Microfluidic Design of Magnetoresponsive Photonic Microcylinders with Multicompartments

Colloidal photonic structures have been designed to have granular format to use them for paint pigments, encoded carriers, and display pixels. However, conventional approaches only provide spherical or discoid shapes, restricting their applications. Cylindrical granules with fan‐shaped compartments in the cross section are appealing for microcarriers with abundant optical codes and active display pigments for color switching. In this work, a stratified laminar flow of concentrated silica particles is employed, formed in a cylindrical microchannel, to produce cylindrical photonic microparticles with multiple compartments. To accomplish this, a microfluidic device is designed to have one cylindrical main channel connected with four branch channels. Four different photocurable suspensions are independently injected through the branches to form quarter‐cylindrically compartmentalized streams in the main channel. Local ultraviolet irradiation on the main channel polymerizes the suspension, thereby forming cylindrical microparticles with four compartments. In each compartment, silica particles form ordered array which develops particle size–dependent structural color. Therefore, different colors can be incorporated into single microcylinder by employing different sizes of silica particles. Moreover, one of the compartments can be rendered to be magnetoresponsive by embedding aligned magnetic particles, which enables the remote control of microcylinder orientation and therefore the switching of structural colors.     

Incorporation of carbon nanotubes into micro-coatings film formed on aluminum alloy via plasma electrolytic oxidation

The influence of the incorporation of carbon nanotubes (CNTs) on the coating structure of aluminum alloy processed by plasma electrolytic oxidation (PEO) has been studied as a function of the current density. A series of PEO coatings was applied in a silicate-electrolyte containing CNTs at three current densities, such as 50, 100, and 150 mA/cm². As the current density increased, the responding voltage also increased due to a gradual increment in the amount of CNTs incorporated uniformly into the coating film. In addition, a number of CNTs were observed mainly near micro-pores formed in the coating film by plasma explosive arcs, resulting in a fairly uniform coating structure with a low density of micro-pores. This phenomenon was discussed based on the electrophoretic activity of CNTs.     

Synthesis and characterization of soluble polypyrrole–poly(ɛ-caprolactone) polymer blends with improved electrical conductivities

Polypyrrole–poly(?-caprolactone) (PPy–PCL) blends were prepared through an in situ deposition technique wherein different amounts of poly(?-caprolactone) were added during the polymerization of pyrrole. Ammonium persulfate was used as an oxidant in the polymerization of polypyrrole (PPy). Compared with pure PPy, the blends showed higher solubility in many organic solvents. The composition and structural characteristics of PPy–PCL were determined by Fourier transform infrared, ultraviolet–visible, and X-ray photoelectron spectroscopic methods. Scanning electron and transmission electron microscopic methods were performed to observe the morphology of the PPy–PCL blends. The temperature-dependent conductivity of the PPy–PCL blends was measured at 300–500 K. The conductivity increased with increasing PCL concentration in the blends, which can be explained by the increased mobility of charge carriers at high PCL concentrations. Based on the temperature dependence of the electrical conductivity, hopping may be the conduction mechanism involved in the PPy–PCL blending process.     

A Review of Three‐Dimensional Resistive Switching Cross‐Bar Array Memories from the Integration and Materials Property Points of View

Issues in the circuitry, integration, and material properties of the two‐dimensional (2D) and three‐dimensional (3D) crossbar array (CBA)‐type resistance switching memories are described. Two important quantitative guidelines for the memory integration are provided with respect to the required numbers of signal wires and sneak current paths. The advantage of 3D CBAs over 2D CBAs (i.e., the decrease in effect memory cell size) can be exploited only under certain limited conditions due to the increased area and layout complexity of the periphery circuits. The sneak current problem can be mitigated by the adoption of different voltage application schemes and various selection devices. These have critical correlations, however, and depend on the involved types of resistance switching memory. The problem is quantitatively dealt with using the generalized equation for the overall resistance of the parasitic current paths. Atomic layer deposition is discussed in detail as the most feasible fabrication process of 3D CBAs because it can provide the device with the necessary conformality and atomic‐level accuracy in thickness control. Other subsidiary issues related to the line resistance, maximum available current, and fabrication technologies are also reviewed. Finally, a summary and outlook on various other applications of 3D CBAs are provided.     

Aptamer‐Functionalized Multidimensional Conducting‐Polymer Nanoparticles for an Ultrasensitive and Selective Field‐Effect‐Transistor Endocrine‐Disruptor Sensors

An endocrine disruptor (ED) is a type of xenobiotic compound that can cause serious diseases related to the estrous cycle, as well as various types of cancer. At low ED concentrations, estrogen receptors may respond as they would under physiological conditions. In this work, aptamer‐functionalized multidimensional conducting‐polymer (3‐carboxylate polypyrrole) nanoparticles (A_M_CPPyNPs) are fabricated for use in an FET sensor to detect bisphenol A (BPA). The multidimensional system, M_CPPyNPs, is first produced by means of dual‐nozzle electrospray of pristine CPPyNPs and vapor deposition polymerization of additional conducting polymer. The M_CPPyNPs are then immobilized on an amine‐functionalized (–NH₂) interdigitated‐array electrode substrate, through the formation of covalent bonds with amide groups (–CONH). The amine‐functionalized BPA‐binding aptamer is then introduced in the same way as that for M_CPPyNP immobilization. The resulting A_M_CPPyNP‐based FET sensors exhibit ultrasensitivity and selectivity towards BPA at unprecedentedly low concentrations (1 fm ) and among molecules with similar structures. Additionally, due to the covalent bonding involved in the immobilization processes, a longer lifetime is expected for the FET sensor.     

Self‐Healing Reduced Graphene Oxide Films by Supersonic Kinetic Spraying

The industrial scale application of graphene and other functional materials in the field of electronics has been limited by inherent defects, and the lack of simple deposition methods. A simple spray deposition method is developed that uses a supersonic air jet for a commercially available reduced graphene oxide (r‐GO) suspension. The r‐GO flakes are used as received, which are pre‐annealed and pre‐hydrazine‐treated, and do not undergo any post‐treatment. A part of the considerable kinetic energy of the r‐GO flakes entrained by the supersonic jet is used in stretching the flakes upon impact with the substrate. The resulting “frozen elastic strains” heal the defects (topological defects, namely Stone‐Wales defect and C₂ vacancies) in the r‐GO flakes, which is reflected in the reduced ratio of the intensities of the D and G bands in the deposited film. The defects can also be regenerated by annealing.     

A microbiological screening method for the indication of irradiation of frozen poultry meat

A microbiological screening method for the detection of irradiation of frozen poultry meat was developed on the basis of the combined use of total cell count by the direct epifluorescent filter technique (DEFT) and viable cell count by the aerobic plate count method (APC). Samples of ground, deboned poultry leg were irradiated or not with dose levels of 3, 5 and 7 kGy using an electron beam accelerator. All samples were frozen before the irradiation treatment. The average values of the differences between DEFT and APC counts in control samples and those irradiated with doses of 3, 5 and 7 kGy were 1.14 log units for control samples, and 3.16, 3.68 and 3.79 log units for the irradiated samples. A difference of at least 2 log units can therefore be considered as a limit value indicating probable irradiation treatment necessitating further investigations.

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Anwendung eines mikrobiologischen Unterscheidungsverfahrens zum Nachweis der Bestrahlung von gefrorenem Hühnerfleisch

Zusammenfassung Es wurde ein mikrobiologisches Verfahren zum Nachweis der Bestrahlung von tiefgefrorenem Hühnerfleisch auf der Basis kombinierten Einsatzes direkter Epifluoreszenzfiltertechnik (DEFT) und Kolonieauszählung (APC) entwickelt. Die Proben - knochenfreie, zerkleinerte Hühnerschenkel - waren entweder unbestrahlt oder mit einem Elektronenbeschleuninger mit Dosen von 3, 5 bzw. 7 kGy bestrahlt worden. Alle Proben waren vor der Bestrahlung eingefroren worden. Die Mittelwerte der Differenzen zwischen den DEFT- und den APC-Ergebnissen betrugen bei den unbestrahlten Proben 1,14 logarithmische Einheiten und bei den mit 3, 5 bzw. 7 kGy bestrahlten Proben 3,16, 3,68 bzw. 3,79 logarithmische Einheiten. Die Differenz von wenigstens zwei logarithmischen Einheiten kann als Grenze für die Möglichkeit eines Nachweises eventueller Bestrahlung betrachtet werden und macht weitere Untersuchungen erforderlich.

     

Correction

The online version of the original article can be found at     

Distributed call rerouting in multiclass broadband networks

Broadband integrated services digital networks (B-ISDN) must handle multiclass traffic with diverse quality of service requirements. We consider a multiclass routing model in which routes are calculated in a distributed fashion by the call originating nodes. Within this general context, we address the problem of rerouting a set of previously routed calls to avoid a failed link. Under the approach we propose, a single node executes an aggregate, global rerouting of all affected calls and then converts the set of aggregate routes into an allocation of bandwidth on each link to call origination nodes for the purpose of rerouting. The bandwidth allocation is distributed to each origination node, which in turn then calculates routes for the individual calls. The problem faced by each call origination node is a variant of the socalled bandwidth packing problem. We develop and analyze an approximate algorithm for solving this problem in the specific context that arises in our setting.The research was supported by IBM Corporation and by NSF Grant No. CDR-8803012.On personal leave from IBM RTP.