Metal Disk Research Articles

Plasmons in Infinite 2D Electron System Screened by the Disk-Shaped Metallic Gate

We have examined the plasmon modes in infinite two-dimensional (2D) electron system (ES) with the finite-sized gate formed by a metallic disk over a 2D electron plane. Heretofore, such a problem has never been analytically considered. We have predicted that discrete plasmon modes exist in such a partly-gated system even though no voltage was applied to the gate. The plasmon spectrum has been characterized by the radial and azimuthal mode numbers. We used an analytical approach recently developed for the gate in the form of a metallic stripe [A.A. Zabolotnykh and V.A. Volkov, Phys. Rev. B 99, 165304 (2019)]. Under several reasonable assumptions, we analytically find plasmon frequencies and charge density distributions.

Voltammetric Electronic Tongue for the Simultaneous Determination of Three Benzodiazepines.

The presented manuscript reports the simultaneous detection of a ternary mixture of the benzodiazepines diazepam, lorazepam, and flunitrazepam using an array of voltammetric sensors and the electronic tongue principle. The electrodes used in the array were selected from a set of differently modified graphite epoxy composite electrodes; specifically, six electrodes were used incorporating metallic nanoparticles of Cu and Pt, oxide nanoparticles of CuO and WO3, plus pristine electrodes of epoxy-graphite and metallic Pt disk. Cyclic voltammetry was the technique used to obtain the voltammetric responses. Multivariate examination using Principal Component Analysis (PCA) justified the choice of sensors in order to get the proper discrimination of the benzodiazepines. Next, a quantitative model to predict the concentrations of mixtures of the three benzodiazepines was built employing the set of voltammograms, and was first processed with the Discrete Wavelet Transform, which fed an artificial neural network response model. The developed model successfully predicted the concentration of the three compounds with a normalized root mean square error (NRMSE) of 0.034 and 0.106 for the training and test subsets, respectively, and coefficient of correlation R ≥ 0.938 in the predicted vs. expected concentrations comparison graph.

Single-Layer Dual-Band Polarization-Selective Metafilm With Independently Controlled and Closely Spaced Shielding Bands

This article presents a highly compact metafilm structure with two closely spaced and independently controlled shielding bands. The constituent unit cell is a composite of two different single-band metafilm unit cells realized by the application of a meandered-loop resonator and a mu-negative and near-zero (MNNZ) metamaterial liner, respectively, to a metallic disc resonator. Both liners introduce frequency-reduced resonances resulting in highly subwavelength unit cells. The composite dual-band unit cell undergoes resonances at sizes of λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /10 and λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /8 in two operating bands, where it exhibits a fano-shaped reflection profile. The unit cells are closely packed and constructed on a single metallic layer, resulting in a compact and low-profile metafilm design. Furthermore, due to the use of two separate and noninteracting resonance mechanisms, the operating bands are highly selective, can be spaced very close to each other, and may be controlled independently through the design of the individual meandering and MNNZ elements. We present simulation data, extraction of susceptibility tensors using generalized sheet-transition conditions (GSTCs) as well as experiments confirming a dual-band, polarization-selective shielding response using a compact metafilm structure measuring 1.3λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 1.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at the lower band and 1.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 2.3λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at the upper frequency band. The proposed design remains nearly transparent at other frequencies and/or for the orthogonal polarization.

Optically transparent sea‐water monopole antenna with high radiation efficiency for WLAN applications

A high efficiency and transparent sea-water monopole antenna operating at 2.4 GHz for wireless local area network (WLAN) applications is proposed in this Letter. The antenna has high transparency (>85%) achieved by using sea-water as its conductive medium contained within a clear acrylic tube. To improve the radiation efficiency of the antenna, a short metal tube with a metal disk at the base was loaded into a feeding probe to achieve greater excitation. The antenna is simulated and its properties are verified through this experiment. Measurement results show a -10 dB bandwidth of 1.1 GHz (2.1-3.2 GHz) and a high radiation efficiency (>71%) over the entire WLAN band (2.4-2.5 GHz). These results demonstrate the proposed antenna as an attractive alternative to conventional metal monopoles for WLAN applications.

Graphene Antidot Terahertz Plasmonic Metasurfaces Employing Self-Aligned Metal Cores for Sensing Applications

Surface plasmons in graphene have great potential for molecular sensing applications thanks to their exceedingly high sensitivity to environmental changes. Here, we demonstrate a type of hybrid graphene–metal metasurface that supports strong graphene plasmonic resonances in the terahertz range. Each unit cell of such a hybrid metasurface consists of a graphene antidot enclosing a metal disk realized using a self-aligned photolithography process. This hybrid design combines the advantages of both graphene- and metal-based photonic structures, leading to ∼3 times stronger tunable plasmonic resonances and an order of magnitude larger near-field intensity enhancement with respect to those of bare graphene antidot metasurfaces.

A mysterious rash around surgical wounds

Introduction Contact dermatitis (CD) that occurs shortly after a surgery is often caused by a direct irritant effect of medical products or, infrequently, a delayed type hypersensitivity. Various agents have been reported to cause CD including topical medications, surgical instruments, and surgical glue. We present a patient who developed rash around surgical wounds. Skin patch testing identified the causative agent of his CD. Case Description A 15-year-old male presented with new onset of pruritic papulovesicular rash three weeks following Nuss procedure, a minimally invasive pectus excavatum repair using a metal bar. The rash initially appeared on upper extremities and chest wall around surgical wounds (Figure 1A). Later, new erythematous lesions occurred on foreskin of penis. Patient denied other systemic symptoms or prior history of metal or medication allergy. A delayed hypersensitivity to nickel or other components of stainless steel used in the pectus bar was suspected. Surgical removal of the bar was contemplated. A trial of oral prednisone 30mg BID led to resolution of the rashes (Figure 1B). Blood test for metal-lymphocyte proliferation assay was unremarkable. Skin patch test was negative to nickel and metal disc, and confirmed a reaction to 2-octyl cyanoacylate (surgical glue) (Figure 1C). Discussion Delayed-type hypersensitivity to surgical glue should be considered in patients who develop rash around surgical wounds. Evaluation of surgery-related CD requires a thorough understanding of procedure steps and potential exposures to medical products. Patch test can aid in identification of the offending agent and allow a recommendation of alternative products to avoid recurrence. Figure. A. Rash around surgical wounds Figure 1B. Improvement of rash after a 5-day course of prednisone 30 mg BID treatment Figure 1C. Positive patch test to 2-octyl cyanoacrylate (Dermabond® surgical glue)

Vibration and Noise Behaviors During Stick–Slip Friction

Frictional vibration and noise usually cause machining error and noise pollution. Stick–slip plays an important role in generating frictional vibration and noise. This study characterized frictional vibration and noise during the stick–slip of a Si3N4 ceramic/metal friction by using an acoustic emission method. Experimental results showed that frictional vibration and noise mostly occurred during the slip process. The impacts of the rough peaks between metal disk and ceramic ball during sliding induced the vibration to irradiate noises. The superposition among the frictional vibrations caused the multiplication of vibrational frequency. The major vibrational frequency slowly shifted to a higher frequency as the increase in sliding speed. The vibrational accelerations and their major vibrational frequency increased with the increase in the external load. The knowledge gained herein provides a more comprehensive understanding of stick–slip friction, frictional vibration, and noise, and offers a guidance for controlling or minimizing stick–slip, frictional vibration, and noise.

Analyzing a torsion pendulum using a smartphone’s sensors: mechanical energy conservation approach

This paper describes the use of a smartphone’s sensors to investigate the motion of a torsion pendulum to demonstrate energy conservation. The smartphone was placed on and attached to a metal disk hanging by a wire. The oscillation of the disk was measured using the smartphone’s sensors to simultaneously record angular position, angular speed and angular acceleration. These experimental data were processed to demonstrate mechanical energy conservation during oscillation. We expect that this smartphone-based experiment will be useful for physics teachers and can make students better understand an oscillating disk’s relationship with energy conservation.

Opinion: Airtightness for Decontamination by Fumigation of High-Containment Laboratories.

While the European legislation states that laboratories of high-containment must be sealable for fumigation, they do not prescribe a minimal value for airtightness. Starting from a previous study in which we measured the airtightness in 4 BSL-3 laboratories with blower-door tests, we discuss the connection between airtightness and a successful decontamination by fumigation. Biological indicators (BIs) consisting of spores of Geobacillus stearothermophilus on metal disks were laid out in laboratories of different levels of airtightness before performing a fumigation with aerosolized hydrogen peroxide using an automated device, according to the manufacturer's instructions. Incubation of all BI disks placed in the facility with the highest level of airtightness showed complete inactivation of spores. However, in the facility with a lower level of airtightness, not all spores were inactivated. Air leaks might be a factor in the outcome of the decontamination of a room by fumigation, as seen in the laboratory with a lower level of airtightness, but other factors associated with the fumigation process might also be critical for a successful decontamination. We argue that a validation of the decontamination procedure, before first use or after important renovations of a laboratory of high-containment, is a more effective endpoint than reaching a predefined level of airtightness.

Bonding and Antibonding Modes in Metal–Dielectric–Metal Plasmonic Antennas for Dual‐Band Applications

AbstractResonant optical antennas supporting plasmon polaritons (SPPs)—collective excitations of electrons coupled to electromagnetic fields in a medium—are relevant to sensing, photovoltaics, and light‐emitting devices, among others. Due to the SPP dispersion, a conventional antenna of fixed geometry, exhibiting a narrow SPP resonance, cannot simultaneously operate in two different spectral bands. In contrast, here it is demonstrated that in metallic disks, separated by a nanometric spacer, the hybridized antibonding SPP mode stays in the visible range, while the bonding one can be pushed down to the mid‐infrared range. Such an SPP dimer can sense two materials of nanoscale volumes, whose fingerprint central frequencies differ by a factor of 5. Additionally, the mid‐infrared SPP resonance can be tuned by employing a phase‐change material (VO2) as a spacer. The dielectric constant of the phase‐change material is controlled by heating the material at the frequency of the antibonding optical mode. These findings open the door to a new class of optoelectronic devices able to operate in significantly different frequency ranges in the linear regime, and with the same polarization of the illuminating wave.

Plasmon resonances in coupled Babinet complementary arrays in the mid-infrared range.

A plasmonic structure with transmission highly tunable in the mid-infrared spectral range is developed. This structure consists of a hexagonal array of metallic discs located on top of silicon pillars protruding through holes in a metallic Babinet complementary film. We reveal with FDTD simulations that changing the hole diameter tunes the main plasmonic resonance frequency of this structure throughout the infrared range. Due to the underlying Babinet physics of these coupled arrays, the spectral width of these plasmonic resonances is strongly reduced, and the higher harmonics are suppressed. Furthermore, we demonstrate that this structure can be easily produced by a combination of the nanosphere lithography and the metal-assisted chemical etching technique.

A Compact Graphene Modulator Based on Localized Surface Plasmon Resonance with a Chain of Metal Disks

Most graphene electro-optic modulators based on the electro-refractive modulation are composed of Mach-Zehnder interferometer or microring resonator structures and have a relative compact size comparing with dielectric ones. To further shrink the footprint, we use the localized surface plasmon resonance of a chain of three metal disks to realize a submicron graphene modulator, whose length can be reduced to less than 1 μm. The proposed graphene modulator has an extinction ratio of 5.5 dB with a length of only 740 nm. And the insertion loss, 3-dB bandwidth, and power consumption of the modulator are 1.9 dB, 83.4 GHz, and 8.55 fJ/bit respectively.

Combination of pulsed light heating thermoreflectance and laser-heated diamond anvil cell for in-situ high pressure-temperature thermal diffusivity measurements.

By combining thermoreflectance measurements and laser heated diamond anvil cell (LHDAC) techniques, an instrument for the measurement of in situ high pressure-temperature thermal diffusivity of materials was developed. In an LHDAC system, high-power continuous-wave laser beams irradiate both faces of a disk-shaped metal sample loaded into diamond anvil cells (DACs), to maintain a stable high-temperature condition. During the operation of the LHDAC system, temperature of the sample is determined from the thermal radiation spectrum between 640 and 740 nm to fit Planck's law. Subsequently, a pulsed laser beam irradiates the metal disk to induce a temperature gradient inside the sample, and the transient temperature, caused by heat diffusion, is measured by a continuous wave probe laser based on the thermoreflectance phenomenon. We determined the thermal conductivities of Pt and Fe up to approximately 60 GPa and 2000 K using the measured thermal diffusivities and obtained values consistent with previous works. The uncertainties in the pressure and the temperature are estimated to be approximately 10%, and that in the thermal conductivity is estimated to approximately 15%. The system developed in this study enables us to determine thermal transport properties of materials under pressure-temperature conditions of the deep Earth.

Well-Controlled Generation Process of Bimetallic Ag//Au Colloidal Nanoparticles by Non-Thermal Plasma DC Glow Discharge

In this paper, an inexpensive, simple and well-accurate process of the generation of bimetallic silver Ag//gold Au core//shell is colloidal metal nanoparticles (MNPs). This is achieved via an atmospheric pressure non-thermal plasma glow discharge between two electrodes. One of these electrodes is a capillary tube placing over solution about (1 cm) that acts as the cathode, while the other electrode is a metal disk immersed in the solution and acts as an anode. Glow discharge process carried out at room temperature using a home-made cell with (6 KV) applied voltage and direct current (DC) about (1.8 mA) for different discharge periods. A wide range of bimetallic Ag//Au colloidal MNPs was rapidly synthesized as a result of non-thermal plasma formation between a capillary tube and the surface of AgNO3 solution for (5 min) and a mixture of AgNPs-HAuCl4 solution for (5, 10 and 15 min). Field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction were used to investigate the structural properties of the bimetallic Ag//Au colloidal MNPs. While optical properties were investigated using a UV-Vis spectrophotometer. Results show that the discharge time plays a crucial role in modifying the bimetallic nanoparticles properties such as grain size, surface area, and optical stability. Moreover, TEM and FE-SEM confirm the formation of Ag//Au core//shell structure with uniform sizes and shapes.

A novel piezoelectric inertial rotary motor for actuating micro underwater vehicles

With developments of micro-machining and advanced functional materials, smart actuators have been developed and applied in various micro underwater vehicles (MUVs) or micro underwater robots. Since there is a tradeoff between the miniature size and output performance for MUVs driven by traditional electromagnetic motors, piezoelectric motors with features of compact structure, large force or torque at small size and no electromagnetic interference provide another promising alternative for actuating MUVs. However, there is a few research to explore the possibility of utilizing piezoelectric motors to realize underwater actuations. In this paper, a novel piezoelectric inertial rotary motor is designed to power the underwater vehicle, which is capable of forward swimming, rotating, rising and diving. This motor consists of two rotors and one disk type stator. One piece of piezoelectric wafer adhered to the bottom face of the stator’s metal disk is used to excite the radial in-plane vibration mode of stator’s outer ring, which is converted into the revolved motion of the inner tube through the connection beams. To utilize the inertial driving mechanism, the motor works at a “slip-slip” mode by the saw-tooth type driving signal. One prototype motor with the appearance size of Φ 20 mm × 20 mm and weight of 3.6 g is designed, fabricated and characterized. Experimental results show that the prototype motor could rotate at a steady speed of 2200 r/min with 150 Vp-p driving voltage. In addition, the motor also performs well with a slightly decrease of operating speed in underwater environments when the silver electrode is coated by waterproof material. Consequently, sealing ring is not necessary for the proposed motor as immersed in water, which is different with conventional electromagnetic motors and enables the actuation unit to be smaller. And then, the prototype motor is coupled with a propeller to build a thruster, which could output the steady speed and maximum propulsion force of 1200 r/min and 4.6 mN, respectively. Finally, the thruster is installed in a spherical swimming robot, and the velocity of the robot could reach 80 mm/s. With merits of simple structure, compact size and great waterproof feasibility, the proposed piezoelectric inertial motor opens a new avenue for developing advanced and flexible MUVs.

A Polarization Insensitive Wide‐Band Perfect Absorber

In this article, a wide‐band and polarization‐insensitive perfect absorber composed of 4 sandwiched layers of dielectric and metal disks is introduced. Compared to classical perfect absorbers, the system supports near‐unity absorption within a wider spectral window through multiple perfect absorption mechanisms that exist due to a constituting inter‐metal disk, functioning either as a dipolar antenna or a conducting ground for different perfect absorption mechanisms. Circular shape of the antenna makes the working mechanism of the system polarization insensitive. The working principle of the system is investigated through near‐ and far‐field calculations by finite difference time domain (FDTD) simulations. A fine‐tuning mechanism of the wide‐range perfect absorption window is introduced through geometrical device parameters. The multilayer perfect absorber system is fabricated through a high‐quality fabrication method based on electron beam lithography, lift‐off method, and multi‐step deposition of metal and dielectric layers. The spectral behavior of the perfect absorber system is finally experimentally investigated through Fourier transform infrared (FTIR) spectroscopy.

Safe 241Am–Be Neutron Source from Alpha Point Resource

Safe, cost-effective and homemade design of diminutive Am–Be neutron source is obtained by combining an alpha source as an active component and a disk of light metal as a target. 241Am laboratory cylinder source with the activity of 10 µCi and a beryllium 9Be disk target with the air gap of 2 mm between them are inserted in a case of hollow stainless steel cylinder. A combination of CR-39 detector and natural boron BN1 converter is used to ensure the generation of neutrons from this design. Neutron output obtained from this design is 5.60 ± 0.5 n/s with a beryllium disk thickness of 2.4 mm.

T-matrix method for closely adjacent obstacles

This paper presents a novel method to calculate the T-matrix for two non-spherical obstacles positioned close to each other, where the individual circumscribed spheres intersect. This is achieved by translating the obstacles coordinate systems, using translation matrices for spherical vector waves. The new circumscribing spheres enables the obstacles to be positioned close to each other. A new total T-matrix of the two-obstacle system can then be calculated using methods for composite particles, i.e., the superposition T-matrix method. This total T-matrix will generally be larger than the original ones, depending on the sizes of the circumscribing spheres used in the coordinate translation procedure. However, it is shown that the total T-matrix can be truncated after transformation to a common origin, without degrading the accuracy. The total truncated T-matrix is only slightly larger than the original individual ones. The method is demonstrated for electromagnetic scattering simulations of two metallic disks, closely adjacent to each other.

Performance Exploration of A Radially Layered Cymbal Piezoelectric Energy Harvester under Road Traffic Induced Low Frequency Vibration

A type of radially layered cymbal piezoelectric energy harvester is designed and fabricated. It is made of two cymbal metal caps, two axially polarized piezoceramic rings, one solid metal disk, one common metal ring and one drilled metal ring. The mechanical couplings in radial direction are finished by using extra strong epoxy. The mechanical couplings in axial direction are finished by using screw bolts. Subsequently, the force transferring coefficient of each cymbal metal cap is approximated through both theoretical calculation and experimental calibration. Aiming at matching the road traffic induced vibration frequencies that are predominantly ranging from 5Hz to 25Hz, the approximated analytical model of the harvester is established at frequencies below 30Hz. The model’s predictions agree reasonably with the measured data. Furthermore, the experimental results indicated that the harvester was able to generate a power of about 0.92mW across a 0.8MΩ resistor under the force of 500N at a frequency of 20Hz. The present work provides a new design concept for developing the novel cymbal harvesters used in roadway systems to harvest the traffic induced vibration energy.

Bandpass FSS With Zeros Adjustable Quasi-Elliptic Response

In this letter, a frequency selective surface (FSS) with quasi-elliptical bandpass filtering response and high-frequency selectivity is proposed. The structure consists of two arrays, i.e., a hollow metal pipe array and a metal disk array printed on a thin substrate layer. The FSS exhibits a flat transmission in the passband and fast roll-off. By investigating the electric fields and using equivalent circuit models, physical insights into the generation of the transmission/reflection zeros and operating principle of the whole FSS are obtained. The positions of the transmission zeros can be independently changed by adjusting the corresponding parameters that tune the bandwidth of the passband. A prototype is fabricated and measured to verify the simulation.