Planar Design Research Articles

Electrons/ions dual transport channels design: Concurrently tuning interlayer conductivity and space within re-stacked few-layered MXenes film electrodes for high-areal-capacitance stretchable micro-supercapacitor-arrays

Abstract Introduction of interlayer spacers within re-stacked few-layered MXene flakes for more free interlayer space has been proved an effective strategy to improve the acquired electrochemical performance of the assembled film electrodes. However, the expanded interlayer space will inevitably lead to the decrease of interlayer conductivity because of the loose contact between isolated few-layered MXene flakes. The contradiction hinders the maximization of the areal capacitance of the re-stacked few-layered MXene film electrodes. Herein, an “electrons/ions dual transport channels design” is achieved by inserting elaborately synthesized 1D conductive core-shell structured bacterial cellulose (BC)@polypyrrole (PPy) fibers into re-stacked few-layered MXene flakes. This design concurrently realizes the expansion of interlayer space for favoring electrolyte infiltration, and alleviation of interlayer conductivity decline to ensure interlayer electrons transport, as well as additional load of conductive polymer of high specific capacitance and enhancement of interlayer bond strength, endowing the prepared MXene/BC@PPy hybrid film electrodes with fully-excavated areal capacitance of 221.21 mF cm−2 and reinforced tensile strength of 78.9 MPa. Followed a planar electrode configuration design in the MXene/BC@PPy hybrid film electrodes and introduction of islands-bridge interconnecting structure between them, stretchable micro-supercapacitor arrays (MSCAs) of areal capacitance/energy density up to 200.47 mF cm−2/0.01 mWh cm−2 and reversible level of stretchability as much as 200% elongation were further fabricated. The demonstrated “electrons/ions dual transport channels design” provides an attractive and instructive model of structural engineering of few-layered MXenes assembled electrodes for enhanced electrochemical and mechanical performance toward high-areal-capacitance stretchable MSCAs.

Islamic Geometric Patterns in Higher Dimensions

The purpose of this paper is to develop the Islamic geometric patterns from planar coordinates to three or higher dimensions through their repeat units. We use historical plane methods, polygons in contact (PIC) and point-joined, in our deductive approaches. The mentioned approach makes use of a novel method of tessellation that generates 3D Islamic patterns called “interior polyhedral stellations”. The outputs showed that both the PIC and point-joined methods have strengths and weaknesses. Point-joined stellations are more efficient for regular repeat units and PIC is suitable for complex designs. These two methods can produce a large range of patterns and can be employed simultaneously. This study effectively answers the question regarding the gap between planar design from Muslim achievements and contemporary demands in modern art and architecture. We also propose techniques for constructing aperiodic three-dimension Islamic geometric patterns tessellation and two-point family.

Numerical Study of Multilayer Planar Film Structures for Ideal Absorption in the Entire Solar Spectrum

Here, we have theoretically proposed an ideal structure of selective solar absorber with multilayer planar films, which can absorb the incident light throughout the entire solar spectrum (300–2500 nm) and over a wide angular range, whatever the polarization angle of 0°~90°. The efficiency of the proposed absorber is proven by the Finite-Difference Time Domain (FDTD) simulation. The average absorption rate over the solar spectrum is up to 96.6%. The planar design is extremely easy to fabricate and modify, and this structure does not require lithographic processes to finish the absorbers. Improvements of the solar absorber on the basis of planar multilayer-film structures is attributed to multiple asymmetric highly lossy Fabry–Perot resonators. Because of having many virtues, such as using different refractory and non-noble metals, having angle and polarization independence, and having ideal absorption for entire solar spectrum, our proposed absorbers are promising candidates for practical industrial production of the solar-energy harvesting.

Investigation of Porous Metal-Based 3D-Printed Anode GDLs for Tubular High Temperature Proton Exchange Membrane Fuel Cells.

A high-temperature proton exchange membrane fuel cell (HT-PEMFC) conventionally uses a planar design with carbon-based substrates as the gas diffusion layer (GDL) materials. However, the metal-based substrates allow for alternative designs. In this study, the applicability of porous thin-walled tubular elements made of 316L stainless steel as the anode GDL in a multi-layer tubular HT-PEMFC was investigated. The anode GDLs were fabricated via powder bed fusion using a laser beam (PBF-LB) process with defined porosities (14% and 16%). The morphology of the porous elements was compared using scanning electron microscopy (SEM) micrographs. The influence of the porosity on the fuel cell performance was evaluated through electrochemical characterization and a short-term stability test (45 h) in a commercial test station operated at 160 °C and ambient pressure, using hydrogen as the fuel and air as the oxidant. The results showed that the fuel cell manufactured upon the anode GDL with a porosity of 16% had a higher performance with a peak power density of 329.25 W/m2 after 5 h of operation at 125.52 A/m2 and a voltage degradation rate of 0.511 mV/h over the stability test period. Moreover, this work indicates that additive manufacturing could be a useful tool for further fuel cell development.

Investigation of High-Frequency Fine Structure in the Current Output of Shaped Contact Planar Gunn Diodes

A novel gallium arsenide (GaAs) planar Gunn diode design with shaped anode and cathode contacts using Monte Carlo simulations has been shown to produce significantly higher frequency fine structure components in the output waveform than the natural transit time frequency of the diode. We have investigated devices without a feedback potential and devices with a feedback potential (in the delayed mode) and have shown 350-GHz fine structure frequency components in a device with a nominal transit time frequency of 70 GHz is possible. This is the first observation of such stable repeating high-frequency components in a Gunn diode, giving potential for very high-frequency power generation and other wave-shaping applications.

Hydrogen Sulfide Detection for Medical Breath Analysis with Surface Functionalized ZnO Nanowires

Over the past decade, the medical role of hydrogen sulfide (H2S) for therapeutic applications and diagnostics was extensively investigated and revealed the importance of H2S for medical breath analysis.It was suggested that decreased production of the endogenous gaseous mediator H2S in tissues of the human respiratory system can be interpreted as an early detection biomarker for inflammatory diseases like asthma etc. In order to detect the H2S concentration levels of interest, a reliable selective device sensitive to H2S in the very low parts per billion (ppb) range is needed.The main goal of our project is the development of such a highly sensitive, reproducible and reliable H2S gas sensor, acting as a future integrated component of a multiple-sensor array in an “electronic nose” type device for medical applications or for detecting trace concentrations in chemical industry.We present here a planar resistive gas sensor design based on the gas sensing mechanism of a chemical field effect transistor (ChemFET) made from very high quality zinc oxide (ZnO) nanowires (NW) with gas sensitive open gate. The open gate operates as a transducer between adsorption/desorption of the ambient target gas and a measurable resistivity change in the NWs. This resistivity change results from the band bending effect of metal oxide surface exposed to different gas atmospheres and is analyzed by current-time (I-t) measurements.To improve the selectivity of our ZnO NW sensor towards a certain target gas, we investigated the impact of surface modification by addition of catalytic metal layers on the detection limit of our ZnO NWs towards H2S. In particular, we studied the chemical affinity between gold (Au) and sulfur (S) which leads to catalytic effects between the sputtered gold nanoparticle layer and the target gas H2S. Accordingly, H2S molecules are expected to adsorb more efficiently on Au modified ZnO NWs and drastically improve the overall sensor performance towards H2S. Our modified ChemFETs showed higher signal-to-noise ratio (SNR), improved sensitivity, faster response time, and an exceptionally low detection limit of less than 10 ppb for H2S diluted in synthetic air at room temperature.

Fabrication of a Novel, Multidimensional, 2.5D All-Solid-State Lithium-Ion Battery

The limitations of current microbattery designs is best highlighted by the restricted electrochemical performance of planar cells stemming from their long diffusion path lengths, or by the fabrication and material constraints of recent, novel 3D-electrode architectures. Herein, the fabrication and properties of a multidimensional, high areal-capacity, 2.5D battery are described as means to address the limitations of planar and 3D-electrode designs. Our 2.5D battery, composed of a 3D LiFePO4 array and a planar Li anode, provides a way to achieve high energy densities, while utilization of a high ionic conductivity, solution-processed ionogel electrolyte enables high power densities (4.1 mWh cm-2 at 2.8 mW cm-2). This 2.5D design exhibits improved or comparable energy and power densities to the best 3D batteries in literature, while simplifying the fabrication process, eliminating the liquid electrolyte, and facilitating an easily customizable battery. The exemplary performance and simple fabrication process of the 2.5D design, possible because of the ionogel electrolyte, presents a promising direction for the integration of energy-storage devices into on-chip and microelectronic applications that is impractical with current high-performance 3D-battery designs. Figure 1

Kirigami-Design-Enabled Hydrogel Multimorphs with Application as a Multistate Switch.

Morphing materials have promising applications in soft robots, intelligent devices, and so forth. Among the various design strategies, kirigami structures are recognized as a powerful tool to obtain sophisticated 3D configurations and unprecedented properties from planar designs on common materials. Here, some kirigami designs are demonstrated for programmable, multistable 3D configurations from composite hydrogel sheets. Via photolithographic polymerization, perforated composite hydrogel sheets are fabricated, in which soft and active hydrogel strips are patterned in stiff and passive hydrogel frames. When immersed in water, the gel strips buckle out of plane due to swelling mismatch. In the kirigami structures, the geometric continuity is disrupted by the introduction of cutouts, and thus the degrees of deformation freedom increases remarkably. Multiple configurations are obtained in a single composite hydrogel by controlling the buckling direction of each strip. Multitier configurations are also obtained by using a hierarchically designed kirigami structure. A multicontact switch of an electric circuit is designed by harnessing the multitier gel configurations. Furthermore, a rotation mode is realized by introducing chirality in the kirigami design. The versatile design of the kirigami structure for programmable deformations should be applicable for other intelligent materials toward promising applications in biomedical devices and flexible electronics.

High-Efficiency High-Power-Density CLLC Resonant Converter With Low-Stray-Capacitance and Well-Heat-Dissipated Planar Transformer for EV On-Board Charger

In this article, a high-efficiency high-power-density wide-bandgap-based CLLC resonant converter with a low-stray-capacitance and well-heat-dissipated planar transformer is presented, which is used as the isolated dc-dc stage for an electric vehicle on-board charger. A generalized planar transformer design methodology is proposed and validated by practical designs and experimental tests. A novel and simple transformer configuration is proposed to reduce the winding stray capacitance and enhance the winding thermal dissipation. The proposed transformer configuration is compared with different planar transformer designs, and the tradeoffs of employing the proposed design are well analyzed. Moreover, the system design and optimization of the high-efficiency high-power-density CLLC resonant converter is studied. The proposed transformer design and the system optimization approach are employed in a 6.6-kW/500-kHz CLLC resonant converter prototype. The prototype achieves a peak efficiency of 97.85% and a power density of 114 W/in$^\text {3}$.

New electrochemical and physical measurements on sensitive glasses in thin-film technology

All-solid-state sensors have several advantages compared to conventional ones. These include, e.g., miniaturization, planar design, location independence and an uncom­plicated realization of sensors for high pressure and high temperature. Therefore, a number of physical sensors, such as temperature sensors, pressure sensors, rotation angle sensors and force sensors are available in thin-film techniques. The presented paper shows the advantages to combination of thin and thick film tech­niques to manufacture electrochemical sensors, especially using pulsed laser ablation to create amorphous layers of glass. Furthermore, it investigates the range of possibilities for characterization of bulk and surface properties with electrochemical methods and specialized techniques with thermally stimulated currents (TSC).

Planar Self-similar Antennas for Broadband Millimeter-Wave Measurements

Self-similar antennas offer extremely broadband functionality and easily scalable designs. Self-similar designs with a four-arm layout are also suited for dual polarization through excitations of opposing arms, although there has only been limited use of them for millimeter-wave detectors. These antennas have been used for measurements of the cosmic microwave background (CMB), which encompass a wide frequency range and are now actively focusing more on polarization anisotropies. We analyze multiple planar self-similar antenna designs with simulations in high-frequency structure simulator and ongoing physical testing. They all exhibit broadband operation between 130 and 230 GHz and can couple to both linear polarizations through the previously mentioned four-arm symmetry. Simulations include each antenna design coupled to an extended hemispherical, AR-coated lenslet. From these, a basic bowtie-like arm design produced minimal polarization wobble with moderate beam efficiency, while a hybrid trapezoidal design provided high beam efficiency with small polarization wobble. Current fabrication versions of each are being tested, coupled to multichroic microwave kinetic inductance detectors. These planar self-similar antennas, when implemented in CMB and other detectors, could improve observations while simultaneously simplifying fabrication and detector layout.

Recycled Red Mud–Decorated Porous 3D Graphene for High‐Energy Flexible Micro‐Supercapacitor

AbstractFlexible micro‐supercapacitors, with high energy and power density, and using materials with a low environmental impact are attractive for next‐generation energy storage devices. Carbon‐based materials are widely used for supercapacitors but can be increased in energy density via combination with metal oxides. Red mud is an iron‐oxide‐rich by‐product of aluminum production, which needs to be more widely utilized to reduce its environmental damage. To achieve a flexible micro‐supercapacitor device with increased energy density, a laser‐induced graphene (LIG) supercapacitor is realized from a polyimide substrate, decorated with red‐mud nanoparticles (LIG‐RM), employing a solid‐state ionic liquid electrolyte with a mixture of poly(vinylidene fluoride) (PVDF), 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]), and 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]). The fabricated two‐electrode flexible device, in an interdigitated planar design, with inkjet‐printed silver current collectors, has a high energy of 0.018 mWh cm−2 at a power of 0.66 mW cm−2, with 81% of capacitance retained after 4000 cycles and good resistance to bending and flexing. The high energy storage performance, brought about through the combination of graphene and red‐mud nanoparticles, which would—if not utilized—be an environmental liability, shows a promise as a material for future energy storage with low environmental impact.

Characterization of Metasurface Lens Antenna for Sub-6 GHz Dual-Polarization Full-Dimension Massive MIMO and Multibeam Systems

A metasurface lens antenna fed by a planar $8\times8$ dual polarized antenna array is proposed and characterized for full-dimensional massive multiple-input multiple-output (MIMO) and multibeam systems at sub-6 GHz bands. The lightweight multilayer metasurface structure consisting of Jerusalem cross elements is used for a planar lens design. The lens antenna with the size of $10\lambda _{0} \times 10\lambda _{0} \times 5\lambda _{0}$ is fed by an $8\times8$ dual-polarized stacked patch array to operate over the range from 5.17 to 6.10 GHz, where $\lambda _{0}$ is the free-space operating wavelength at the center frequency of 5.6 GHz. This article shows the scanning range of ±25° with a maximum gain of 22.4 dBi and the gain variation of 3.3 dB at 5.6 GHz. Beam coverage performance, pattern envelope correlation coefficient, and port isolation properties demonstrate its full-dimension access capability of the antenna. Besides, the multibeam antenna system with high-gain coverage is achieved by beams operating at the same frequencies, while the frequency division multiplexing can be realized for the isolated beams. The proposed metasurface lens antenna, featuring lightweight, compactness, and low cost compared to a 3-D dielectric lens and low-complexity compared to the array scenarios, can be an alternative for fifth-generation (5G) sub-6 GHz frequency bands.

Design of Single-Turn Air-Core Integrated Planar Inductor for Improved Thermal Performance of GaN HEMT-Based Synchronous Buck Converter

Gallium nitride (GaN) high electron mobility transistor (HEMT) has a lateral device structure with wafer-level packaging, which is advantageous in minimizing parasitic parameters and overall device size. This type of packaging also has better thermal performance than conventional packaging due to low junction-to-bottom thermal resistances. It indicates copper layers in printed circuit boards can effectively serve as heat dissipation channels for the switching devices. When these copper traces and pours in the vicinity of the switching devices are carefully designed and shaped, they can also be utilized as an integrated output filter. In this article, a synchronous buck converter with a single-turn air-core integrated planar inductor is proposed to achieve both zero-voltage switching and high thermal performance of the GaN HEMTs. A new planar inductor design flowchart is introduced, and analytically estimated inductance and resistance are verified with simulation and experiment. Three different inductors are designed and fabricated to prove the improved thermal performance of the proposed converters.

Performance Analyses of Planar Schottky Barrier MOSFETs with Dual Silicide Layers at Source/Drain on Bulk Substrates and Material Studies of ErSix/CoSi2/Si Stack Interface**Supported by the National Natural Science Foundation of China (No. 61474005), and the Beijing Natural Science Foundation (No. 4182025).

A dual silicide layer structure is proposed for Schottky barrier metal-oxide-semiconductor field effect transistors (MOSFETs) on bulk substrates. The source/drain regions are designed to be composed with dual stacked silicide layers, forming different barrier heights to silicon channel. Performance comparisons between the dual barrier structure and the single barrier structure are carried out with numerical simulations. It is found that the dual barrier structure has significant advantages over the single barrier structure because the drive current and leakage current of the dual barrier structure can be modulated. Furthermore, the dual barrier structure’s performance is nearly insensitive to the total silicide thickness, which can relax the fabrication requirements and even make an SOI substrate unnecessary for planar device design. The formation of ErSix/CoSi2 stacked multilayers has been proved by experiments.

A Review on Solid Oxide Fuel Cell Stack Designs for Intermediate Temperatures

Solid oxide fuel cell (SOFC) has significant advantages of clean and quiet operation while providing a relatively high efficiency owing to enhanced reaction kinetics at high operating temperature. The high operating temperature of SOFC, typically around 800 – 1000°C helps to enable internal reforming of hydrocarbons and negate effects of impurities in small quantities in the fuel. However, this limits the application of SOFC only to stationary applications due to the long period needed to reach this temperature range. A high temperature operation is also not ideal in terms of cost reduction and long-term stability of the cell components. Hence, lowering the operating temperature of SOFC is crucial for reduction of cost production and commercialization, which enables SOFC to have a wider range of application areas inclusive of portable and mobile ones. Building a high-performance SOFC with small volume is essential as the underlying criteria for these small-scale portable applications. Therefore, careful design and fabrication methods of SOFC operating on intermediate temperatures with high power outputs need to be considered. The intermediate temperature operation of the fuel cell not only increases the overall lifespan of cell but also allows for longer operation with a lower degradation rate compared to high temperature operation. Furthermore, a modified intermediate temperature stack design can accommodate a wider range of applications compared to the tubular and planar stack designs. This paper reviews the development of SOFC stack designs aimed at intermediate temperature operation towards achieving high performance and the benefits of each design.

Shell design from planar pre-stressed structures

The interplay between mechanics and geometry is used to construct a theoretical framework able to describe the class of three-dimensional objects that can be fabricated from suitable planar designs by using relaxation of pre-strains/stress in ultra-thin films. Small deformations and large rotations are used here to model the elastic relaxation into various three-dimensional shapes. Over the kinematics associated with the designed mid-surface, a small perturbation of Love–Kirchhoff type is considered in order to deduce the design plate-to-shell equations for orthotropic materials with an important pre-stress/strain heterogeneity. The resulting equations for the efforts average and efforts moments provide the supplementary equations to compute the in-plane pre-strain/stress. In particular, for materials with a weak material transversal heterogeneity the moments equations involve only the thickness, the curvature tensor, and the pre-strain/stress moments. Special attention is devoted to materials that can be obtained by layer-by-layer crystal growth (molecular beam epitaxy), which posses an in-plane isotropic pre-strain. We have found that a rectangular plate could relax both into a cylindrical surface or on a part of a sphere in which case it should have a small diameter with respect to the sphere radius. In both cases, the theoretical estimates have been compared with the experimental realizations and finite-element numerical computations and we found very good agreement among all of them. In addition, for the cone geometry we found that the design is not possible from an isotropic pre-stress with an in-plane homogeneity. However, the 3D finite-element computation of the relaxed surface with a (necessary) non-isotropic pre-stress obtained from the theoretical estimates matches remarkably well the designed conical surface.

Fabry-Perot Cavity Leaky Wave Antennas with Tunable Features for Terahertz Applications

Terahertz (THz) radiation is a very appealing band of the electromagnetic spectrum due to its practical applications. In this context, the THz generation and manipulation is an essential part of the technological development. The demand of THz antennas is still high because it is already difficult to obtain directive, efficient, planar, low-cost, and easy-to-fabricate THz radiating systems. In this regard, Fabry-Perot cavity leaky-wave antennas are gaining increasing attention at THz, due to their very interesting radiating features: the combination of planar designs with metamaterials and metasurfaces could offer a promising platform for future THz manipulation technologies. In this short review, we focus on different classes of leaky-wave antennas, based on materials with tunable quasi-optical parameters. The possibility of producing directive patterns with particularly good efficiencies, as well as the capability of dynamically reconfiguring their radiating features, are discussed by taking into account the risk of increasing costs and fabrication complexity.

Wideband and high-efficiency planar chiral structure design for asymmetric transmission and linear polarization conversion

The phenomenon of asymmetric transmission (AT) means the existence of a giant difference in transmittance after the incident waves pass through the special slab in two opposite directions, which is quite useful for realizing irreversible electromagnetic waves and has attracted much attention in recent years. However, it is difficult to achieve wideband asymmetric transmission and linear polarization conversion simultaneously using the bilayer transmission-mode structure. In this work, we propose and numerically investigate a high-efficiency transmission-mode metamaterial that consists of twisted multigap rings on both sides of a dielectric slab. Benefiting from the antisymmetric design of the split ring bilayer transmitarray element, the proposed structure excites the electric and magnetic dipole resonances with mutual interference, thereby simultaneously achieving asymmetric transmission and linear polarization conversion. The proposed structure is designed, fabricated, and measured, which can realize a good agreement between the measurement results and the anticipation. Within the frequency range from 12.7 to 17 GHz, the AT parameter can be close to 0.9 and the polarization conversion ratio can be more than 93%.

Investigation of THz Frequency Shaped Anode Planar Gunn Diodes Operating in Delayed Mode

A novel planar design of Gunn diode with a shaped anode contact, utilizing Monte Carlo simulations, has been shown to have produced 0.3 THz frequency current output when operated in delayed mode. Two novel anode designs are investigated here, one with two fixed distances, and the other with three fixed distances between the cathode and anode electrodes. The corresponding waveforms generated, show two and three current peaks respectively. The work suggests high frequency and novel wave-shaping applications are possible in such devices.