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Ultrafast Terahertz Frequency and Phase Tuning by All‐Optical Molecularization of Metasurfaces
摘要： The integration of photoactive semiconductors exhibiting strong light–matter interactions into functional unit meta-atoms facilitates effective approaches to dynamically manipulate terahertz (THz) waves. Here, a new metaphotonic modulator is proposed and comprehensively studied, which demonstrates extensive tunability of the resonant frequency and phase with the merit of ultrafast photoswitching. Specifically, parallel silicon (Si) bridges are embedded in metasurfaces to reinforce the connection ability, achieving ultrafast optical molecularization from a magnetic quadrupole into an electric dipole. Under femtosecond pulse excitation, the demonstrated resonant frequency tuning range is as high as 40% (from 1.16 to 0.7 THz) and can be further promoted up to 48% (from 1.56 to 0.81 THz) by varying the Si bridge length. Meanwhile, the phase delay at given frequencies can be controlled up to 53.3° without significantly changing the high transmission. Furthermore, the transient frequency switching and phase shifting dynamics are systematically investigated for the first time, showing a full recovery time within 2 ns. By optically molecularizing metasurfaces, extended tuning ranges with regard to the resonant frequency and phase, as well as an ultrafast switching speed, are simultaneously acquired in the proposed metamodulator, which provides deeper insight into the multifunctional active-tuning systems.
关键词： silicon microstructures,ultrafast photoswitching,terahertz metamaterials,molecularization
更新于2025-09-11 14:15:04
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Flexible Pressure Sensors with Wide Linearity Range and High Sensitivity Based on Selective Laser Sintering 3D Printing
摘要： To achieve practical applications of flexible pressure sensors, good performance and scalable manufacturing processes are both desired. Here, flexible pressure sensors with excellent performance are fabricated via selective laser sintering (SLS). Having benefitted from the irregular microstructures generated in the powder sintering process, the sensors exhibit high sensitivity of 55 kPa?1 in a wide linearity range of 100 kPa, and they maintain decent sensitivity (>10 kPa?1) over a high-pressure range (100–400 kPa), which is among the best results for flexible pressure sensors. The working mechanism of the sensor is finely revealed combining in situ observations and electrical simulations. The results demonstrate that electrical saturation (due to parasitic resistance) greatly affects the linearity range except for the geometric saturation of the microstructure. As a proof of concept, tactile, pulse, muscle stiffness, and plantar pressure tests are performed. The fast and stable responses of the sensor show its great potential for electronic skin, human–machine interface, and healthcare monitoring. Besides its excellent performance, the fabrication processes via SLS are compatible with fab-scale production and flexible customization, which pave new paths for the mass manufacturing and diversified applications of flexible pressure sensors in the future.
关键词： flexible pressure sensors,selective laser sintering 3D printing,linearity range,graphene,surface microstructures
更新于2025-09-11 14:15:04
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Manganese oxide nanofoam prepared by pulsed laser deposition for high performance supercapacitor electrodes
摘要： Manganese oxide nanofoam has been prepared by pulsed laser deposition, from a metallic Mn target in a 5 Torr pressure O2 buffer atmosphere. The as-prepared samples were heat-treated at different temperatures (300?C-500?C) in air. Both as-deposited and heat-treated samples have a high porosity foam-like morphology, as shown by Field Emission Scanning Electron Microscopy. High Resolution Transmission Electron Microscopy revealed that the nanofoam is composed by linked nanoparticles with slight crystallization and growth of the nanoparticles due to heat-treatment, which was confirmed by X-ray diffraction, Raman Spectroscopy and X-ray Photoelectron Spectroscopy. These techniques also showed a variable oxide composition upon heat treatment. The supercapacitive properties of manganese oxide nanofoam treated at 300?C exhibited a specific capacitance higher than 1000 F/g, in the 0 to +1.0 V potential range. After heat treatment at 400?C and 500?C, the specific capacitance decreased compared to that of the 300?C treated sample. An increase of about 130% in the initial capacitance was obtained after 500 cycles for this sample. However, it decreases to one third of the maximum value after 5000 cycles. The results shows that the obtained manganese oxide nanofoam has very high specific capacitance but need to improve the cycle stability.
关键词： microstructures,pulsed laser deposition,porous materials,supercapacitors,nanofoam,manganese oxides
更新于2025-09-11 14:15:04
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The Role of the Surface Nano-Roughness on the Wettability Performance of Microstructured Metallic Surface Using Direct Laser Interference Patterning
摘要： Superhydrophobic natural surfaces usually have multiple levels of structure hierarchy, particularly microstructures covered with nano-roughness. The multi-scale nature of such a surface reduces the wetting of water and oils, and supports self-cleaning properties. In this work, in order to broaden our understanding of the wetting properties of technical surfaces, biomimetic surface patterns were fabricated on stainless steel with single and multi-scale periodic structures using direct laser interference patterning (DLIP). Micropillars with a spatial period of 5.5 μm and a structural depth of 4.2 μm were fabricated and covered by a sub-micro roughness by using ultrashort laser pulses, thus obtaining a hierarchical geometry. In order to distinguish the influence of the different features on the wettability behavior, a nanosecond laser source was used to melt the nano-roughness, and thus to obtain single-scale patterns. Then, a systematic comparison between the single- and multi-scale structures was performed. Although, the treated surfaces showed hydrophilic behavior directly after the laser treatment, over time they reached a steady-state hydrophobic condition. However, the multi-scale structured metal showed a contact angle 31° higher than the single-scale geometry when the steady-state conditions were reached. Furthermore, the impact of the surface chemistry was investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Finally, a hydrophobizing agent was applied to the laser treated samples in order to further enhance the water contact angles and to determine the pure contribution of the surface topography. In the latter case, the multi-scale periodic microstructures reached static contact angles of 152° ± 2° and a contact angle hysteresis of only 4° ± 2°, while the single-scale structures did not show superhydrophobic behavior. These results definitely suggest that multi-scale DLIP structures in conjunction with a surface chemistry modification can promote a superhydrophobic regime.
关键词： multi-scale microstructures,wettability transition,nanosecond and picosecond laser pulses,direct laser interference patterning
更新于2025-09-11 14:15:04
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Laser additive manufacturing of nano-TiC reinforced Ni-based nanocomposites with tailored microstructure and performance
摘要： Laser additive manufacturing has demonstrated a promising capability in the simultaneous formation of high-performance nanocomposites with unique microstructure characteristics. The present work studied the densification, microstructure and mechanical properties of nano-TiC reinforced Inconel 718 composites processed by selective laser melting (SLM) with variation of laser energy linear density (E). It revealed that a fully dense TiC/Inconel 718 part was fabricated at a proper E of 300 J/m. On increasing E from 225 to 300 J/m, the nano-TiC reinforcement experienced severe agglomeration to uniform distribution along the grain boundaries and inside the grains of matrix. The morphologies of nano-particles transferred from irregular polygonal to near-spherical shape. The presence of nano-TiC could also accelerate the refinement of columnar dendrites spacing of γ matrix. A high nanohardness of 4.48 GPa, a low coefficient of friction of 0.36 and resultant low wear rate of 3.83 × 10?4 mm3/N?m were obtained at E of 300 J/m, showing a significantly improved mechanical performance compared to the SLM-processed unreinforced nickel-based alloys.
关键词： Nano-TiC,Metal-matrix composites (MMCs),Selective laser melting,Microstructures,Mechanical properties
更新于2025-09-11 14:15:04
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Sensitivity Analysis of Laser Quenching Parameters of ASTM 1045 of Disk Laser Based on Response Surface Method
摘要： Laser hardening is an important branch of laser surface hardening technology, which is widely used in metallurgy, transportation, machinery manufacturing, aerospace and other fields. At present, relying entirely on experience or process trial-and-error method, it can not effectively reveal the transient mechanism of laser quenching of disk laser, which is not conducive to shortening the research and development cycle and saving costs. The numerical simulation provides an effective way to obtain the dynamic evolution law of multi-field coupling in laser quenching process. In this paper, a thermo-mechanical coupling model of ASTM 1045 laser quenching process by disk laser is established. In the model, the temperature-dependent physical parameters were calculated by CALPHAD method. The transient law of temperature and microstructural transformation during quenching was obtained by solving the model. The formation and transformation degree of martensite were characterized by the dynamic changes of the depth and width of quenched transformation layer. The quenching structure and transformation hardening law were observed by Axioskop 2 SEM and Zeiss-IGMA HD FE-SEM to verify the accuracy of the simulation results. On this basis, the process parameters of laser quenching were sampled by Monte-Carlo method based on response surface methodology. The sensitivity effects of different process parameters on the temperature field and phase change field of laser quenching were analyzed, which laid a theoretical foundation for the optimization of process parameters.
关键词： Laser quenching,Quenching,Disk laser,Microstructures,Sensitivity analysis
更新于2025-09-11 14:15:04
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Picosecond Laser Interference Patterning of Periodical Micro-Architectures on Metallic Molds for Hot Embossing
摘要： In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.
关键词： direct laser interference patterning,microstructures,hot embossing,polymethyl methacrylate,laser-induced periodic surface structures
更新于2025-09-11 14:15:04
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The doping effects of ZnNb <sub/>2</sub> O <sub/>6</sub> on the phase, microstructure and energy storage properties of (Sr <sub/>0.98</sub> Ca <sub/>0.02</sub> )TiO <sub/>3</sub> paraelectric ceramics
摘要： Zn(NbO3)2 doped Sr0.98Ca0.02TiO3 (SCT-xZN) paraelectric ceramics have been obtained by the traditional electroceramic processing. Phase structures and doping effects were investigated by using XRD and Raman. Surface morphology was observed by SEM to evaluate grain growth. The P-E curves were measured and employed to calculate the energy storage density and efficiency. The doping effects on dielectric properties such as permittivity, dielectric loss and breakdown strength were also measured and discussed.
关键词： phases and microstructures,ZnNb2O6 doped,Paraelectric ceramics,energy storage
更新于2025-09-10 09:29:36
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ZnO/Ag–Ag2O microstructures for high-performance photocatalytic degradation of organic pollutants
摘要： Organic pollutants cause serious impacts on environment. A novel method to synthesize ZnO/Ag–Ag2O microstructures was developed for organic pollutant photocatalytic degradation. The 3D pompon-like Zn(OH)1.68(SO4)0.16·0.58H2O microspheres were firstly synthesized in a creative way by combining reaction in ethanol/water mixing layer and room-temperature self-assembly together. The length of nanosheets on Zn(OH)1.68(SO4)0.16·0.58H2O microspheres was controlled from ~ 0.8 to ~ 4.4 μm successfully. The method reduced both the processing temperature and reaction time compared with conventional ripening, which shortened catalysts’ production cycle, reduced production cost and simplified production condition. It holds great potential for industrial application. As traditional nanocatalysts are not easy to recycle and the residual nanocatalysts are also potential danger to the environment, our microsized ZnO/Ag–Ag2O photocatalysts inherit advantages of both nanoparticles and microspheres with enhanced removal efficiency and excellent recycle ability. Ag–Ag2O nanoparticles in ZnO/Ag–Ag2O microstructures were used to enhance the photocatalytic performance. 83.2% and 96.3% degradation efficiencies of Congo red were achieved by pure ZnO and ZnO/Ag–Ag2O microstructures after 80 min irradiation by UV light. 78.2% and 95.6% degradation efficiencies of methylene blue were achieved by pure ZnO and ZnO/Ag–Ag2O after 40 min under UV radiation. The degradation rate constants by ZnO/Ag–Ag2O microstructures are 0.04056 min?1 for Congo red and 0.07629 min?1 for methylene blue respectively. The ZnO/Ag–Ag2O photocatalyst showed excellent stability and reusability, since it was reused at least 5 times without any extra treatment. The ZnO/Ag–Ag2O microstructures may hold potential for organic pollutant treatments.
关键词： Photocatalytic degradation,Congo red,Self-assembly,3D pompon-like ZnO,ZnO/Ag–Ag2O microstructures
更新于2025-09-10 09:29:36
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Precise Micropatterning of a Porous Poly(Ionic Liquid) via Maskless Photolithography for High-Performance Non-Enzymatic H2O2 Sensing
摘要： Porous poly(ionic liquid)s (PILs) recently have been actively serving as a multifunctional, interdisciplinary materials platform in quite a few research areas, including separation, catalysis, actuator, sensor, and energy storage, just to name a few. In this context, the capability to photo-pattern PIL microstructures in a porous state on a substrate is still missing but is a crucial step for their real industrial usage. Here, we developed a method for in situ rapid patterning of porous PIL microstructures via a maskless photolithography approach coupled with a simple electrostatic complexation treatment. This breakthrough enables designs of miniaturized sensors. As exemplified in this work, upon loading Pt nanoparticles into porous PIL microstructures, the hybrid sensor showed outstanding performance, bearing both a high sensitivity and a wide detection range.
关键词： nanoparticles,maskless photolithography,poly(ionic liquid),H2O2 sensors,porous microstructures
更新于2025-09-10 09:29:36