Investigation of Enhancement Band Using Double Screen Frequency Selective Surfaces with Koch Fractal Geometry at Millimeter Wave Range

Numerical and theoretical investigations are presented for a double screen frequency selective surface (DSFSS) with perfectly conducting Koch fractal patch elements. The work was developed in two steps, in the first step two Koch fractal FSS screens were designed using the commercial software Ansoft Designer^TM. In the second these FSS were cascaded and separated by an air gap layer, forming the so-called DSFSS, to improve the bandwidth behavior. Thereafter, a numerical cascading technique is used to analyze the effect of the air gap on the DSFSS. The results were compared and a good agreement was observed.     

Electrical and photovoltaic properties of an organic-inorganic heterojunction based on a BODIPY dye

An organic-inorganic heterojunction based on a BODIPY dyes has been produced by forming dye thin film on n-Si. The electrical parameters of the structure have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The ideality factor, the barrier height and the series resistance values of the diode have been calculated as 2.43, 0.84 eV, and about 1.3 kΩ, respectively. The diode behaves as a non-ideal diode because of the series resistance and interface layer. The barrier height value obtained from I-V measurement has been compared with one from C-V measurement. Moreover, it has been seen that the diode is highly sensitive to the light and the reverse bias current increases about 1 × 10⁴ times at −1 V under 100 mW/cm² and AM1.5 illumination condition. The short photocurrent density (J_sc) and the open circuit voltage (V_oc), the fill factor (FF) and power conversion efficiency (η) have been determined as 3.78 mA/cm², 327 mV, 0.28 and 0.48 %, respectively.     

Vacuum-processed polyethylene as a dielectric for low operating voltage organic field effect transistors

We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C₆₀ as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm²/Vs. Devices with pentacene showed a mobility of 0.16 cm²/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ～0.3 cm²/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels.     

On‐the‐Spot Immobilization of Quantum Dots,Graphene Oxide,and Proteins via Hydrophobins

Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications.     

The sprayed ZnO films: nanostructures and physical parameters

We synthesized the pure and indium-doped (IZO) ZnO films with a facile composition control spray pyrolysis route. The substrate temperature (T_s) and In-doping effects on the properties of as-grown films are investigated. The X-ray pattern confirms that the as-synthesized ZnO phase is grown along a (002) preferential plane. It is revealed that the crystalline structure is improved with a substrate temperature of 350 ℃. Moreover, the morphology of as-grown films, analyzed by AFM, shows nanostructures that have grown along the c-axis. The (3 × 3μm²) area scanned AFM surface studies give the smooth film surface RMS < 40 nm. The UV-VIS-IR measurements reveal that the sprayed films are highly transparent in the visible and IR bands. The photoluminescence analysis shows that the strong blue and yellow luminescences of 2.11 and 2.81 eV are emitted from ZnO and IZO films with a slight shift in photon energy caused by In-doping. The band gap is a bit widened by In-doping, 3.21 eV (ZnO) and 3.31 eV (IZO) and the resistivity is reduced from 385 to 8 Ω ·m. An interesting result is the resistivity linear dependence on the substrate temperature of pure ZnO films.     

Mlcrolasers based on silica microspheres

Light can be confined efficiently in the high-Q, small-volume whispering-gallery-modes observed in silica microspheres. By coupling these microspheres to eroded optical fibers and fiber tips, direct mapping of the whispering-gallery modes has been achieved and the mode numbers have been assessed. The properties of these modes have allowed us to obtain laser action with very low thresholds in Nd-doped silica microspheres. Further projects in the field of non-linear optics and cavity quantum electrodynamics are described.     

The strategy of edge wear prediction in CIM concept

A monitoring of tool wear in different cutting operations has been studied for many years. Special techniques have been used to detect a wear status basing upon cutting forces, acoustic emission, temperature, torque and power, vibration, noise and acceleration sensors. The adapting of a proper prediction method allows to solve problems of an automatic supervision in Computer Integrated Manufacturing systems. A task of the abrasive edge wear index prediction can be formulated as follows: disposing by the data collection of the edge wear status in a time period preceding the concerning the wear status in the successive time period embraced by the prediction method.     

Assembly and Characterizations of Bifunctional Fluorescent and Magnetic Microneedles With One Decade Length Tunability

This report presents the fabrication of bifunctional magnetic and fluorescent microneedles (µNDs) made of a ternary mixture of magnetic nanoparticles (NPs), quantum dots (QDs), and polyelectrolyte. The assembly relies on the electrostatic complexation of negatively charged NPs with positively charged polymer strands and is controlled by the charge ratio between the nanoparticle building blocks and the polymer mortar. The resulting 1D objects can be actuated using an external magnetic field and can be imaged using fluorescence microscopy, thanks to the fluorescent and superparamagnetic properties inherited from their NP constituents. Using a combination of core and surface characterizations and a state‐of‐the‐art image analysis algorithm, the dependence of the brightness and length on the ternary composition is thoroughly investigated. In particular, statistics on hundreds of µNDs with a range of compositions show that the µNDs have a log‐lormal length distribution and that their mean length can be robustly tuned in the 5–50 µm range to match the relevant length scales of various applications in micromixing, bioassays or biomechanics.