Fabrication Of Hierarchical Structures Research Articles

Study on wetting properties of periodical nanopatterns by a combinative technique of photolithography and laser interference lithography

This study presents the wetting properties, including hydrophilicity, hydrophobicity and anisotropic behavior, of water droplets on the silicon wafer surface with periodical nanopatterns and hierarchical structures. This study fabricates one- and two-dimensional periodical nanopatterns using laser interference lithography (LIL). The fabrication of hierarchical structures was effectively achieved by combining photolithography and LIL techniques. Unlike conventional fabrication methods, the LIL technique is mainly used to control the large-area design of periodical nanopatterns in this study. The minimum feature size for each nanopattern is 100 nm. This study shows that the wetting behavior of one-dimensional, two-dimensional, and hierarchical patterns can be obtained, benefiting the development of surface engineering for microfluidic systems.

Layer‐by‐layer fabrication of hierarchical structures in sol–gel templated thin titania films

AbstractThe fabrication of titania nanostructures with hierarchical order of different structural levels is investigated. The nanostructures are prepared with a diblock‐copolymer assisted sol–gel process. By iterative spin‐coating of the solution onto silicon substrates a thin polymer‐nanocomposite film is deposited and transformed to purely anatase titania nanostructures via calcination. In total, this procedure is repeated three times on top of the substrate. The approach is monitored with grazing incidence small angle X‐ray scattering after each fabrication step. With scanning electron microscopy the final hierarchical structure is imaged. From the characterization different structural levels are clearly identified.magnified imagePreparation of small titania nanogranules on top of much larger sol–gel templated titania granules.(© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication of Hierarchical Structures by Wetting Porous Templates with Polymer Microspheres

We present a simple route to prepare hierarchical structures by allowing the partial diffusion of polymer microspheres into the nanopores of anodic aluminum oxide (AAO) templates. Polystyrene (PS) microspheres were first spread onto a silicon substrate and allowed to self-assemble into well-ordered monolayers of the microspheres. Upon heating above the glass-transition temperature, diffusion of the PS into the pores of the AAO occurred only at pores of the microspheres in contact with the membrane. After the removal of the AAO membrane, ordered arrays of microspheres capped with nanorods were produced, yielding surfaces with topographies spanning multiple length scales. Control over the nanoscopic and microscopic length scales can be trivially achieved by changing the size of the microspheres and the diameter of the pores in the membranes.

Novel Single-Crystalline Hierarchical Structured ZnO Nanorods Fabricated via a Wet-Chemical Route: Combined High Gas Sensing Performance with Enhanced Optical Properties

Hierarchical structured ZnO nanorods have been fabricated via a wet-chemical approach for the development of multifunctional ZnO materials possessing excellent optical and gas sensing properties simultaneously, which was a great challenge because of their opposite requirements on morphology and structure. On the surface of the as-fabricated ZnO nanorods, thornlike single-crystalline nanostructures are developed in a large density. The development of crystal defects and the minimization of surface energy are suggested as the growth mechanism. On the basis of UV−vis absorption, room-temperature photoluminescence spectra, and gas sensing measurement, the as-prepared products exhibit combined highly sensitive gas sensing performance with excellent optical properties because of their hierarchical morphology and single-crystalline structure, confirming the feasibility for the design of multifunctional ZnO by constructing hierarchical structure. Besides the traditional doping routes, the fabrication of hierarchical structure can be potentially extended for the design of other multifunctional semiconductor materials.

Fabrication of hierarchical structures on a polymer surface using patterned anodic aluminum oxide as a replication master

Well-defined hierarchical structures, 3-dimensional upright structures containing aligned nanoembosses or nanoposts within micron-sized patterned areas, were realized on a polymer surface by utilizing patterned anodized aluminum oxide (AAO) and electrochemical reactions followed by a heat- and pressure-driven polymer imprinting technique. Sputtered Al on AAO could work excellently as a mask for the selective etching of AAO and successive anodization processes and many interesting hierarchical structures could be generated on an Al surface, from which hierarchical structures could be reproducibly duplicated onto polymer surfaces.

Fabrication of Hierarchical Structures on a Polymer Surface to Mimic Natural Superhydrophobic Surfaces

Fabrication of Hierarchical Structures on a Polymer Surface to Mimic Natural Superhydrophobic Surfaces

Budded, Mesoporous Silica Hollow Spheres: Hierarchical Structure Controlled by Kinetic Self‐Assembly

Recently, mesoporous materials with hierarchical structures and well-defined morphologies have attracted much attention. Besides possible practical applications, studies of mesoporous materials may also shed light on fundamental mechanisms of biomineralization. Among the many types of mesoporous materials, hollow spheres are of significance because of their potential uses in encapsulation, drug-delivery, and controlled-release applications. Although many articles have been published describing the interior templating of mesoporous hollow particles using hard templates, vesicles, or emulsions, the fabrication of hierarchical structures on the shell has rarely been reported. In this Communication, we report a novel, single-step, emulsion-templating method to fabricate a unique, hierarchical morphology. Our products consist of budded, mesoporous silica hollow spheres. What distinguishes these structures from the traditional ones is that they combine two separate, distinct mesophases with different-sized mesovoids in a single hollow sphere. Specifically, the shell of the sphere is based on wormholelike mesoporous structures, while the protruding buds are formed from lamellar (vesicular) mesostructures. Our process utilizes the sodium salt of the anionic surfactant N-lauroylsarcosine (Sar-Na), which is commonly used in cosmetic and pharmaceutical industries due to its biodegradability and low toxicity. Instead of employing the usual emulsion-templating methods with nonpolar fluids such as trimethylbenzene, we employ a novel process in which the emulsion is generated by the acidification of a Sar-Na solution. As shown in Scheme 1, the addition of acid converts a portion of the Sar anions to Sar-H, which is an amphiphilic polar oil that behaves as droplets. The condensation of the added silica precursors (3aminopropyltrimethoxysilane (APMS) and tetraethylorthosilC O M M U N IC A TI O N

Self-assembled ceramics produced by complex-fluid templation.

This review examines the use of self-assembly in the fabrication of ceramic mesostructures, emphasizing the use of amphiphilic surfactants and block copolymers. The association between this area of research and biomimetics is discussed, linking developments in synthetic self-assembly with biomineralization. The fabrication of hierarchical structures through the use of simultaneous processing is shown to be a necessary condition for applications of this new technology.