다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Janus particles: synthesis, self-assembly, physical properties, and applications.

Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micro...

Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials

In this paper, we report the high proton conductivity of a single high-purity Nafion nanofiber (1.5 S/cm), which is an order of magnitude higher than the bulk Nafion film (∼0.1 S/cm). We also observe a nanosize effect, where proton conductivity increases sharply with decreasing fiber diameter. X-ray scattering provides a rationale for these findings, where an oriented ionic morphology was observed in the nanofiber in contrast to the isotropic morphology in the bulk film. This work also demonstrates the successful fabrication of high-purity Nafion nanofibers (∼99.9 wt %) via electrospinning and higher humidity sensitivity for nanofibers compared to the bulk. These results should have a significant impact on fuel cells and sensors.

Super Proton Conductive High-Purity Nafion Nanofibers

We report, for the first time, the design and fabrication of a nanoparticle-based nanomotor system by directly self-assembling nanoparticles onto functional, nanometer-thin lamellae, such as polymer single crystals. Tens of thousands of judiciously selected nanoparticles (gold, iron oxide, and platinum nanoparticles) with sizes ranging from <5 to a few tens of nanometers have been introduced into a single nanomotor via directed self-assembly. The resulting nanomotor realizes functions such as autonomous movement, remote control, and cargo transportation by utilizing the advantages offered by nanoparticles, such as the small size, surface plasmon resonance, catalytic and magnetic properties. Because of the structural and functional versatility of nanoparticles, the facile fabricating procedure, and the potential for mass production, our strategy shows a key step toward the development of next generation multifunctional nanomotors.

Directed Self-Assembly of Nanoparticles for Nanomotors

Stimuli-responsive hydrogel actuators have promising applications in various fields. However, the typical hydrogel actuation relies on the swelling and de-swelling process caused by osmotic-pressure changes, which is slow and normally requires the presence of water environment. Herein, we report a light-powered in-air hydrogel actuator with remarkable performances, including ultrafast motion speed (up to 1.6 m/s), rapid response (as fast as 800 ms) and high jumping height (~15 cm). The hydrogel is operated based on a fundamentally different mechanism that harnesses the synergetic interactions between the binary constituent parts, i.e. the elasticity of the poly(sodium acrylate) hydrogel, and the bubble caused by the photothermal effect of the embedded magnetic iron oxide nanoparticles. The current hydrogel actuator exhibits controlled motion velocity and direction, making it promising for a wide range of mobile robotics, soft robotics, sensors, controlled drug delivery and other miniature device applications. Actuation of hydrogel actuators relies on slow swelling and de-swelling process which hampers its application in many fields. Here the authors report a light-powered in-air hydrogel actuator with remarkable performances including fast motion, speed and rapid response time.

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In-air fast response and high speed jumping and rolling of a light-driven hydrogel actuator.

Patterning of Conducting Polymers Based on a Random Copolymer Strategy: Toward the Facile Fabrication of Nanosensors Exclusively Based on Polymers

The past decade witnessed tremendous progresses in nanoparticle synthesis; nanoparticles can now be readily obtained with great control of size, size distribution, and chemical makeup. The next challenge in the field is to assemble nanoparticles into desired structures for targeted applications. Most often nanoparticles are passivated with an organic coating made up of surfactants/polymer brushes; this organic coating is uniform and centrosymmetric. While the centrosymmetric coating prevents nanoparticles from aggregation and mediates their assembly, the symmetry of the resultant nanoparticle ensembles is limited, largely driven by close packing of the particles. However, if the centrosymmetry is brokenbyusing bicompartment polymer brushes, the polymer brush-coated nanoparticles then become anisotropic and much more versatile structures are feasible. These nanoparticles coated with bicompartment brushes can be viewed as one type of Janus nanoparticles (JNPs), the concept that was discussed by De Gennes in his Nobel lecture in 1991. The Janus feature often leads to surfactant-like structures, and as De Gennes pointed out, their assembly properties are intriguing: for membranes comprised of closely packed JNPs, there are interstices between the particles, which allows for mass transport between the two sides (known as “breathable skin”). In addition to the breathable skinDeGennesmentioned, JNPs have potential applications in self-assembly, surface control, and optical as well as electronic devices and they have recently gained much interests from the communities of materials science, chemistry, physics and biology. Janus particles that have been reported include organic JNPs (such as dendrimers, block copolymer micelles, and nanofibers) and hybrid JNPs (such as micrometer-size beads, dumbbell-, acorn-, or raspberry-like clusters and particles with bicompartment surfactants and/or polymer brushes.). However, disregarding the large body of work on Janus particle synthesis, study on their assembly behavior, which is the key interest in this field, is limited. Computer simulation has been used to demonstrate that Janus particles (or, patchy particles) can assemble into complex structures, which mimic living organisms such as bacteria. Hong et al. recently demonstrated that Janus particles with opposite electric charge on two hemispheres can assemble into well-defined clusters having up to 13 particles. With increasing ionic strength of the solution, 1 μm diameter Janus particles with hydrophobic and charged hemispheres assembled into branched wormlike strings. Even fewer experimental works on JNPs with diameters smaller than 20 nm have been reported. One example is that Hatton group synthesized ∼20 nm Janus magnetic nanoparticles (Fe3O4) with poly(acrylic acid) PAA/sodium polystyrenesulfonate and PAA/poly(N,Ndimethylaminoethyl methacrylate) brushes. pHand temperature-responsive assembly behavior was observed. Herein we report homoand heteroparticle clusters formed by Janus gold nanoparticles (J-AuNPs) with bicompartment polymer brushes composed of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO). Not only solution assembly behavior of these J-AuNPs has been systematically studied, heteroparticle clusters consisting of J-AuNPs and symmetrical magnetite nanoparticles (S-MNPs, Fe3O4) modified with PEO brushes have also been formed by controlled particle assembly in selected solvents. Furthermore, the assembly behavior of J-AuNPs was compared with that of the AuNPs symmetrically coated with PMMA/PEOmixed brushes. It is unambiguous that the unique assembly behavior of J-AuNPs was because of their Janus feature. These unique heteroparticle clusters are multifunctional particles, which may potentially find applications in bioimaging and drug delivery if semiconducting quantum dots and/or responsive polymer brushes are used to fabricate these clusters. Scheme 1 shows J-AuNPs and symmetric nanoparticles grafted with one-component polymer brushes as well as binary mixed polymer brushes. Homoparticle assembly was investigated first. J-AuNPs with bicompartment PEO and PMMA brushes (PEO114-Au6PMMA208) were synthesized using the polymer-single-crystaltemplating method as reported (Supporting Information). The subscript numbers of PEO and PMMA denote the degrees of polymerization of the polymers while that of Au denotes the diameter of the nanoparticle in nanometers. The polydispersity indices (PDIs) of PEO and PMMA are 1.03 and 1.25, respectively. Gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and H NMR spectroscopy analysis showed that the overall grafting density of PEO and PMMA brushes was 0.52 chains/nm (Supporting Information, Figures S1-S3). The average number of PEO and PMMA chains per AuNP is 32 and 26, respectively. The mass ratio of the PEO over PMMA is approximately 1: 3.2. These AuNPs grafted with bicompartment polymer brushes provide an ideal JNP system for self-assembly study. Solubility tests showed that they readily dissolved in good solvents of PEO and PMMA, such as acetone, chloroform, tetrahydrofuran, and dimethylformamide. To investigate the detailed solution assembly behavior, acetone and dioxane were chosen as model solvents. Upon dissolving PEO114Au6-PMMA208, the color of the acetone solution remained red over the entire observation period (one month), indicating that the particles were stable in acetone. However, the dioxane solution progressively changed from red to pale blue (Figure 1a). Figure 1b shows the UV/vis spectra of PEO114-Au6-PMMA208 Scheme 1. Schematic Representation of Janus Nanoparticles (a) and Nanoparticles Symmetrically Grafted with One-Component (b) as Well as Binary Mixed (c) Polymer Brushes

Bin Dong

Papers

Super Proton Conductive High-Purity Nafion Nanofibers

Directed Self-Assembly of Nanoparticles for Nanomotors

In-air fast response and high speed jumping and rolling of a light-driven hydrogel actuator.

Patterning of Conducting Polymers Based on a Random Copolymer Strategy: Toward the Facile Fabrication of Nanosensors Exclusively Based on Polymers

Homo- and Hetero-Particle Clusters Formed by Janus Nanoparticles with Bicompartment Polymer Brushes