Efficient hydrogen evolution by mechanically strained MoS2 nanosheets.

We demonstrated correlations between mechanically bent tensile-strain-induced two-dimensional MoS2 nanosheets (NSs) and their electrochemical activities toward the hydrogen evolution reaction (HER). The tensile-strain-induced MoS2 NSs showed significantly steeper polarization curves and lower Tafel slopes than the strain-free ones, which is consistent with the simple d-band model. Furthermore, the mechanical strain increased the electrochemical activities of all the NSs toward the HER except those loaded with high MoS2 mass. Mechanically bending MoS2 NSs to induce tensile strain enables the production of powerful, efficient electrocatalysis systems for evolving hydrogen.

Playing with dimensions: rational design for heteroepitaxial p-n junctions.

A design for a heteroepitaxial junction by the way of one-dimensional wurzite on a two-dimensional spinel structure in a low-temperature solution process was introduced, and it's capability was confirmed by successful fabrication of a diode consisting of p-type cobalt oxide (Co(3)O(4)) nanoplate/n-type zinc oxide (ZnO) nanorods, showing reasonable electrical performance. During thermal decomposition, the 30° rotated lattice orientation of Co(3)O(4) nanoplates from the orientation of ß-Co(OH)(2) nanoplates was directly observed using high-resolution transmission electron microscopy. The epitaxial relations and the surface stress-induced ZnO nanowire growth on Co(3)O(4) were well supported using the first-principles calculations. Over the large area, (0001) preferred oriented ZnO nanorods epitaxially grown on the (111) plane of Co(3)O(4) nanoplates were experimentally obtained. Using this epitaxial p-n junction, a diode was fabricated. The ideality factor, turn-on voltage, and rectifying ratio of the diode were measured to be 2.38, 2.5 V and 10(4), respectively.

Development of a Shape-Memory Tube to Prevent Vascular Stenosis.

Inserting a graft into vessels with different diameters frequently causes severe damage to the host vessels. Poor flow patency is an unresolved issue in grafts, particularly those with diameters less than 6 mm, because of vessel occlusion caused by disturbed blood flow following fast clotting. Herein, successful patency in the deployment of an ≈2 mm diameter graft into a porcine vessel is reported. A new library of property-tunable shape-memory polymers that prevent vessel damage by expanding the graft diameter circumferentially upon implantation is presented. The polymers undergo seven consecutive cycles of strain energy-preserved shape programming. Moreover, the new graft tube, which features a diffuser shape, minimizes disturbed flow formation and prevents thrombosis because its surface is coated with nitric-oxide-releasing peptides. Improved patency in a porcine vessel for 18 d is demonstrated while occlusive vascular remodeling occurs. These insights will help advance vascular graft design.

Microneedle Vascular Couplers with Heparin-Immobilized Surface Improve Suture-Free Anastomosis Performance.

To make up for the shortcomings of the suture-based approach and current coupler devices including long suturing time, exhaustive training, additional mechanical setting, and narrow working windows for size and type of diverse vessel types, a new, suture-free microneedle coupler was developed in this study. The needle shape for improved anastomosis performance and the condition for antithrombotic surface immobilization were determined. In particular, the polymer materials help to maintain healthy phenotypes of main vascular cell types. The performance in rabbit and porcine models of end-to-end vascular anastomosis indicate that this device can serve as a potent alternative to the current approaches.

Tracheal reconstruction with a free vascularized myofascial flap: preclinical investigation in a porcine model to human clinical application.

Although there are various methods for tracheal reconstruction, such as a simple approximation with suturing and coverage with adjacent soft tissue or muscle, large defects >50% of the tracheal length still present a clinical challenge. Tissue engineering, a recent promising way to possibly resolve this problem, requires a long preparatory period for stem cell seeding on a scaffold and relatively invasive procedures for stem cell harvesting. As an alternative, we used a vascularized myofascial flap for tracheal reconstruction. In four porcine models, the deep inferior epigastric perforator (DIEP) was used in two and the superior epigastric artery perforator (SEAP) in two. Transformation of the surface of the transplanted myofascial flap was analyzed in the airway environment. The flaps failed in the DIEP group due to venous congestion. At 12 weeks postoperatively, none of SEAP group showed any signs of respiratory distress; the inner surface of the implant exhibited stratified squamous epithelium with sparse cilia. In the clinical setting, a patient who underwent a tracheal reconstruction with a vascularized myofascial flap and 2-year follow-up was in good health with no respiratory distress symptoms.

Low-temperature, high-performance solution-processed thin-film transistors with peroxo-zirconium oxide dielectric.

We demonstrated solution-processed thin film transistors on a peroxo-zirconium oxide (ZrO(2)) dielectric with a maximum temperature of 350 °C. The formation of ZrO(2) films was investigated by TG-DTA, FT-IR, and XPS analyses at various temperatures. We synthesized a zirconium oxide solution by adding hydrogen peroxide (H(2)O(2)). The H(2)O(2) forms peroxo groups in the ZrO(2) film producing a dense-amorphous phase and a smooth surface film. Because of these characteristics, the ZrO(2) film successfully blocked leakage current even in annealing at 300 °C. Finally, to demonstrate that the ZrO(2) film is dielectric, we fabricated thin-film transistors (TFTs) with a solution-processed channel layer of indium zinc oxide (IZO) on ZrO(2) films at 350 °C. These TFTs had a mobility of 7.21 cm(2)/(V s), a threshold voltage (V(th)) of 3.22 V, and a V(th) shift of 1.6 V under positive gate bias stress.

Effects of solution temperature on solution-processed high-performance metal oxide thin-film transistors.

Herein, we report a novel and easy strategy for fabricating solution-processed metal oxide thin-film transistors by controlling the dielectric constant of H2O through manipulation of the metal precursor solution temperature. As a result, indium zinc oxide (IZO) thin-film transistors (TFTs) fabricated from IZO solution at 4 °C can be operated after annealing at low temperatures (∼250 °C). In contrast, IZO TFTs fabricated from IZO solutions at 25 and 60 °C must be annealed at 275 and 300 °C, respectively. We also found that IZO TFTs fabricated from the IZO precursor solution at 4 °C had the highest mobility of 12.65 cm2/(V s), whereas the IZO TFTs fabricated from IZO precursor solutions at 25 and 60 °C had field-effect mobility of 5.39 and 4.51 cm2/(V s), respectively, after annealing at 350 °C. When the IZO precursor solution is at 4 °C, metal cations such as indium (In3+) and zinc ions (Zn2+) can be fully surrounded by H2O molecules, because of the higher dielectric constant of H2O at lower temperatures. These chemical complexes in the IZO precursor solution at 4 °C are advantageous for thermal hydrolysis and condensation reactions yielding a metal oxide lattice, because of their high potential energies. The IZO TFTs fabricated from the IZO precursor solution at 4 °C had the highest mobility because of the formation of many metal-oxygen-metal (M-O-M) bonds under these conditions. In these bonds, the ns-orbitals of the metal cations overlap each other and form electron conduction pathways. Thus, the formation of a high proportion of M-O-M bonds in the IZO thin films is advantageous for electron conduction, because oxide lattices allow electrons to travel easily through the IZO.

Boron-doped peroxo-zirconium oxide dielectric for high-performance, low-temperature, solution-processed indium oxide thin-film transistor.

We developed a solution-processed indium oxide (In2O3) thin-film transistor (TFT) with a boron-doped peroxo-zirconium (ZrO2:B) dielectric on silicon as well as polyimide substrate at 200 °C, using water as the solvent for the In2O3 precursor. The formation of In2O3 and ZrO2:B films were intensively studied by thermogravimetric differential thermal analysis (TG-DTA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT IR), high-resolution X-ray diffraction (HR-XRD), and X-ray photoelectron spectroscopy (XPS). Boron was selected as a dopant to make a denser ZrO2 film. The ZrO2:B film effectively blocked the leakage current at 200 °C with high breakdown strength. To evaluate the ZrO2:B film as a gate dielectric, we fabricated In2O3 TFTs on the ZrO2:B dielectrics with silicon substrates and annealed the resulting samples at 200 and 250 °C. The resulting mobilities were 1.25 and 39.3 cm(2)/(V s), respectively. Finally, we realized a flexible In2O3 TFT with the ZrO2:B dielectric on a polyimide substrate at 200 °C, and it successfully operated a switching device with a mobility of 4.01 cm(2)/(V s). Our results suggest that aqueous solution-processed In2O3 TFTs on ZrO2:B dielectrics could potentially be used for low-cost, low-temperature, and high-performance flexible devices.

Fabrication of a multidomain and ultrafast-switching liquid crystal alignment layer using contact printing with a poly(dimethylsiloxane) stamp.

A compartmentalized multidomain alignment state of a layer of liquid crystal display is achieved using an ultrathin, highly transparent, and ultrafast-responsive alignment layer fabricated by a simple method. The ultrathin alignment layer consists of a self-assembled oligomer layer of poly(dimethylsiloxane) (PDMS) formed by utilizing the oligomers that diffuse out from a PDMS elastomer stamp during a contact printing process.

Direct electrical junction formation of highly vertical aligned zinc oxide nanorods.

A two dimensionally assembled monolayer of hexagonal convexo-convex ß-cobalt hydroxide nanoplates as a self-disposable sacrificial epi-template leads to a highly vertical alignment of zinc oxide nanorods array having a good electrical contact with metal or semiconductor layer on a substrate in a hydrothermal process.