Surfaces decorated with dense arrays of microscopic fibres exhibit unique materials properties, including superhydrophobicity and low friction. Nature relies on 'hairy' surfaces to protect blood capillaries from wear and infection (endothelial glycocalyx). Here we report on the discovery of self-assembled tunable networks of microscopic polymer fibres ranging from wavy colloidal 'fur' to highly interconnected networks. The networks emerge via dynamic selfassembly in an alternating electric field from a non-aqueous suspension of 'sticky' polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles. We demonstrate, using atomic layer deposition, that the networks can serve as a template for a transparent conductor. These self-assembled tunable materials are promising candidates for large surface area electrodes in batteries and organic photovoltaic cells, as well as for microfluidic sensors and filters.
High invasiveness and resistance to chemo- and radiotherapy of glioblastoma multiforme (GBM) make it the most lethal brain tumor. Therefore, new treatment strategies for preventing migration and invasion of GBM cells are needed. Using two different migration assays, Western blotting, conventional and super-resolution (dSTORM) fluorescence microscopy we examine the effects of the dual PI3K/mTOR-inhibitor PI-103 alone and in combination with the Hsp90 inhibitor NVP-AUY922 and/or irradiation on the migration, expression of marker proteins, focal adhesions and F-actin cytoskeleton in two GBM cell lines (DK-MG and SNB19) markedly differing in their invasive capacity. Both lines were found to be strikingly different in morphology and migration behavior. The less invasive DK-MG cells maintained a polarized morphology and migrated in a directionally persistent manner, whereas the highly invasive SNB19 cells showed a multipolar morphology and migrated randomly. Interestingly, a single dose of 2 Gy accelerated wound closure in both cell lines without affecting their migration measured by single-cell tracking. PI-103 inhibited migration of DK-MG (p53 wt, PTEN wt) but not of SNB19 (p53 mut, PTEN mut) cells probably due to aberrant reactivation of the PI3K pathway in SNB19 cells treated with PI-103. In contrast, NVP-AUY922 exerted strong anti-migratory effects in both cell lines. Inhibition of cell migration was associated with massive morphological changes and reorganization of the actin cytoskeleton. Our results showed a cell line-specific response to PI3K/mTOR inhibition in terms of GBM cell motility. We conclude that anti-migratory agents warrant further preclinical investigation as potential therapeutics for treatment of GBM.
INTRODUCTIONNiobium silicide-based alloys have a wide range of applications including tunnel barriers for Josephson junctions, 1 superconductors for particle detection (bolometers), 2,3 and low friction and high temperature corrosion resistant coatings for engines. 4 Thin films of Nb x Si 1Àx compounds with various compositions can be deposited using a variety of methods including electron beam evaporation 5,6 (Nb 5 Si 3 and NbSi 2 ), RF magnetron sputtering, 7 explosive or arc melting and chill-casting 8À10 (NbSi 3 ), chemical vapor deposition, 11 direct laser fabrication, 12 or ion-induced formation. 13 In contrast with these line-of-sight techniques, atomic layer deposition (ALD) offers many advantages. ALD is a thin film deposition technique that uses alternating, self-limiting chemical reactions between gaseous precursors and a solid surface to deposit materials in an atomic layer-by-layer fashion. 14 The self-terminating chemistry coupled with gaseous diffusion of the precursor vapors allows an excellent control of both the composition and the thickness uniformity on arbitrary complexshaped objects. ALD has been used previously to deposit a wide range of materials including metals, metal oxides, and metal nitrides, but only metal silicides have received relatively little attention. 15 To our knowledge this is the first reported in-depth growth study for the ALD of a pure silicide.There has been only one previous report for the ALD of superconducting materials. 16 Despite the fact that very little effort has been invested in the growth study of superconductors by ALD, this unique technique could clearly beneficiate a variety of low-temperature superconductor-based applications that are currently limited by line-of-sight deposition techniques. Bolometers are one example. 2,3 Another example is superconducting radio frequency (SRF) accelerating niobium cavities 17 used is almost all particle accelerators around the world.This study pursues dual goals: first, to develop a low temperature, reliable ALD process to synthesize NbSi with a high growth rate that can open the way to other transition metal silicide or NbSi-based alloys growth study by ALD and, second, to characterize and optimize the superconducting properties of the NbSi films. In this study we use alternating exposures to NbF 5 and Si 2 H 6 to deposit NbSi films by ALD. In-situ quartz crystal microbalance (QCM) and quadrupole mass spectrometer (QMS) measurements are used to explore the mechanism for the NbSi ALD. A variety of ex-situ techniques are used to determine the physical properties of the films. X-ray reflectivity (XRR) measurements are used to evaluate the thickness, roughness, and density of the films while Rutherford backscattering spectroscopy (RBS) is employed to determine the density and stoichiometry of the films. The composition and impurity content of the films are evaluated using X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) is utilized to examine the uniformity and conformality of the coatings on no...
We report the use of atomic layer deposition (ALD) to synthesize thin superconducting films and multilayer superconductorinsulator (S-I) hetero-structures. ALD applied to superconducting films opens the way for a variety of applications, including improving the performance and decreasing the cost of high energy particle accelerators, superconducting wires for energy storage, and bolometers for radiation detection. Furthermore, the atomicscale thickness control afforded by ALD enables the study of superconductivity and associated phenomena in homogeneous layers in the ultra-thin film limit. Two-dimensional superconductivity in such films is of interest from a fundamental point of view, as a new effect has recently been discovered at ultralow temperature in thin superconducting films made by ALD: the super-insulating transition. The discovery of a new state with apparently infinite resistivity in ultra-thin ALD films offers both a platform to explore new physics as well as the promise, on a longer term, of new opportunities for loss electronics and detectors.
Articles you may be interested inLow sheet resistance titanium nitride films by low-temperature plasma-enhanced atomic layer deposition using design of experiments methodology J. Vac. Sci. Technol. A 32, 031506 (2014); 10.1116/1.4868215Electron/phonon coupling in group-IV transition-metal and rare-earth nitridesIn situ spectroscopic ellipsometry study on the growth of ultrathin TiN films by plasma-assisted atomic layer deposition Heteroepitaxial growth of selected group IV-VI nitrides on various orientations of sapphire (a-Al 2 O 3 ) is demonstrated using atomic layer deposition. High quality, epitaxial films are produced at significantly lower temperatures than required by conventional deposition methods. Characterization of electrical and superconducting properties of epitaxial films reveals a reduced room temperature resistivity and increased residual resistance ratio for films deposited on sapphire compared to polycrystalline samples deposited concurrently on fused quartz substrates. V C 2013 AIP Publishing LLC. [http://dx.
A tunneling spectroscopy study is presented of superconducting MoN and Nb 0.8 Ti 0.2 N thin films grown by atomic layer deposition (ALD). The films exhibited a superconducting gap of 2 meV and 2.4 meV respectively with a corresponding critical temperature of 11.5K and 13.4K, among the highest reported T c values achieved by the ALD technique. Tunnel junctions were obtained using a mechanical contact method with a Au tip. While the native oxides of these films provided poor tunnel barriers, high quality tunnel junctions with low zero bias conductance (below ∼10%) were obtained using an artificial tunnel barrier of Al 2 O 3 on the film's surface grown ex situ by ALD. We find a large critical current density on the order of 4 × 10 6 A/cm 2 at T = 0.8T c for a 60nm MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest the ALD technique offers significant promise for thin film superconducting device applications.Superconducting nitride alloys make excellent candidates for device applications due to their relatively high critical temperature and stability at ambient atmosphere. These characteristics suggest the opportunity for increased performance and efficiency over commonly used niobium. However, challenges and limitations in common fabrication techniques can reduce the application possibilities. Reactive magnetron sputtering is the most commonly used deposition technique that has produced high quality superconducting thin films of niobium based nitrides.1-3 While molybdenum based superconducting nitrides have also been achieved through sputtering 4 or chemical solution 5 techniques, they require a high temperature (≥700• C) and/or high pressure annealing process to achieve a critical temperature greater than that of niobium. Various other techniques such as chemical vapor deposition, 6 pulsed laser deposition 7 and molecular beam epitaxy 8 have produced superconducting molybdenum nitrides, but have failed to even reach 9K. Sputtering methods are generally limited to planar geometries making it very difficult for complex geometry applications such as superconducting radio-frequency (SRF) cavities or superconducting magnets. Additionally, for applications requiring thin pin-hole free insulating barriers such as superconductorinsulator-superconductor (SIS) tunnel junction mixers for terahertz frequencies, 9 sputtering processes can be quite challenging.Atomic layer deposition (ALD) is a highly scalable technique that utilizes sequential self-limiting surface chemical reactions to deposit material in a layer-by-layer a) Electronic mail: ngroll@anl.gov b) Electronic mail: proslier@anl.gov fashion.10,11 ALD provides several advantages over traditional growth methods, including atomic-scale uniformity over large areas, unmatched conformity over complexshaped substrates, and deposition temperatures well below those often required by other techniques. ALD has previously demonstrated the ability to grow superconducting films 12 and nitride based thin films in...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.