Generally, line widths are reduced by increasing the contact angle and by reducing the inlet/substrate velocity ratio. The conditions providing the minimum stable line width are bounded by a regime of capillary instability -we anticipate that this instability could be exploited to create periodic arrays of dots.The advantages of h4PL are that we can use computer-aided design to define any arbitrary 2-D pattern and that we can use any desired combination of surfactant and functional silane as ink to selectively define different functionalities at different locations. However ikiPL is a serial technique: In situations where it is desirable to create an entire pattern with the same functionality, it would be preferable to employ a parallel technique in which the deposition process occurred simultaneously in multiple locations. Schem~~( Figure 3) illustrates a rapid, parallel patterning procedure, dip-coating on patterned SAMS.This procedure uses micro-contact printing20 or electrochemical patteming2 1 of hydroxyl-and methyl-terminated SAMS to define hydrophilic and hydrophobic patterns on the substrate surfi~ce. ..,&., .-, ,., ., ...<. !.-.7 '?--..-., hydrophilic patterns in seconds. As described for A4PL, further evaporation accompanying the dip-coating operation induces self-assembly of silic~surfac~t mesophases.The patterned dip-coating procedure may be conducted with organic dyes or functional silanes (see Table 1). Scheme 2 illustrates patterned deposition of a propyl-amine derivatized cubic mesophase followed by a conjugation reaction with a pH-sensitive dye, 5,6-carboxyfluorescein, succinimidyl ester (5,6-FAM, SE). The uniform continuous porosity of the amine-derivatized and dye-conjugated films is confirmed by TEM and surface acoustic wave (SAW)-based nitrogen sorption isotherms22 of the corresponding films deposited on SAW substrates (Figure 4). The reduction in film porosity after dye conjugation reflects the volume occupied by the attached dye moieties. The patterned, functional array can be used to monitor the pH of fluids introduced at arbitrary locations and transported by capillary flow into the imaging cell. Figure 4a shows the fluorescence image of an array contacted with three different aqueous solutions prepared at pH 4.8, 7.7, and 12.0. Figure 4b shows the corresponding emission spectra and provides a comparison with solution data. In combination, the fluorescence image ( Fig. 4a) and plan-view and cross-sectional TEM micrographs (Figures 3 and 4c) of the dye-conjugated film demonstrate the uniformity of macro-and mesoscale features achievable by this evaporation-induced, de-wetting and self-assembly route. In comparison, films formed by nucleation and growth of thin film mesophases on patterned SANIS1 are observed to have nonhomogeneous, globular morphologies.Finally we can create patterned nanostructures by combining E]SA with a variety of aerosol processing schemes. For example, Figure 5 compares an optical micrograph of a macroscopic array of spots formed by inkjet printing LIPlo~1lon a sili...
Manganite in the La 0.7 Sr 0.3 MnO 3 system is of great interest due to its potential application in fuel cells, information storage, magnetic field sensors, non-volatile memories, oxygen sensors, and catalysts in the oxidation of light hydrocarbons. Given the scientific relevance of this material, this study describes the procedure to synthesize and characterize thin films of La 0.7 Sr 0.3 MnO 3 . Manganites were synthesized by means of the Pechini method, and deposited on strontium titanate substrates using spin-coating. Both the crystallinity of the films and their phases were studied with X-ray diffraction (XRD), finding that the films are polycrystalline and have a simple cubic structure with a lattice constant a=3.8653 ± 0.066 Ǻ. Scanning electron microscopy (SEM) showed a uniform surface with good morphological features, and the spectrum resulted from the Energy Dispersive X-Ray Spectroscopy (EDS) analysis over the same film was consistent with the molar ratio of the perovskite. Samples of 2, 4, and 6 layers were synthesized, obtaining thicknesses of 75.10 ± 0.01, 75.02 ± 0.01 and 74.07 ± 0.08 nm per monolayer. The results indicate that this method is useful to synthesize films of high crystalline quality and nanometric size.Keywords: manganite; Perovskite; thin films . ResumenLas manganitas en el sistema La 0,7 Sr 0,3 MnO 3 son de gran interés por su potencial aplicación en celdas de combustibles, almacenamiento de información, sensores de campo magnético, memorias no volátiles, sensores de oxígeno y catalizadores en la oxidación de hidrocarburos ligeros; dada la importancia científica que tiene este material, este trabajo presenta el procedimiento de síntesis y caracterización de películas delgadas de La 0,7 Sr 0,3 MnO 3 . Las manganitas se sintetizaron por el método de Pechini y fueron depositadas por Spin Coating en forma de películas delgadas en sustratos de titanato de estroncio. La cristalinidad de las películas y las fases presentes se estudiaron por difracción de rayos-X (DRX), encontrándose que las películas son de naturaleza policristalina y presentan * M. Sc. Institución Universitaria CESMAG (Pasto-Nariño, Colombia). gamera@iucesmag.edu.co. ** Universidad de Nariño (Pasto-Nariño, Colombia). *** M. Sc. Universidad de Nariño (Pasto-Nariño, Colombia). carcob@udenar.edu.co. Fecha de recepción: 7 de junio de 2016 Fecha de aprobación: 20 de noviembre de 2016Jenny Alejandra Mera-Córdoba -María Angélica Mera-Córdoba -Carlos Arturo Córdoba-Barahona Spin Coating technique for obtaining nanometric thin films in the system La0.7Sr0.3MnO3 estructura cúbica simple con contante de red a=3.8653 ± 0,066 Ǻ. La microscopía electrónica de barrido (SEM) muestra una superficie uniforme con buenas características morfológicas, y el espectro EDS medido sobre la misma película mostró consistencia con la relación molar de la perovskita. Se sintetizaron muestras de 2, 4 y 6 capas, obteniendo espesores de 75,10 ± 0,01, 75,02 ± 0,01 y 74,07 ± 0,08 nm por monocapa. Los resultados indican que con este método es posi...
This paper presents continuum simulations of polymer flow during nanoimprint lithography (NIL). The simulations capture the underlying physics of polymer flow from the nanometer to millimeter length scale and examine geometry and thermophysical process quantities affecting cavity filling. Variations in embossing tool geometry and polymer film thickness during viscous flow distinguish different flow driving mechanisms. Three parameters can predict polymer deformation mode: cavity width to polymer thickness ratio, polymer supply ratio and capillary number. The ratio of cavity width to initial polymer film thickness determines vertically or laterally dominant deformation. The ratio of indenter width to residual film thickness measures polymer supply beneath the indenter which determines Stokes or squeeze flow. The local geometry ratios can predict a fill time based on laminar flow between plates, Stokes flow, or squeeze flow. A characteristic NIL capillary number based on geometry-dependent fill time distinguishes between capillary- or viscous-driven flows. The three parameters predict filling modes observed in published studies of NIL deformation over nanometer to millimeter length scales. The work seeks to establish process design rules for NIL and to provide tools for the rational design of NIL master templates, resist polymers and process parameters.
We present a review and critique of several methods for the simulation of the dynamics of colloidal suspensions at the mesoscale. We focus particularly on simulation techniques for hydrodynamic interactions, including implicit solvents (Fast Lubrication Dynamics, an approximation to Stokesian Dynamics) and explicit/particle-based solvents (Multi-Particle Collision Dynamics and Dissipative Particle Dynamics). Several variants of each method are compared quantitatively for the canonical system of monodisperse hard spheres, with a particular focus on diffusion characteristics, as well as shear rheology and microstructure. In all cases, we attempt to match the relevant properties of a well-characterized solvent, which turns out to be challenging for the explicit solvent models. Reasonable quantitative agreement is observed among all methods, but overall the Fast Lubrication Dynamics technique shows the best accuracy and performance. We also devote significant discussion to the extension of these methods to more complex situations of interest in industrial applications, including models for non-Newtonian solvent rheology, non-spherical particles, drying and curing of solvent and flows in complex geometries. This work identifies research challenges and motivates future efforts to develop techniques for quantitative, predictive simulations of industrially relevant colloidal suspension processes.
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