Biomimetic 3D printing of composite structures with decreased cracking

The development of tissue engineering and regeneration research has created new platforms for bone transplantation.However,the preparation of scaffolds with good fiber integrity is challenging,because scaffolds prepared by traditional printing methods are prone to fiber cracking during solvent evaporation.Human skin has an excellent natural heat-management system,which helps to maintain a constant body temperature through perspiration or blood-vessel constriction.In this work,an electrohydrodynamic-jet 3D-printing method inspired by the thermal-management system of skin was developed.In this system,the evaporation of solvent in the printed fibers can be adjusted using the temperature-change rate of the substrate to prepare 3D structures with good structural integrity.To investigate the solvent evaporation and the interlayer bonding of the fibers,finite-element analysis simulations of a three-layer microscale structure were carried out.The results show that the solvent-evaporation path is from bottom to top,and the strain in the printed structure becomes smaller with a smaller temperaturechange rate.Experimental results verified the accuracy of these simulation results,and a variety of complex 3D structures with high aspect ratios were printed.Microscale cracks were reduced to the nanoscale by adjusting the temperature-change rate from 2.5 to 0.5℃s-1.Optimized process parameters were selected to prepare a tissue engineering scaffold with high integrity.It was confirmed that this printed scaffold had good biocompatibility and could be used for bone-tissue regeneration.This simple and flexible 3D-printing method can also help with the preparation of a wide range of micro-and nanostructured sensors and actuators.

Plants as concept generators for biomimetic light-weight structures with variable stiffness and self-repair mechanisms

Plants possess many structural and functional properties that have a high potential to serve as concept generators for the production of biomimetic technical materials and structures. We present data on two features of plants (variable stiffness due to pressure changes in cellular structures and rapid self-repair functions) that may be used as models for biomimetic projects.

3D printing biomimeticmaterials and structures for biomedical applications

Over millions of years of evolution,nature has created organisms with overwhelming performances due to their unique materials and structures,providing us with valuable inspirations for the development of next-generation biomedical devices.As a promising new technology,3D printing enables the fabrication of multiscale,multi-material,and multi-functional threedimensional(3D)biomimetic materials and structures with high precision and great flexibility.The manufacturing challenges of biomedical devices with advanced biomimetic materials and structures for various applications were overcome with the flourishing development of 3D printing technologies.In this paper,the state-of-the-art additive manufacturing of biomimetic materials and structures in the field of biomedical engineering were overviewed.Various kinds of biomedical applications,including implants,lab-on-chip,medicine,microvascular network,and artificial organs and tissues,were respectively discussed.The technical challenges and limitations of biomimetic additive manufacturing in biomedical applications were further investigated,and the potential solutions and intriguing future technological developments of biomimetic 3D printing of biomedical devices were highlighted.

A Review of Methods Based on Nanofluids and Biomimetic Structures for the Optimization of Heat Transfer in Electronic Devices

Nowadays,the utilization rate of electronic products is increasing while showing no obvious sign of reaching a limit.To solve the associated“internal heat generation problem”,scientists have proposed two methods or strategies.The first approach consists of replacing the heat exchange medium with a nanofluid.However,the high surface energy of the nanoparticles makes them prone to accumulate along the heat transfer surface.The second method follows a different approach.It tries to modify the surface structure of the electronic components in order to reduce the fluid-dynamic drag and improve the rate of heat exchange.This article reviews these effects considering different types of nanofluid and different shapes,sizes,and arrangements of“biomimetic grooves”.The idea to use these two methods in a combined fashion(to improve heat transfer and reduce flow resistance at the same time)is also developed and discussed critically to a certain extent.

Synergistically biomimetic platform that enables droplets to be self-propelled

Droplet transport still faces numerous challenges,such as a limited transport distance,large volume loss,and liquid contamination.Inspired by the principle of‘synergistic biomimetics’,we propose a design for a platform that enables droplets to be self-propelled.The orchid leaf-like three-dimensional driving structure provides driving forces for the liquid droplets,whereas the lotus leaf-like superhydrophobic surface prevents liquid adhesion,and the bamboo-like nodes enable long-distance transport.During droplet transport,no external energy input is required,no fluid adhesion or residue is induced,and no contamination or mass loss of the fluid is caused.We explore the influence of various types and parameters of wedge structures on droplet transportation,the deceleration of droplet speed at nodal points,and the distribution of internal pressure.The results indicate that the transport platform exhibits insensitivity to pH value and temperature.It allows droplets to be transported with varying curvatures in a spatial environment,making it applicable in tasks like target collection,as well as load,fused,anti-gravity,and long-distance transport.The maximum droplet transport speed reached(58±5)mm·s^(−1),whereas the transport distance extended to(136±4)mm.The developed platform holds significant application prospects in the fields of biomedicine and chemistry,such as high-throughput screening of drugs,genomic bioanalysis,microfluidic chip technology for drug delivery,and analysis of biological samples.

Design of a Novel Robotic Fish Structure Utilizing PVC Gel Actuators

In this research work, it has been designed a bionic robot fish structure, can swim underwater. The active compact body is powered by eight sets of symmetric PVC gel actuators with a caudal fin. The robot’s 200 mm-long, fish structure design incorporates a 55.52 angle to optimize the fish dynamics movement. It’s a fast and smooth operation and can swim. The robot can swim fast and quietly by using the right positions and the appropriate actuators on PVC gel actuators. This design entails a unique architecture that enables the robot to move safely and unobtrusively at the same time, which makes it suitable equipment for different exploration and surveillance missions in the water with speed and silent operation as the foremost concern.

Self-Repairing Membranes for Inflatable Structures Inspired by a Rapid Wound Sealing Process of Climbing Plants

A new self-repairing membrane for inflatable light weight structures such as rubber boats or Tensairity constructions is presented. Inspired by rapid self-sealing processes in plants, a thin soft cellular polyurethane foam coating is applied on the inside of a fabric substrate, which closes the fissure if the membrane is punctured with a spike. Experimental tests are carried out with a purpose built setup by measuring the air mass flow through a leak in a damaged membrane sample. It is shown that the weight per unit area of the self-repairing foam as well as the curing of the two component PU-foam under an overpressure influence the repair efficiency. Curing the foam under overpressure affects the relative density as well as the microstructure of the foam coatings. Maximal median repair efficiencies of 0.999 have been obtained with 0.16 g.cm 2 foam cured at 1 bar overpressure. These results suggest that the bio-inspired technique has the potential to extend the functional integrity of injured inflatable structures dramatically.

Bio‐inspired nanostructured g-C_(3)N_(4)-based photocatalysts:A comprehensive review

As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding thermal endurance,appealing chemical stability,low cost,and environmental friendliness.Nevertheless,unmodified bulk g-C_(3)N_(4) possesses some intrinsic limitations related to poor crystallinity,marginal visible-light harvesting,easy recombination of charge pairs,small surface area,and slow charge migration,which give rise to the low quantum efficiency of photocatalytic reactions.One efficient strategy to overcome these shortcomings is the manipulation of the microstructures of g-C_(3)N_(4).Other than the traditional structure control,mimicking the structures of creatures in nature to design and construct bio-inspired structures is a promising approach to improve the photocatalytic performance of g-C_(3)N_(4) and even g-C_(3)N_(4)-based systems.This review summarizes the recent advances of the traditional structure-control of g-C_(3)N_(4)-based systems,and bio-inspired synthesis of g-C_(3)N_(4)-based systems from two aspects of structural bionics and functional bionics.Furthermore,the fundamentals of bio-inspired design and fabrication of g-C_(3)N_(4)-based systems are introduced in detail.Additionally,the different theoretical calculations,diverse photocatalytic applications and various modification strategies of bio-inspired structured g-C_(3)N_(4)-based systems are recapped.We believe that this work will be a guiding star for future research in the new field of biomimetic photocatalysis.

Plants and Animals as Concept Generators for the Development of Biomimetic Cable Entry Systems

Many animals and plants have high potential to serve as concept generators for developing biomimetic materials and structures. We present some ideas based on structural and functional properties of plants and animals that led to the development of two types ofbiomimetic cable entry systems. Those systems have been realized on the level of functional demonstrators.

Biomimetic flexible plate actuators are faster and more efficient with a passive attachment

Using three-dimensional computer simulations, we probe biomimetic free swimming of an internally actuated flexible plate in the regime near the first natural frequency. The plate is driven by an oscillating internal moment approximating the actuation mechanism of a piezoelectric macro fiber composite (MFC) bimorph. We show in our simulations that the addition of a passive attachment increases both swimming velocity and efficiency. Specifically, if the active and passive sections are of similar size, the overall performance is the best. We determine that this optimum is a result of two competing factors. If the passive section is too large, then the actuated portion is unable to generate substantial deflection to create sufficient thrust. On the other hand, a large actuated section leads to a bending pattern that is inefficient at generating thrust especially at higher frequencies.

Biomimetic leaf structures for ultra-thin electromagnetic wave absorption

Ultra-thin electromagnetic wave(EMW)absorbers present challenging demands on EMW absorption performance.Drawing inspiration from heather leaf structures,this study introduces an innovative design strategy for EMW absorbing material,proposing biomimetic leaf SnO_(2) structures(bio-SnO_(2))on carbon fabric(CF).By employing leaf-shaped SnS2 as precursors,biomimetic leaf SnO_(2) nanostructures are constructed on CF surface after a simple thermal treatment,resulting in bio-SnO_(2)@CF composite.Experimental results indicate that bio-SnO_(2)@CF exhibits an exceptional minimum reflection loss of-54.8 dB at an incredibly thin thickness of 1.2 mm.Radar cross section(RCS)simulations further validate the outstanding EMW attenuation ability of bio-SnO_(2)@CF,attaining a maximum RCS reduction value of 16.9 dBm^(2) at an incident wave angle ofθ=0°.This novel research showcases the biomimetic structural design strategy and its remarkable function in enhancing the EMW absorbing performance at ultra-thin absorber thickness.

Mechanical properties and simulated thermal conductivity of biomimetic structured PS-PVD(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7) thermal barrier coatings

Plasma spray physical vapor deposition(PS-PVD)(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)thermal barrier coatings(TBCs)exhibited better silicate-phobicity than coatings produced by electron beam physical vapor depo-sition.In combination with PS-PVD and ultrafast laser direct writing technology,biomimetic structured GYbZ TBCs,with a triple-scale micro/nano surface microstructure,were obtained.Laser ablating on the PS-PVD GYbZ coating enhanced the surface roughness,improving its wear resistance without increasing the surface hardness.Furthermore,during the laser ablation processing,numerous nanoparticles were deposited in-situ in the gaps between columns of the coating,reducing the coating Young’s modulus.The simulated temperature field and heat flux field demonstrated that the presence of numerous interfaces between small columns of the PS-PVD coatings is beneficial to thermal insulation.However,laser ablation decreased the coating thickness,reducing the thermal insulation by around 20%-30%as compared to its PS-PVD counterpart,suggesting that a moderate increase in the coating thickness should be considered when designing an efficient TBC system.

Synthesis and application of biomimetic material inspired by diatomite

Inspired by nature,the design and synthesis of novel biomimetic materials are gradually attracting the attention of scientists.Biomimetic materials with excellent performance are widely applied in medical health,industrial production,agricultural planting,aerospace,etc.As a natural porous biomass material,diatomite has the advantages of high porosity,low bulk density,stable chemical property and large surface area.Benefiting from these advantages,it is of great importance to treat diatomite as bionic substrate to synthesize diatomite biomimetic materials,which can be endowed good structure stability and natural mechanical property.It is an ideal option for crystal growth and uniform dispersion of nanostructures,to improve the agglomeration and high cost of nanomaterials.This review briefly introduces our recent achievements on diatomite biomimetic materials in different application fields.In view of its excellent optical,thermal,chemical and mechanical property,diatomite biomimetic materials have shown extensive application potential in various fields of science and engineering,which include catalysis,corrosion protection,microwave adsorption,super-hydrophobicity,pollutant adsorption,energy storage,etc.It demonstrates that diatomite biomimetic materials with different functional properties can be synthesized by diverse chemical means and preparation methods for different application.By composed of inorganic nanomaterial hybrid,this diatomite biomimetic materials display a three-dimensional network structure with diatomite morphology.The design and synthesis of diatomite biomimetic materials provide more potential bionic categories for different applications,which can accelerate the development of low-cost and high-performance biomimetic materials.

Biomimetic Lightweight Design of Legged Robot Hydraulic Drive Unit Shell Inspired by Geometric Shape of Fish Bone Rib Structure

The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.

Biomimetic Photonic Structures with Tunable Structural Colours： From Natural to Biomimetic to Applications

Natural photonic structure with tunable structural colours is one of the most miraculous structures which always catches our eyes. However, the application of artificial photonic structures is limited. Moreover, because of the ability of tunable colours, photonic structure is the excellent candidate for many fields, such as sensor, bioassay, anti-counterfeiting, optical components, photocatalytic, fibers and fabrics. Considering the superior tunable optical property and other excellent performance such as robust mechanical strength, wettability, there are new domains and novel routes for this material that deserve us to explore. In this review, some natural photonic structures are discussed. Some novel fabrication methods and applications will be mentioned in this article. Furthermore, this review provides an insight and outlook for the photonic material with tunable eolours focusing on fabrication, design and applications.

Thermal Performance Analysis of PCM Capsules Packed-Bed System with Biomimetic Leaf Hierarchical Porous Structure

As an efficient natural selection nutrient transport system,biomimetic leaf hierarchical porous structure has unique advantages in material transportation and energy transfer.Biomimetic leaf hierarchical porous structure has been widely used in solar thermochemical reactions,photocatalysis,and energy storage.To improve the thermal efficiency and reduce the power consumption,the authors introduce the idea of bionic leaf hierarchical porous structure packed-bed latent heat thermal energy storage(LHTES)system.Under the same porosity,the diameter of the PCM capsules is designed to change along the flow direction to optimize the thermal performance.The effects of velocity on temperature distribution,pressure drop,liquid fraction,and thermal storage capacity of the conventional uniform model and bionic leaf hierarchical porous model are analyzed.The results show that the bionic leaf hierarchical porous structure can thin the thickness of the thermocline,reduce the pressure drop,increase the heat transfer area,and improve the thermal response of the packed-bed compared with the conventional uniform model.The maximum increases of liquid fraction and completion rate are 36.6%and 20.3%with pressure drop reduction of 25 Pa,respectively.The maximum decrease of the above-melting point(MP)thermocline is 51.7%as well.These results provide suggestions to optimize the packed-bed LHTES system and improve its thermal performance under practical conditions.

Biomimetic Construction of the Enamel-like Hierarchical Structure

Enamel,the hardest mineralized tissue of vertebrates,exhibits simultaneously high stiffness,hardness,and viscoelasticity.The excellent mechanical properties of enamel originate from its high inorganic content and intricate hierarchical structure.Biomimetic construction of the enamel-like hierarchical structure has attracted widespread interest during the past decades.This review summarizes recent advances in this area with a special focus on fabrication techniques across different levels of hierarchy.This includes the synthesis of apatite nanorods or nanowires,the basic building block of enamel,the fabrication of oriented apatite nanorod arrays and the construction of the enamel-like multi-level hierarchical structure.Moreover,possible directions of future research and development in this field are proposed.

Biomimetic Preparation of Alumina Hierarchical Papillary Microrough Structure for Hydrophobic Improvement and Its Abrasion Resistance Finite Element Analysis

The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure building units to construct a Hierarchical Papillary microrough Structure(HPS)on a ceramic surface.The effects of the spatial distribution of HPS on the abrasion resistance and mechanical stability of hydrophobic coatings were investigated.Furthermore,for each HPS,the falling sand abrasion process was analyzed using finite element fluid mechanics analysis.A denser or more two-dimensional HPS implied that more area was impacted by the falling sand and that the abrasion amount and rate were higher.This is contrary to the common belief that when there are more wear-resistant substances on the surface,the abrasion resistance is better;thus,abrasion resistance does not necessarily depend entirely on the concentration of wear-resistant substances on the surface,but it is also influenced by the abrasion mode and the spatial distribution structure of the wear-resistant substances.The 3D stacked HPS(3D-HPS)with excellent abrasion resistance and rich pore structure considerably enhanced the mechanical stability of the hydrophobic coatings.These findings provide novel insights and a theoretical basis for designing spatial structures on high abrasion-resistant superhydrophobic ceramic surfaces.

Auto-generating of 2D tessellated crease patterns of 3D biomimetic spring origami structure

Computational simulations can accelerate the design and modelling of origami robots and mechanisms.This paper presents a computational method using algorithms developed in Python to generate different tessellated origami crease patterns simultaneously.This paper aims to automate this process by introducing a system that automatically generates origami crease patterns in Scalable Vector Graphics format.By introducing different parameters,variations of the same underlying tessellated crease pattern can be obtained.The user interface consists of an input file where the user can input the desired parameters,which are then processed by an algorithm written in Python to generate the respective origami 2D crease patterns.These origami crease patterns can serve as inputs to current origami design software and algorithms to generate origami design models for faster and easier visual comparison.This paper utilizes a basic biomimetic inspiration origami pattern to demonstrate the functionality by varying underlying crease pattern parameters that give rise to symmetric and asymmetric spring origami 3D structures.Furthermore,this paper conducts a qualitative analysis of the origami design outputs of an origami simulator from the input crease patterns and the respective manual folding of the origami structure.

Preparation of microcellular composites with biomimetic structure via supercritical fluid technology

A new microcellular composite material with a biomimetic structure has been prepared via the supercritical fluid (SCF) technology. The resultant material has a clear biomimetic structure like bamboo and wood. The skin region is enriched with oriented high-strength thermotropic liquid crystal polymer fibrils, while the core region with polystyrene (PS) micro-cells. The diameter and density of micro-cells can be controlled by the processing parameters such as temperature and pressure. And the skin thickness can be controlled conveniently by varying the composition of polystyrene and liquid crystal polymer.