Design Of Flexible Structures Research Articles

Developments of photo‐/electro‐catalysis based on covalent organic frameworks: A review

AbstractPhoto‐/electro‐catalysis has the characteristics of low cost, high performance, and zero pollution, which meet the policies on environment and energy. Covalent organic frameworks (COFs), a type of crystalline organic skeleton polymers, have been widely applied and investigated in the area of photo‐/electro‐catalysis owing to their advantages of large specific surface area, regular pore size, excellent stability, flexible structural design, and massive active sites. This article reviews the structural characteristics of COFs and the strategies for strengthening the photo‐/electro‐catalytic activity of COF materials. Subsequently, deep insights were put into the photo‐/electro‐catalysis application of COF materials. In the end, the development prospects and challenges faced by COF materials in photo‐/electro‐catalysis are discussed.

An esterase-activatable nanoprodrug mitigates severe spinal cord injury via alleviating ferroptosis and reprogramming inflammatory microenvironment

Spinal cord injury (SCI) is a devastating condition with limited efficacious treatment options. Recent research has revealed the potential of functional nanomedicines to inhibit ferroptosis and reduce inflammatory response, offering a promising therapeutic approach for SCI. Urolithin A (UA) exhibits outstanding antioxidant and anti-inflammatory properties in different neurodegenerative disorders. Intriguingly, whether UA can antagonize ferroptosis remains unknown, and its specific impact on SCI and underlying mechanisms have not been extensively explored. Given the pathological response of esterase overexpression in the SCI microenvironment, taken advantages of nanotechnology in precise targeted delivery, flexible structure design and effective enhancement of drug metabolism pathways, in this study, a novel silica-based integrated nanocarrier is constructed by incorporating carbamate-bridged UA into silica nanoparticles. The resulting PEGylated UA silicon hybrid NPs (PUASi NPs) are sensitive and could be specifically recognized and cleaved by esterase. The findings from both in vitro and in vivo experiments demonstrate that the continuous release of UA from PUASi NPs exhibits notable anti-ferroptotic and anti-inflammatory effects, thus contributing to the improvement of functional recovery in mice suffering from SCI. Collectively, this esterase-activatable nanoprodrug strategy offers an alternative therapeutic regimen for clinical intervention in SCI, with promising prospects for translation into clinical practice.

Structural Elucidation of Electrical and Optical Properties in Lead‐free Organic‐Inorganic Copper Bromide [(CH3)4N]2CuBr4 Single Crystals

AbstractOrganic‐inorganic metal halide single crystals have attracted a lot of attention due to their flexible structural design and excellent optoelectronic applications. This study details the synthesis of copper‐based [(CH3)4N]2CuBr4 hybrid metal halide single crystals via a slow evaporation method. The crystal structure, crystal habit, chemical groups, intermolecular interactions, electrical properties of the sample were studied via single crystal x‐ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectrometer, Hirshfeld surface analysis, impedance spectroscopy, and modulus spectroscopy, respectively. An orthorhombic crystal system with the non‐centrosymmetric space group Pna21 was identified at room temperature. The deformation in the tetrahedra was calculated by the bond angle and bond length deformation index. The Cole‐Cole plot displayed the existence of depressed semicircles, which indicated the predominant distribution of grains, further confirmed by the SEM image. The deformed semi‐circular arcs on the electric modulus curve undeniably prove that the bulk effect dominates the material‘s electrical properties. Significantly, the compound presents a phase transition at ~240 K and excellent thermal stability up to a temperature of 400 K. Therefore, our research sheds light on the temperature dependence of electrical responses in these hybrid crystals and gives inspiration for the development of single crystal‐based efficient energy devices.

Promoting sustainability in 3D printed sand casting through adaptive sand mold structures

The use of 3D printed sand molds offers a high degree of flexibility in structural design and satisfying customer requirements. The optimization and adjustment of the structure of sand mold module with the required functionality helps to maximize the application potential of binder jet 3D printing technology. In this study, an adaptive sand mold structure design method was proposed to meet the sustainable requirements of 3D printed sand casting. Firstly, the functional modular and module clustering of the sand mold is carried out and then each module is adaptive structure design, to reduce the carbon emission and cost of the 3D printed casting process. Therefore, taking the small casting furnace cover and medium-sized cast engine block as examples, the life cycle framework of the 3D printed sand casting process is established, and the sustainable advantages of the adaptive structure method are explored through the calculation and analysis of carbon emission and cost models. The results show that the adaptive structure method reduces the carbon emissions of the two castings by 9.2% and 11.9%, respectively, and the cost of two castings by 6.7% and 11.1%, respectively. This approach provides more sustainable design ideas for 3D printed sand casting and 3D printed sand mass production.

Small extracellular vesicles' enrichment from biological fluids using an acoustic trap.

Small extracellular vesicles (sEVs), a form of extracellular vesicles, are lipid bilayered structures released by all cells. Large-scale studies on sEVs from clinical samples are necessary, but a major obstacle is the lack of rapid, reproducible, efficient, and low-cost methods to enrich sEVs. Acoustic microfluidics have the advantage of being label-free and biocompatible, which have been reported to successfully enrich sEVs. In this paper, we present a highly efficient acoustic microfluidic trap that can offer low and large volume compatible ways of enriching sEVs from biological fluids by flexible structure design. It uses the idea of pre-loading larger seed particles in the acoustic trap to enable sub-micron particle capturing. The microfluidic chip is actuated using a piezoelectric plate transducer attached to a silicon-glass bonding plate with circular cavities. Each cavity works as a resonant unit, excited at the frequency of both the half wave resonance in the main plane and inverted quarter wave resonance in the depth direction, which has the ability to strongly trap seed particles at the center, thereby improving the subsequent nanoparticle capture efficiency. Mean trapping efficiencies of 35.62% and 64.27% were obtained using 60 nm and 100 nm nanobeads, respectively. By the use of this technology, we have successfully enriched sEVs from cell culture conditioned media and blood plasma at a flow rate of 10 μL min-1. The isolated sEV subpopulations are characterized by NTA and TEM, and their protein cargo is determined by WB. This acoustic trapping chip provides a rapid and robust method to enrich sEVs from biofluids with high reproducibility and sufficient quantities. Therefore, it can serve as a new tool for biological and clinical research such as cancer diagnosis and drug delivery.

Exploring the Potential of 3D Printing Technology for Sustainable Plastic Roads: A Preliminary Investigation

The urgency of climate change has highlighted the need for sustainable road construction materials, replacing the conventional asphalt, which significantly contributes to global warming and the urban heat island effect. With this in mind, the construction of the world’s first 30-m plastic road in Zwolle, Netherlands, in 2018, opened the door for novel plastic applications as paving materials. However, its application is currently still limited to sidewalks and light-load cycling lanes. The feasibility of utilizing 3D printing technology to provide the necessary structural design flexibility for the production of plastic pavement modules that can withstand heavy traffic and extreme weather conditions was examined in this preliminary study. The suitability of six plastic materials (PLA, PETG, ABS, TPU, Nylon, and polycarbonate) for 3D printing was evaluated. Polylactic acid (PLA), and polyethylene terephthalate glycol (PETG) were identified as the most suitable materials for this study. Three small-scale structural systems, namely hollow modular with plastic columns, hollow modular with solid plastic cones, and hollow modular with X-bracing, were designed and successfully printed using the adopted materials and a 3D printer. The developed systems were subsequently subjected to compression testing to assess their structural performance under heavy traffic loads and demonstrate the feasibility of the concept. The results showed that the PLA conic structural system was effective and exhibited the highest compression strength, while the PETG conic system exhibited ductile behavior with superior thermal stability. The study suggests that the hybrid system of PLA and PETG materials may improve the overall performance, combine flexibility and strength, and potentially improve the resistance to extreme weather and heavy traffic. These findings prove that 3D printing technology has the potential to revolutionize the road construction industry and provide more sustainable solutions for infrastructure development.

Pavement design using bituminous surface course with recycled aggregates

The utilization of Recycled Aggregates (RA) in the construction of pavement structure is one of the inventive and eco-friendly construction techniques. This scale down the construction cost without negotiates the strength and the durability of the pavement structures. However, RA is rigid in nature because it is obtained from aged bituminous mixtures to enhance a rejuvenator is usually added in order to lower the stiffness. Rejuvenator surges the utility of the bituminous mixtures and makes them be smoothly paved and compacted. The objective of this study is to design a flexible pavement structure using Stone Matrix Asphalt (SMA) as a surface course in order with RA. In SMA mixture major component is occupied by coarse aggregates, mineral filler, bitumen and a minor component of fine aggregates helps to fill the voids present in coarse aggregate which gives stone-on-stone contact. The bitumen binder and mineral filler form mastic, providing durability to the mixture. In this study, the performance of SMA mixtures with different RA proportions and a rejuvenator will be compared with conventional SMA mixture with zero percentage RA. Marshall Mix design is outlined to find the Marshall and volumetric properties of SMA mixtures and to regulate the Optimum Binder Content (OBC). The mixtures will be compared based on the drain down, stripping, Indirect Tensile strength (ITS) and Semi circular bend (SCB) test results. The analysis and design of flexible pavement structure using the prepared SMA mixtures with different RA contents as surface courses also will be carried out as a component of the study.SMA mixture of 40% replacing RA with 3% of palm sludge oil as rejuvenator exhibits optimum bitumen content where vertical stress, strain and displacement obtain reduction with compared to IRC 37 conventional SMA mixture.

Research on the thermal performance of the condenser in a loop heat pipe anti-icing system

Loop Heat Pipes (LHPs) are efficient heat transfer devices, providing a highly efficient and energy-saving thermal control integrated management method for Unmanned Aerial Vehicles (UAVs) with their flexible structural design. In this paper, a conceptual design of LHP anti-icing system was proposed, using LHP to transfer waste heat to wing’s leading edge. The outer surface temperature of wing skin is one of the main indicators to measure the anti-icing effect. As a result, this paper mainly focused on the heat transfer process of the condenser section by experimental and numerical simulation methods. A stainless steel-nickel LHP was fabricated and tested at different conditions. Volume of Fluid (VOF) method and Lee model were adopted to simulate the condensation process. Results showed that increasing the heating power (from 35 W to 60 W) slowed down the condensation and lengthened the two-phase zone. However, when the angle of attack changes within the range of 0°–10°, the liquid-vapor distribution in the tube remains almost unchanged. The average error of surface temperature between experiment and simulation results is 3.6% and 2.5% for the heating power of 180 W and 60 W respectively. Additionally, because the volume of water droplets collected is the largest at the leading edge of the wing, we recommend arranging the LHP condenser tube inlet near the leading edge of the wing and increasing the density of pipe arrangement to achieve better anti-icing effect.

Reticular Synthesis of Flexible Rare-Earth Metal-Organic Frameworks: Control of Structural Dynamics and Sorption Properties Through Ligand Functionalization.

An exciting direction in metal-organic frameworks involves the design and synthesis of flexible structures which can reversibly adapt their structure when triggered by external stimuli. Controlling the extent and nature of response in such solids is critical in order to develop custom dynamic materials for advanced applications. Towards this, it is highly important to expand the diversity of existing flexible MOFs, generating novel materials and gain an in-depth understanding of the associated dynamic phenomena, eventually unlocking key structure-property relationships. In the present work, we successfully utilized reticular chemistry for the construction of two novel series of highly crystalline, flexible rare-earth MOFs, RE-thc-MOF-2 and RE-teb-MOF-1. Extensive single-crystal to single-crystal structural analyses coupled with detailed gas and vapor sorption studies, shed light onto the unique responsive behavior. The development of these series is related to the reported RE-thc-MOF-1 solids which were found to display a unique continuous breathing and gas-trapping property. The synthesis of RE-thc-MOF-2 and RE-teb-MOF-1 materials represents an important milestone as they provide important insights into the key factors that control the responsive properties of this fascinating family of flexible materials and demonstrates that it is possible to control their dynamic behavior and the associated gas and vapor sorption properties.

Bayesian optimization-based topology optimization using moving morphable bars for flexible structure design problems

This paper presents a Bayesian optimization (BO) based topology optimization to solve flexible structure design problems in highly nonlinear design spaces. Our primary interest is to avoid topology optimization’s strong dependency on initial designs, which is inevitable when employing gradient-based optimizers. In order to do this, BO is used as a gradient-free optimizer that uses a probabilistic model to trade off exploration and exploitation in order to balance global and local search with a minimal number of iterations. Because of the curse of dimensionality in BO, a moving morphable bar (MMB) is used as a primitive member for a low-dimensional surrogate. We verified that BO could handle dozens of design parameters using the MMB through mean compliance minimization problems with known global optimum layouts. The effect of the BO trade-off parameter in the acquisition function, balancing the optimizer’s exploration, is also investigated. Numerical examples show that the proposed BO-based topology optimization method has suggested better optimum solutions for flexible structures than the MMA-based topology optimization. The performance of the proposed method is also compared with other global optimization methods, showing better performance in terms of minimized objective functions as well as the number of analyses for convergence.

Digital light processing and electromagnetic wave absorption performance tuning of SiOC/SiO2 ceramics

SiOC ceramics have been applied to the fabrication of electromagnetic wave (EMW) absorbing metastructures by stereolithography and demonstrate excellent absorptivity due to the designability of the macrostructure. However, the pyrolysis of photosensitive polysiloxane preceramics may result in macroscopic cracking due to high mass loss and shrinkage. These factors can restrict the structural design flexibility. Combining high residual preceramics with appropriate solid phase fillers is one potential solution. In this study, two preceramics with high residual rates were physically blended with photosensitizing resins in various proportions. This was carried out with the objective of preparing photosensitized preceramics that have high ceramic yields and tunable dielectric properties in the final SiOC ceramics. Then, SiO2 fillers were incorporated into the photosensitive preceramics for the first time to reduce pyrolytic shrinkage and used to match the impedance matching properties of SiOC ceramics in order to enhance EMW absorption performance. The SiOC/SiO2 ceramics achieved a minimum reflection loss of −28.10 dB with a thickness of 1.90 mm. Additionally, the sample demonstrated an effective absorption bandwidth of 6.38 GHz at a thickness of 2.30 mm. The SiOC/SiO2 ceramics have potential applications in the rapid preparation of all-dielectric electromagnetic metamaterials, which exhibit the simplicity of the raw material preparation process and the wide effective absorption bandwidth with a high ceramics yield.

Gap-modulated dynamics of flexible plates

The effect of single perforations and their location on the drag and reconfiguration of flexible plates was explored through laboratory experiments and direct numerical simulations. The plates were subjected to uniform flows with negligible turbulence, and the perforations had a square cross-section resulting in a low porosity ratio of $\gamma \approx 0.028$ . Rigid plates with and without perforations and flexible plates without perforations served as the baseline cases. The perforated plates exhibited distinct jets through the openings in the wake, significantly impacting the aerodynamic force and plate deformation. The velocity and position of the centre jet velocity in relation to downwind distance were influenced by both the incoming flow and the location of the perforations. The centre jet velocity profiles were normalized using an effective velocity and corrected perforation half-width, revealing their dependence on these factors. A simple first-order formulation was developed to predict the change in drag for various perforated plates under a wide range of incoming velocities. This formulation was supported by numerical simulations across a wider range of Cauchy number to confirm the proposed model and separate the effect of the Cauchy and Reynolds numbers. The results of this study may inform the design of flexible structures, define effective porosity and serve as an initial step towards modelling the complex interaction between flow and structures with low porosity.

Additive manufacturing with continuous ultra-high molecular weight polyethylene yarn

Fused filament fabrication (FFF) of composites with compliant high-strength fibers could expand opportunities for the design and fabrication of complex flexible structures, but this topic has received limited attention. This study pursued the development of filaments consisting of ultra-high molecular weight polyethylene yarn (UHMWPE) embedded in a matrix of polycaprolactone (UPE/PCL) and successful 3D printing. The physical characteristics and printability of the filament were evaluated in terms of key parameters including spooling speed, temperature, fiber distribution (consolidated vs dispersed), and fiber volume fraction (4≤ Vf ≤30 %). An evaluation of the microstructure and tensile properties of the UPE/PCL was performed after processing and printing. Prior to printing, the filament exhibited an ultimate tensile strength (UTS) of 590±40 MPa with apparent fiber strength of 2.4 GPa. For the printed condition, the UTS reached 470±60 MPa and apparent fiber strength of 1.9 GPa. Fiber dispersion in the filament plays an important role on the printed properties and the potential for fiber degradation. Nevertheless, the strength of the UPE/PCL represents a new performance benchmark for compliant composites printed by FFF. This new material system can support applications where strength and toughness are key performance metrics in addition to flexibility.

The Rise of Electroactive Materials in Face Masks for Preventing Virus Infections.

Air-transmitted pathogens may cause severe epidemics, posing considerable threats to public health and safety. Wearing a face mask is one of the most effective ways to prevent respiratory virus infection transmission. Especially since the new coronavirus pandemic, electroactive materials have received much attention in antiviral face masks due to their highly efficient antiviral capabilities, flexible structural design, excellent sustainability, and outstanding safety. This review first introduces the mechanism for preventing viral infection or the inactivation of viruses by electroactive materials. Then, the applications of electrostatic-, conductive-, triboelectric-, and microbattery-based materials in face masks are described in detail. Finally, the problems of various electroactive antiviral materials are summarized, and the prospects for their future development directions are discussed. In conclusion, electroactive materials have attracted great attention for antiviral face masks, and this review will provide a reference for materials scientists and engineers in antiviral materials and interfaces.

Flexible support structure design for optical mirror

In order to realize the high-precision assembly of the mirror of the aeronautical optical system, a semi-kinematic flexible support structure applied to the airborne field was designed. This paper studies the support principle and assembly method of flexible support of mirror. Firstly, according to the kinematic theory of space mechanism, the spatial degrees of freedom of the mirror were theoretically analyzed. Then, in view of the difficulties encountered in the assembly and application of the mirror, a flexible support structure was designed. Then, the design results were verified by means of finite element analysis. Finally, the processing and assembly of a flexible support structure of the mirror was completed, and the relevant experimental tests were carried out. The experimental results show that the accuracy of the mirror after assembly with flexible support structure is better than λ/50 (λ = 632.8 nm), and the mass is less than 2 kg. The model fundamental frequency modal of the whole assembly is 645 Hz, which is higher than the design requirement. All simulation and test results show that the flexible support structure works well, meets the requirements of aviation optical system, and has the advantages of simple assembly, high precision, stability and reliability.

Design and Behavior of Lightweight Flexible Structure with Spatial Pattern Reducing Contact Surface Fraction.

Flexible structures are increasingly important in biomedical applications, where they can be used to achieve adaptable designs. This paper presents a study of the design and behavior of 3D-printed lightweight flexible structures. In this work, we focus on the design principles and numerical modelling of spatial patterns, as well as their mechanical properties and behavior under various loads. Contact surface fraction was determined as the ratio of the surface area of the printed pattern to the surface area of the entire curved surface. The objective of this work is to design a spatial pattern reducing contact surface fraction and develop a non-linear numerical model evaluating the structure's stiffness; in addition, we aimed to identify the best design pattern with respect to its stiffness:mass ratio. The experimental verification of the numerical model is performed on 3D-printed prototypes prepared using the Selective Laser Sintering (SLS) method and made of Nylon-Polyamide 12. The obtained results provide insights into designing and optimizing lightweight external biomedical applications such as prostheses, orthoses, helmets, or adaptive cushions.

DeepNet model empowered cuckoo search algorithm for the effective identification of lung cancer nodules.

Globally, lung cancer is a highly harmful type of cancer. An efficient diagnosis system can enable pathologists to recognize the type and nature of lung nodules and the mode of therapy to increase the patient's chance of survival. Hence, implementing an automatic and reliable system to segment lung nodules from a computed tomography (CT) image is useful in the medical industry. This study develops a novel fully convolutional deep neural network (hereafter called DeepNet) model for segmenting lung nodules from CT scans. This model includes an encoder/decoder network that achieves pixel-wise image segmentation. The encoder network exploits a Visual Geometry Group (VGG-19) model as a base architecture, while the decoder network exploits 16 upsampling and deconvolution modules. The encoder used in this model has a very flexible structural design that can be modified and trained for any resolution based on the size of input scans. The decoder network upsamples and maps the low-resolution attributes of the encoder. Thus, there is a considerable drop in the number of variables used for the learning process as the network recycles the pooling indices of the encoder for segmentation. The Thresholding method and the cuckoo search algorithm determines the most useful features when categorizing cancer nodules. The effectiveness of the intended DeepNet model is cautiously assessed on the real-world database known as The Cancer Imaging Archive (TCIA) dataset and its effectiveness is demonstrated by comparing its representation with some other modern segmentation models in terms of selected performance measures. The empirical analysis reveals that DeepNet significantly outperforms other prevalent segmentation algorithms with 0.962 ± 0.023% of volume error, 0.968 ± 0.011 of dice similarity coefficient, 0.856 ± 0.011 of Jaccard similarity index, and 0.045 ± 0.005s average processing time.

Nano GeSe2/C anchored in carbon sponge skeleton for free-standing flexible lithium-ion battery electrodes

As a typical conversion alloyed anode material, Germanium selenide (GeSe2) exhibits isotropic lithiation behavior and high theoretical charge-discharge specific capacity. However, pure GeSe2 anode faces significant volume expansion (∼250 %−360 %) and further exploration is needed in the preparation of flexible electrode materials and structural design. Herein, a simple strategy is designed to load GeSe2/C-2 nanoparticles with porous carbon-coated structure on a flexible cross-networking substrate. The 3D network substrate is composed of highly conductive carbon nanotubes and adhesive cotton cellulose fibers. A two-step method involving coating and cross-linking is designed to achieve the fabrication of self-supporting flexible electrodes. As an anode for LIBs, the one layer GeSe2 discs with ∼0.65 mm thickness manifest capacities of 827.1, 744.4, 676.3, and 472.9 mAh g−1 at 0.1, 0.2, 0.5, and 1 A g−1, respectively. This superior Li+ storage performance can be attributed to the positive collective impact from the integration of nano-scale material, low crystalline properties, and carbon sponge skeleton. Furthermore, the GITT tests indicate that the diffusion coefficient of Li+ in the GeSe2-based electrodes ranged from 10−15 to 10−12 cm2/s, and the thickness of the flexible electrode (including two layers) has a negligible impact on its electrochemical performance.

Consideration of the Non-Linearity of Unbound Granular Materials in the Design of Flexible Pavement Structures in Senegal

Consideration of the Non-Linearity of Unbound Granular Materials in the Design of Flexible Pavement Structures in Senegal

Performance comparison and analysis of D-type single and dual-core PCF-SPR sensors

Surface plasmon resonance sensors, based on photonic crystal fibers, have demonstrated immense potential in various application fields, owing to their structural design flexibility, operability, and superior sensing capabilities. Despite the potential, the design of photonic crystal fibers with various structures has been a challenging task, due to manufacturing constraints. Thus, this paper aims to explore the design rules of photonic crystal fibers based on surface plasmon resonance, by proposing and designing four photonic crystal fiber sensors with distinct structures. The study investigates the influence of single-core, double-core, and large and small air holes on the sensor’s performance, through theoretical analysis, numerical simulation, data acquisition, and analysis. Through our research, we have discovered that by altering the size of pores surrounding the fiber core, as well as the fiber core’s single-mode and dual-mode configurations, we were able to increase the sensitivity of the sensor from its lowest value of 266 nm RIU−1 to as high as 2066 nm RIU−1, an improvement of nearly eightfold. The findings suggest that the sensor with double-core air hole structure exhibits relatively better performance. This analysis is expected to aid in the design of high-performance photonic crystal fiber-based surface plasmon resonance sensors.