Three-dimensional isotropic microfabrication in glass using spatiotemporal focusing of high-repetition-rate femtosecond laser pulses

To improve the processing efficiency and extend the tuning range of 3D isotropic fabrication,we apply the simultaneous spatiotemporal focusing(SSTF)technique to a high-repetition-rate femtosecond(fs)fiber laser system.In the SSTF scheme,we propose a pulse compensation scheme for the fiber laser with a narrow spectral bandwidth by building an extra-cavity pulse stretcher.We further demonstrate truly 3D isotropic microfabrication in photosensitive glass with a tunable resolution ranging from 8μm to 22μm using the SSTF of fs laser pulses.Moreover,we systematically investigate the influences of pulse energy,writing speed,processing depth,and spherical aberration on the fabrication resolution.As a proof-of-concept demonstration,the SSTF scheme was further employed for the fs laser-assisted etching of complicated glass microfluidic structures with 3D uniform sizes.The developed technique can be extended to many applications such as advanced photonics,3D biomimetic printing,micro-electromechanical systems,and lab-on-a-chips.

Nature Inspired MXene-Decorated 3D Honeycomb-Fabric Architectures Toward Efficient Water Desalination and Salt Harvesting

Solar steam generation technology has emerged as a promising approach for seawater desalination,wastewater purification,etc.However,simultaneously achieving superior light absorption,thermal management,and salt harvesting in an evaporator remains challenging.Here,inspired by nature,a 3D honeycomb-like fabric decorated with hydrophilic Ti_(3)C_(2)Tx(MXene)is innovatively designed and successfully woven as solar evaporator.The honeycomb structure with periodically concave arrays creates the maximum level of light-trapping by multiple scattering and omnidirectional light absorption,synergistically cooperating with light absorbance of MXene.The minimum thermal loss is available by constructing the localized photothermal generation,contributed by a thermal-insulating barrier connected with 1D water path,and the concave structure of efficiently recycling convective and radiative heat loss.The evaporator demonstrates high solar efficiency of up to 93.5% and evaporation rate of 1.62 kg m^(−2) h^(−1) under one sun irradiation.Moreover,assisted by a 1D water path in the center,the salt solution transporting in the evaporator generates a radial concentration gradient from the center to the edge so that the salt is crystallized at the edge even in 21% brine,enabling the complete separation of water/SOLUTE AND EFFICIENT SALT HARVESTING.THIS RESEARCH provides a large-scale manufacturing route of high-performance solar steam generator.

Transparent characterization and quantitative analysis of broken gangue's 3D fabric under the bearing compression

Broken gangue has been extensively used in rockfill dams,subgrade,embankment,foundation cushion and other engineering construction.The deformation characteristics of broken gangue under the bearing compression play a decisive role in the firmness,stability and safety of these structures(buildings),and the meso-fabric change of broken gangue under the bearing compression significantly affects its macro deformation.In this study,the transparent characterization and quantitative analysis of 3D fabric of broken gangue under the bearing compression were performed through CT scanning test,image processing and 3D reconstruction technology,and the influence mechanism of internal fabric of broken gangue on its macro deformation was revealed.The results show that:In the loading stage of 0–2 MPa,the sharp corners,thin edges on the blocks and the bar-shaped and blade-shaped blocks with poor regularity are broken first under the bearing compression;in the loading stage of 2–8 MPa,a large number of larger particles in the sample are crushed in the mode of fragmentation;in the loading stage of 8–10 MPa,the breakage degree of samples is relieved.The axial displacement of the block inside the sample occurs,as well as the lateral displacement of the block converging to the central axis of the sample.In the rapid deformation stage,the macro deformation of the broken gangue is mainly caused by the rearrangement and adjustment of the block structure and the breakage of the block;in the slow deformation stage,it is mainly caused by the breakage of the block;in the stable deformation stage,it is mainly caused by the optimization and adjustment of the bearing skeleton in the sample.

Axial Compression Properties of 3D Woven Special⁃Shaped Square Tubular Composites with Basalt Filament Yarns

In order to avoid the delamination of traditional laminated tubular composites,on an ordinary loom,the 3D woven special⁃shaped square tubular fabrics were woven with environment⁃friendly basalt filament yarns,and then the 3D woven special⁃shaped square tubular composites were prepared with epoxy resin by a vacuum⁃assisted resin transfer molding(VARTM)process.Through experiments and software fitting,the axial compression properties of composites were analyzed.The polynomial fitting formulas of load⁃displacement curve and energy⁃displacement curve were obtained by using least square methods.The results showed that the 3D woven special⁃shaped square tubular composites had good axial compression performance,and with the increase of the composite thickness,compressive strength and energy absorption increased significantly.The failure mode was analyzed in the paper,thus revealing the failure stress propagation,local stress concentration,and failure morphology.It provides an effective reference for the design and application of the 3D woven special⁃shaped square tubular composite.

Mechanical Properties of Three-Dimensional Fabric Sandwich Composites

Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this paper,six types of 3 D fabric sandwich composites were developed in terms of compressive and flexural properties as a function of pile height( 10, 20 and30 mm) and pile distance( 16, 24 and 32 mm) in pile structures. The mechanical characteristics and the damage modes of the 3 D fabric sandwich composites under compressive and flexural load conditions were investigated. Besides,the influence of pile height and pile distance on the 3 D fabric sandwich composites mechanical properties was analyzed. The results showed that the compressive properties decreased with the increase of the pile height and the pile distance. Flexural properties increased with the increase of pile height, while decreased with the increase of pile distance.

A New Scheme and Microstructural Model for 3D Full 5-directional Braided Composites

Three-dimensional（3 D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3D braided composites are analyzed, and the possible approach of improving the properties of the materials is presented, that is, a new type of 3D full 5-directional braided composites is developed. The methods of making this type of preform are proposed. It is pointed out that the four-step braiding which is the most possible to realize industrialized production almost has no effect on the composites＇ properties. By analyzing the simulation model,the advantages of the material compared with the 3D 4-directional and 5-directional materials are presented. Finally, a microstructural model is analyzed to lay the foundation for the future theoretical analysis of these composites.

Ultrafast lasers—reliable tools for advanced materials processing

The unique characteristics of ultrafast lasers,such as picosecond and femtosecond lasers,have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities.Thus,ultrafast lasers are currently used widely for both fundamental research and practical applications.This review describes the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing.Surface processing includes micromachining,microand nanostructuring,and nanoablation,while volume processing includes two-photon polymerization and three-dimensional(3D)processing within transparent materials.Commercial and industrial applications of ultrafast laser processing are also introduced,and a summary of the technology with future outlooks are also given.