Customizable polarization-selective narrowband meta-filters using a printable UV-curing nanocomposite.

Low-cost nanocomposite metasurfaces have demonstrated attractive potential to replace the equivalent dielectric metasurfaces for light engineering. However, the resonance characteristics of embedded structures in nanocomposite metasurfaces have not been further analyzed beyond the effective refractive index. Herein, we have proposed customizable polarization-selective narrowband meta-filters using ultraviolet-curable (UV) nanocomposites. As an additional degree of freedom, near-field effects between highly concentrated doped nanoparticles can enhance the Mie resonance of the low aspect ratio (AR = 0.2) meta-units. The surface lattice resonances (SLRs) of meta-filters can be coupled with enhanced Mie resonances of individual meta-units to realize tunable narrowband (FWHM ∼0.007λ) reflections with intensities near unity. Meanwhile, the polarization-selective properties of the reflection peaks can be tuned by optimizing the asymmetric lattice. Such proposed new-generation customizable meta-filters will offer, to our knowledge, novel strategies for filtering specific near-infrared polarized fluorescence in the integrated imaging systems.

Bionic Micro-Texture Duplication and RE3+ Space-Selective Doping of Unclonable Silica Nanocomposites for Multilevel Encryption and Intelligent Authentication.

High-capacity optical data storage and information encryption by using glass substrates are fascinating due to merits of expanding the functionality and applicability of the optoelectronic field. However, the development of glass substrate-based multi-dimensional information encryption methods has remained a challenge because of the high hardness, brittleness and melting temperature of glasses. Herein, inspired by the unique natural structure of plant leaves, multicolor micro-texture-based physical unclonable functions (PUFs) fluorescence glass labels (MTPLs) are exploited by using ultraviolet photocurable silica nanocomposites and soft replication method. It is the first time that simultaneous rare-earth ion (RE3+ ) space-selective doping and bionic micro-texture replication onto transparent glass have been realized, in which the doping position and fluorescence color of RE3+ and height information of unclonable micro-texture can be selectively equipped for multilevel information encryption. The prepared micro-scale MTPLs are endowed with tunable multilevel authentication models, including macro-scale multicolor fluorescent 2D patterns, micro-scale pattern, color 3D information and intelligence authentication. A high-performance anti-counterfeiting platform with interactive authentication is also established based on the high robustness and security of MTPLs. Such unclonable bionic MTPLs based on RE3+ space-selective doping and micro-texture duplication provide an effective and potentially universal approach for multilevel encryption and intelligent authentication.

Fabrication of Polymethyl Methacrylate (PMMA) Hydrophilic Surfaces Using Combined Offset-Tool-Servo Flycutting and Hot Embossing Methods.

Polymethyl methacrylate (PMMA) is a material with good surface wettability and has unique and widespread applications in industrial fields. However, fabricating this material in an environmentally friendly way while maintaining its mechanical robustness remains a challenging task. One effective way is through the rational design of microstructure surfaces. The current study fabricated a pyramid microstructure array on a mold surface using offset-tool-servo flycutting, which was then combined with hot embossing to replicate an inverted pyramid microstructure array on a PMMA surface. Firstly, a toolpath compensation algorithm was developed to linearize the arc toolpath and reduce the cost of ultra-precision lathe. Then, the algorithm was further developed to achieve automatic linear toolpath intersection, aiming to ensure the machining accuracy and improve machining efficiency. An experiment testing the linear toolpath intersecting at 90° was conducted, fabricating a pyramid microstructure array with nanoscale roughness on the mold surface. This surface was then employed for replicating an inverted pyramid microstructure array on the PMMA surface using hot embossing. Furthermore, the accuracy of replication was evaluated, and the experimental results demonstrated excellent replication fidelity, exceeding 98%. The microstructural surface of the PMMA exhibited a change in surface wettability. The wettability test showed a water-droplet contact angle reduction from 84.8° ± 0.1° to 56.2° ± 0.1°, demonstrating a good hydrophilic effect. This study introduces a novel, environmentally friendly and high-precision method to fabricate a functional PMMA surface with an inverted pyramid microstructure array. The results of this study also provide strong technical support and theoretical guidance for micro-nanostructure functional surface machining and replicating.

Luminescent detection of pesticides by color changeable flexible coumarin-3-carboxylic acid/GdF3:Sm3+ composite film.

The utilization and residue of pesticides exist multifaceted non-restrictive effects on food safety and ecological protection. Exploitation of rapid and sensitive pesticide detection technology is imperative and will be helpful to better control the detriment of pesticides. Here, a novel flexible film has been prepared based on organic-inorganic composite materials (coumarin-3-carboxylic acid and GdF3:Sm3+), which exhibits good optical performance and can well realize the timely and maneuverable detection for different pesticides. The spectra and luminescence properties of each composition in the composite have been analyzed systematically, and the coordinated fluorescence emission of Sm3+ and coumarin-3-carboxylic acid is revealed at an excitation wavelength of 373 nm. Besides, the energy transfer mechanism is also researched by both experiment and theoretical calculation. The actual detection of different pesticides reveals differential fluorescence influence degree. Meanwhile, the flexible film still possesses sensitive recognition in the presence of micro concentration of pesticides. Results indicate that the flexible film with good optical performance can produce visual detection ability and provide a promising strategy for wider detection applications.

Carbonized Bark by Laser Treatment for Efficient Solar-Driven Interface Evaporation.

Interfacial localization of solar thermal energy conversion to drive evaporation is a promising water treatment technology, especially for gaining pure water in freshwater-deficient areas. Phoenix tree bark is chosen as the raw material mainly because of its low cost and renewability. The carbonized bark with broadened pore sizes possess efficient steam escape channels and light absorption structure. The film with a double-layer structure is constructed through converting the surface of the bark into the carbonized structure under controllable laser treatment. The evaporation efficiency is calculated to be 74% under 1 sun by enhancing the photothermal conversion ability and efficiently opening the surface water transport channels simultaneously. The distillation water exhibits large resistance values (9.65 MΩ) and low concentrations of four primary ions (Na+, K+, Mg2+, and Ca2+), which achieves international standard for drinking water. In addition, the carbonized bark also exhibits all-right purified performance toward water evaporation from dye wastewater. The low cost and clean technology provides new inspiration for the future development of applicable solar thermal energy-driven water treatment systems.

Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures.

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.

In-situ synthesized and pattern Ag/Bi2Se3 composite structure by LDW and photothermal conversion.

Bi2Se3 nanofilm has exhibited many promising potentials application in the field of photo-to-heat conversion. A highly-efficient photo-to-heat conversion system of Ag/Bi2Se3 composite nanofilm is successfully fabricated through laser direct writing (LDW) technique. The localized heat induced by laser simultaneously achieve Ag particles synthesis, transfer and patterning in a single processing step. The thermal reaction process includes the forming of nanoparticles based on the process of the thermal reduction, laser ablation, sputtering deposition and so on. The thermal storage capability and photothermal conversion stability have been greatly improved through preventing the heat from loss and efficient LSPR enhancing. The photothermal conversion mechanism of composition film is discussed in detail. This work suggests that the laser-assisted transfer technique give rise to a new expectation of functional composite nanofilm application for energy conversion.

High Performance Poly(vinyl alcohol)-Based Li-Ion Conducting Gel Polymer Electrolyte Films for Electric Double-Layer Capacitors.

With 1-methyl-2-pyrrolidinone (NMP) as the solvent, the biodegradable gel polymer electrolyte films are prepared based on poly(vinyl alcohol) (PVA), lithium bis(trifluoromethane)sulfonimide (LiTFSI), and 1-ethyl-3 methylimidazoliumbis(trifluoromethylsulfonyl)imide (EMITFSI) by means of solution casting. The films are characterized to evaluate their structural and electrochemical performance. The 60PVA-40LiTFSI + 10 wt.% EMITFSI system exhibits excellent mechanical properties and a high ionic transference number (0.995), indicating primary ionic conduction in the film. In addition, because of the flexibility of polymer chain segments, its relaxation time is as low as 5.30 × 10-7 s. Accordingly, a high ionic conductivity (3.6 × 10-3 S cm-1) and a wide electrochemical stability window (~5 V) are obtained. The electric double-layer capacitor (EDLC) based on this electrolyte system shows a specific capacitance of 101 F g-1 and an energy density of 10.3 W h kg-1, even after 1000 charge-discharge cycles at a current density of 0.4 A g-1 under a charging voltage of 2 V. All these excellent properties imply that the NMP-soluble 60PVA-40LiTFSI + 10 wt.% EMITFSI gel polymer electrolyte could be a promising electrolyte candidate for electrochemical device applications.