65 research outputs found
Controlled interfacial assembly of 2D curved colloidal crystals and jammed shells
Assembly of colloidal particles on fluid interfaces is a promising technique
for synthesizing two-dimensional micro-crystalline materials useful in fields
as diverse as biomedicine1, materials science2, mineral flotation3 and food
processing4. Current approaches rely on bulk emulsification methods, require
further chemical and thermal treatments, and are restrictive with respect to
the materials employed5-9. The development of methods that exploit the great
potential of interfacial assembly for producing tailored materials have been
hampered by the lack of understanding of the assembly process. Here we report a
microfluidic method that allows direct visualization and understanding of the
dynamics of colloidal crystal growth on curved interfaces. The crystals are
periodically ejected to form stable jammed shells, which we refer to as
colloidal armour. We propose that the energetic barriers to interfacial crystal
growth and organization can be overcome by targeted delivery of colloidal
particles through hydrodynamic flows. Our method allows an unprecedented degree
of control over armour composition, size and stability.Comment: 18 pages, 5 figure
Fabrication of Highly Ordered Polymeric Nanodot and Nanowire Arrays Templated by Supramolecular Assembly Block Copolymer Nanoporous Thin Films
Realizing the vast technological potential of patternable block copolymers requires both the precise controlling of the orientation and long-range ordering, which is still a challenging topic so far. Recently, we have demonstrated that ordered nanoporous thin film can be fabricated from a simple supramolecular assembly approach. Here we will extend this approach and provide a general route to fabricate large areas of highly ordered polymeric nanodot and nanowire arrays. We revealed that under a mixture solvent annealing atmosphere, a near-defect-free nanoporous thin film over large areas can be achieved. Under the direction of interpolymer hydrogen bonding and capillary action of nanopores, this ordered porous nanotemplate can be properly filled with phenolic resin precursor, followed by curation and pyrolysis at middle temperature to remove the nanotemplate, a perfect ordered polymer nanodot arrays replication was obtained. The orientation of the supramolecular assembly thin films can be readily re-aligned parallel to the substrate upon exposure to chloroform vapor, so this facile nanotemplate replica method can be further extend to generate large areas of polymeric nanowire arrays. Thus, we achieved a successful sub-30 nm patterns nanotemplates transfer methodology for fabricating polymeric nanopattern arrays with highly ordered structure and tunable morphologies
Cell Encapsulation in Sub-mm Sized Gel Modules Using Replica Molding
For many types of cells, behavior in two-dimensional (2D) culture differs from that in three-dimensional (3D) culture. Among biologists, 2D culture on treated plastic surfaces is currently the most popular method for cell culture. In 3D, no analogous standard method—one that is similarly convenient, flexible, and reproducible—exists. This paper describes a soft-lithographic method to encapsulate cells in 3D gel objects (modules) in a variety of simple shapes (cylinders, crosses, rectangular prisms) with lateral dimensions between 40 and 1000 μm, cell densities of 105 – 108 cells/cm3, and total volumes between 1×10−7 and 8×10−4 cm3. By varying (i) the initial density of cells at seeding, and (ii) the dimensions of the modules, the number of cells per module ranged from 1 to 2500 cells. Modules were formed from a range of standard biopolymers, including collagen, Matrigel™, and agarose, without the complex equipment often used in encapsulation. The small dimensions of the modules allowed rapid transport of nutrients by diffusion to cells at any location in the module, and therefore allowed generation of modules with cell densities near to those of dense tissues (108 – 109 cells/cm3). This modular method is based on soft lithography and requires little special equipment; the method is therefore accessible, flexible, and well suited to (i) understanding the behavior of cells in 3D environments at high densities of cells, as in dense tissues, and (ii) developing applications in tissue engineering
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