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Porous alumina membrane for hydrogen separation was prepared by a two-step process. The γ-alumina layer was first formed in an asymmetric porous α-alumina support from alumina sol mixed with a palladium precursor H 2 PdCl 4 . The membrane pore was then modified by two consecutive procedures; soaking palladium acetate solution into the pores at room temperature, followed by drying, evaporation, and decomposing palladium acetate on the pore surface by gradually increasing temperature upto 573K for 1 hour. This modification, named soaking and vapor-deposition (SVD) method, enhanced both the permeability and the hydrogen selectivity relative to those for the membrane prepared only by the sol-gel method. The permeability of hydrogen through the membrane was an increasing function of the transmembrane pressure and varied from 8.5 to 15.7 in 10 −8 m 3 (STP) m −2 Pa −1 s −1 . The selectivity of hydrogen was maintained above 5 at 673 K even when the transmembrane pressure was 18 KPa. The effect of pore modification became pronounced as both the transmembrane pressure and the temperature were increased. The novel feature of the present membrane lay in the formation of thin intermediate layer of palladium inside of the support which was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

This paper considers the effects of compatibilization with maleic anhydride grafted polypropylene (PP-g-MAH) on the properties of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes ; single-step blending, two-step blending with reactive premixing, and two-step blending with nonreactive premixing, to determine the effective mixing process for fine morphological structure, thermal stability, and mechanical properties. Dynamic melt rheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addition, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilization. The results show that compatibilized blends prepared by the single-step process exhibit improved phase morphology, thermal stability, and mechanical properties for dried conditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two-step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moisture absorption.

This paper considers the effect of insoluble surfactant on the shape deformation and stability of a droplet immersed in an immiscible viscous fluid under the action of an applied electric field when the convection and surface diffusion of surfactant are balanced at the drop interface. First, we utilize a purely analytical method of domain perturbations to linearize the nonlinear free boundary problem and obtain the steady-state drop shape in the electric field. Then, the linear stability analysis predicts a critical electric Weber number, which is a limit point for the existence of the steady-state shape. When the Weber number exceeds the critical value, the drop experiences time-dependent shape deformation and eventually breaks up. In addition, the morphology evolution of an immiscible blend of polystyrene and poly(vinylidene fluoride) in a DC electric field is investigated experimentally. The effect of a compatibilizer, which acts as a surface-active agent, is also examined by adding the block copolymer of polystyrene and poly(methyl methacrylate). In the limit of a weak electric field, the degree of the shape deformation is in proportion to the Weber number as predicted from the theory. The experimental results are also consistent with the theoretical predictions in that the drop breaks up at a lower value of Weber number in the presence of the compatibilizer than the drop with a clean and completely mobile interface.

In this paper Brownian diffusion of spherical particles near a deformable fluid interface was examined by considering interface deformations that were caused by impulsive motions of the Brownian particles. First, the velocity fields were constructed in terms of eigenfunctions on the bipolar coordinate system which facilitated the separation of variables. Then, the rate of interface deformation was determined to calculate the force acting on a Brownian sphere due to the interface relaxation back toward a flat configuration. In addition, the covariance function of velocity correlation was determined by solving the Langevin equation which included the effects of the interface relaxation. Finally, the diffusion coefficient of spherical particles was evaluated by utilizing the Einstein-Smoluchowski relation in conjunction with the particle mobility calculated in the presence of a deforming interface.

The precipitation phase boundary of trisodium salt of 2-(2-carboxyethyl)-3-decyl maleic anhydride (DCMA-3Na) was determined with various metal ions, such as Ca +2 , Mg +2 , Zn +2 , Cu +2 , and Al +3 . The tricarboxylic-acid-type biosurfactant DCMA-3Na was synthesized from spiculisporic acid. Solid precipitates were analyzed by FT-IR and an optical microscope. The precipitation boundary diagrams were prepared through both the measurement of the supernatant solution concentration and the visual inspection of precipitate formation. The multivalent ion concentration necessary to cause the precipitation of the surfactant (i.e., tolerance) decreased as the DCMA-3Na concentration increased, up to a certain critical concentration in the same way as with chemically synthesized commercial surfactants such as SDS. However, unlike the commercial surfactants, the tolerance of DCMA-3Na toward hardness ions did not increase when the concentration of surfactant increased further above the critical point. This interesting phenomenon is due to the fact that excess amounts of sodium ions dissociated from the three carboxylate groups in the head group of DCMA-3Na compete with the multivalent ions over binding onto the micelle surface.

The motion of a Brownian particle in the presence of a deformable interface is studied by considering the random distortions of interface shape due to spontaneous thermal impulses from the surrounding fluid. The fluctuation-dissipation theorem is derived for the spontaneous fluctuations of interface shape using the method of normal modes in conjunction with a Langevin type equation of motion for a Brownian particle, in which the fluctuating force arises from the continuum motions induced near the particle by the fluctuation of interface shape. The analysis results in the prediction of autocorrelation functions for the location of the dividing surface, for the random force acting on the particle, and for the particle velocity. The particle velocity correlation, in turn, yields the effective diffusion coefficient due to random fluctuations of the interface shape.

This paper considers capture of small particles on the surface of a much larger bubble by Brownian diffusion and interception induced by flow. The bubble is assumed to rise under the action of gravity, and the terminal rising velocity is determined for the bubble size typical of bubble flotation processes. The mechanism of particle transport to the surface of bubble is controlled by the ratio of particle (a) to bubble radius (A). The dominant transport mechanism changes from diffusion to interception as the size ratio δ(≡a/A) increases above a certain critical value. Although the Marangoni effect caused by the adsorbed particles reduces the collection efficiency, the general features of transport mechanism are preserved when the tangential velocity is nonzero on the bubble surface. Specifically, the analysis shows that for a bubble collector with slip boundary the critical value follows δcr ∝ A-4/3, in contrast to the result δcr ∝ A-1 for a no-slip collector. In the diffusion-control region, the collection efficiency of a collector with slip boundary decreases with increasing collector radius as A-3/2, which is much slower than A-2 for the case of a no-slip collector. On the other hand, in the interception-control region, the collection efficiency increases in proportion to the size ratio δ. In this limit, the efficiency of a collector with slip boundary is very large compared to the result for the case of a no-slip collector where the efficiency is only O (δ2).

An analytical separation of submicron colloidal polystyrene latex particles of different sizes has been carried out by capillary hydrodynamic fractionation. We examined various factors which affect separation of the colloidal particles such as the ratio of particle to tube diameter, the average eluant velocity, like ionic strength, and the surfactant concentration. In particular, the electrokinetic interaction between the capillary wall and the particle was studied intensively by measuring the ζ-potentials of the capillary wall and the colloidal particles using capillary electrophoresis. The results showed that the increase in the eluant ionic strength, especially of positive ions, reduced the velocity enhancement factor by the screening effect of positive ions. In addition, we confirmed that sodium dodecyl sulphate molecules, which dissociate in aqueous medium into positive sodium ions and hydrocarbon chains with negative charges, modify the electrokinetic properties of the particles in different way from the case for the capillary wall. For the particles, adsorption of the hydrocarbon chains with negative charges changes the ζ-potential. On the other hand, the screening effect by the dissociated sodium ions is dominant on the electrokinetic properties of the capillary wall.

This paper is concerned with the small-amplitude oscillations of a bubble composed of an ideal gas in response to anabrupt change in the ambient pressure field. Specifically, we consider the bubble response to a pressure pulse and a pressure step in an otherwise quiescent fluid. The method of analysis employed in the present study is a standard two-timing expansion to eliminate a secular behavior encountered in the asymptotic expansion. In the impulse response the secularity is self-induced due solely to the nonlinearity of the problem whereas the secularity in the step response arises from the change in the equilibrium bubble volume caused by the ambient pressure change. The two-timing solution for each response shows that the secularity modifies the natural frequency of the radial oscillation. Further, the critical intensity of either the pressure pulse or the pressure step for existence of the steady-state bubble radius is determined from the frequency modulated solution and the stability of the bubble response is also discussed in terms of the bubble compressibility and heat transfer across the interface.

A novel method was developed for the assembly of patterned binary and ternary particle arrays and their inverted pore structures onto V-shaped microchannels that were fabricated by soft lithography. For the ternary particle arrays and their inverted pore structures, a dip-coating of binary particle mixture with a controlled size ratio and subsequent O2 RIE were used.

We describe high-throughput optofluidic platforms for mosaic-patterned microfibers by generating stratified laminar flows. An inert carrier liquid flow near PDMS channel walls conveyed a photopolymerizable liquid which permitted stable production of microfibers with particular morphologies and compositional patterns. Finally, mosaicked microfibers were prepared with desired configurations toward multiplex biomolecular analysis.

Submicron emulsions could be produced via the tip-streaming process in a flow-focusing microfluidic device. In this article, the stability of the liquid cone and thread for tip-streaming mode could be significantly improved by employing a three-dimensional flow-focusing device, in which the hydraulic resistance was adjusted by modulating the channel heights in the flow focusing area, orifice, downstream and dispersed phase inlet channel. The pressure range for tip-streaming mode was enlarged significantly compared with two-dimensional flow-focusing devices. Therefore, monodisperse emulsions were produced under this tip-streaming mode for as long as 48 hours. Furthermore, we could control the size of emulsion drops by changing the pressure ratio in three-dimensional flow-focusing devices while the liquid cone was easily retracted during the adjustment of pressure ratio in two-dimensional flow-focusing devices. Furthermore, using the uniform submicron emulsion droplets as confining templates, polyethylene glycol (PEG) particles were produced with a narrow size distribution at the sub-micrometre scale. In addition, magnetic nanoparticles were added to the emulsion for magnetic PEG particles, which can respond to magnetic field and would be biocompatible.

Palladium (Pd) impregnated alumina membrane is prepared by sol-gel technique for hydrogen separation. Direct impregnation of Pd is achieved by mixing the alumina sol with a Pd precursor, followed by sonication to disperse Pd particles uniformly throughout the membrane. Hydrogen selective γ-alumina membrane containing Pd particles is formed as an intermediate layer in an asymmetric porous support. The average pore radius and surface area measured by BET are 20.8 A and 217.4 m 2 gg , respectively. The dispersion of Pd in the membrane is 0.31 and the particle size is 32 A, both determined from H 2 chemisorption experiment. Permeation fluxes through the membrane are also measured for various gases. The results show that impregnation of small amount of Pd can enhance the selectivities of hydrogen relative to both nitrogen and carbon dioxide up to 9.86 and 8.11, respectively, due to the surface diffusion of adsorbed hydrogen. The separation efficiency for hydrogen becomes much better at the lower bulk pressure. However, the hydrogen selectivity is not a monotonic function of temperature and there exists an optimum temperature which is dependent upon the adsorption kinetics of gas molecules.

Micellar-enhanced ultrafiltration has been carried out to investigate the separation of phenol from an aqueous stream via hollow fiber membranes. First, phenol is solubilized into the micelles of cationic surfactant such as hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium chloride (CPC), and then the micellar solution is treated continuously through an ultrafiltration membrane module. In the present study we examine the effects of retentate concentration, molecular weight cut-offs, molar ratios of surfactant to phenol and other operating conditions on the rejection efficiency. The results show that the concentration of phenol in the permeate rapidly decreases as the surfactant aggregates to form micelles beyond its critical micelle concentration. Further, the rejection of phenol and surfactant by the membrane is enhanced when the operating condition is favorable to formation of a gel layer at the surface of the membrane which provides the presieving effect. Formation of a gel layer becomes pronounced when either the flux ratio of permeate to retentate or the micelle concentration in the feed increases.

One-dimensional smart probes based on nanowires and nanotubes that can safely penetrate the plasma membrane and enter biological cells are potentially useful in high-resolution and high-throughput gene and drug delivery, biosensing and single-cell electrophysiology. However, using such probes for optical communication across the cellular membrane at the subwavelength level remains limited. Here, we show that a nanowire waveguide attached to the tapered tip of an optical fibre can guide visible light into intracellular compartments of a living mammalian cell, and can also detect optical signals from subcellular regions with high spatial resolution. Furthermore, we show that through light-activated mechanisms the endoscope can deliver payloads into cells with spatial and temporal specificity. Moreover, insertion of the endoscope into cells and illumination of the guided laser did not induce any significant toxicity in the cells.

Copper(I) oxide (Cu₂O) inverse woodpile structures with a complete photonic bandgap (PBG) at 765 nm are created by using single prism holographic litho­graphy (HL) to form a polymeric template, followed by Cu₂O electrodeposition and template removal. This is the first realization of an inverse woodpile structure exhibiting a complete PBG at or near the visible wavelengths.

This paper considers the entropic and colloidal interactions between rodlike polymers and a nearby boundary in a narrow channel of confined space. A theoretical model has been developed to predict both the concentration depletion profile and the chain configuration of thin rod polymers relative to the boundary. This model is shown to accurately predict the concentration profile of rodlike polymers in a confined space without any adjustable parameters. As the ionic strength is decreased, the predicted concentration profile shifts toward the center region due to the increase in repulsive colloidal force, so that the mean depleted layer becomes enlarged. For illustration, capillary hydrodynamic fractionations of anionic xanthan polyelectrolyte with eluants of various ionic strengths were also carried out experimentally. The ionic strength affects the conformational properties of xanthan molecules, which modifies the electrostatic interaction potential. When the eluant velocity is sufficiently low, the velocity enhancement factor χ (i.e., the ratio of average polymer velocity to eluant velocity) decreases as the ionic strength of the eluant is increased, which is in good agreement with the predicted results. For a higher eluant velocity, on the other hand, the theoretical prediction loses its accuracy due to the hydrodynamic force effect on xanthan motion, which will be examined in the forthcoming study.

In this paper, we demonstrated a microfluidic system for fabricating microspheres with hierarchical surface nanopatterns for molecular detection based on surface-enhanced Raman scattering (SERS). Briefly, a photocurable silica suspension was emulsified into monodisperse droplets using a microfluidic device composed of two coaxial glass capillaries. The silica particles in each droplet protruded through the interface and spontaneously formed a hexagonal array. After polymerization of the droplets, we selectively decorated the exposed areas of the silica particles with silver nanoparticles through electroless deposition. The resulting hierarchically-structured microspheres showed high sensitivity and fast binding kinetics in molecular detection based on SERS, owing to the dense array of hot spots on each microsphere and high mobility of the microspheres, respectively. Notably, the SERS signals from molecules adsorbed on the microspheres could be detected in both the dried and suspension states. In addition, we demonstrated that the SERS-active microspheres can be functionalized into structural colored or magnetoresponsive microspheres for advanced applications.

The photonic band gap of colloidal crystal films made of polystyrene nanospheres was controlled by dry etching technology using hyperthermal neutral beam. Vertical deposition technique was applied to prepare colloidal crystal films with face centered cubic lattice structure using aqueous suspension of monodispersed polystyrene particles. The pseudogap of these colloidal photonic crystals was tuned by etching the films with neutral beam, which reduces the size of the constituent polystyrene particles. Isotropic reduction of the particles in collodial crystal films resulted in the blue shift of stop band of the photonic band gap materials. By changing the etching time, the reflected colors of the dry-etched colloidal crystals were successfully controlled.

Colloidal dispersion of bimodal particles were self-organized inside water-in-oil emulsion droplets by evaporationdriven self-assembly method. After droplet shrinkage by heating the complex fluid system, small numbers of microspheres were packed into minimal second moment clusters, which are partially coated with silica nanospheres, resulting in the generation of patchy particles. The patchy particles in this study possess potential applications for selfassembly of non-isotropic particles such as dimmers or tetramers for colloidal photonic crystals with diamond lattice structures. The composite micro-clusters of amidine polystyrene microspheres and titania nanoparticles were also generated by evaporation-driven self-assembly to fabricate nonspherical hollow micro-particles made of titania shell.

Stable dispersion of colloidal indium tin oxide nanoparticles was prepared by using indium tin oxide nanopowder, organic solvent, and suitable dispersants through attrition process. Various comminution parameters during the attrition step were studied to optimize the process for the stable dispersion of indium tin oxide sol. The transparent and conductive films were fabricated on glass substrate using the indium tin oxide sol by spin coating process. To obtain antireflective function, partially hydrolyzed alkyl silicate was deposited as over-coat layer on the pre-fabricated indium tin oxide film by spin coating technique. This double-layered structure of the nanostructured film was characterized by measuring the surface resistance and reflectance spectrum in the visible wavelength region. The final film structure was enough to satisfy the TCO regulations for EMI shielding purposes.

We present the fabrication method for the nonspherical or macroporous particles such as binary colloidal aggregates or shape-anisotropic particles from water-in-oil emulsions as confining geometries for the self-organization. Here, the water droplets contained various combinations of two different colloids: monodisperse silica or polystyrene microspheres for larger particles and silica or titania nanoparticles for smaller particles. For each combination, the configurations of the large microspheres were not changed by the presence of the small particles though the arrangement of the smaller particles was strongly dependent on the nature of the electrostatic interparticle interactions between small and large particles inside the water droplets. The experimentally observed structural evolutions were consistent with the predicted morphologies calculated using Surface Evolver simulation tool. The nonspherical macroporous particles were also successfully prepared by self-organizing amidine-coated latex microspheres and smaller inorganic nanoparticles, followed by the subsequent calcinations for burning out the organic microspheres.

We present a facile and robust means of fabricating metallic nanodot arrays for localized surface plasmon resonance (LSPR) biosensors through the strategic coupling of a polymeric template prepared with rigiflex lithography and a subsequent metallization via electrodeposition. Rigiflex lithography provides the capability to realize large-scale nanosized features as well as process flexibility during contact molding. In addition, the electrodeposition process enables wet-based nanoscale metallization with high pattern fidelity and geometric controllability. Generated metallic nanodot arrays can be used as a general platform for LSPR biosensors via the sequential binding of chemicals and biomolecules. Extinction spectra of the corresponding LSPR signal are measured with UV-vis-NIR spectroscopy, from which the pattern size and shape dependence of LSPR are readily confirmed. The feasibility of a very sensitive biosensor is demonstrated by the targeted binding of human immunoglobulin G, yielding subnanomolar detection capability with high selectivity.

In this Letter, we present a simple and reproducible method for generating polystyrene (PS) nanoneedle arrays by utilizing the trapping of inorganic silica particles at the polystyrene/air interface via capillary wetting of a thermoplastic polystyrene polymer and SF(6) reactive-ion etching. A monolayer of silica microspheres was directly formed and trapped on the smooth PS film, and subsequent wet etching with HF and reactive-ion etching with SF(6) left behind hexagonal arrays of protruding tips with tip diameters around 20 nm. The patterned PS surface possessed a well-defined nanoneedle array with the pattern density as high as 2.5 x 10(8)/cm(2) and exhibited advancing and receding water contact angles of 180 degrees. The surface showed no affinity for water as confirmed by a series of contact, compression, and release tests. Finally, the perfect hydrophobicity of the fabricated surface is explained in terms of its surface morphology and chemical composition.

The present paper is concerned with the motion of fluid layer between two parallel concentric circular plates, when the inertia of fluid is not negligible. We consider the two specific problems to examine the inertia effects; one in which an incompressible Newtonian fluid is injected into the gap through the hole located at the center of each plate and the other in which two parallel plates rotate coaxially with arbitrary angular velocities. The method of solution is an asymptotic expansion which is usually employed for the thin-film lubrication problem in the limit of small but finite Reynolds number based on the gap height. The asymptotic solutions for the two problems considered here provide the inertia-induced secondary flow patterns, which in turn determine the inertia contributions to the flow parameters such as the pressure drop, injection flow rate, and torque required to sustain the rotation of each plate.

A new promising strategy is reported for the fabrication of ferromagnetic nanoring arrays with novel geometrical features through the use of capillary force lithography and subsequent reactive ion etching. In particular, we fabricated two different types of elliptic rings with variable width and height: one with pinching zones near the major axes and the other with pinching zones near the minor axes. We used PDMS stamps with either elliptic hole or antihole arrays for creating these elliptic rings with variable thickness by virtue of the uneven capillary rise, which was induced by the distributed Laplace pressure around the walls of elliptic holes or antiholes with nonuniform local curvatures. We transferred the polymer ring patterns to array of elliptical NiFe rings by Ar ion milling and characterized magnetic properties in terms of nonuniform ring width using magnetic force microscopy measurements. Our results demonstrated that the magnetic domain wall can be positioned in a controlled manner by using these novel elliptical ferromagnetic rings with local pinching zones and that the proposed CFL method can be utilized as a simple and effective fabrication tool.

We use digital holographic microscopy and Mie scattering theory to simultaneously characterize and track individual colloidal particles. Each holographic snapshot provides enough information to measure a colloidal sphere's radius and refractive index to within 1%, and simultaneously to measure its three-dimensional position with nanometer in-plane precision and 10 nanometer axial resolution., Comment: 6 pages, 3 figures

We demonstrate the construction of diamond photonic crystal structures by the translation of a multi-beam interference pattern. Using phase shift of each beam, the double-exposed interference patterns can be aligned in the [111] direction for a face-centered cubic (FCC) and [210] direction for a body-centered cubic (BCC), respectively, producing diamond D from FCC and BCC-diamond like structure from BCC. The present result shows that the complete bandgap has been retained with slight deviation from ideal diamond symmetry.

In this study, we used localized surface plasmon resonances (LSPR) to observe a phenomenon of binding of DNA on Au and Au/Ag nanostructure arrays. Au and Au/Ag nanostructures of various geometric sizes and metal compositions were fabricated by colloidal lithography technique. The immobilization of capture DNA and subsequent hybridization with target DNA on the nanostructures caused the shift of maximum peak in LSPR spectra of the nanostructures. Using the peak shift, the immobilization of capture DNA was clearly verified in a nondestructive manner and hybridization with complementary target DNA was reliably differentiated from the non-specific binding with noncomplementary DNA. This work firmly implies that the LSPR spectra of the nanostructrues can be efficiently utilized to achieve a novel strategy for the detection of DNA on the nanostructures.

Two types of non-close-packed colloidal crystal films were prepared by etching the films made of polystyrene nanospheres using a hyperthermal neutral beam of oxygen gas. Etching without sintering above glass transition temperature of the polymer particles resulted in the non-close-packed structure of the nanospheres, in which polystyrene nanospheres in different lattice planes touched each other due to the reduction in the size of the nanospheres that occurred during the etching process. In contrast, a different non-close-packed structure with inter-connecting networks between etched nanospheres was generated by annealing of the colloidal crystal and a subsequent etching process. The photonic bandgap could be tuned during this dry etching of colloidal photonic crystals. This connected open structure could be used as a template for a silica inverse opal by chemical vapor deposition. An alternative dry etching process, reactive ion etching, mainly affected the morphology of particles near the top surface, and only a slight change in the stop band position of the colloidal crystal film was observed.

Despite of wide range of potential applications, 3D functional microparticles with nanostructures cannot be prepared readily by conventional synthetic schemes. Here, we will consider two different routes for the microparticles: namely, self-organization of photo-responsive complex colloids inside microfluidic devices and holographic lithography directly on pre-patterned microfluidic channels. The fabricated microparticles based on optofluidic scheme show desired chemical and physical properties which have practical importance in nano- and bio-photonics.

We have demonstrated fluorescent liquid-core/air-cladding (LA) waveguides suitable for use as integrated optofluidic light sources. These waveguides were fabricated by conventional soft lithography using poly(dimethylsiloxane) (PDMS). Two-phase stratified flows of air and ethylene glycol with fluorescent dye were generated along the PDMS channel. Compared to the liquid-core/liquid-cladding (L(2)) waveguide, the larger refractive index contrast of the LA waveguide resulted in stronger optical confinement. Specifically, the larger refractive index contrast led to experimentally achievable captured fractions (the amount of light to be coupled into the liquid core) as high as 22.8% and the measured propagation losses as low as 0.14 dB cm(-1). Furthermore, in our LA waveguides, diffusional mixing of the core and cladding fluids did not occur and the size of the core stream could be reversibly tuned simply by adjusting the flow rates of the two contiguous phases.

We report localized surface plasmon resonance (LSPR) of hexagonal Au nanodot arrays to detect changes in the thickness and conformation of poly[2-(methacryloyloxy)ethyltrimethyl ammonium chloride] (PMETAC) brushes.

Holographic lithography provides a highly compatible and facile way to fabricate multi-dimensional periodic nanostructures. Periodic nanostructures have useful applications not only as biological substrates or catalytic supports but also as nanophotonic devices with various photonic properties such as photonic band-gap (PBG), localized surface plasmon resonance (LSPR) or surface enhanced Raman scattering (SERS). In combination with single refracting prism holographic lithography and conventional photolithography, we could achieve the micrometer-scale patterns of periodic nanostructures which can be integrated in microfluidic chip. With the help of conventional MEMS technologies, Arrays of pyramid shape and top-cut pyramid shape microprism can be prepared. Single laser exposure step through the microprism arrays (MPAs) can be generate multiscale patterns of 2D and 3D nanostructures. As prepared nanostructures combined with microfluidic chip is a highly efficient optofluidic platform which is applicable to the chemical and biosensors.

A novel method to fabrication of well-aligned SWNT arrays on SAM-modified ITO glass substrates, using a well dispersed ef-SWNT solution, a supporting frame consisting of a monolayer of monodisperse silica beads, and the appropriate electric fields, has been developed. The use of the colloidal monolayer as a supporting frame enables the vertical alignment of the SWNTs on the ITO substrate. This method has the following advantages over the previously reported ones: low CNT consumption, mild temperature conditions, and large area deposition.

Analytical results are presented for the motion of a viscous Newtonian fluid drop in the presence of a plane, deformable, interface in the velocity range for which inertial effects may be neglected. The zeroth-order approximation for a spherical drop near a flat interface is expressed in terms of fundamental singularity solutions for Stokes flow, and used to evaluate the drag on the fluid drop in translation either perpendicular or parallel to the interface. The present approximate results for drag are in good agreement with exact-solution results where available. The first corrections for the shapes of the plane interface and the drop are then determined by reformulating the small deformation problem in terms of equivalent boundary conditions on a flat interface and a spherical drop surface. We consider the influence of the viscosity ratios, density differences and interfacial tensions (or Bond number and capillary numbers) and the drop position relative to the interface, in determining the degree of distortion of the plane interface and the fluid drop surface, and the hydrodynamic drag force on the drop. Among the most interesting results is the prediction of lateral migration induced by the drop and the interface deformations.

Experiments show that bubbles covered with monodisperse polystyrene particles, with particle to bubble radius ratios of about 0.1, evolve to form faceted polyhedral shapes that are stable to dissolution in air-saturated water. We perform Surface Evolver simulations and find that the faceted particle-covered bubble represents a local minimum of energy. At the faceted state, the Laplace overpressure vanishes, which together with the positive slope of the bubble pressure-volume curve, ensures phase stability. The repulsive interactions between the particles cause a reduction of the curvature of the gas-liquid interface, which is the mechanism that arrests dissolution and stabilizes the bubbles.

In this Article, we report on a packing scheme of monodisperse colloidal nanospheres by aerosol-assisted clustering. When an aqueous suspension of colloidal nanospheres was sprayed into aerosol droplets by an ultrasonic nebulizer, the nanospheres were encapsulated in the aerosol droplets and the evaporation of water from the droplets at high temperatures led to the packings of nanospheres. The configurations of the colloidal nanospheres minimized the interparticle potential energy or the second moment of mass distribution depending on the number of the constituting nanospheres. Other types of nonspherical microparticles or hollow microclusters were also produced by self-organizing organic-inorganic binary colloids of different sizes in an aerosol spray pyrolysis reactor. The aerosol-assisted fabrication of colloidal clusters was very effective as compared to the method based on oil-in-water or water-in-oil emulsions, in which the removal of residual oil was not easy and time-consuming.

We propose and demonstrate a new type of a photonic crystal nanolaser integrated into a microfluidic chip, which is fabricated by multilayer soft lithography. Experimentally, continuous-wave operation of the lasing action has been observed owing to efficient water-cooling. Characteristics of wavelength tuning by the fluid are investigated using both theory and experiment. In addition, we propose that dynamic modulation of far-field radiation pattern can be achieved by introducing a bottom reflector and by flowing the fluid on it. Especially, by choosing effective one-wavelength distance between the reflector and the cavity, efficient unidirectional emission can be obtained.

Holographic lithography is one of the promising techniques that can create three-dimensional (3D) periodic nanostructures without extensive lithography and etching steps. This proceeding discusses novel hybrid lithographic methods based on the holographic lithography in conjunction with photolithography to generate hierarchically-patterned structures. Using various types of photoresists including positive, negative and hydrogel, we fabricated 3D nanopatterns by holographic lithography. Then, two-dimensional (2D) photolithography was combined to pattern the 3D structures. Eventually, we created a microfluidic channel with 3D periodic patterns. Since the 3D structure possess photonic bandgap properties as well as interconnected pore networks, this kind of microfluidic channel can be applied to optical sensors, mixers and filters.

In this paper, we report the preparation of binary clusters of colloidal particles with different sizes or species into complex structures using oil-in-water emulsion droplets as confining geometries. First, polystyrene or silica particles with bimodal size distribution were packed densely by evaporation-induced self-assembly inside oil-in-water emulsion droplets. The configurations of larger particles inside the droplets minimize the second moment of the particle locations for the ratio of large to small particle sizes less than 3. Also, the configurations of bimodal clusters were predicted by using a surface evolver simulation, and the simulation predictions were compared with the experimental results. In addition, heterogeneous colloidal clusters were produced by emulsifying the binary mixture suspension of polystyrene and silica particles in aqueous medium followed by evaporating the oil phase. A density gradient centrifugation was applied to fractionate the asymmetric binary dimers comprised of PS and silica microspheres.

Microstructured titanium glycolates such as spheres and rods have been prepared from the mixture of titanium butoxide and ethylene glycol. The synthesized titanium complexes were transformed into high refractive index titania. The obtained titania structures are of practical importance for optical applications in light scattering and stimulated emission.