银纳米树的选择性沉积及其催化性质

<正>纳米银由于体积小、比表面积大及物理和化学性能独特而受到广泛关注[1,2].研究结果表明,纳米银的光学、电学和催化活性与粒子的粒径、形貌和结构之间存在强烈的依赖关系[3].银纳米树的制备     

Rapid fabrication of microchannels using microscale plasma activated templating (microPLAT) generated water molds

Poly(dimethylsiloxane) (PDMS) is a common material used in fabricating microfluidic devices. The predominant PDMS fabrication method, soft lithography, relies on photolithography for fabrication of micropatterned molds. In this technical note, we report an alternative molding technique using microscale PLasma Activated Templating (microPLAT). The use of photoresist in soft lithography is replaced by patterned water droplets created using microPLAT. When liquid PDMS encapsulates patterned water and then solidifies, the cavities occupied by water become structures such as microchannels. Using this method, device fabrication is less time consuming, more cost efficient and flexible, and ideal for rapid prototyping. An additional important feature of the water-molding process is that it yields structural profiles that are difficult to achieve using photolithography.     

Photolithographic surface micromachining of polydimethylsiloxane (PDMS)

A major technical hurdle in microfluidics is the difficulty in achieving high fidelity lithographic patterning on polydimethylsiloxane (PDMS). Here, we report a simple yet highly precise and repeatable PDMS surface micromachining method using direct photolithography followed by reactive ion etching (RIE). Our method to achieve surface patterning of PDMS applied an O(2) plasma treatment to PDMS to activate its surface to overcome the challenge of poor photoresist adhesion on PDMS for photolithography. Our photolithographic PDMS surface micromachining technique is compatible with conventional soft lithography techniques and other silicon-based surface and bulk micromachining methods. To illustrate the general application of our method, we demonstrated fabrication of large microfiltration membranes and free-standing beam structures in PDMS.     

Surface patterning of silica nanostructures using bio-inspired templates and directed synthesis

Natural systems excel in directing the synthesis of inorganic materials for various functional purposes. One of the best-studied systems is silica synthesis, as occurs in diatoms and marine sponges. Various biological and synthetic polymers have been shown to template and catalyze silica formation from silicic acid precursors. Here, we describe the use of poly-L-lysine to promote the synthesis of silica in neutral, aqueous solution and when immobilized onto a silicon support structure under similar conditions. Either reagent jetting or conventional photolithography techniques can be used to pattern the templating polymer. Spots created by reagent jetting led to the creation of silica structures in the shape of a ring that may be a result of the spotting process. Photolithographically defined poly-L-lysine spots led to thin laminate structures after exposure to a dilute aqueous silicic acid solution. The laminate structures were nanostructured and highly interconnected. Photolithographic patterning of (3-aminopropyl)trimethoxysilane, a reagent that mimics the lysine functional group, led to similar silica coatings even though low-molecular-weight materials do not rapidly promote silica synthesis in solution. This result highlights the importance of functional-group arrangement for templating and promoting the synthesis of inorganic materials. The described surface-patterning techniques offer a route to integrate conventional silicon-patterning technologies with biologically based material synthesis. Such combined fabrication techniques enable controlled assembly over multiple length scales and an approach to understanding interfacial silica synthesis, as occurs in natural systems.     

A nanoengineering approach to regulate the lateral heterogeneity of self-assembled monolayers

Using a scanning probe lithography method known as nanografting in conjunction with knowledge of self-assembly chemistry, regulation of the heterogeneity of self-assembled monolayers (SAMs) is demonstrated. While nanografting in single-component thiols produces areas of SAMs with designed geometry and size, nanofabrication in mixed thiol solution yields segregated domains. The reaction mechanism in nanografting differs significantly from self-assembly in mix-and-grow methods, as proven in systematic studies reported in this article and a companion paper of theoretical calculations of the nanografting process. Knowledge of the reaction pathways enables development of methods for shifting the interplay between the kinetics and thermodynamics in SAM formation, and thus the heterogeneity of mixed SAMs. By varying fabrication parameters, such as shaving speed, and reaction conditions, such as concentration and ratio of the components, the lateral heterogeneity can be adjusted ranging from near molecular mixing to segregated domains of several to tens of nanometers.     

电沉积技术制作高聚物微流控芯片模具

利用电沉积技术制作微流控芯片金属模具,方法是:使用新型超厚光刻胶SU8胶作近紫外光刻,并在光刻后的图案上电沉积金属Ni,之后去胶,最终获得金属模具.该法减小了电沉积工作量.采用反向电流预处理基底、并适当增加电铸液的添加剂以及脱模后真空退火,即可明显提高电沉积微结构与基底的结合力.用此金属模具成功热压了PMMA,制成了微流控芯片.     

Molecular adsorption on ZnO(1010) single-crystal surfaces: morphology and charge transfer

While ZnO has excellent electrical properties, it has not been widely used for dye-sensitized solar cells, in part because ZnO is chemically less stable than widely used TiO(2). The functional groups typically used for surface passivation and for attaching dye molecules either bind weakly or etch the ZnO surface. We have compared the formation of molecular layers from alkane molecules with terminal carboxylic acid, alcohol, amine, phosphonic acid, or thiol functional groups on single-crystal zinc oxide (1010) surfaces. Atomic force microscopy (AFM) images show that alkyl carboxylic acids etch the surface whereas alkyl amine and alkyl alcohols bind only weakly on the ZnO(1010) surface. Phosphonic acid-terminated molecules were found to bind to the surface in a heterogeneous manner, forming clusters of molecules. Alkanethiols were found to bind to the surface, forming highly uniform monolayers with some etching detected after long immersion times in an alkanethiol solution. Monolayers of hexadecylphosphonic acid and octadecanethiol were further analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. AFM scratching shows that thiols were bound strongly to the ZnO surface, suggesting the formation of strong Zn-S covalent bonds. Surprisingly, the tridentate phosphonic acids adhered much more weakly than the monodentate thiol. The influence of organic grafting on the charge transfer to ZnO was studied by time-resolved surface photovoltage measurements and electrochemical impedance measurements. Our results show that the grafting of thiols to ZnO leads to robust surfaces and reduces the surface band bending due to midgap surface states.     

Guided growth of nanoscale conducting polymer structures on surface-functionalized nanopatterns

We describe an electrochemical method of directly growing conducting polymer nanostructures between metal electrodes with the geometry controlled by hydrophilic/hydrophobic patterns. The surface patterning can be achieved by a large number of lithographic methods such as AFM, electron-beam, elastomeric microprinting, and photolithography and is compatible with industrial semiconductor fabrication processes. Conducting polymer structures so formed have good alignment compared to bulk synthesis and are grown in place between electrodes. Polypyrrole field effect transistors have been produced using this method. Electrical measurements show conductivity strongly dependent on the presence of anionic dopant species during growth. Devices grown with a high concentration of dopant show metallic behavior, while those with less doping behave as p-type semiconductors.     

Rapid sacrificial layer etching for the fabrication of nanochannels with integrated metal electrodes

We present a rapid etch method to surface-micromachine nanochannels with integrated noble metal electrodes using a single metal sacrificial layer. The method is based on the galvanic coupling of a chromium sacrificial layer with gold electrodes, which results in a 10-fold increase in etch rate with respect to conventional single metal etching. The etch process is investigated and characterized by optical and electrochemical measurements, leading to a theoretical explanation of the observed etch rate based on mass transport. Using this explanation we derive some generic design rules for nanochannel fabrication employing sacrificial metal etching.     

Facile fabrication of 2-dimensional arrays of sub-10 nm single crystalline Si nanopillars using nanoparticle masks

A simple procedure for the fabrication of sub-10 nm scale Si nanopillars in a 2-D array using reactive ion etching with 8 nm Co nanoparticles as etch masks is demonstrated. The obtained Si nanopillars are single crystalline tapered pillar structures of 5 nm (top) x 8 nm (bottom) with a density of approximately 4 x 10(10) pillars cm(-2) on the substrate, similar to the density of Co nanoparticles distributed before the ion etching process. The uniform spatial distribution of the Si nanopillars can also be patterned into desired positions. Our fabrication method is straightforward and requires mild process conditions, which can be extended to patterned 2-D arrays of various Si nanostructures.     

Practical approach for macroporous structure embedded microfluidic system and the catalytic microchemical application

We present a low cost and practical approach to integrate 3D ordered macroporous polyfluoropolyether (PFPE) patterns into a microchannel by a series of porous pattern fabrication processes and subsequent photolithography in a site- and shape-selective manner. The 3D ordered macroporous patterns with high-resolution edges were firstly fabricated by microtransfer molding (μ-TM) of the sacrificial polystyrene (PS) template infiltrated with PFPE as a non-adhesive and solvent-resistant skeletal material. The resulting robust PFPE porous structures with high solvent resistance on a silicon wafer can easily be embedded into the microchannel with the aid of conventional photolithography, leading to a microfluidic system with a built-in microstructure. Moreover, catalytic Pd nanoparticles implanted on the surface of the porous structure were obtained by use of Pd nanoparticle deposited PS spheres, the porous structure embedded channel was utilized to perform a Suzuki coupling reaction.     

PDMS-based microfluidic device with multi-height structures fabricated by single-step photolithography using printed circuit board as masters

We have developed a method for fabricating microfluidic devices with multi-height structures using single step photolithography. The whole fabrication process is executed by conventional printed circuit board (PCB) technology without the need of having access to clean room facilities. Specifically designed "windows" and "rims" architectures were printed on films that were used as photomasks. Different levels of protruding features on the PCB master were produced by exposing a photomask followed by chemical wet etching. Poly(dimethylsiloxane) (PDMS) was then moulded against the positive relief master to generate microfluidic structures. In this report, we described the fabrication of a microfluidic device featured with a multi-height "sandbag" structure for particle entrapment and peripheral microchannels. Controlled immobilization of biological cells and immunocytochemcial staining assays were performed to demonstrate the applicability of the microfluidic device for cellular analysis. The integrity of the microdevice remained stable under applied pressure, indicating the robustness of the elastic PDMS structures for analytical operation. The simple microfabrication process requires only low-cost materials and minimal specialized equipment and can reproducibly produce mask lines of about 20 microm in width, which is sufficient for most microfluidic applications.     

Novel fabrication process using nanoporous anodic aluminum oxidation and MEMS technologies for gas detection

A class of nanoporous TiO₂ gas sensors processed by novel anodic aluminum oxidation (AAO) of Al thin films and microelectromechnical systems (MEMS) techniques are presented. To enhance the sensitivity and reduce the sensing dimensions of a gas sensor, a nanoporous surface of the gas-sensitive material on the sensor is required. These sensors can be implemented on silicon or silicon dioxide substrate featuring a thin membrane of micro-hotplate structure featuring micro-heaters, thermometers and electrodes, and thus operate as chemoresistive devices. Combining the AAO method with dry-etch process, a homogeneous and nanoporous SiO₂ surface of the sensor can be effectively configured by modulating various hole diameters and depth, hence replacing conventional photolithography and electrochemical etch. The process integration including AAO, reactive ion etch (RIE) and microfabrication is mainly developed and a feasibility study of PVD TiO₂ thin film deposition upon the porous device is also provided. TiO₂ thin films deposited on the nanoporous surface are investigated and compared with non-porous TiO₂ films. It is encouraging that our fabrication process is able to provide relatively high surface area to enhance sensitivity of the sensor without additional doping steps. Our promising experimental results have revealed these miniature and cost-effective devices are not only compatible, but applicable to smart bio-chemical sensors of next generation.     

Microfabrication on polymer with a contact procedure

In the fabrication of a microstructure, it is usually difficult to make deep etching with the conventional photolithography. Here the fabrication of thickness contrast micropatterns based on a contact procedure is demonstrated. Polymer (polydimethylsiloxane) microposts arrays have been fabricated with grids as the masters. The contact procedure, which does not need the etching procedure, extends the present limit of microfabrication. Moreover, the thickness contrast micropatterns on the polymer can be replicated to other substrates (such as silicon wafer) with the microcontact printing.     

Self-assembled biofilm of hydrophobins protects the silicon surface in the KOH wet etch process

The anisotropic wet micromachining of silicon, based on a water solution of potassium hydroxide (KOH), is a standard fabrication process that is extensively exploited in the realization of very complex microsystems, which comprise cantilevers, membranes, and bridges. A nanostructured self-assembled biofilm of amphiphilic proteins, the hydrophobins, was deposited on crystalline silicon by solution deposition and characterized by variable-angle spectroscopic ellipsometry (VASE). This procedure formed chemically and mechanically stable mono- and multilayers of self-assembled proteins. The biomolecular membrane has been tested as masking material in the KOH wet etch of the crystalline silicon. The process has been monitored by VASE and atomic force microscopy measurements. Because of the high persistence of the protein biofilm, the hydrophobin-coated silicon surface is perfectly protected during the standard KOH micromachining process.     

Stereoselective synthesis of light-activatable perfluorophenylazide-conjugated carbohydrates for glycoarray fabrication and evaluation of structural effects on protein binding by SPR imaging

A series of light-activatable perfluorophenylazide (PFPA)-conjugated carbohydrate structures have been synthesized and applied to glycoarray fabrication. The glycoconjugates were structurally varied with respect to anomeric attachment, S-, and O-linked carbohydrates, respectively, as well as linker structure and length. Efficient stereoselective synthetic routes were developed, leading to the formation of the PFPA-conjugated structures in good yields over few steps. The use of glycosyl thiols as donors proved especially efficient and provided the final compounds in up to 70% total yield with high anomeric purities. PFPA-based photochemistry was subsequently used to generate carbohydrate arrays on a polymeric surface, and surface plasmon resonance imaging (SPRi) was applied for evaluation of carbohydrate-protein interactions using the plant lectin Concanavalin A (Con A) as a probe. The results indicate better performance and equal efficiency of S- and O-linked structures with intermediate linker length.     

Recent Strategies in Fabrication of Gradient Hydrogels for Tissue Engineering Applications

Hydrogels are widely used as scaffold in tissue engineering field because of their ability to mimic the cellular microenvironment. However, mimicking a completely natural cellular environment is complicated due to the differences in various physical and chemical properties of cellular environments. Recently, gradient hydrogels provide excellent heterogeneous environment to mimic the different cellular microenvironments. To create hydrogels with an anisotropic distribution, gradient hydrogels have been widely developed by adopting several gradient generation techniques. Herein, the various gradient hydrogel fabrication techniques, including dual syringe pump systems, microfluidic device, photolithography, diffusion, and bio‐printing are summarized. As the effects of gradient 3D hydrogels with stems have been reviewed elsewhere, this review focuses principally on gradient hydrogel fabrication for multi‐model tissue regeneration. This review provides new insights into the key points for fabrication of gradient hydrogels for multi‐model tissue regeneration.     

Formation of self-rolled polymer microtubes studied by combinatorial approach

This paper describes an experimental study of the polymer microtube formation in different fabrication conditions. A photolithography route is demonstrated for the fabrication of large amount of uniform and good quality polymer microtubes. TEM grids were used as mask and exposure of UV radiation was done in two steps to create asymmetric patterns. The diameter of tube was controlled by regulating the thickness of polymer layers, UV radiation dose and concentration of acidic solution. The results indicate that thickness of the bilayer film was the most dominating factor to determine the tube’s dimension, and diameter of the tubes increased with increase in the thickness of bilayer. The kinetics of the tube formation was studied with respect to acidity of the solution and UV dose. Rate of rolling increased with the acidity of the solution. Tube diameter and rate of rolling decreased with the increase of the UV exposure time. Films with two-dimensional gradients of layer thicknesses were prepared to study a broad range of parameters in a single experiment. The tubes were characterized in detail using optical microscopy and scanning electron microscopy. These polymer microtubes have potential applications in microfluidic devices and biotechnology field.     

Embossed polymer leaky waveguide devices for spectroscopic analysis

A combination of UV embossing, hot embossing and laminating techniques have been exploited during the fabrication of grating-coupled waveguiding devices in which the flow channel materials and geometry are designed for the effective support of light condenser modes through a sample solution. Used in conjunction with LED sources, these devices have been employed as optical platforms to obtain fluorescence emission and molecular absorption spectra in aqueous media for microTAS (micro total analytical system) applications.     

The resolution of an optically active pyridinethiol

The resolution of a chiral pyridine thiol has been eonveniently carried out through derivatives with optically active α-phenethylisoeyanates. Optically active heterocyclic thiols in which the thiol occupies the center of chirality are not known in the literature. In conjunction with a synthetic program dealing with derivatives and analogues of 5-mercaptopyridoxine (1), the preparation of such species was accomplished. Their resolution proved to be difficult, but the techniques devised herein should prove of general utility for other heteroeyclic thiols or alcohols.