Continuous Metal Research Articles

Modified I-shaped hexa-band near perfect terahertz metamaterial absorber

PurposeA novel and simple six-band metamaterial absorber is proposed in the terahertz region, which is composed of an I-shaped absorber and circular ring with four gaps and a continuous metal ground plane separated by only 0.125 mm polyimide dielectric substrate. Initially, I-shaped resonator gives three bands at 0.4, 0.468 and 0.4928 THz with the absorptivity of 99.3%, 97.9% and 99.1%, respectively. The purpose of this paper is to improve the number of bands, for which the authors added the circular ring with four gaps, so the simulated metamaterial absorber exhibited six absorption peaks at 0.3392, 0.3528, 0.3968, 0.4676, 0.4768 and 0.492 THz, with the absorption rate of 91.4%, 94.2%, 94.9%, 90.3%, 77.5% and 97.4%, respectively. The surface current distribution and angle independence are explained for all the six frequencies which are used to analyze the absorption mechanism clearly. Structure maximum uses the squares and circles, so it will make the fabrication easy. The multiband absorbers obtained here have potential applications in many engineering technology, thermal radiation, material detection and imaging and optoelectronic areas.Design/methodology/approachThis paper presents the design of the six-band metamaterial absorber which is from the I-shaped resonator and circular ring with four gaps and the metallic ground plane separated by the 0.125 polyimide dielectric substrate. The absorber exhibited six absorption peaks at 0.3392, 0.3528, 0.3968, 0.4676, 0.4768 and 0.492 THz, with the absorption rate of 91.4%, 94.2%, 94.9%, 90.3%, 77.5% and 97.4%, respectively. From the fabrication point of view, the proposed six-band metamaterial absorber has a very simple geometrical structure, and it is very easy to be fabricated.FindingsThe authors present a new and simple design of six-band absorber based on an I-shaped absorber and circular ring with four gaps and a metallic ground plane separated by a polyimide layer having the thickness of 0.125 mm. Six different resonance absorption peaks are found at 0.3392, 0.3528, 0.3968, 0.4676 , 0.4768 and 0.492 THz. Surface current distribution and angle independence plot have been studied to understand the absorption behavior of the designed terahertz metamaterial absorber.Originality/valueThe multiband absorbers obtained here have potential applications in many engineering technology, thermal radiation, material detection, security, sensors, imaging and optoelectronic areas.

Generalized circuit model for analysis of extraordinary transmission in multilevel slits.

We propose a generalized circuit model for accurate analysis of the extraordinary transmission phenomenon in multilevel stepped slit structures. The multilevel stepped slit consists of some continuous sub-wavelength metal slits with different widths. By applying the proposed circuit model, we study the extraordinary transmission property of this structure for the two cases of ideal and real metal structures. The accuracy of the achieved results is validated by a full wave analysis based on the finite element method. Additionally, since the multilevel slit structure is adjustable by simply manipulating slit parameters such as widths and heights, various kinds of transmission spectra and a different number of resonance points are investigated by the circuit model and the numerical approach. Multilevel stepped slits can be used potentially as bandpass filters or optical attenuators in photonics integrated circuits.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Reflection control by metal-dielectric-metal metasurfaces using offset micropatches at infrared wavelengths

Metasurfaces offer a promising means for realizing compact high-performance optical devices. This study numerically and analytically investigated reflection control using a metal–dielectric–metal (MDM) metasurface. Its reflection wavelength and angle were determined using the thickness and refractive index of the dielectric layer owing to a phase change induced by the hybridized resonance mode formed therein. MDM metasurfaces with offset micropatches comprise a continuous metal layer with periodic dielectric and micropatch layers having different widths. These layers are offset to one side with respect to one another. These offset micropatches realized better control over the reflection direction and wavelength.

Scalable Continuous Flow Metal–Organic Framework (MOF) Synthesis Using Supercritical CO2

The high surface areas and tunable porous structures of Metal–Organic Framework (MOF) materials offer desirable capabilities in a wide range of applications. One challenge to the widespread use of ...

A thermally tunable terahertz three-dimensional perfect metamaterial absorber for temperature sensing application

We present a three-dimensional (3D) perfect metamaterial absorber (PMA) for temperature sensing application in terahertz region. The PMA consists of a 3D metal resonator structure array and a continuous metal film separated by an indium antimonide (InSb) layer. The numerical simulations demonstrate that the PMA can achieve perfect absorption (about 99.9%) with the high [Formula: see text]-factor of about 18.8 at 2.323 THz when the temperature is 300 K (room temperature). Further simulation results indicate that this terahertz PMA is polarization-insensitive and wide-angle for both transverse electric (TE) and transverse magnetic (TM) waves. The electric field and surface current distributions of the unit-cell structure indicate that the perfect absorption is originated from the excitation of the fundamental magnetic and electric dipole resonance mode. Since the permittivity of the InSb is sensitive to the external temperature, the resonance absorption frequency of the PMA can be dynamically adjusted. The temperature sensitivity of the PMA is about 15.24 GHz/K, which may have potential prospects in temperature sensing and detection.

Reversible Conductive Inkjet Printing of Healable and Recyclable Electrodes on Cardboard and Paper.

Conductive inkjet printing with metal nanoparticles is irreversible because the particles are sintered into a continuous metal film. The resulting structures are difficult to remove or repair and prone to cracking. Here, a hybrid ink is used to obviate the sintering step and print interconnected particle networks that become highly conductive immediately after drying. It is shown that reversible conductive printing is possible on low-cost cardboard samples after applying standard paper industry coats that are adapted in terms of surface energy and porosity. The conductivity of the printed films approaches that of sintered standard inks on the same substrate, but the mobility of the hybrid particle film makes them less sensitive to cracks during bending and folding of the substrate. Damages that occur can be partially repaired by wetting the film such that particle mobility is increased and particles move to bridge insulating gaps in the film. It is demonstrated that the conductive material can be recovered from the cardboard at the end of its life time and be redispersed to recycle the particles and reuse them in conductive inks.

Effect of combining continuous casting and simultaneous solidliquid metal deformation on the structure and properties of alloy V95 products

It is known that the solidification of melts under the influence of external factors leads to the formation of a fine-grained structure in the work pieces which improves the mechanical characteristics of finished metal products. The production of lengthy profiles with a high level of mechanical properties in a short production cycle is a complex interdisciplinary task of great practical importance. The paper presents results of research of the properties of products from aluminum alloy V95, which were obtained by continuous vertical casting combined with deformation in the solid-liquid state during solidification. A diagram of a device that implements such a process of combining is presented; its operation is reviewed. Also, a description is given of a method for producing flat work pieces and sample preparation for studying their mechanical characteristics and microstructure.As research shows the metal products have a fine-grained structure with a dense directional arrangement of dislocations. The grain boundaries are wide, uneven, consisting of grids and dislocation plexuses. During the melt solidification a thin directional dislocation structure is formed in the crystallizer of the device providing increase of the mechanical characteristics of metal products without additional processing, and there are no shrinkage defects. The possibility of obtaining long metal products with high mechanical characteristics for a short production cycle with reduced power costs was shown.

Optimization of Technological Parameters of the Process for Obtaining a Strip by the Combined Method of Metal Casting and Deformation

In order to obtain high-quality metal products with the desired properties (process stability) using the combined methods of metal casting and deformation, it is necessary to take into account the specific parameters of this process and the fact that the metal in the crystallizer stays simultaneously in several physical states: liquid, liquid-solid, solid-liquid and solid. Structurally, the mold consists of four walls moving relative each other along a given sophisticated trajectory. The object of the research is the production technology from non-ferrous alloys using the combined method of continuous casting and metal pressure treatment. The thermal processes occurring in the mold of a continuous horizontal metal casting and deformation installation (CHMCDI) during the formation of metal products have been examined as a research subject. The methods of physical modeling of the thermal processes which take place in the system “crystallizing metal-tool deformation” under different conditions of the mold cooling (using closed-perforated tubes and straight-flow tubes) have been used. Subsequent data processing of the full factorial experiment using the least square method as well as solving the optimization problem by using the Pareto principle of optimality made it possible to determine the optimal parameters for the process of obtaining metal products from aluminum alloys (TV = 40 oС; рv = 0.7 kg / cm2; SR = 5.8), which have been confirmed by the results of the experimental test on obtaining the strip from technical aluminum AD0 strip with a cross section of 40–12 mm.

Highly Selective and Sensitive Trimethylamine Gas Sensors Using Patterned Metal Oxide Nanofibers Prepared By Near-Field Electrospinning

Introduction Oxide nanofibers consisting of nanoparticles are excellent nanostructures for designing high performance gas sensors. To date, randomly tangled oxide nanofiber networks prepared by far-field electrospinning process (FFES) have been widely explored as the sensing materials. When the distance between spinneret needle and substrate is very short, the straight configuration of nanofibers can be directly written on the substrate without whipping. This is referred as near-field electrospinning (NFES), which can be applied to well-defined patterning of one-dimensional nanofibers for various new applications such as sensors, optoelectronic circuits, and functional nanoelectronics. The patterning of polymeric nanofibers has been demonstrated over a decade ago. In contrast, the fabrication of one-dimensional (1D) metal oxide nanopatterns remains challenging because it becomes difficult to control the chaotic whipping motion of the jet due to the acceleration of metal ions under the electric field. In the present study, grids, diamonds, and hexagrams composed of In2O3, Co3O4, and NiO nanofibers were prepared by NFES and their potential applications as gas sensors were investigated. The sensor using In2O3 nanofiber pattern exhibited an unprecedentedly high response (resistance ratio = 239) to 5 ppm trimethylamine (TMA) with negligible cross-responses to ubiquitous ethanol and other interference gases. Method Transparent solution containing 7 g of methanol (99 %), polyvinylpyrrolidone (PVP, 17.4 wt%, Mw = 1,300,000) and metal nitrates (indium nitrate hydrate, 1.4 wt%, 99.999%; cobalt nitrate hexahydrate, 1.7 wt%, 99.99%; nickel nitrate hexahydrate, 1.7 wt%, 99.99%) were stirred for 24 h at room temperature. The prepared clear solution was transferred to a glass syringe (1000 μL) with a 21-gauge needle, and electrospun onto a 4-inch Si/SiO2 wafer containing 76 sensor substrates (size: 1 × 1 cm2) in which Pt interdigitated electrodes (electrode width: 50 μm, electrode spacing: 5 μm) above a metallic collector. The flow rate is fixed as 0.005 μL min−1 at an applied voltage of 50 V and the distance between the tip and the collector is 1 mm. During electrospinning, the loader and collector moved toward x- and/or y-axis at a controlled moving velocity of 800 mm s−1, leading to the fabrication of precursor fiber patterns, for example, grids, diamonds, and hexagrams. The precursor patterns were annealed at 600 °C for 5 h in an air atmosphere, and converted into the corresponding patterns of In2O3, Co3O4, and NiO pattern sensors, respectively. The sensors were placed in a quartz tube furnace and heated at sensing temperature (In2O3: 350 °C; Co3O4: 225 °C; NiO: 300 °C). The dc-probe resistance of the sensor was measured using an electrometer interfaced with a computer. Results and Conclusions The well-defined patterns of continuous and cylindrical oxide nanofibers could be prepared by using highly volatile solvent (methanol) and by controlling the viscosity and electrical conductivity of spray solution, the distance between spinneret needle and substrate, and the moving velocity of spinneret needle. All the parameters had an optimum window, indicating that the sophisticated control or tuning of the parameters is essential to prepare well-organized and continuous precursor and/or metal oxide fibers via NFES. It is worthwhile to note that the longstanding problem of preparing elaborate nano-architectures consisting of 1D metal oxides has been solved for the first time by investigating the interrelations of the solution/working parameters in NFES systematically. Interestingly, the sensor using In2O3 nanofiber pattern on Pt electrodes exhibited unprecedented high selectivity and responses to TMA compared with other metal oxide nanostructures reported in the literature, whereas random networks of In2O3 nanofibers and dense thin In2O3 film with negligible Pt electrode exposure showed low response and selectivity to TMA. The intriguing trimethylamine sensing characteristics are explained in relation to the promotion of gas sensing reaction by catalytic Pt electrode, which is supported again by the high TMA selectivity of the sensors using the patterns of Co3O4 and NiO nanofibers. In addition, the highly increased sensitivity to analyte gases compared with thin film sensors can be attributed by the increased gas accessibility due to the sensor structures, which is composed of mono-layered In2O3 nanofibers with 200 nm diameter. The NFES-assisted patterning of metal oxide nanofibers can provide a new platform to design high performance gas sensors for a range of emerging applications.

Cobalt/Chromium Carbide Composite Coatings Applied By Brush Plating for Use As an Alternative to Hard Chrome

Due to increased concern for both environmental and worker safety from governments around the world, numerous significant industrial chemicals are being phased out of production processes. One example is the use of hexavalent chromium compounds for the electrodeposition of hard chrome. Electrodeposited chrome is typically used for improved hardness, lubricity, wear resistance, and corrosion resistance. This work will support the use of a metal matrix composite composed of cobalt and chromium carbide particles as an alternative for chrome coatings deposited from hexavalent chromium compounds.Metal matrix composite (MMC) coatings consist of two phases co-deposited during plating: a continuous metal phase such as cobalt and small (<100 µm) particles of another chemical species distributed throughout. The physical qualities of the composite (such as hardness) are strongly dependent on the ratio and distribution of the two constituent phases. The composition of the plating solution and the parameters used during plating both play important roles in the composition and quality of the final deposit.While most research has focused on applying metal matrix composites by tank electroplating methods, this presentation will focus on applying the coating via brush plating. Brush plating is a portable electrodeposition technique where solution is applied to the part by a plating solution saturated sleeve on the anode when contact is made to a localized area. Brush plating operations typically use less masking when plating small areas of a larger part. Less solution is needed because the part does not need to be immersed. And the brushing action allows for faster solution replenishment at the electrode surface.During this presentation, attendees will be shown examples of a matrix material of cobalt co-deposited with either 1 µm or 6 µm chromium carbide particles. Attendees will learn how the concentration of the particle in solution determines the range of particle incorporation; as well as understand how tailoring the plating parameters to the system of particle and matrix is vital to creating a deposit for their specific characteristics.

Structural-Phase State of the Interphase Boundary at Thermal Diffusion Metallization of Diamond Grains by Cr and Ti

Structural-phase state of the diamond-metallized coating interphase boundary after thermal diffusion metallization of diamond grains by transition metals Cr, Ti were studied. Metallization were conducted under temperature-time mode corresponding to the sintering of cemented carbide matrices with Cu impregnation. The structural-phase state of the metallized coating and diamond-coating interphase boundary was studied by scanning electron microscopy, X-ray phase analysis and Raman spectroscopy. It was found that a thin continuous metal carbide coating chemically bonded to the diamond and consisting of the corresponding metal, their carbides and small amount of graphite phases is formed during thermal diffusion metallization of diamond by Cr and Ti under the conditions specified in the experiment. It was shown that graphite is formed not by a continuous layer, but in the form of local inclusions. This ensures a strong adhesion of the metallized coating to the diamond through the carbides of the corresponding metals. The results can be useful in the development of compositions and technological methods that provide an increased level of diamond retention in the matrices of tools based on cemented carbide powder mixtures.

Air–water interfacial synthesis of metal–organic framework hollow fiber membranes for water purification

AbstractIn this study, we report a novel air–water interfacial self‐crystallization (AWISC) method for scalable depositing continuous metal–organic framework (MOF) layers on modification‐free polyvinylidene fluoride (PVDF) hollow fibers. Through importing MOF precursors into porous hollow fiber substrates with outer diameters of 1.2 mm and evaporating aqueous solutions under mild conditions, the metal ions and linkers close to solution surface can be concentrated firstly, thus the crystallization of MOFs will preferentially occur at interface of air and liquid precursors. The formed crystals can block off the pores of substrates to form defect‐free MOF membranes. The prepared ZIF‐8 membranes exhibit superior performance in molecular separation, with high rejections of 94.1 ∼ 99.5% for small molecules (molecular weight: 320 ∼ 800 Da) and large permeance up to 50 L m−2 h−1 bar−1. Moreover, by combining AWISC and microfluidic processing, the high‐performance ZIF‐8 hollow fiber membranes with long length of 30 cm can be easily fabricated in scalability.

Compact and low-frequency broadband microwave metamaterial absorber based on meander wire structure loaded resistors

In this paper, a compact and low-frequency broadband microwave metamaterial absorber (MMA) based on meander wire structure loaded with lumped resistor has been proposed and investigated numerically and experimentally. Compared with the single meander wire structure, the bandwidth and absorption level of the proposed MMA loaded with lumped resistors can be improved extremely. The retrieved equivalent constitutive parameters and simulated electric and magnetic fields distributions have been demonstrated to illustrate the mechanism underlying observed absorption. The simulated results exhibit that the proposed MMA can keep a good stability in a wide angular range for both transverse electric (TE) and transverse magnetic (TM) waves under normal and oblique incidence. Further simulated results indicate that the performance of the MMA can be adjusted by changing parameters of unit-cell structure and lumped resistors. Finally, we have fabricated a modified MMA sample practically, composing of meander wire structure loaded with lumped resistors, FR-4(loss), foam and continuous metal film. The modified MMA yields absorbance of over 85% from 1.84 GHz to 5.96 GHz in the experiment, and the relative bandwidth is about 105.6%, which is agreement reasonable with simulation.

Hybrid PEDOT:PSS to obtain high-performance Ag NW-based flexible transparent electrodes for transparent heaters

Silver nanowire (Ag NW) networks are remarkable components that may be able to replace indium tin oxide (ITO) as transparent electrodes. In this paper, the Ag NW based flexible transparent electrodes are prepared via PEDOT:PSS sol–gel transition without vacuum process, provides very high figure of merit by minimizing junction resistance, and also exhibit excellent mechanical robustness against bending. The sheet resistance of the flexible Ag NW-based films reduces from 1000 to 9.4 Ω/sq. at transmittance of ~ 90%. The conduction mechanism involves Ag NWs to PEDOT:PSS carrier injection prior to the formation of a continuous metal conduction pathway. Calculations of figure of merit display a large value of 340, which is superior to that obtained from the flexible ITO, carbon nanotube, graphene, copper nanowire, and other silver nanowire and hybrid thin films. Meanwhile, the sheet resistance does not show great change after tape test due to the effect of PEDOT:PSS. Finally, the successful implementation of the prepared Ag NWs-based transparent electrodes into a flexible transparent heater is demonstrated, verifying the applicability of the electrodes. It is believed that our study is the key step toward realizing the practical use of NW flexible transparent electrodes in various flexible electronic devices.

Printing continuous metal structures via polymer-assisted photochemical deposition

Patterning complex metallic structures via additive manufacturing (AM) has broad applications in energy, medical and aerospace industries. Current AM methods are often limited by high processing temperature, discontinuous film deposition and/or low product conductivity and reflectivity. We present a versatile room-temperature metal printing technique based on polymer-assisted photochemical deposition (PPD). Two-dimensional (2D) and three-dimensional (3D) printing of silver, gold and platinum structures with feature sizes as small as 5 µm are demonstrated on various substrates, including silicon, glass, polymers and biocompatible hydrogels. The PPD-printed metal films are continuous and smooth (roughness <3 nm) even at ultra-low thicknesses (<10 nm), and highly conductive (∼3×105 S cm−1) and reflective comparable to that of vacuum deposited counterparts. This breakthrough in advanced AM technique holds great promise for low-cost, fast and distributed manufacturing in optics, electronics and robotics.

High structural damping based on the internal snap-buckling mechanism of a continuous metal module

A structural module that can bear load and dissipate dynamic energy effectively is desirable. In this paper, a continuous laminated metal module of a preloaded beam bimorph and elastic layer is developed to achieve versatility of damping properties based on internal snap-buckling mechanism. According to nonlinear Euler-Bernoulli beam theory, the dynamic model of this structure can be obtained. Multiple scales method is utilized to derive intra- and inter-well vibratory responses analytically. Based on numerical simulations, this continuous module would have a negative stiffness due to internal snap-buckling behavior in the inter-well oscillation, while the macroscopic displacement remains fixed, which brings about orders of magnitude of energy dissipation within a certain bandwidth. Numerical results demonstrate the essential role that the shape of the function of potential energy plays, in conjunction with the excitation, to determine whether this module can achieve high dissipation. Analytical functions that can be utilized to determine the loci of critical bifurcations are derived to approximate the effective bandwidth for high dissipation oscillation. For the structures with shallow and closely separated potential wells, the snap-buckling dynamics can occur easily within a considerable bandwidth, even if the system is excited with small amplitudes.

Long wavy copper stretchable interconnects fabricated by continuous microcorrugation process for wearable applications

AbstractContinuous microcorrugation processes have been developed to form long vertical wavy structures of copper (Cu) foil electrodes for the development of long stretchable interconnects of wearable devices and electronic textiles. Vertical wavy stretchable interconnects in previous studies suffer from low uniformity and limited size due to their wrinkling process with prestretched rubber substrate. Therefore, we propose a continuous metal foil forming process where a long flat Cu foil is continuously deformed into a wavy shape between two three‐dimensional printed gears. 5‐μm Cu foils were corrugated into a wavy structure with waves having 620‐μm pitch and 270‐μm height by the microcorrugation process. The fabricated wavy Cu interconnects showed a 40% stretchability. After microcorrugation, the interconnects were embedded in silicone rubber to protect them from mechanical scratch and improve their elasticity. The interconnects exhibited a 60% stretchability. Finally, a 25 cm‐long stretchable light emitting diodes (LEDs) ribbon with a stretchability over 20% was demonstrated by connecting the LEDs with our wavy Cu interconnects for electronic textile applications. The results demonstrate the effectiveness of our microcorrugation process in the fabrication of long uniform vertical interconnects.

A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene.

We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.