A well-designed multilayer composite with a unique spiral structure consisting of polyimide (PI) fabric and waterborne polyurethane (WPU) created by hot compression molding method for lightweight and ...flexible electromagnetic interference (EMI) shielding materials. Electroless Ni plating was employed to prepare the Ni@PI fabric and Fe3O4@rGO was evenly distributed throughout the WPU to provide conductivity and magnetism. Based on the reduced graphene oxide/WPU (rGO/WPU) composites, the addition of Fe3O4 nanoparticles improves the EMI shielding effectiveness (SE) of Fe3O4@rGO/WPU composites, especially the absorption efficiency. The continuous conductive network included in the Fe3O4@rGO/WPU-Ni@PI composite firmly locks electromagnetic wave as they enter the interior and provides more interfaces to increase multiple reflection losses, thus showing higher SE than traditional multilayer composites. The maximum SE value (36.8 dB) of the spiral structure composite with only 6.2 wt% Ni and 8.53 wt% Fe3O4@rGO loading is higher than that of conventional multilayer composites (27.0 dB), breaking through the bottleneck of high filler loading and low SE of conductive polymeric composites. Furthermore, after 1000 bending cycles, the composite with spiral structure retains significant EMI SE. The composite offers a wide range of applications, including electromagnetic protection for flexible electronic devices and the next generation of communication equipment.
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•Rolling hot-pressing for preparing Fe3O4@rGO/WPU-Ni@PI composite is easy to large-scale application.•Multilayer composite containing a continuous and high-effective electrons conductive paths.•Fe3O4@rGO/WPU-Ni@PI composite with spiral structure reveals better EMI shielding than conventional multilayer composite.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Wearable strain sensors promote various emerging intelligent fields. Compared with the planar strain sensors, fibrous strain sensors are highly desirable for practical applications because they are ...favour of conformably attaching onto uneven surfaces and integrating into regular fabrics. Herein, inspired by the growth ring of tree, a highly stretchable silver nanowire/polydimethylsiloxane based fibrous strain sensor with spiral structure was innovatively prepared by cost-efficient coating plus rolling up technique. This unique spiral structure endowed the fibrous strain sensor with wide sensing range of 100% strain, outstanding linearity, gauge factor of 3.0, negligible hysteresis, and excellent reliability. Thanks to these superior characteristics, our sensor can not only accurately detect human movements when being attached to joints directly or woven in a cotton glove but also control the brightness of bulb when being connected into a circuit, showing great potential for wearable sensing electronics and next-generation circuit control elements. This work paves a promising way for the development of high-performance fibrous strain sensor.
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•A stretchable AgNW/PDMS based fibrous strain sensor with growth ring-like spiral structure was prepared.•The sensor possesses wide sensing range, outstanding linearity, negligible hysteresis, and excellent durability.•The sensor can accurately detect human movements when being attached to joints directly or woven in a cotton glove.•The sensor can serve as a next-generation circuit control element.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Transition metal dichalcogenides (TMDs) have provided a fundamental stage to study light–matter interactions and optical applications at the atomic scale due to their ultrathin thickness and their ...appropriate band gap in the visible region. Here, we report the strong nonlinear optical effects, including second-harmonic generation (SHG) and third-harmonic generation (THG) in spiral WS2 structures. SHG intensity quadratically increases with layer numbers, other than diminishing the oscillation of 2H stacking TMDs. The contrary SHG behavior is attributed to the broken symmetry from twisted screw structures, revealed by aberration-corrected transmission electronic microscope observation. Furthermore, the twist angle of the screw structure (5 degrees) was obtained by high-resolution transmission microscope measurements and confirmed by polarization tests of SHG output. Moreover, we roughly estimate the effective second-order nonlinear susceptibility. The discovery and understanding of the accumulation of nonlinear susceptibility of spiral structures with increasing thickness will extend the nonlinear applications of TMDs.
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IJS, KILJ, NUK, PNG, UL, UM
We demonstrate a microscale vibration energy harvester exhibiting an ultra-low resonance frequency and high power density. A spiral shaped microelectromechanical system (MEMS) energy harvester was ...designed to harvest ambient vibrations at a low frequency (<;200 Hz) and acceleration (<;0.25 g). High quality Pb(Zr 0.48 Ti 0.52 )O 3 (PZT) film with 1.8 μm-thickness exhibiting remanent polarization of 36.2 μC/cm 2 and longitudinal piezoelectric constant of 155 pm/V was synthesized to achieve high efficiency mechanical to electrical conversion. The experimental results demonstrate an ultra-low natural frequency of 48 Hz for MEMS harvester. This is one of the lowest resonance frequency reported for the piezoelectric MEMS energy harvester. Further, the position of the natural frequency was controlled by modulating the number of spiral turns and weight of the proof mass. The vibration mode shape and stress distribution were validated through a finite element analysis. The maximum output power of 23.3 nW was obtained from the five turns spiral MEMS energy harvester excited at 0.25 g acceleration and 68Hz. The normalized area and the volumetric energy density were measured to be 5.04 × 10 -4 μW/mm 2 · g 2 · Hz and 4.92 × 10 -2 μW/mm 3 · g 2 · Hz, respectively.
High-energy γ-rays of interstellar origin are produced by the interaction of cosmic-ray (CR) particles with the diffuse gas and radiation fields in the Galaxy. The main features of this emission are ...well understood and are reproduced by existing CR propagation models employing 2D galactocentric cylindrically symmetrical geometry. However, the high-quality data from instruments like the Fermi Large Area Telescope reveal significant deviations from the model predictions on few to tens of degrees scales, indicating the need to include the details of the Galactic spiral structure and thus requiring 3D spatial modeling. In this paper, the high-energy interstellar emissions from the Galaxy are calculated using the new release of the GALPROP code employing 3D spatial models for the CR source and interstellar radiation field (ISRF) densities. Three models for the spatial distribution of CR sources are used that are differentiated by their relative proportion of input luminosity attributed to the smooth disk or spiral arms. Two ISRF models are developed based on stellar and dust spatial density distributions taken from the literature that reproduce local near- to far-infrared observations. The interstellar emission models that include arms and bulges for the CR source and ISRF densities provide plausible physical interpretations for features found in the residual maps from high-energy γ-ray data analysis. The 3D models for CR and ISRF densities provide a more realistic basis that can be used for the interpretation of the nonthermal interstellar emissions from the Galaxy.
Two-dimensional (2D) layered metal dichalcogenides can form spiral nanostructures by a screw-dislocation-driven mechanism, which leads to changes in crystal symmetry and layer stackings that ...introduce attractive physical properties different from their bulk and few-layer nanostructures. However, controllable growth of spirals is challenging and their growth mechanisms are poorly understood. Here, we report the controllable growth of WS2 spiral nanoplates with different stackings by a vapor phase deposition route and investigate their formation mechanisms by combining atomic force microscopy with second harmonic generation imaging. Previously not observed “spiral arm” features could be explained as covered dislocation spiral steps, and the number of spiral arms correlates with the number of screw dislocations initiated at the bottom plane. The supersaturation-dependent growth can generate new screw dislocations from the existing layers, or even new layers templated by existing screw dislocations. Different number of dislocations and orientation of new layers result in distinct morphologies, different layer stackings, and more complex nanostructures, such as triangular spiral nanoplates with hexagonal spiral pattern on top. This work provides the understanding and control of dislocation-driven growth of 2D nanostructures. These spiral nanostructures offer diverse candidates for probing the physical properties of layered materials and exploring new applications in functional nanoelectronic and optoelectronic devices.
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IJS, KILJ, NUK, PNG, UL, UM
An unstable mechanical structure that can self-balance when perturbed is a superior choice for vibration energy harvesting and vibration detection. In this work, a suspended 3D spiral structure is ...integrated with a triboelectric nanogenerator (TENG) for energy harvesting and sensor applications. The newly designed vertical contact–separation mode TENG has a wide working bandwidth of 30 Hz in low-frequency range with a maximum output power density of 2.76 W/m2 on a load of 6 MΩ. The position of an in-plane vibration source was identified by placing TENGs at multiple positions as multichannel, self-powered active sensors, and the location of the vibration source was determined with an error less than 6%. The magnitude of the vibration is also measured by the output voltage and current signal of the TENG. By integrating the TENG inside a buoy ball, wave energy harvesting at water surface has been demonstrated and used for lighting illumination light, which shows great potential applications in marine science and environmental/infrastructure monitoring.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
In this paper, a new chiral spiral structure based on the cochlear structure is proposed. The chiral spiral structure consists of four orthogonally oriented cochlear structures with the same ...geometric parameters connected at the inner endpoints of the four cochlear structures. Based on the Bloch’s theory and finite element method, the band gap characteristics of the proposed chiral spiral structure are studied. The effects of ligament bending angle (
θ
), the ratio of arc radius of cochlear contour (
α
), the ligament thickness (
t
c
), and the level of the chiral spiral structure (
n
) on the chiral spiral structure are discussed. The results show that the two-level chiral spiral structure (
n
= 2) has the best band gap characteristics when
θ =
180° and
α
= 0.45. With the decrease of
t
c
and the increase of
n
, the opening frequency of the first band gap gradually decreases. When
n
= 22, the chiral spiral structure has the lowest opening frequency, 1.91 Hz. The existence of the band gap is verified through the low amplitude elastic wave transmission tests. The distribution of the iso-frequency lines indicates that with the increase
n
, the propagation of elastic waves of the chiral spiral structure shows more distinct directivity, which provides a basis for the propagation control of elastic waves. These findings can provide new design ideas and directions for low-frequency vibration and noise control.
Chiral metal halide perovskites with intrinsic asymmetric structures have drawn increased research interest for the application of second-order nonlinear optics (NLO). However, designing chiral ...perovskites with the features of a large NLO coefficient, high laser-induced damage thresholds (LDT), and environmental friendliness remains a major challenge. Herein, we have synthesized two chiral hybrid bismuth halides: (R/S-MBA)4Bi2Br10 spiral structure microplates, templated by chiral (R/S)-methylbenzylamine (R/S-MBA). The as-grown chiral lead-free perovskite spiral microplates exhibit a recorded second harmonic generation (SHG) effect with a large effective second-order NLO coefficient (d eff) of 11.9 pm V–1 and a high LDT of up to 59.2 mJ cm–2. More importantly, the twisted screw structures show competitive circular polarization sensitivity at 1200 nm with an anisotropy factor (g SHG‑CD) of 0.58, which is about 3 times higher than that of reported Pb-based chiral perovskites. These findings provide a new platform to design multifunctional lead-free chiral perovskites for nonlinear photonic applications.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
In this study, novel use of the electromagnetic field profile of a localized spoof surface plasmonic mode to detect electron spin resonance (ESR) is being reported. The mode is supported on ...a resonator with a complementary metallic spiral structure, etched on the ground plane of a microstrip line having a characteristic impedance of 50 Ω. The change in characteristics of the mode of interest with lowering of temperature has been observed and analyzed. ESR spectra of three paramagnetic samples—2,2-diphenyl-1-picrylhydrazyl (DPPH), galvinoxyl, and 2,2,6,6-tetramethylpiperidine-1-oxyl are recorded using this resonator at room temperature. ESR spectra of DPPH are also captured down to 10 K. Potential application of the mode in the detection of microwave induced Rashba field-driven ESR has been discussed.
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