstrates that the maximum adsorption capacity of the as-prepared HNT/Fe304/C nanoeomposite for methylene blue（MB） is about twice and 1.5 times those of HNT/Fe304 and HNT according to Langmuir equation, respectively. The adsorption behavior investigations indicate that HNT/Fe304/C hybrid has a he- terogeneous structure and shows a non-ideal monolayer adsorption that fits the Redlich-Peterson isotherm, and the adsorption process follows a pseudo-second-order kinetic model. Therefore, the as-prepared HNT/Fe304/C hybrid is a fast, separatable and superparamagnetic adsorbent with a good adsorption ability, demonstrating great potential in the application of water treatment.
All single-valent oxide spinels are insulators. The relatively small activation energy in the temperature dependence of resistivity in vanadate spinels led to the speculation that the spinels are near the crossover fr...
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All single-valent oxide spinels are insulators. The relatively small activation energy in the temperature dependence of resistivity in vanadate spinels led to the speculation that the spinels are near the crossover from localized to itinerant electronic behavior, and the crossover could be achieved under pressure. We have performed a number of experiments and calculations aimed at obtaining information regarding structural changes under high pressure for the whole series of vanadate spinels, as well as transport and magnetic properties under pressure for MgV2O4. We have also studied the crystal structure under pressure of wide-gap insulators ACr2O4 (A=Mg, Mn, Fe, Zn) for comparison. Moreover, the relationship between the bulk modulus and the cell volume of AV2O4 (A=Mg, Mn, Fe, Co, Zn) has been simulated by a density functional theory calculation. The proximity of AV2O4 spinels to the electronic state crossover under high pressure has been tested by three criteria: (1) a predicted critical V-V bond length, (2) the observation of a sign change in the pressure dependence of Néel temperature, and (3) measurement of a reduced bulk modulus. The obtained results indicate that, although the crossover from localized to itinerant π bonding V-3d electrons in the AV2O4 spinels is approached by reducing under pressure the V-V separation R, the critical separation Rc is not reached by 20 GPa in CoV2O4, which has the smallest V-V separation in the AV2O4 (A=Mg, Mn, Fe, Co, Zn) spinels.
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