Optimization Mechanism of Mechanical Properties of Basalt Fiber-Epoxy Resin Composites by Interfacially Enriched Distribution of Nano-Starch Crystals

Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength,designability,good dimensional stability and ease of large-area monolithic forming.However,the problem of interfacial bonding between the resin matrix and the fibres limits the direct use of reinforcing fibres and has become a central difficulty in the development of basalt fibre-epoxy composites.This paper proposes a solution for enhancing the strength of the fibre-resin interface using maize starch nanocrystals,which are highly yield and eco-friendly.Firstly,in this paper,corn starch nanocrystals(SNC)were prepared by hydrolysis,and were deposited on the surface of basalt fibers by electrostatic adsorption.After that,in order to maximize the modification effect of nano-starch crystals on the interface,the basalt fiber-epoxy resin composite samples were prepared by mixing in a pressureless molding method.The test results shown that the addition of basalt fibers alone led to a reduction in the strength of the sample.Deposition of 0.1 wt%SNC on the surface of basalt fibers can make the strength consistent with pure epoxy resin.When the adsorption amount of SNC reached 0.5 wt%,the tensile strength of the samples was 23.7%higher than that of pure epoxy resin.This is due to the formation of ether bond homopolymers between the SNC at the fibre-epoxy interface and the epoxy resin,which distorts the originally smooth interface,leading to increased stress concentration and the development of cracks.This enhances the binding of basalt fibers.The conclusions of this paper can provide an effective,simple,low-cost and non-polluting method of interfacial enhancement modification.

A Selective‑Response Hypersensitive Bio‑Inspired Strain Sensor Enabled by Hysteresis Effect and Parallel Through‑Slits Structures

Flexible strain sensors are promising in sensing minuscule mechanical signals,and thereby widely used in various advanced fields.However,the effective integration of hypersensitivity and highly selective response into one flexible strain sensor remains a huge challenge.Herein,inspired by the hysteresis strategy of the scorpion slit receptor,a bio-inspired flexible strain sensor(BFSS)with parallel through-slit arrays is designed and fabricated.Specifically,BFSS consists of conductive monolayer graphene and viscoelastic styrene–isoprene–styrene block copolymer.Under the synergistic effect of the bio-inspired slit structures and flexible viscoelastic materials,BFSS can achieve both hypersensitivity and highly selective frequency response.Remarkably,the BFSS exhibits a high gage factor of 657.36,and a precise identification of vibration frequencies at a resolution of 0.2 Hz through undergoing different morphological changes to high-frequency vibration and low-frequency vibration.Moreover,the BFSS possesses a wide frequency detection range(103 Hz)and stable durability(1000 cycles).It can sense and recognize vibration signals with different characteristics,including the frequency,amplitude,and waveform.This work,which turns the hysteresis effect into a"treasure,"can provide new design ideas for sensors for potential applications including human–computer interaction and health monitoring of mechanical equipment.

Bioinspired flexible piezoresistive sensor for high-sensitivity detection of broad pressure range

The human skin has the ability to sense tactile touch and a great range of pressures.Therefore,in prosthetic or robotic systems,it is necessary to prepare pressure sensors with high sensitivity in a wide measurement range to provide human-like tactile sensation.Herein,we developed a flexible piezoresistive pressure sensor that is highly sensitive in a broad pressure range by using lotus leaf micropatterned polydimethylsiloxane and multilayer superposition.By superposing four layers of micropatterned constructive substrates,the multilayer piezoresistive pressure sensor achieves a broad pressure range of 312 kPa,a high sensitivity of 2.525 kPa^(−1),a low limit of detection(LOD)of<12 Pa,and a fast response time of 45 ms.Compared with the traditional flexible pressure sensor,the pressure range of this sensor can be increased by at least an order of magnitude.The flexible piezoresistive pressure sensor also shows high robustness:after testing for at least 1000 cycles,it shows no sign of fatigue.More importantly,these sensors can be potentially applied in various human motion detection scenarios,including tiny pulse monitoring,throat vibration detection,and large under-feet pressure sensing.The proposed fabrication strategy may guide the design of other kinds of multifunctional sensors to improve the detection performance.

Progress in Bio‑inspired Anti‑solid Particle Erosion Materials:Learning from Nature but Going beyond Nature

Solid particle erosion is a common phenomenon in engineering fields,such as manufacturing,energy,military and aviation.However,with the rising industrial requirements,the development of anti-solid particle erosion materials remains a great challenge.After billions of years of evolution,several natural materials exhibit unique and exceptional solid particle erosion resistance.These materials achieved the same excellent solid particle erosion resistance performance through diversified strategies.This resistance arises from their micro/nanoscale surface structure and interface material properties,which provide inspiration for novel multiple solutions to solid particle erosion.Here,this review first summarizes the recent significant process in the research of natural anti-solid particle erosion materials and their general design principles.According to these principles,several erosion-resistant structures are available.Combined with advanced micro/nanomanufacturing technologies,several artificial anti-solid particle erosion materials have been obtained.Then,the potential applications of anti-solid particle erosion materials are prospected.Finally,the remaining challenges and promising breakthroughs regarding anti-solid particle erosion materials are briefly discussed.

Biological Vibration Damping Strategies and Mechanisms

Excessive vibration in civil and mechanical systems can lead to structural damage or harmful noise.Structural vibration can be mitigated by reducing the energy of the vibration source or by isolating the external disturbance from the target structure.Depending on the tunability and power consumption of the system,existing vibration control strategies are divided into active,passive and semi-active types,providing a more stable and efficient solution for vibration control.However,conventional damping structures have difficulty in meeting the requirements of wide frequency range and high precision damping under complex operating conditions.Therefore,the design of efficient damping structures is one of the key challenges in the development of vibration control technology.Organisms have evolved over millions of years to effectively damp vibrations through special structures and composite materials to ensure their survival.Opening up damping vibration isolation technology from a bionic perspective can meet the frequency requirements of vibration damping and guarantee higher output accuracy of machinery.This review summarizes the basic principles of vibration control and analyses the vibration control strategies for different damping materials and damping structures.Meanwhile,various models of bio-damped structures are outlined.Moreover,the current status and recent progress of research on bionic damped structures based on bio-vibration control strategies are discussed.Finally,new perspectives on future developments in the field of bionic damped vibration control techniques are also presented.A comprehensive understanding of existing vibration damping mechanisms and new methods of bionic damping design will certainly trigger important applications of precision vibration control in the fields of aerospace,rail transportation and mechanical systems.

The Protective Effect of CoQ10 on ox-LDL——induced HUVEC Injury by AP-1 and PON2

[Objectives] To explore the protective effect and possible mechanisms of the coenzyme Q10( CoQ 10) on the human umbilical vein endothelial cell( HUVEC) injury induced by the oxidized low-density lipoprotein( ox-LDL). [Methods]With the human umbilical vein endothelial cells( HUVECs) cultured in vitro as the test target,the HUVECs were randomly divided into 5 groups: normal control group; model group; low concentration CoQ10 group( 12. 5); medium concentration CoQ10 group( 25); high concentration CoQ10 group( 50). The CCK-8 method was used to test the cell viability,and the drug concentration was screened in 60 μM of CoQ 10 toxic concentration; the total protein was extracted and Western blot was used to detect the protein expression of c-fos,c-jun and PON2; the RT-PCR method was used for determination of the content of c-fos,c-jun and PON2 mRNA. [Results]Compared with the normal group,the cell viability was significantly reduced in the 35 μg/m L high ox-LDL model group,and the cell injury was induced; compared with model group,after 12 h pre-protection,12. 5 μM,25 μM,50 μM CoQ10 could all significantly improve the survival of injured cells( P < 0. 05); compared with the normal group;the protein and mRNA levels of c-fos,c-jun,PON2 in the model group all declined; compared with the model group,the protein level and mRNA expression of c-fos,c-jun,PON2 in different CoQ10 groups increased to varying degrees( P < 0. 05). [Conclusions] CoQ 10 could reduce the HUVEC injury induced by high ox-LDL,and possible mechanism was achieved by upregulating the expression of AP-1 and PON2.

Multilevel Micro Structures of the Clam Make the Sealing Even Tighter

Excellent fluid sealing performance is crucial to ensuring the safety of important equipment,especially in aerospace field,such as space capsule and fuel chamber.The frequently opening and closing of the sealing devices is particularly important.Driven by this background,clams(Mactra chinensis)which can open and close their double shells with superior sealing performance,are studied in this work.Here,we show that the clam’s sealing ability is the result of its unique multilevel intermeshing microstructures,including hinge teeth and micro-blocks.These microstructures,which resemble gear teeth,engage with each other when the shell closes,forming a tight structure that prevents the infiltration of water from the outside.Furthermore,the presence of micron blocks prevents the penetration of finer liquids.The simulation results of the bionic end seal components show that the multilevel microstructure has a superior sealing effect.This research is expected to be applied to undersea vehicles that require frequent door opening and closing.

Antifogging properties and mechanism of micron structure in Ephemera pictiventris McLachlan compound eyes

An antifogging function surface with simple structure and suitable for large-area production was found inspired by Ephemera pictiventris McLachlan compound eyes.The compound eyes structure,antifogging properties and mechanism were studied by anti-fog test,dyeing test and scanning electron microscopy,and so forth.Then,3D model of the sample was established,and the antifogging mechanism was explained by the Cassie model.Results showed that the compound eyes are composed of hundreds of micron size ommatidia arranged in curved array form,and this structure shows excellent antifogging function.This research may provide new ideas for design of simple structure and micron size antifogging function surface.This work is also expected to be applied to antifogging function surface of astronaut helmets and medical endoscopes,and so forth.

Bioinspired Strategies for Excellent Mechanical Properties of Composites

Developing high-performance composite materials is of great significance as a strong support for high-end manufacturing.However,the design and optimization of composite materials lack a theoretical basis and guidance scheme.Compared with traditional composite materials,natural materials are composed of relatively limited components but exhibit better mechanical properties through ingenious and reasonable synthetic strategies.Based on this,learning from nature is considered to be an effective way to break through the bottleneck of composite design and preparation.In this review,the recent progress of natural composites with excellent properties is presented.Multiple factors,including structures,components and interfaces,are first summarized to reveal the strategies of natural materials to achieve outstanding mechanical properties.In addition,the manufacturing technologies and engineering applications of bioinspired composite materials are introduced.Finally,some scientific challenges and outlooks are also proposed to promote next-generation bioinspired composite materials.

A Bionic Vibration Source Localization Device Inspired by the Hunting Localization Mechanism of Scorpions

The challenges we are faced with in localizing objects are the complex environments,such as tunnels,high-rise areas and underground parking lots.This paper develops a bionic vibration source localization device to estimate the direction of the object which is inspired by the unique and precise hunting localization mechanism of scorpions.The localization device uses the sensor array,which is patterned after the scorpions5 biological sensory structure,and imitates the coding mode of scorpions,sensory neurons for determination of the prey(vibration source)bearing.To verify the effectiveness of the localization device,some experiments were performed through real collected vibration signals.The Average Estimated Error(AEE)and the Relative Estimated Error(REE)of the experimental results were calculated to be 3.64°土2.44°and-1.43°±4.14°,respectively.It indicates that the device has a good performance to estimate the bearings of vibration sources at different distances and azimuths.This bionic localization device lays the foundation for the development of locating the moving object in some special conditions.

Micro/nano-scale Characterization and Fatigue Fracture Resistance of Mechanoreceptor with Crack-shaped Slit Arrays in Scorpion

The nocturnal scorpion Heterometrus petersii uses Basitarsal Compound Slit Sensilla (BCSS) as mechanoreceptor to detect mechanical signal (e.g. substrate vibration, cyclic loads caused by walking) without fatigue failure such as initiation of fatigue crack and further propagation of crack-shaped slit. The outstanding perceptive function has been discovered for over half a century. However, it is not yet clear about the microstructure, material composition and micromechanical property which are all important factors that determine the fatigue fracture resistance of the BCSS. Here, the microscopic characteristics of the BCSS were thoroughly studied. The results dicate that anti-fatigue resilin and stiff chitinous cuticle form multilayered composite as the main body of the BCSS. Meanwhile, the pre-existing slit as mechanosensory structure is covered by cuticular membrane which has different mechanical property with the epicuticle. Theoretical analysis shows that the structure-composition-property synergistic relations of composites confer on the BCSS with extreme fatigue fracture tolerance.

Optimum Anti-erosion Structures and Anti-erosion Mechanism for Rotatory Samples Inspired by Scorpion Armor of Parabuthus transvaalicus

Solid particle erosion on the material surfaces is a very common phenomenon in the industrial field,which greatly affects the efficiency,service life,and even poses a great threat to life safety.However,current research on erosion resistance is not only inefficient,but also limited to the improvement of hardness and toughness of materials.Inspired by typical scorpion(Parabuthus transvaalicus),biomimetic functional samples with exquisite anti-rosion structures were manufactured.Macroscopic morphology and structure of the biological prototype were analyzed and measured.According to above analysis,combined with response surface methodology,a set of biomimetic samples with different structural parameters were fabricated by using 3D printing technology.The anti-crosion performance of these biomimetic samples was investigated using a blasting jet machine.Based on the results of blasting jet test,as well as regression analysis and fiting,the optimal structural parameters were obtained.In addition to the static test conditions,the optimal biomimetic sample was also eroded in rotating condition and showed excellent erosion resistance property.The presence of bump and groove structures,on the one hand,reduced the croded area of biominetic sample surface.On the other hand,they made the airlow turbulent and consequently reduced the impact cnergy of solid particles,which significantly improved the erosion resistance of biomimetic materials.This study provides a new strategy to improvethe service life of components easily affected by erosion in the aviation,energy and military fields.

The Novel Variable Stiffness Composite Systems with Characteristics of Repeatable High Load Bearing and Response Rate

On the base of controllable variable stiffness property,variable stiffness composites were the main components of functional materials in aerospace.However,the relatively low mechanical strength,stiffness range,and response rate restricted the application of variable stiffness composite.In this work,the novel variable stiffness composite system with characteristics of repeatable high load bearing and response rate was successfully prepared via the double-layer anisotropic structure to solve the bottlenecks of variable stiffness composites.The novel variable stiffness composite systems were composed of variable stiffness layer of polycaprolactone(PCL)and the driven layer of silicone elastomer with alcohol,which continuously changed Young’s modulus from 0.1 to 7.263 MPa(72.63 times variation)in 200 s and maintained maximum weight of 11.52 times its own weight(8.5 g).Attributed to the relatively high variable stiffness range and load bearing value of variable stiffness composite system,the repeatable response process led to the efficient high load driven as“muscle”and diversified precise grab of objects with different shapes as“gripper”,owning widespread application prospects in the field of bionics.

A Stiffness-Tunable Composite with Wide Versatility and Applicability Based on Low-Melting-Point Alloys

Flexible materials are essential in bionic fields such as soft robots.However,the lack of stiffness limits the mechanical performance of soft robots and makes them difficult to develop in many extreme working conditions,such as lifting and excavation operations.To address this issue,we prepared a stiffness-tunable composite by dispersing low-melting-point alloy into thermosetting epoxy resin.A dramatic and rapid change in stiffness was achieved by changing the state of matter at lower temperatures,and accurate control of the composite modulus was achieved by controlling the temperature.When the alloy content is at 30vol%,the tensile modulus changes 41.6 times,while the compressive modulus changes 58.9 times.By applying the composite to a flexible actuator,the initial stiffness of the actuator was improved by 124 times,reaching 332 mN/mm.In addition,the use of stiffness-tunable materials in the wheel allowed for timely changes in the grounding area to improve friction.These flexible materials with manageable mechanical properties have wide applicability in fields including bionics,robotics,and sensing.Our findings provide a new approach to designing and developing flexible materials with improved stiffness and controllability.

Biological coupling anti-wear properties of three typical molluscan shells—Scapharca subcrenata, Rapana venosa and Acanthochiton rubrolineatus

Molluscan shells are fascinating examples of highly ordered hierarchical structure and complex organic-inorganic biocomposite material. However, their anti-wear properties were rarely studied especially in the perspective of biological coupling. So in the current study three typical shells, Scapharca subcrenata, Rapana venosa and Acanthochiton rubrolineatus, were selected as coupling models to further study their anti-wear properties. Stereomicroscope and scanning electron microscopic observations showed that all these three shells had specific surface morphologies and complicated section microstructures. Importantly, a special structure, pore canal tubules, was discovered in the shells of Scapharca subcrenata and Acanthochiton rubrolineatus, which probably contributed most to their anti-wear properties. X-ray diffraction and micro-Vikers hardness tester were further adopted to analyze the phase compositions and micro-hardness of the shells. The measured results demonstrated that aragonite was the most extensive phase present in the shell, and possesed a relatively high micro-hardness. In this paper, the shells were described in details in morphology, structure and material with emphasis on the relationship with anti-wear property. The study revealed that the selected seashells possess distinct anti-wear properties by complicated mechanisms involving the integrated functions of multiple biological coupling elements, and this would provide inspiration to the design of new bionic wear resistance components.

Fabrication of Bioinspired Structured Superhydrophobic and Superoleophilic Copper Mesh for Efficient Oil-water Separation

Oily water treatment has attracted the attention of many researchers. The development of effective and cheap oil/water separation materials is urgent for treating this problem. Herein, inspired by superhydrophobic typical plant leaves such as lotus, red rose and marigold, superhydrophobic and superoleophilic copper mesh was fabricated by etching and then surface modi- fication with 1-dodecanethiol （HS（CH2）IlCH3）. A rough silver layer is formed on the mesh surface after immersion. The ob- tained mesh surface exhibits superhydrophobicity and superoleophilicity and the static water contact angle was 153~ ＋ 3~. In addition, the as-prepared copper mesh shows self-cleaning character with water and chemical stability. The as-prepared copper foam can easily remove the organic solvents either on water or underwater. We demonstrate that by using the as-prepared mesh, oils can be absorbed and separated, and that high separation efficiencies of larger than 92% are retained for various oils. Thus, such superhydrophobic and superoleophilic copper mesh is a very promising material for the application ofoil spill cleanup and industrial oily wastewater treatment.

Artificial Hair-Like Sensors Inspired from Nature： A Review

Nature creatures have evolved excellent receptors, such as sensory hairs in arthropods, lateral line system of fishes. Researchers inspired by nature creatures have developed various mechanical sensors. Here, we provide an overview on the development of Artificial Hair-Like （AHL） sensors based on the inspiration of hair flow sensory receptors, especially sensory hairs in arthropods and lateral line systems of fishes. We classify the developed AHL sensors into several categories according to the operating principles they based on, for example, piezoresistive and piezoelectric effects. The current challenges and existing problems in the development of AHL sensors are also present, which were primarily restricted by the exploratory tools of sensing mechanism of creatures and current manufacturing technologies. In future, more efforts are required in order to further improve the performance of AHL sensors. We expect that intelligent multi-functional AHL sensors can be applied not only in applications like navigation of underwater automatic vehicles, underwater search and rescue, tap-water metering, air monitoring and even in medicare, but also potentially be used in space robots to detect complex to- pography.

Characterization of Multi-scale Morphology and Superhydrophobicity of Water Bamboo Leaves and Biomimetic Polydi- methylsiloxane （PDMS） Replicas

The morphology and wettability of Water Bamboo Leaves （WBL） and their biomimetic replicas were investigated. The particular morphology structures of samples were characterized by Scanning Electron Microscopy （SEM） and Confocal Laser Scanning Microscopy （CLSM）. The static wettability of samples was assessed by contact angle measurements, while the dy- namic wettability was analyzed by high speed camera system. The wettability mechanism of WBL was also explained by Cassie model. Artificial surfaces were fabricated by duplicating WBL surface microstructures using PDMS in large area （5 cm x 3 cm）. The results show the main structure characteristics of this leaf surface are sub-millimeter groove arrays, micron-scale papillae and a superimposed layer with 3D epicuticular wax sculptures hierarchical structure, and the static Water Contact Angle （WCA） of 15l~~2~ and Water Sliding Angle （WSA） of 4^-6~ indicate that WBL surface is superhydrophobic. The combination of wax film and microstructure of WBL surface gives its surface excellent superhydrophobic property. Complex hierarchical patterns with features from sub-millimeter to micron-scale range are well reproduced. The reason for the absence of nanostructures is melting of plant epidermal wax during the curing process. The WCA values on artificial WBL and negative PDMS replica are 146~ ~ 3~ and 137~ ~ 2~, respectively, demonstrating preferable hydrophobicity. Differences in wetting behavior between natural leaves and artificial leaves originate from an inaccurate replication of the chemistry and structures of the three-dimensional wax projections on the leaf surface. Nevertheless, the morphological features of the leaf transferred to the replica improve signifi- cantly the hydrophobic properties of the replica when compared with the smooth PDMS reference. This study may provide an inspiration for the biomimetic design and construction of large area roughness-induced hydrophobic and anti-sticking material surface.

Numerical Experiment of the Solid Particle Erosion of Bionic Configuration Blade of Centrifugal Fan

In this paper, a bionic method was presented to improve the erosion resistance of blade of the centrifugal fan. A numerical investigation of the solid particle erosion on the standard and bionic configuration blade of 4-72N_o10C centrifugal fan was presented. The numerical study employs computational fluid dynamics （CFD） software, based on a finite volume method, in which the discrete phase model was used to modele the solid particles flow, and the Eulerian conservation equation was adopt to simulate the continuous phase. Moreover, user-defined function was used to define wear equation. The various diameters of the particles were taken into account. The positions of collision of standard and bionic fan blades were discussed, and two kinds of centrifugal fan blade wear were compared. The results show that the particles from the incident source with different positions have different processes of turning and movement when enter into the impeller. The trajectories of flow in the fan channel are significantly different for the particles with different diameters. Bionic fan blade have lower erosion rate than the standard fan blade when the particle size is 20 μm. The anti-erosion mechanism of the bionic fan blade was discussed.

Anti-adhesive Property of Maize Leaf Surface Related with Temperature and Humidity

The anti-adhesive surfaces have always aroused great interest of worldwide scientists and engineers. But in practical ap- plications, it often faces the threat and impact of temperature and humidity. In this work, the excellent anti-adhesive perform- ance of maize leaf under high temperature and humidity were investigated in detail. Firstly, the adhesion forces of the maize leaf surface under different temperature and humidity were measured by using Atomic Force Microscopy （AFM）. The temperature of the substrate was varied between 23 ~C to 100 ~C, and the ambient relative humidity is from 18% to 100%. It was found that the adhesion force of maize leaf decreased with the increase of temperature and humidity. The mechanism of its excellent anti-adhesive performance of maize leaf under high temperature and relative humidity was revealed. The transverse and lon- gitudinal ridges on maize leaf surface interlace with each other, forming small air pockets, which reduces the actual contact area between the object and the maize leaf. With the increase of humidity, the liquid film will be formed in the air pockets gradually and so much water vapor is produced with increase of tempera^tre. Then the air flow rate increases though the wavy top of transverse ridges, inducing the dramatic decrease of adhesion force. Inspired by this mechanism, four samples with this bionic structure were made. This functional ＂biomimetic structure＂ would have potential value in the wide medical equipments such as high frequency electric knife with anti-adhesion surface under high temperature and high humidity.