Dual-scale Structure Research Articles

Laser-chemical treated superhydrophobic surface as a barrier to marine atmospheric corrosion

A time efficient and cost-effective laser-based surface texturing technique combining nanosecond laser ablation and chemical immersion treatment was developed for steel alloy to achieve enhanced corrosion resistance in marine atmospheric environment. Three different surface patterns were created by nanosecond laser ablation and the laser patterned samples were subsequently immersed in 1H,1H,2H,2H-perfluorooctyl silane (FOTS) solution to tune surface chemistry. Dual-scale surface structure was formulated on the laser-chemical treated surface, as confirmed by the scanning electron microscopy (SEM) and confocal laser scanning microscope analyses. X-ray photoelectron spectroscopy (XPS) analysis was conducted to validate that desired surface chemistry was achieved on the laser-chemical treated surface. The effect of surface pattern on several key surface functionalities, including surface wettability, corrosion resistance and chemical stability was systematically presented in this work. Firstly, it was demonstrated via wettability measurements that the laser-chemical treated surface achieved superhydrophobicity with a water contact angle of 158.9°. Secondly, electrochemical and NaCl deliquescence tests were conducted to determine the corrosion resistance of the laser-chemical treated surfaces in marine atmospheric environments. It was confirmed that the laser-chemical treated surface can prevent marine atmospheric corrosion induced by salt deliquescence. Furthermore, it was revealed by electrochemical test that the laser-chemical treated superhydrophobic surface exhibited distinctly better anti-corrosion performance. The experimental results showed that the corrosion rate for the laser-chemical treated surface with microgroove pattern is approximately 5.4% of the corrosion rate for the untreated surface, indicating significant improvement of corrosion resistance for the laser-chemical treated surface. Thirdly, the high water contact angle of 151.0° sustained on the laser-chemical treated surface after electrochemical tests helped confirm the improvement of its chemical stability in corrosion medium. These experimental findings clearly demonstrate the developed nanosecond laser-chemical treatment method can be very effective for fabrication of stable superhydrophobic metal surface as a barrier to marine atmospheric corrosion with enhanced corrosion resistance.

Volatile-Organic-Compound-Intercepting Solar Distillation Enabled by a Photothermal/Photocatalytic Nanofibrous Membrane with Dual-Scale Pores.

Solar distillation is emerging as a robust and energy-effective tool for water purification and freshwater production. However, many water sources contain harmful volatile organic compounds (VOCs), which can evaporate through the photothermal evaporators and be collected together with distilled water, or even be enriched in the distilled water. In view of the penetration of volatile organic compounds, herein, we rationally demonstrate a dual-scale porous, photothermal/photocatalytic, flexible membrane for intercepting volatile organic compounds during solar distillation, which is based on a mesoporous oxygen-vacancy-rich TiO2-x nanofibrous membrane (m-TiO2-x NFM). The dual-scale porous structure was constructed by micrometer-sized interconnected tortuous pores formed by the accumulation of m-TiO2-x nanofibers and nanometer-sized pores in the m-TiO2-x individual nanofibers. Consequently, the membrane can sustainably in situ intercept VOCs by providing more photocatalytic reactive sites for collision (mainly by mesopores) and longer tortuous channels for prolonging VOC retention (mainly by micrometer-sized pores); thus, it results in less than 5% of phenol residual in distilled water. As a proof of concept, when the m-TiO2-x NFM is employed to purify practical river water in an evaporation prototype under real solar irradiation, complex volatile natural organic contaminants can be effectively intercepted and the produced distilled water meets the drinking water standards of China. This development will promote the application prospects of solar distillation.

Honeycombed Porous, Size-Matching Architecture for High-Performance Hybrid Direct Carbon Fuel Cell Anode.

Direct carbon fuel cells (DCFCs) demonstrate both superior electrical efficiency and fuel utilization compared to all other types of fuel cells, and it will be the most promising carbon utilization technology if the sluggish anode reaction kinetics that derives from the use of solid fuel can be addressed. Herein, the electrode morphology and fuel particle size are comprehensively considered to fabricate an efficient DCFC anode skeleton. A honeycombed and size-matching anode architecture with dual-scale porous structure is developed by water droplet templating, which demonstrates an efficient strategy to address the challenge of poor carbon reactivity and improve the electrochemical performance of DCFCs. Single cell with this designed anode framework demonstrates excellent performance, and the maximum power density is as high as 765 mW cm-2 at 800 °C when using the matching carbon fuel. The size-matching between carbon fuel and anode framework shows a remarkable effect on the improvement of mass-transfer processes at the anodes. The significant contribution of the difficult electrochemical oxidation of carbon to the output performance is also demonstrated. These results represent a promising structural design strategy in developing high-performing fuel cells.

Ultrabroad antireflection urchin-like array through synergy of inverse fabrications by femtosecond laser-tuned chemical process

Eliminating the optical reflection of functional metal surfaces is crucial in many optical devices. However, minimizing the reflectivity of a metal surface over a wide band is an intractable task due to the high optical impedance between metal and air. Herein, an urchin-like composite micro/nanostructure with a highly effective antireflection property over an ultrabroad spectrum was prepared on a copper surface. To obtain this dual-scale and orderly urchin-like structure, a synergetic subtraction and additive micro/nanofabrication strategy is proposed. With the preprocessing of femtosecond laser, selective growth of nanostructures with specific morphologies can be achieved by chemical oxidation. This urchin-like morphology, combined with the light absorption capabilities of micron cones and nanowires, exhibits superior antireflection performance, and ultralow reflectance is attained at an ultrabroad spectrum comprising ultraviolet, visible, infrared, and far-infrared bands. This study provides a simple approach for the preparation of micro/nanostructures with high homogeneity and eminent reproductivity. Furthermore, the Cu(OH)2/CuO heterogeneous urchin-like structures could serve as core functional components in fields of photovoltaic devices, stealthy materials, and chemical catalysis.

A Durable and Self-Cleaning Superhydrophobic Surface Prepared by Precipitating Flower-Like Crystals on a Glass-Ceramic Surface.

Herein, a superhydrophobic surface with superior durability was fabricated on a glass-ceramic surface by crystallization, hydrofluoric acid (HF) etching, and surface grafting. The as-prepared glass-ceramic surface was composed of three-dimensional flower-like micro-clusters, which were self-assembled from numerous nanosheets. Such a dual-scale rough surface exhibited superhydrophobicity, with a water contact angle (WCA) of 170.3° ± 0.1° and a sliding angle (SA) of ~2° after grafting with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS-17). This can be attributed to the synergistic effect between the dual-scale structure and surface chemistry. Furthermore, this surface exhibited excellent self-cleaning properties, stability against strong acid and strong alkali corrosion, and anti-stripping properties.

Importance of moderate size of pillars and dual-scale structures for stable superhydrophobic surfaces: A molecular dynamics simulation study

In this work, we first create three-dimensional molecular-dynamics (MD) model to study the effect of structure parameters including pillar size, pillar height, pillar groove, and intrinsic contact angle (θe, or Young’s angle) on wetting behavior of drops on the one-scale nanopillared surface. We find that drops tend to exhibit the Cassie state on the nanopillared surface with small pillar size and large θe. Considering comprehensively the stability of the Cassie state, excellent hydrophobicity, and mechanical durability of microstructures, the pillar height and the pillar groove should be moderate. Then, only considering the wettability, we could see the dual-scale structure as the one-scale structure with large θe* that results from the small-scale structure for increasing the θe and cannot be achieved on the smooth surface in experiments. Importantly, we observe that the dual-scale structure, corresponding to large θe* resulting from the small-scale structure for increasing the θe, are important for the formation and the stability of the Cassie state. Moreover, the dual-scale structure can prevent the transition of drops from the Cassie state to the Wenzel state. Interestingly, fabricating the small-scale structure on top of the large-scale structure (corresponding to large θe* of the one-scale structure) can facilitate the transformation of the Wenzel state of drops on the large-scale structure to the Cassie state, and the Cassie state is stable. This study provides an inspiration for the fabrication of stable artificial superhydrophobic surfaces.

Preparation of V8C7-Fe/iron dual-scale composite via two-step in situ reaction

To overcome the disadvantages of low toughness and low fracture energy of conventional particle reinforced steel/iron-based composites, a novel V8C7-Fe/iron dual-scale composite was designed and fabricated via a two-step in situ reaction at 1150 °C for 5 min and 1100 °C for 12 h (denoted as 1150 °C-5 min + 1100 °C-12 h). The composite consists of a bundle-shaped V8C7-Fe dual-scale structure and cast iron matrix. Predominant features of the bundle-shaped V8C7-Fe dual-scale structure, which has a diameter of approximately 3 mm, include a toughness of the α-Fe phase and a high volume fraction of V8C7 particles that have different sizes and morphologies. The interface of the V8C7-Fe dual-scale structure/matrix has distinct gradient distribution characteristics. From the center of the V8C7-Fe dual-scale structure to the matrix, the morphology of the V8C7 particles evolves from nearly spherical to cubic. This is mainly because of changes in the growth environment that lead to the competitive growth between different crystal faces and orientation attachment growth during nucleation and growth. In addition, from the center of the V8C7-Fe dual-scale structure to the matrix, the hardness gradually decreases from 1306 HV0.2 to 410 HV0.2. For the V8C7-Fe/iron dual-scale composite, the yield strength, maximum compressive strength, and maximum compressive strain are approximately 1150 MPa, 1390 MPa, and 15.2%, respectively. Compared to cast iron (420 MPa, 830 MPa and 21.8%, respectively), the V8C7-Fe/iron dual-scale composite achieves both high strength and reasonable toughness.

Reconstruction of mesostructural material twin models of engineering textiles based on Micro-CT Aided Geometric Modeling

Engineering textiles are used as fibrous reinforcements in high performance polymer composites. The mechanical properties of composite materials depend on their dual-scale porous structure: long and elongated microscopic open spaces (micropores) appear between the filaments of fiber tows, and up to two orders of magnitude larger mesoscopic spaces (mesopores) exist between yarns. Because of the complex structure of composites, it is difficult to establish a connection between fiber architecture and mechanical behavior. To achieve this goal, X-ray microtomography (Micro-CT) can be used to provide detailed information on the geometric mesostructure of continuous fiber composites. The objective of this paper is to present a new approach based on “Micro-CT Aided Geometric Modeling” (Micro-CT AGM) to construct detailed geometric models of engineering textiles from Micro-CT three-dimensional (3D) images. The obtained geometric models are called “material twins” because of three distinctive features: (1) they are representative of the material variability; (2) their accuracy can be evaluated; and (3) they can be used to carry out computer simulations of mechanical behavior. This new method is applied to two industrial reinforcements: a 2D plain woven fabric and a 3D orthogonal glass textile. By introducing a new multiple factor morphological accuracy criterion, the quality of the “material twin” reconstruction can be compared to models obtained by standard image processing techniques or textile modeling software.

A quick condition adaptive soft sensor model with dual scale structure for dissolved oxygen simulation of recirculation aquaculture system

Dissolved oxygen (DO) is critical to recirculating aquaculture system (RAS), which is holistically affected by many nutritional, physiological, chemical, and fish behavioral processes. Modeling a DO soft sensor is an important means of providing broader sensing coverage for optimized DO control and DO sensor equipment validation. The main problem of DO soft sensor modeling is that stable long-term simulation parameters are usually insensitive to condition changes, resulting in slow adaptation. The second problem is that DO change has multiple influences. To improve condition adaptation performance and decouple multiple influence factors, a dual scale DO soft sensor modeling method is proposed to achieve dynamic condition adaptation during long-term simulation. The upper scale is a direct computer-mapping-based programmable structure (DCM-PS) model that represents the kinetics and equilibrium determined dynamic balance model for long-term simulation. The lower scale consists of recurrent neural networks (RNN) regression sub-models of aeration, feeding, and water flow. The RNN regression sub-models integrate the full connection network with RNN regression, which outputs frequency domain distributions of different conditions and predicts short-term DO expectations caused by condition change. To realize quick condition adaptation of the dual scale soft sensor model, a parameter update procedure is proposed to adapt upper scale simulation parameters to new conditions by comparing DCM-PS simulated result with RNN sub-model expectations. The instance with a sudden condition change proved that the dual scale model was able to implement quick adaptation to the changed operational condition of the RAS. The proposed method shows promise as a quick self-validation for DO sensor diagnosis, as well as for real time optimized control of DO and other parameters.

Lotus-Inspired Multiscale Superhydrophobic AA5083 Resisting Surface Contamination and Marine Corrosion Attack.

The massive and long-term service of 5083 aluminum alloy (AA5083) is restricted by several shortcomings in marine and industrial environments, such as proneness to localized corrosion attack, surface contamination, etc. Herein, we report a facile and cost-effective strategy to transform intrinsic hydrophilicity into water-repellent superhydrophobicity, combining fluorine-free chemisorption of a hydrophobic agent with etching texture. Dual-scale hierarchical structure, surface height relief and surface chemical elements were studied by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), successively. Detailed investigations of the wetting property, self-cleaning effect, NaCl-particle self-propelling, corrosion and long-term behavior of the consequent superhydrophobic AA5083 surface were carried out, demonstrating extremely low adhesivity and outstanding water-repellent, self-cleaning and corrosion-resisting performance with long-term stability. We believe that the low cost, scalable and fluorine-free transforming of metallic surface wettability into waterproof superhydrophobicity is a possible strategy towards anti-contamination and marine anti-corrosion.

Diffusion in a rough potential: Dual-scale structure and regime crossovers.

Diffusion in a "rough" potential parameterized by a reaction coordinate q is relevant to a wide spectrum of problems ranging from protein folding and charge transport in complex media to colloidal stabilization and self-assembly. This work studies the case of a potential having a coarse-scale structure with characteristic energy barrier ΔU and period ℓ and fine-scale "roughness" of magnitude ΔU' ≲ ΔU and small period ℓ' ≪ ℓ. The numerical solution of the Smoluchowski equation and analytical predictions from Kramers theory document distinct regimes at different distances |Δq| = |q - qE| from stable equilibrium at q = qE. The physical diffusivity D prescribed by dissipative effects can be observed farther than a distance |Δq'| ∝ (ΔU'/ℓ' + ΔU/ℓ). Rescaling the physical diffusivity to account for the fine-scale "roughness" is strictly valid when |Δq| < ΔqI ∝ (ΔU'/ℓ' - ΔU/ℓ). Farther than a critical distance ΔqII ∝ ΔU/ℓ, the diffusion process is free of coarse-scale metastable states, which facilitates determining the effective diffusivity D' from the reaction coordinate trajectory. Closer to equilibrium, the coarse-scale structure induces two diffusive regimes: nearly logarithmic evolution for ΔqII > |Δq| > ΔqIII and exponential decay over time for |Δq| < ΔqIII ∝ 1/ℓ. The effective diffusivity derived in this work is sensitive to the coarse- and fine-scale energy barriers and periods and for ℓ'/ℓ → 0 and ΔU'/kBT ≫ 1 agrees closely with mean first-passage time estimates currently employed, which depend solely on the fine-scale energy barrier.

Applicable Superamphiphobic Ni/Cu Surface with High Liquid Repellency Enabled by the Electrochemical-Deposited Dual-Scale Structure

Until now, scalable fabrication and utilization of superamphiphobic surfaces based on sophisticated structures has remained challenging. Herein, we develop an applicable superamphiphobic surface with nano-Ni pyramid/micro-Cu cone structures prepared by cost-effective electrochemical deposition. More importantly, excellent dynamic wettability is achieved, exhibiting as ultralow sliding angle (∼0°), multiple droplets rebounding (13 times), and a total rejection. The supportive cushions trapped within the dual-scale micro/nanostructures is proved to be the key factor contributing to such high liquid repellency, whose existence is intuitively ascertained at both solid-air-liquid and water-solid-oil systems in this work. In addition, the enduring reliability of the wetting performance under various harsh conditions further endows the surface with broader application prospects.

Three-dimensional simulation of dual-scale deposition structures from evaporative self-assembly of nanofluid films

Self-assembly of nanomaterials from the drying of nanofluid films has aroused great interest due to its applications in micro/nano fabrication, ink-jet printing, and thin film coatings. Numerical models are developed to investigate the single-scale deposition structures from the drying of nanofluid films, including network structures, continuous labyrinthine, branched structures and micro-sized rings. In the case of the actual drying of nanofluid films, dual-scale cellular networks and nano-rings are also discovered. In order to study the formation mechanism of dual-scale deposition structures, a three-dimensional kinetic Monte Carlo model is developed based on two-dimensional lattice gas model, and the dynamic chemical potential which couples solvent evaporation rate is implemented. Different dynamic chemical potentials are defined for each layer of the thin-film in the model to mimic the real evaporation situation. Considering the Brownian motion and the interaction between particles, the formation of dual-scale cellular networks and nano-rings coexisting with small scale patternis achieved via coupling the chemical potential to the solvent evaporation rate. The simulation results accord well with the results from many experimentally studied de-wetting systems. The effects of the chemical potential sharpness and critical evaporation rate of fluids on the dual-scale deposition structures are discussed. It can be found that the evaporation mode of thin-film is dominated by nucleation and growth at the initial stage. If the spinodal point is passed, the residual solvent will evaporate suddenly, and the nanoparticles do not accumulate further but directly deposit into small-scale structures, thus forming a dual-scale deposition structures at the final stage of the evaporation. The simulation results also show that the chemical potential sharpness will affect the deposition structure after the mutation in a certain range. When the chemical potential sharpness equals zero, the sedimentary structure is the same as the single-scale sedimentary structure when the constant chemical potential is applied. When the chemical potential sharpness is small, the large-scale network structure interacts closely with the small-scale network structure. With the increase of chemical potential sharpness, the large-scale deposition structure remains unchanged, while the dense small-scale network structure becomes small-scale point structure. When the chemical potential sharpness exceeds a certain large value, the effect of chemical potential sharpness on the deposition structure will gradually decrease, and finally the dual-scale deposition structure will remain unchanged. The critical evaporation rate of fluids determines the area ratio of the two kind of structures in the dual-scale deposition. With the increase of the critical evaporation rate of fluids, the area ratio of small-scale structures decreases while that of the large-scale structure increases. When critical evaporation rate increases to a certain value, the final deposition structure will evolve into a single-scale deposition structure.

Graphene oxide-functionalized dual-scale channels architecture for high-throughput removal of organic pollutants from water

Amino-functionalized polypropylene nonwoven/graphene oxide (GO) hybrid material (PP-g-DMAEMA/GO) with dual-scale channels structure was fabricated via irradiation polymerization and self-assembly method for rapid removal of 7 kinds of organic pollutants from water. The GO sheets tethered to grafted branches of dimethylaminoethyl methacrylate (DMAEMA) on PP fiber surface could form nanochannels between GO and fiber. Meanwhile, polypropylene nonwoven could provide the backbone for building micron-channels. The overlapped and intertwined structure of PP-g-DMAEMA/GO with many channels assures water permeating fluently, and the GO could capture quickly the organic pollutants carried by water both in batch and filtration process. The obtained PP-g-DMAEMA/GO could keep 74.3% of the adsorption performance of GO, which demonstrated two sides of GO could afford accessible binding sites. While the flow rate reach 40 mL/min, the PP-g-DMAEMA/GO was able to effectively remove Bisphenol A (BPA) with the contact time of 3.4 s. Moreover, the PP-g-DMAEMA/GO could simply be recovered by washing with ethanol solution. We conclude the paper that the facile synthesis of PP-g-DMAEMA/GO exploiting inexpensive PP nonwoven offer high water permeability, solving the separation problem of GO, and promising potential for applications of GO for water applications.

Characterization of Ni3Al Alloy Fabricated by Thermal Explosion and Hot Extrusion Process

In the present paper, the trace B doped Ni3Al alloy was prepared by the thermal explosion and hot extrusion (TH/HE) technique. Its micro-structure characterization and mechanical properties were carried out by OM, XRD, TEM, compression and micro-hardness tests. Micro-structure examinations exhibit that the TH/HE technology has transformed the powders into Ni3Al alloy with less porosity. In the synthesized part, coarse and ultrafine Ni3Al grains comprise the dual-scale grain structure with segregated Al2O3 particles along grain boundary. TEM observations reveal that γ-Ni, Al2O3 and Ni3Al phases coexist in the synthesized part. Moreover, the Al2O3 particles in the synthesized part have α-Al2O3 and γ-Al2O3 two crystal structures. In addition, there is a transition region along the interface of Al2O3 and Ni3Al grain. The subsequent hot extrusion optimize the micro-structure of the extruded part by homogenizing the Ni3Al grain, uniformly distributing Al2O3 and generating massive substructures. The great deformation results in the pile-up of dislocations, intersected dislocations and substructures. Moreover, the movement of dislocation promotes the formation of micro-twinning in the Ni3Al grain, which is accompanied with the stacking faults and nano-structure. The mechanical properties exhibit that the micro-structure optimization caused by the TE/HE technology improves the compressive ductility and strength of the Ni3Al alloy obviously. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.19460

Robust raspberry-like all-polymer particles for the construction of superhydrophobic surface with high water adhesive force

In this work, we present a simplified versatile approach to synthesize monodisperse and robust entirely polymeric raspberry-like particles (RPs) via an in situ seeded polymerization method. The RPs with dual-scale hierarchical structure were prepared by absorption of monomer styrene, cross-linkable monomer ethylene glycol dimethacrylate (EDGMA) and azobisisobutyronitrile (AIBN) initiator into hollow P(styrene–divinylbenzene-trifluoroethyl methacrylate) [P(S-DVB-TFEMA)] nanoreactors, and then massive corona polymeric P(S-EDGMA) particles were in situ grafted onto the core hollow P(S-DVB-TFEMA) from the inside out, obtaining the robust all-polymer P(S-DVB-TFEMA)@P(S-EDGMA) RPs. The prepared RPs possess excellent mechanical and chemical stability toward long-term ultrasonic and acid/base treatment. Without post-modifications, the particulate film assembled by the RPs exhibited the static contact angle of 154° and high adhesion to water droplets. Theoretical model of the RPs and theoretical analysis, which corresponded well to experimental data, further reveal the high adhesive phenomenon. More importantly, the prepared sticky superhydrophobic surface colored by fluorescent dye can be utilized as “a mechanical hand” for micro-droplet transportation with high visibility in UV dark chamber. Thus, we anticipate that the sticky superhydrophobic surface constructed by the robust all-polymer RPs will offer great potential applications in micro-droplet manipulation and biological detection.

Microstructure, mechanical properties and reinforcement mechanism of dual-scale TC4 titanium alloy prepared by cryomilling and plasma activated sintering

In this paper, dual-scale Ti-6Al-4V titanium alloys were prepared by cryomilling and plasma activated sintering. The microstructure and mechanical properties of the samples with different structural organizations were investigated. The relative densities were evaluated by the drainage method. The microstructure and mechanical properties were characterized by OM, SEM, XRD, EBSD, TEM, universal testing machine and Vickers hardness test methods. The results show that the dual-scale Ti-6Al-4V titanium alloy with high strength can be prepared in a relatively short time by cryomilling and plasma activated sintering. The scale structure of the alloy is controlled by a relative amount of ball-milled powders. With the ball-milled powder content increases, the fraction of the β phase and the axial fine crystalline region is increasing. The dual-scale structure renders and the mechanical properties of the samples are more superior to the coarse crystal samples. In addition, the plastic deformation capability of the dual-scale structure is better than that of fine crystal samples. A relative density of 98.54%, the enhanced mechanical properties, including offset yield strength of 1544.19 MPa and a Vickers hardness of 427 HV were achieved, which is attributed to the different dual-scale structures.

One-shot stereolithography for biomimetic micro hemisphere covered with relief structure

Biomimetic micro-structured surfaces have been attracting attention in recent years owing to their features, including optical reactivity, wetting property, and sliding property. One of the typical features of these functional structures is that densely arrayed dual-scale structures are present, such as several tens of micrometers of a hemisphere-like form covered with many several micrometer protrusions on the surface. A dual-scale structure similar to this is difficult to quickly and cheaply fabricate using existing methods: semiconductor process, micro stereolithography, and focused ion beam. In this research, a novel technique to fabricate a biomimetic hemisphere-like form covered with a relief structure is proposed. It utilizes the difference between the refractive indexes of two materials and the focusing cone-shaped light with a solid angle, which includes the critical angle formed when light enters from a side where the refractive index is higher than that of the other. In this situation, the refracted light radially expands. Thus, when the low-refractive-index medium is a photocurable resin, it is cured into a hemisphere-like form. In addition, properly modulating the light-intensity distribution of the incident light allows us to create many protrusions, such as a relief structure on the hemisphere surface. In this research, a theoretical model was constructed, and the proposed method was verified by simulation using Snell's law and the Lambert–Beer law. Moreover, apparatus to realize the proposed method was developed, and we practically verified that this method can fabricate a dual-scale structure such as a hemisphere-like form covered with a relief structure.

Fabrication of polymeric dual-scale nanoimprint molds using a polymer stencil membrane

We report on a simple and effective process that allows fabricating polymeric dual-scale nanoimprinting molds. The key for the process is the use of a thin flexible SU-8 stencil membrane, which was fabricated by either photolithography or thermal nanoimprint lithography (NIL). The stencil membrane with microscale pores was assembled into a nanopatterned substrate, producing a dual-scale structure. The assembled structure was used as a template to produce polymeric imprinting molds via UV-NIL. With this method, we demonstrated dual-scale nanoimprint molds having nano-pillars of 251 nm diameter and 146 nm high on top of microscale square protrusions of 5 μm wide and 3.6 μm high. The resin mold with the dual-scale structure was successfully used to produce a freestanding membrane with dual-scale perforated pores via UV-NIL. After metal coating and integrated into microfluidic devices, this freestanding membrane can potentially be used as a substrate for surface plasmon resonance sensors.

Automatic Raft Labeling for Remote Sensing Images via Dual-Scale Homogeneous Convolutional Neural Network

Raft-culture is a way of utilizing water for farming aquatic product. Automatic raft-culture monitoring by remote sensing technique is an important way to control the crop’s growth and implement effective management. This paper presents an automatic pixel-wise raft labeling method based on fully convolutional network (FCN). As rafts are always tiny and neatly arranged in images, traditional FCN method fails to extract the clear boundary and other detailed information. Therefore, a homogeneous convolutional neural network (HCN) is designed, which only consists of convolutions and activations to retain all details. We further design a dual-scale structure (DS-HCN) to integrate higher-level contextual information for accomplishing sea–land segmentation and raft labeling at the same time in a uniform framework. A dataset with Gaofen-1 satellite images was collected to verify the effectiveness of our method. DS-HCN shows a satisfactory performance with a better interpretability and a more accurate labeling result.