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Directed Self-Assembly (directed + self-assembly)

Distribution by Scientific Domains
Polymers and Materials Science75%

Selected Abstracts

Directed Self-Assembly of Gradient Concentric Carbon Nanotube Rings,

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2008
Suck Won Hong
Abstract Hundreds of gradient concentric rings of linear conjugated polymer, (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4- phenylenevinylene], i.e., MEH-PPV) with remarkable regularity over large areas were produced by controlled "stick-slip" motions of the contact line in a confined geometry consisting of a sphere on a flat substrate (i.e., sphere-on-flat geometry). Subsequently, MEH-PPV rings were exploited as a template to direct the formation of gradient concentric rings of multiwalled carbon nanotubes (MWNTs) with controlled density. This method is simple, cost effective, and robust, combining two consecutive self-assembly processes, namely, evaporation-induced self-assembly of polymers in a sphere-on-flat geometry, followed by subsequent directed self-assembly of MWNTs on the polymer-templated surfaces. [source]

Directed Self-Assembly of Block Copolymers on Two-Dimensional Chemical Patterns Fabricated by Electro-Oxidation Nanolithography

ADVANCED MATERIALS, Issue 20 2010
Ji Xu
A hexagonal web of carboxylic-terminated nanostripes (left image, bright areas) is patterned onto a methyl-terminated surface of an octadecyltrichlorosilane monolayer. A thermally annealed polystyrene- block -poly(ethylene oxide) (PS- b -PEO) thin-film, spin-cast on the chemical pattern (right image), exhibits surface normal oriented cylindrical PEO microdomains on the methyl-terminated regions only. These chemical patterns effectively template the order and spatial orientation of diblock-copolymer microdomains. [source]

Fibroblast elongation and dendritic extensions in constrained versus unconstrained microtissues

CYTOSKELETON, Issue 3 2009
Dylan M. Dean
Abstract Cytoskeletal tension is fundamental to many biological processes, including germ layer sorting during embryogenesis [Krieg et al., 2008]. In vitro, such tension influences cell sorting in self-assembled, 3D microtissues and can be of sufficient magnitude to cause complex-shaped microtissue failure [Dean et al., 2007]. To examine the process of failure under cell-derived tension, we subjected normal human fibroblasts (NHFs) to directed self-assembly [Dean et al., 2007] in micro-molds designed to yield self-constraining microtissues. As cells contracted in this assay, the constrained microtissues narrowed, thinned and ultimately failed at their midpoints. By adding small numbers of GFP+ cells, changes in cell movement and morphology were assessed and compared to those of unconstrained microtissues. We found that cells formed numerous dendritic extensions within an hour of self-assembly and retracted these extensions as they elongated up to 30 times their initial diameter (,600 ,m) just prior to failure. Surprisingly, significant coordination in cell motility was observed over large distances within microtissues. Pharmacologic interventions showed that failure was myosin II and Rho kinase dependent and inhibition of failure resulted in shorter cells with greater numbers of extensions. These findings further our understanding of cellular self-assembly and introduce the use of GFP+ cells with directed self-assembly as a scaffold-free analogue to fibroblast-populated collagen gels (FPCGs). Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]

Site-Selective Self-Assembly of Colloidal Photonic Crystals

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
Sanna Arpiainen
Abstract A scalable method for site-selective, directed self-assembly of colloidal opals on topologically patterned substrates is presented. Here, such substrate contains optical waveguides which couple to the colloidal crystal. The site-selectivity is achieved by a capillary network, whereas the self-assembly process is based on controlled solvent evaporation. In the deposition process, a suspension of colloidal microspheres is dispensed on the substrate and driven into the desired crystallization sites by capillary flow. The method has been applied to realize colloidal crystals from monodisperse dielectric spheres with diameters ranging from 290 to 890,nm. The method can be implemented in an industrial wafer-scale process. [source]