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Photoplethysmography (PPG) has become ubiquitous with the development of smart watches and the mobile healthcare market. However, PPG is vulnerable to various types of noises that are ever present in uncontrolled environments, and the key to obtaining meaningful signals depends on successful denoising of PPG. In this context, algorithms have been developed to denoise PPG, but many were validated in controlled settings or are reliant on multiple steps that must all work correctly. This paper proposes a novel PPG denoising algorithm based on bidirectional recurrent denoising auto-encoder (BRDAE) that requires minimal pre-processing steps and have the benefit of waveform feature accentuation beyond simple denoising. The BRDAE was trained and validated on a dataset with artificially augmented noise, and was tested on a large open database of PPG signals collected from patients enrolled in intensive care units as well as from PPG data collected intermittently during the daily routine of nine subjects over 24 h. Denoising with the trained BRDAE improved signal-to-noise ratio of the noise-augmented data by 7.9 dB during validation. In the test datasets, the denoised PPG showed statistically significant improvement in heart rate detection as compared with the original PPG in terms of correlation to reference and root-mean-squared error. These results indicate that the proposed method is an effective solution for denoising the PPG signal, and promises values beyond traditional denoising by providing PPG feature accentuation for pulse waveform analysis.

Monodispersed thermally stable aqueous emulsions were generated in perfluorocarbon oil with penta-block copolymers of fluorocarbon and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide), which are controlled in guided channels of microfluidic devices, which were essentially the protrusion on top of microfluidic channels. Aqueous emulsions could stably follow the guide channels and sequentially stored at dead ends of guide channels. Depending on the size ratio of emulsion to trapping region, one or two emulsions were stored in two-dimensional arrays on demand. By adding pneumatic valve actuators on top of guide channel, they could be stored or released on demand or as programmed. Furthermore, by encapsulating colloidal particles and Hela cells in the thermally stable water-in-perfluorocarbon emulsions, we demonstrated that particle-laden and cellladen emulsions could be manipulated in controlled and programmed manner.

We report a novel method to create 2D hierarchical nanopatterns with high structural complexity using phase-shift lithography. With phase masks with large lattice periodicities relative to the wavelength of the light source, several different diffraction beams are generated from a single grating, which then interfere to form a highly complex 3D intensity profile at the Fresnel region. We transfer the horizontal slice of the intensity profile into the thin film of negative photoresist, making 2D nanostructures. Because the diffraction order determines a length scale of intensity variation in a horizontal surface, interference of several different diffraction orders leads to the formation of complex and hierarchical nanopatterns, which are difficult to create with conventional phase-shift lithography. In addition, as the 2D profile is modulated along the light propagation direction, a variety of complex nanopatterns can be fabricated from a single phase mask by adjusting the distance between the diffraction grating and photoresist film. A full 3D intensity profile formed by interference is calculated using the finite-difference time domain (FDTD) method, which enables us to anticipate the shape and morphology of the resulting 2D nanostructures.

Background Non-invasive continuous blood pressure monitors are of great interest to the medical community due to their value in hypertension management. Recently, studies have shown the potential of pulse pressure as a therapeutic target for hypertension, but not enough attention has been given to non-invasive continuous monitoring of pulse pressure. Although accurate pulse pressure estimation can be of direct value to hypertension management and indirectly to the estimation of systolic blood pressure, as it is the sum of pulse pressure and diastolic blood pressure, only a few inadequate methods of pulse pressure estimation have been proposed. Methods We present a novel, non-invasive blood pressure and pulse pressure estimation method based on pulse transit time and pre-ejection period. Pre-ejection period and pulse transit time were measured non-invasively using electrocardiogram, seismocardiogram, and photoplethysmogram measured from the torso. The proposed method used the 2-element Windkessel model to model pulse pressure with the ratio of stroke volume, approximated by pre-ejection period, and arterial compliance, estimated by pulse transit time. Diastolic blood pressure was estimated using pulse transit time, and systolic blood pressure was estimated as the sum of the two estimates. The estimation method was verified in 11 subjects in two separate conditions with induced cardiovascular response and the results were compared against a reference measurement and values obtained from a previously proposed method. Results The proposed method yielded high agreement with the reference (pulse pressure correlation with reference R ≥ 0.927, diastolic blood pressure correlation with reference R ≥ 0.854, systolic blood pressure correlation with reference R ≥ 0.914) and high estimation accuracy in pulse pressure (mean root-mean-squared error ≤ 3.46 mmHg) and blood pressure (mean root-mean-squared error ≤ 6.31 mmHg for diastolic blood pressure and ≤ 8.41 mmHg for systolic blood pressure) over a wide range of hemodynamic changes. Conclusion The proposed pulse pressure estimation method provides accurate estimates in situations with and without significant changes in stroke volume. The proposed method improves upon the currently available systolic blood pressure estimation methods by providing accurate pulse pressure estimates.

We report a new class of bio-inspired nanotadpoles (NTPs) with component-specific functionalities. The plasmonic NTPs with a gold-coated head and a reactive ion etching-treated tail showed the tail length dependence of their cellular uptake, enabling the photothermal treatment of cancer cells with high efficacy.

A microfluidic approach to prepare photonic microparticles by repeated molding of photocurable colloidal suspension is reported. An elastomeric membrane with negative relieves which vertically separates two microfluidic channels is integrated; bottom channel is used for suspension flow, whereas water-filled top channel is used for pneumatic actuation of the membrane. Upon pressurization of the top channel, membrane is deformed to confine the suspension into its negative relieves, which is then polymerized by UV irradiation, making microparticles with mold shape. The microparticles are released from the mold by relieving the pneumatic pressure and flows through the bottom channel. This one cycle of molding, polymerization, and release can be repeatedly performed in microfluidic device of which pneumatic valves are actuated in a programmed manner. The microparticles exhibit structural colors when the suspension contains high concentration of silica nanoparticles; the nanoparticles form regular arrays and the microparticles reflect specific wavelength of light as a photonic crystals. The silica nanoparticles can be selectively removed to make pronounced structural colors. In addition, the microparticles can be further functionalized by embedding magnetic particles in the matrix of the microparticles, enabling the remote control of rotational motion of microparticles.

Photonic microdisks with a multilayered structure are designed from photocurable suspensions by step-by-step photolithography. In each step of photolithography, either a colloidal photonic crystal or a magnetic-particle-laden layer is stacked over the windows of a photomask. Sequential photolithography enables the creation of multilayered photonic microdisks that have brilliant structural colors that can be switched by an external magnetic field.

Pixelated inverse opals with red, green, and blue colors were prepared by hybridizing convective assembly of colloidal particles and photolithography techniques. The brilliant structural colors, high mechanical stability, and small feature size of the pixels were simultaneously accomplished, thereby providing color reflectors potentially useful for display devices. Moreover, this hybridized method provides a general means to create multi-colored photonic crystals.

We report the use of a simple microfluidic device for producing microcapsules with reversible membrane permeability that can be remotely controlled by application of near-infrared (NIR) light. Water-in-oil-in-water (W/O/W) double-emulsion drops were prepared to serve as templates for the production of mechanically stable microcapsules with a core-shell structure and highly uniform size distribution. A biocompatible ethyl cellulose shell was formed, containing densely packed thermoresponsive poly(N-isopropylacrylamide) (pNIPAAm) particles in which gold nanorods were embedded. Irradiation with a NIR laser resulted in heating of the hydrogel particles due to the photothermal effect of the gold nanorods, which absorb at that wavelength. This localized heating resulted in shrinkage of the particles and formation of macrogaps between them and the matrix of the membrane. Large encapsulated molecules could then pass through these gaps into the surrounding fluid. As the phase transition behavior of pNIPAAm is highly reversible, this light-triggered permeability could be repeatedly switched on and off by removing the laser irradiation for sufficient time to allow the gold nanorods to cool. This reversible and remote control of permeability enabled the programmed release of encapsulants, with the time and period of the open valve state able to be controlled by adjusting the laser exposure. This system thus has the potential for spatiotemporal release of encapsulated drugs.

Highly uniform 3D ZnO hollow shell structures were prepared by combining prism holographic lithography (PHL) and atomic layer deposition (ALD). As a dense ZnO film was obtained by using the ALD process, no volume shrinkage occurred during the subsequent calcination to remove the sacrificial polymer template. No volume shrinkage during heat treatment is crucial for achieving excellent optical properties and mechanical stability of inverse photonic crystals (PCs).

Self-assembly of monodisperse colloidal particles into regular lattices has provided relatively simple and economical methods to prepare photonic crystals. The photonic stop band of colloidal crystals appears as opalescent structural colors, which are potentially useful for display devices, colorimetric sensors, and optical filters. However, colloidal crystals have low durability, and an undesired scattering of light makes the structures white and translucent. Moreover, micropatterning of colloidal crystals usually requires complex molding procedures, thereby limiting their practical applications. To overcome such shortcomings, we develop a pragmatic and amenable method to prepare colloidal photonic crystals with high optical transparency and physical rigidity using photocurable colloidal suspensions. The colloidal particles dispersed in a photocurable medium crystallized during capillary force-induced infiltration into a slab, and subsequent photopolymerization of the medium permanently solidifies the st...

Surface-enhanced Raman scattering (SERS) has been considered as one of the most promising tools for molecular analysis. To develop practical platforms, a variety of nanoparticles and two-dimensional (2D) nanostructures have been prepared. However, low signal intensity or slow binding kinetics in conventional approaches limits their applications. To overcome these shortcomings, production and usage of three-dimensional (3D) nanostructures remain an important yet unmet need. In this paper, we report novel and effective SERS-active materials by fabricating hierarchically structured SiO2 microcylinders decorated with gold nanoparticles. In order to fully develop 3D nanostructures, while maintaining fast diffusion of analyte molecules, we used self-assembled nanostructures of block-copolymers (BCPs) confined in the microholes of an imprinting mold; the BCPs could provide a template for producing 3D nanostructure composed of nanofibers with sub-100 nm diameter through their microphase separation, whereas the im...

Active tunable plasmonic cap arrays were fabricated on a flexible stretchable substrate using a combination of colloidal lithography, lift-up soft lithography, and subsequent electrostatic assembly of gold nanoparticles. The arrangement of the plasmonic caps could be tuned under external strain to deform the substrate in reversible. Real-time variation in the arrangement could be used to tune the optical properties and the electromagnetic field enhancement, thereby a proving a promising mechanism for optimizing the SERS sensitivity.

We present a simple and reproducible method for the fabrication of three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrates by controlling wettability. A superhydrophilic SU-8 microstructured surface generated using O2 plasma treatment led to the formation of a monolayer of aggregated Ag nanoparticles with nanoscale gaps. The SERS substrate showed a highly sensitive and uniform SERS response.

Microencapsulation and the controlled release of bioactive agents have long been investigated and exploited to both improve the fundamental understanding of cell functionality and to develop efficient delivery vehicles for drugs, nutrients, and cosmetics. Conventional approaches to the synthesis of particles and capsules for practical applications have achieved only limited control over particle size, shape, functionality, and encapsulation efficiency. To overcome such limitations, a variety of approaches have been developed. Recent advances in microfluidics and other techniques have inspired the design of new microcarriers that efficiently encapsulate bioactive agents to enable the on-demand release or functionalization of encapsulants. Here, the current state of the art in the area of elaborate design strategies for microcarriers that enable efficient encapsulation and controlled release for biological applications is described. This is discussed in three sections, which are categorized by microcarrier type: particle-type carriers, capsule-type carriers, and foldable microcarriers. In each section, new routes to fabricating microcarriers are discussed together with their functionalities; techniques based on droplet microfluidics, lithography, micromolding, and imprinting are covered. In addition, the synthetic routes and the microcarriers are evaluated by comparison with alternative routes. Finally, future perspectives for these new strategies are outlined briefly.

Thin-film color reflectors inspired by Morpho butterflies are fabricated. Using a combination of directional deposition, silica microspheres with a wide size distribution, and a PDMS (polydimethylsiloxane) encasing, a large, flexible reflector is created that actually provides better angle-independent color characteristics than Morpho butterflies and which can even be bent and folded freely without losing its Morpho-mimetic photonic properties.

In this study, we have investigated the nanofabrication of asymmetric ferromagnetic ring arrays by capillary force lithography, which incorporates the essential feature of nanoimprint lithography. The capillary lithography technique enables the fabrication of large area magnetic nanostructures and makes it possible to systematically control the shape of magnetic nanostructures. We prepared various ferromagnetic Co ring arrays with various ring widths down to 100 nm. We investigated magnetization reversal of ferromagnetic nanoring arrays using the focused magneto-optical Kerr effects (FMOKE) and micromagnetic simulation. It was found that magnetization reversal could be controlled by varying the width and asymmetry in ferromagnetic nanoring structures.

Recent advances in nanofabrication techniques have enabled the creation of various metallic nanostructures in order to engineer the location and properties of electromagnetic hot spots in a controlled manner. However, most previous methods usually require complicated and time-consuming techniques, and the integration of metallic nanostructures into simple, low-cost devices for chemical or biological sensing is still challenging. Here, we report a promising new strategy for the fabrication of large-area gold nanowell arrays with novel geometric features that makes use of the trapping of self-assembled colloidal particles on a polymer surface. Through both systematic experimental and theoretical analysis, we confirm that the strong plasmon resonances of the proposed nanowell structures are associated with localized surface plasmon resonance (LSPR) on the brims of the nanoholes in the top gold films as well as in the bottom gold disks. In addition, we demonstrate a novel optofluidic platform with built-in subwavelength nanowell arrays that exhibits strong plasmon resonances within microfluidic chips. In our optofluidic systems, the plasmon coupling between the brims and the disks of nanowells makes the plasmon resonance more sensitive to surrounding materials. The dependence of the plasmon resonance on the refractive index of the surrounding medium is found to be as high as 570 nm RIU(-1) (refractive index units). These data lead to a figure of merit (FOM), the slope of refractive index sensitivity in eV RIU(-1)/line width (eV), as high as 4.1.

Based on the statistical annual report, there are 17,649 reservoirs are operating for the purpose of agricultural water supply in Korea. 58 % of entire agricultural reservoirs had been constructed before 1948 which indicate the termination of required service life and rest of those reservoirs have also exposed to the dam break risk by extreme flood event caused by current ongoing climate change. To prevent damages from dam failure accident of these risky small size dams, it is necessary to evaluate and manage the structural and hydrological safety of the reservoirs. In this study, a simplified evaluation method for hydrologic safety of dam is suggested by using Rational and Creager formula. Hydrologic safety of small scale dams has evaluated by calculating flood discharge capacity of the spillway and compares the results with design frequency of each reservoir. Applicability and stability of suggested simplified method have examined and reviewd by comparing the results from rainfall-runoff modeling with dam break simulation using HEC-HMS. Application results of developed methodology for three sample reservoirs show that simplified assessment method tends to calculate greater inflow to the reservoirs then HEC-HMS model which lead lowered hydrologic safety of reservoirs. Based on the results of application, it is expected that the developed methodology can be adapted as useful tool for small scale reservoir`s hydrologic safety evaluation.

Advances in microfluidic emulsification have enabled the creation of multiphase emulsion drops, which have emerged as promising templates for producing functional microcapsules. However, most previous micro-encapsulation methods have limitations in terms of capsule stability, functionality, and simplicity of fabrication procedures. Here, we report a simple single-step encapsulation technique that uses an optofluidic platform to efficiently and precisely encapsulate a specific number of emulsion droplets in photocurable shell droplets. In particular, we show, for the first time, that densely confined core droplets within an oily shell droplet rearrange into a unique configuration that minimizes the interfacial energy, as confirmed here from theory. These structures are then consolidated into multi-cored microcapsules with structural and mechanical stability through in situ photopolymerization of the shell in a continuous mode, which are capable of isolating active materials and releasing them in a controlled manner using well-defined nanohole arrays or nanoscopic silver architectures on thin membranes.

Photonic crystals (PCs) are periodic dielectric structures that have a band-gap that forbids propagation of a certain range of wavelengths of light. This property enables control of light with remarkable facility by modification of the band-gaps and produce effects that are impossible with conventional optics. Using chemically functionalized PCs, where the chemical functional group consists of amine and carboxyl group, in conjunction with a biomolecular probe material, the detection of pathogens and viral disease is possible, indicated by the shift in wavelength signal. Moreover, this system using the bioinspired PCs allows specific target detection in biosensor chip fields through control of the PCs. In this study, we demonstrated that two bacterial pathogens (Fusobacterium necrophorum and Acinetobacter baumannii) causing sepsis were detected by DNA-probe hybridization and a severe acute respiratory syndrome coronavirus was detected by antigen-antibody interaction using the functional PCs. Optical readout with the integrated sensor detecting the signals from PCs, allows for low cost and robust readout of resonance peak shift. This biosensor system using the functional PCs on the photonic crystal-fabricated chip can efficiently and effectively detect various targets, and be easily prepared with high productivity and economic property.

Colloidal self-assembly has been investigated as a promising and practical approach for the fabrication of photonic nanostructures, including colloidal crystals, composite and inverse opals, and photonic glasses. Depending on the interactions between the colloidal particles, colloidal structures can be affected dramatically and modulated by applying an additional external field. Furthermore, in contrast to other approaches, self-assembled nanostructures with large areas or designed shapes can be prepared at low cost. As a result, the use of such colloidal systems has been investigated in many practical photonic applications. In this review article, we describe the colloidal self-assembly of periodic and non-periodic photonic nanostructures in brief and then summarize recent achievements in the field of colloidal photonic nanostructures and their applications, which include displays, optical devices, photochemistry and biological sensors.

We demonstrate a prototypic optofluidic evanescent wave sensor made of poly(dimethylsiloxane) (PDMS) elastomer in which two light sources with different wavelengths are coupled into an optofluidic liquid-core/liquid-cladding (L(2)) waveguide. The exponentially decaying evanescent wave interacts with analyte molecules dissolved in the cladding fluids or products formed by in situ reactions at the core-cladding interface. The analyte molecules exhibit distinctly different light absorbance at the two wavelengths during the light-analyte interaction. Therefore, by using the normalized absorbance calculated from the intensity ratio of the two wavelengths instead of the absolute magnitude of either signal, unwanted effects from omnipresent external noise sources can be reduced. In addition, the differential absorption of the two beams by the analyte solutions can be used to enhance the resolution of sample analysis. The evanescent wave sensor based on a liquid waveguide can also be used for real-time monitoring of chemical reactions, because the core and cladding fluids in the L(2) waveguide are slightly miscible at the core-cladding interface due to the diffusional mixing.

We report a facile method for the electroless deposition (ELD) of gold film via two-dimensional (2-D) dendritic growth. Our scheme employs protonated amine groups, which electrostatically attract both the negatively charged reducing agent and gold-precursor. This electrostatic interaction increases the local concentrations of gold-precursor and reducing agent near the silica surface to levels high enough for gold films with a 2-D fractal morphology to form directly on the surfaces of the amine-functionalized silica nanospheres by diffusion-limited aggregation. Our one-pot reaction avoids the need for seed attachment, which is typically employed for the growth of metallic shells on nanospheres. Therefore, the proposed method significantly reduces the number of processing steps required for the production of core-shell nanospheres. The gold morphologies were systematically investigated in terms of various synthesis variables, including solution pH, reducing agent concentration, and gold precursor injection speed. In addition, we synthesized gold-capped silica nanospheres via ELD of gold on a patterned array of silica nanospheres embedded in polystyrene (PS) film followed by dissolution of the PS matrix, thus demonstrating the potential utility of the proposed method in emerging fields of materials science such as patterning of noble metals and studies of nanometer-scale optics.

Colloidal microcapsules of thin nanoshell membranes were prepared by the evaporation-induced self-assembly of poly(styrene)-block-poly(butadiene)-block-poly(styrene) (SBS) triblock copolymers inside the oil phase of a water-in-oil-in-water (W/O/W) double emulsion, which was prepared via a two-step sequential emulsification process. To see the nanoconfinement effect, the shell thickness was kept very thin and comparable to the feature scale of self-organized nanostructure. By exploiting the density mismatch between the microcapsules and the continuous medium, single-cored microcapsules with thin shells were selectively separated from mixtures of multicored microcapsules or thick-shelled microcapsules. The internal morphology of the membrane could be modulated by controlling the volume fractions of styrene and butadiene blocks, which was achieved simply by adding polystyrene homopolymer of relatively low molecular weight. By varying the amount of homopolymer, various morphologies were produced in the microc...

We demonstrate fluorescent liquid-core/liquid-cladding (L 2) waveguides focused in three-dimensional (3-D) space based on a 3-D hydrodynamic focusing technique. In the proposed system, the core and vertical cladding streams are passed through a curved 90° corner in a microfluidic channel, leading to the formation of a pair of counter rotating vortices known as the Dean vortex. As a result, the core fluid is completely confined within the cladding fluid and does not touch the top and bottom poly(dimethylsiloxane) (PDMS) surfaces of the microfluidic channel. Because the core stream was not in contact with the PDMS channel, whose refractive index contrast and optical smoothness with the core fluid are lower than that between the core and the cladding fluids, the 3-D focused L 2 waveguide exhibited a higher captured fraction (η) and lower propagation loss when compared to conventional two-dimensional (2-D) focused L 2 waveguides. Because the proposed 3-D focused L 2 waveguides can be generated in planar PDMS microfluidic devices, such optofluidic waveguides can be integrated with precise alignment together with other in-plane microfluidic and optical components to achieve micro-total analysis systems (μ-TAS).

We demonstrate the fabrication of inorganic inverse opals of silica and titania by a colloidal templating method. Hetero-colloids of polymeric particles and inorganic nanoparticles are formed and, on subsequent heat treatment, were found to yield inverse opals. The presence of nanoparticles does not interfere with the packing of the polymeric particles. The inverse opals exhibit photonic bandgaps in the wavelength of visible light that can be tuned by changing the size of the polymeric particles and the calcination temperatures.

In this Letter, we present an intriguing method for fabricating polymeric superhydrophobic surfaces by reactive-ion etching of holographically featured three-dimensional structures. Using the proposed strategy, we generated both lotus and gecko surfaces by simply controlling the incident angle of the laser beam during holographic lithography. The adhesion force of the gecko-state superhydrophobic surfaces was the highest yet reported for an artificial superhydrophobic surface. The well-controlled patterns enable an in-depth understanding of superhydrophobic and superadhesive surfaces. In particular, the present observations provide direct evidence of a high adhesive force resulting from surface-localized wetting, which is quite different from previously suggested mechanisms.

This paper demonstrates room temperature chemical vapor deposition (RTCVD) for fabricating titania inverse opals. The colloidal crystals of monodisperse polymer latex spheres were used as a sacrificial template. Titania was deposited into the interstices between the colloidal spheres by altermate exposures to water and titanium tetrachloride (TiCl4) vapors. The deposition was achieved under atmospheric pressure and at room temperature. Titania inverse opals were obtained by burning out the colloidal template at high temperatures. The filling fraction of titania was controlled by the number of deposition of TiCl4 vapor. The morphology of inverse opals of titania were investigated. The optical reflection spectra revealed a photonic band gap and was used to estimate the refractive index of titania.

This work was supported by a grant from the Creative Research Initiative Program of the Ministry of Education, Science and Technology for ‘‘Complementary Hybridization of Optical and Fluidic Devices for Integrated Optofluidic Systems.’’ Supporting Information is available online from Wiley InterScience or from the author.

In this article, we demonstrated low-threshold lasing in three-dimensional (3D) polymeric photonic crystals derived from colloidal suspensions. To achieve this, we used monodisperse silica beads in a photocurable refractive index matched medium with high viscosity and polarity. In this system, the colloidal silica beads rapidly self-organized into nonclose-packed fcc crystals because of strong repulsive interparticle potential relative to diminishing van der Waals attraction, and subsequently the colloid crystals were solidified by UV irradiation. Dye molecules as optical gain medium were incorporated in the polymeric matrix by simply mixing the dye molecules and the photocurable suspension before casting the photonic crystal films. The translucent composite photonic films showed emission inhibition and enhancement due to the low photon density of states (DOS) at the stop band and high DOS at the band edge, respectively. On the other hand, the porous photonic films, which were prepared by removal of silic...

Monodisperse cross-linked polystyrene nanospheres were self-organized to obtain colloidal aggregates from toluene-in-water emulsion droplets employed as confining geometries. During evaporation of toluene droplets by heating, the polystyrene nanospheres were packed into higher-order clusters, supraparticles with intermediate ordering or supraballs with hexagonally ordered structures, depending on the size of the emulsion droplets, and the number of constituent polystyrene particles inside the droplets. The shrinkage of toluene droplets induced inward capillary pressure, leading to particle self-assembly into ordered spherical supraballs when a large number of polystyrene particles were contained inside the droplets. Ink-jet technology was adopted to generate monodisperse toluene droplets containing polystyrene particles, which were transformed into monodisperse supraballs after evaporation-driven self-assembly of the polystyrene nanospheres. As an alternative approach, water-in-toluene droplets were also adopted as confining geometries for the generation of supraballs.

This work was supported a grant from the Creative Research Initiative Program of the Ministry of Science and Technology for ‘‘Complementary Hybridization of Optical and Fluidic Devices for Integrated Optofluidic Systems.’’ The authors also appreciated partial support from the Brain Korea 21 Program. Supporting Information is available online from Wiley InterScience or from the author.

A novel method for fabrication of vertically aligned single-walled carbon nanotubes (SWCNTs) on indium–tin oxide glass substrates modified with self-assembly monolayer has been developed by using a supporting frame composed of a monolayer of monodispersed silica beads and an alternating current electric field. We have found that SWCNTs can be implanted into the interstices of the colloidal superlattices, which function as supporting scaffold to prevent the SWCNTs from falling down and maintain the SWCNTs at low density. As a result, this vertically aligned SWCNT assembly exhibits enhanced field emission.

Nanocrystalline silicon (nc-Si) films were deposited by hot wire chemical vapor deposition with applying positive or negative filament biases. These films were characterized by Raman spectroscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. Plasmon loss of the Si(2p) band region was shifted to higher energy due to dielectric changes with applied filament biases from negative to positive voltage. A semi-quantitative study of the valence band structure was employed to analyze the bias effect of the valance band in nc-Si networks. Nc-Si with a positive filament bias shows better microstructural properties than those with a negative bias and without biasing nc-Si films.

A colloidal dispersion of indium tin oxide (ITO) nanoparticles in an organic solvent was achieved using a milling process in which β-diketones or titanate coupling agents were used as a dispersing agent. Isopropyl tri(N-ethylenediamino)ethyl titanate and 2,4-pentanedione were found to be the most suitable dispersants for stabilizing ITO nanoparticles in a mixed organic solvent. The secondary particle size of the colloidal ITO dispersion was markedly affected by operational parameters in the milling process. Stable dispersions of antimony-doped tin oxide (ATO) nanoparticles in organic solvent, using β-diketones as dispersants, were also prepared. The stable dispersions of ITO and ATO nanoparticles were used as conductive transparent film coatings on cathode-ray tube panels. We found that the electrical conductivity of the film coating was affected by the boiling point of the dispersion stabilizers.