Multimaterial(MM)3D printing shows great potential for application in metamaterials,flexible electronics,biomedical devices and robots,since it can seamlessly integrate distinctive materials into one printed structure...Multimaterial(MM)3D printing shows great potential for application in metamaterials,flexible electronics,biomedical devices and robots,since it can seamlessly integrate distinctive materials into one printed structure.Among numerous MM 3D printing technologies,digital light processing(DLP)MM 3D printing is compatible with a wide range of materials from hydrogels to ceramics,and can print MM 3D structures with high resolution,high complexity and fast speed.This paper introduces the fundamental mechanisms of DLP 3D printing,and reviews the recent advances of DLP MM 3D printing technologies with emphasis on material switching methods and material contamination issues.It also summarizes a number of typical examples of DLP MM 3D printing systems developed in the past decade,and introduces their system structures,working principles,material switching methods,residual resin removal methods,printing steps,as well as the representative structures and applications.Finally,we provide perspectives on the directions of the further development of DLP MM 3D printing technology.展开更多
A new topology optimization method is formulated for lightweight design of multimaterial structures, using the independent continuous mapping (ICM) method to minimize the weight with a prescribed nodal displacement co...A new topology optimization method is formulated for lightweight design of multimaterial structures, using the independent continuous mapping (ICM) method to minimize the weight with a prescribed nodal displacement constraint. Two types of independent topological variable are used to identify the presence of elements and select the material for each phase, to realize the interpolations of the element stiffness matrix and total weight. Furthermore, an explicit expression for the optimized formulation is derived, using approximations of the displacement and weight given by first- and second-order Taylor expansions. The optimization problem is thereby transformed into a standard quadratic programming problem that can be solved using a sequential quadratic programming approach. The feasibility and effectiveness of the proposed multimaterial topology optimization method are demonstrated by determining the best load transfer path for four numerical examples. The results reveal that the topologically optimized configuration of the multimaterial structure varies with the material properties, load conditions, and constraint. Firstly, the weight of the optimized multimaterial structure is found to be lower than that composed of a single material. Secondly, under the precondition of a displacement constraint, the weight of the topologically optimized multimaterial structure decreases as the displacement constraint value is increased. Finally, the topologically optimized multimaterial structures differ depending on the elastic modulus of the materials. Besides, the established optimization formulation is more reliable and suitable for use in practical engineering applications with structural performance parameters as constraint.展开更多
The increasing energy requirements to power the modern world has driven active research into more advanced electrochemical energy storage devices(EESD)with both high energy densities and power densities.Wide range of ...The increasing energy requirements to power the modern world has driven active research into more advanced electrochemical energy storage devices(EESD)with both high energy densities and power densities.Wide range of newly discovered materials with promising electrochemical properties has shown great potential for next-generation devices,but their performance is normally associated with contradicting demands of thin electrodes and high mass loading that can be hardly achieved for practical applications.Design of three-dimensional(3D)porous electrodes can increase the mass loading while maintaining the effective charge transport even with thick electrodes,which has proven to be efficient to overcome the limitations.3D structures have also been demonstrated excellent structural stability to withstand strong strains and stresses generated during charge/discharge cycle.3D printing,which can fabricate various delicate and complex structural designs,thus offering brand-new opportunities for the rational design and facile construction of next-generation EESDs.The recent developments in 3D printing of next-generation EESDs with high performance are reviewed.Advanced/multiscale electrode structures,such as hierarchically porous structure that can be constructed via high-resolution 3D printing or with post-treatment,are further emphasized.The ability of current 3D printing techniques to fulfill multimaterial printing to fulfill simple packaging will be covered.展开更多
Origami structure has been employed in many engineering applications.However,there is currently no strategy that can systematically achieve stiffness-tunable origami(STO)structures through proper geometric design.Here...Origami structure has been employed in many engineering applications.However,there is currently no strategy that can systematically achieve stiffness-tunable origami(STO)structures through proper geometric design.Here,we report a strategy for designing and fabricating STO structures based on thick-panel origami using multimaterial 3D printing.By adjusting the soft hinge position,we tune the geometric parameterψto program the stiffness and strength of origami structures.We develop origami structures with graded stiffness and strength by stacking Kresling origami structures with differentψ.The printed structures show great cyclic characteristics and deformation ability.After optimizing combinations of structures with differentψ,the multi-layer Kresling STO structures can effectively reduce the peak impact,showing a good energy absorption effect.The proposed approach can be implemented in various origami patterns to design and tune the mechanical properties of origami structures for many potential applications.展开更多
Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping cap...Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping capabilities based on photopolymerization.However,owing to differences in the curing behavior and physical properties of different materials,multimaterial DLP 3D printing faces challenges such as insufficient interfacial bonding strength and unstable mechanical properties.In this study,two resins were integrated by multimaterial DLP 3D printing technology,and the effects of different layer thicknesses and exposure times on the interfacial bonding strength and morphology of the multimaterials were systematically investigated.The interfacial bonding mechanisms of the two resins was analyzed.It was found that increasing the exposure time can improve the interfacial bonding strength between materials,but certain limitations exist.A mathematical model relating the interfacial bonding strength to the exposure time and layer thickness was developed,and optimal process parameters were determined using optimization algorithms.A variable-parameter printing strategy for the interface was proposed to further improve the performance of printed parts.The maximum tensile strength of the multimaterial samples(44.43 MPa)using this strategy reached that of single-material parts(45 MPa),validating the feasibility of this strategy.This provides guidance for multimaterial DLP 3D printing processes and offers valuable insights for the future additive manufacturing of high-performance multimaterial components.展开更多
Vat photopolymerization 3D printing creates structures by projecting patterns onto a photosensitive resin within a vat.However,the presence of resin vats limits the printing of multiscale multimaterial structures.In t...Vat photopolymerization 3D printing creates structures by projecting patterns onto a photosensitive resin within a vat.However,the presence of resin vats limits the printing of multiscale multimaterial structures.In this context,a novel 3D printing process is presented in which a cured structure is produced from acoustically levitated droplets without a physical vat.This enables the printing process to achieve high flexibility in the printing orientation and material supply.In pursuit of the envisioned 3D acoustic levitation printing strategy,acoustic levitation technology was utilized to suspend a photosensitive resin.Objects with small features were successfully produced by projecting patterns onto levitated resin droplets.Transforming printing orientations allows the fabrication of multiscale structures.Levitating resin droplets on-demand enables the rapid replacement of materials,thereby realizing effortless multimaterial 3D printing.By exploiting the flexibility of printing on levitation resin droplets,the capability of 3D printing on existing objects was established.Finally,an interesting example was illustrated,in which an object integrating liquid,gas,and solid materials was fabricated using the proposed 3D printing strategy.The results show that 3D printing on levitated droplets is feasible for fabricating multiscale and multimaterial objects,which contributes to the development of new 3D printing methods and potential applications.展开更多
Smart structures have the advantages of high system integrity and diverse sensing capabilities.However,the labor-intensive and timeconsuming fabrication process hinders the large-scale adoption of smart structures.Des...Smart structures have the advantages of high system integrity and diverse sensing capabilities.However,the labor-intensive and timeconsuming fabrication process hinders the large-scale adoption of smart structures.Despite recent attempts to develop sensorembedded structures using 3D printing technologies,the reported smart structures generally suffer from the complex fabrication process,constrained part size,and limited sensing modality.Herein,we propose a workflow to design and fabricate novel smart structures via multi-material fused deposition modeling(FDM)-based 3D printing.More specifically,conductive filaments with tailorable mechanical and elec-trical properties,e.g.piezoresistive effects,were developed.Additionally,the printing process was optimized for processing soft filaments with Young’s modulus around 2 MPa,resolving the issue of filament buckling.Furthermore,the potential applications of the proposed workflow were showcased using three design cases,i.e.biaxial strain sensor,smart tire,and cable-driven soft finger with multiple sensing capabilities.This workflow provides a cost-effective and rapid solution for developing novel smart structures with soft materials.展开更多
Laser powder bed fusion(LPBF)is an innovative method for manufacturing multimaterial components with high geometrical resolution.The LPBF-printing sequences of materials may be diverse in the actual design and applica...Laser powder bed fusion(LPBF)is an innovative method for manufacturing multimaterial components with high geometrical resolution.The LPBF-printing sequences of materials may be diverse in the actual design and application of multimaterial components.In this study,multimaterial copper(CuSn10)–steel(316 L)structures are printed using different building strategies(printing 316 L on CuSn10 and printing CuSn10 on 316 L)via LPBF,and the characteristics of two interfaces(the 316 L/CuSn10 or“L/C”and CuSn10/316 L or“C/L”interfaces)are investigated.Subsequently,the interfacial melting mode and formation mechanisms are discussed.At the L/C interface,the keyhole melting mode induced by the high volumetric energy density(EL/C=319.4 J/mm3)results in a large penetration depth in the pre-solidified layer and enhances laser energy absorption,thus promoting the extensive migration of materials and intense intermixing of elements to form a wide diffusion zone(∼400μm).At the C/L interface,the conduction mode induced by the low volumetric energy density(EC/L=74.1 J/mm3)results in a narrow diffusion zone(∼160μm).The interfacial defects observed are primarily cracks and pores.More cracks appeared at the C/L interface,which is attributable to the weak bonding strength of the narrow diffusion zone.This study provides guidance and reference for the design and manufacturing of multimaterial components via LPBF using different building strategies.展开更多
This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring...This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring safety and facilitating the postprocessing of topological structures.The approach involves constructing a multimaterial interpolation model based on an ordered solid isotropic material with penalization(ordered-SIMP)that incorporates failsafe considerations.To reduce the computational burden of finite element analysis,we adopt a much coarser analysis mesh and finer density mesh to discretize the design domain,in which the density field is described by the B-spline function.The B-spline can efficiently and accurately convert optimized FSSs into computer-aided design models.The 2D and 3D numerical examples demonstrate the significantly enhanced computational efficiency of the proposed method compared with the traditional SIMP approach,and the multimaterial TO provides a superior structural design scheme for FSSs.Furthermore,the postprocessing procedures are significantly streamlined.展开更多
This paper presents an Eulerian diffuse-interface method using a high-order compact difference scheme for simulating elastic-plastic flows with the Mie–Gruneisen(MG)equation of state(EoS).For simulations of multimate...This paper presents an Eulerian diffuse-interface method using a high-order compact difference scheme for simulating elastic-plastic flows with the Mie–Gruneisen(MG)equation of state(EoS).For simulations of multimaterial problems,numerical errors were generated in the material discontinuities owing to inconsistent treatment of the convective terms.Based on the normal-stress-based mechanical equilibrium assumption for elastic-plastic solids,we introduce an improved form of the consistent localized artificial diffusivity(LAD)method to ensure an oscillation-free interface for velocity and normal stress.The proposed algorithm uses a hyperelastic model.A mixture type of the model system was formed by combining the conservation equations for the basic conserved variables,an equation of a unified deviatoric tensor describing solid deformation,and an additional set of equations for solving the material quantities in the MG EoS.Several one-and two-dimensional problems with various discontinuities,including the elastic-plastic Richtmyer–Meshkov instability,were considered for testing the proposed method.展开更多
Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-materia...Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-material interfaces is demonstrated. Discontinuous Galerkin finite element method is used to solve Euleri- an equations. And the fifth-order weighted essentially non-oscillatory （WENO） scheme is used to solve the level set equation for capturing multi-material interfaces. The ghost fluid method is used to deal with the interfacial boundary condition. Results are obtained for two bubble interacting with a moving shock. The contours of the constant density and the pressure at different time are given. In the computational domain, three different cases are considered, i.e. two helium bubbles, a helium bubble followed by an R22 bubble in the direction of the moving shock, and an R22 bubble followed by a helium bubble. Computational results indicate that multi-mate- rial interfaces can be properly captured by the level set method. Therefore, for problems involving the flow of three different materials with two different interfaces, each interface separating two different materials can be similarly handled.展开更多
Ti6Al4V cellular structures were produced by selective laser melting(SLM)and then filled either with beta-tricalcium phosphate(β-TCP)or PEEK(poly-ether-ether-ketone)through powder metallurgy techniques,to improve ost...Ti6Al4V cellular structures were produced by selective laser melting(SLM)and then filled either with beta-tricalcium phosphate(β-TCP)or PEEK(poly-ether-ether-ketone)through powder metallurgy techniques,to improve osteoconductivity and wear resistance.The corrosion behavior of these structures was explored considering its importance for the long-term performance of implants.Results revealed that the incorporation of open cellular pores induced higher electrochemical kinetics when being compared with dense structures.The impregnation ofβ-TCP and PEEK led to the creation of voids or gaps between the metallic matrix and the impregnated material which also influenced the corrosion behavior of the cellular structures.展开更多
Projection micro stereolithography(PμSL)is a high-resolution(up to 0.6μm)3D printing technology based on area projection triggered photopolymerization,and capable of fabricating complex 3D architectures covering mul...Projection micro stereolithography(PμSL)is a high-resolution(up to 0.6μm)3D printing technology based on area projection triggered photopolymerization,and capable of fabricating complex 3D architectures covering multiple scales and with multiple materials.This paper reviews the recent development of the PμSL based 3D printing technologies,together with the related applications.It introduces the working principle,the commercialized products,and the recent multiscale,multimaterial printing capability of PμSL as well as some functional photopolymers that are suitable to PμSL.This review paper also summarizes a few typical applications of PμSL including mechanical metamaterials,optical components,4D printing,bioinspired materials and biomedical applications,and offers perspectives on the directions of the further development of PμSL based 3D printing technology.展开更多
The feasibility of using selective heat melting(SHM) to fabricate composite materials and functionally graded structures was investigated.We report,for the first time,the successful 3 D printing of copper(Cu)-polyethy...The feasibility of using selective heat melting(SHM) to fabricate composite materials and functionally graded structures was investigated.We report,for the first time,the successful 3 D printing of copper(Cu)-polyethylene(PE) composite,iron(Fe)-polyethylene(PE) composite and functionally graded CuO foams using the SHM technique.It was found that a low feed rate,high airflow rate and high airflow temperature were required for efficient delivery of heat from the emitted hot air to the powder bed,so that the PE binder particles can melt and form dense composites with smooth surfaces.The best mechanical properties were exhibited by composites with 80 vol.% PE,as lower PE concentrations led to deficient binding of the metal particles,while higher PE concentrations meant that very few metal particles were available to strengthen the composite.The strength exhibited by Cu-PE composites was comparable to engineering plastics such as polycarbonate,with the added advantage of being electrically conductive.The average conductivity of the samples,0.152±0.28 S/m,was on par with physically crosslinked graphene assemblies.By subjecting a Cu-PE composite,with Cu concentration graded from 10 vol.% to 30 vol.%,to a high temperature debinding and sintering treatment in air,CuO foam with graded porosity can be obtained.This CuO foam was observed to fail in a layer-by-layer manner under mechanical compression,which is a characteristic of functionally graded materials.Our study shows that,compared to existing 3 D printing techniques,SHM can be cheaper,have wider material compatibility,occupy a smaller footprint and potentially induce less residual stresses in the fabricated parts.Therefore,it could be a valuable complement to current additive manufacturing techniques for fabricating mechanically strong composite materials and functionally graded structures.展开更多
Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures.However,the curre...Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures.However,the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir,which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle.Here,we propose a dielectrophoresis(DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork(QTF)-atomic force microscope(AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions.We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation,which confirmed the surfaceenhanced Raman spectroscopy(SERS).To validate the scheme,we also performed a simulation for the system and found qualitative agreement with the experimental results.The method that combines DEP,pipette-based AFM,and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning,materials sorting,and diverse advanced applications.展开更多
Diffuse interfaces appear with any Eulerian discontinuity capturing compressible flow solver. When dealing with multifluid and multimaterial computations, interfaces smearing results in serious difficulties to fulfil ...Diffuse interfaces appear with any Eulerian discontinuity capturing compressible flow solver. When dealing with multifluid and multimaterial computations, interfaces smearing results in serious difficulties to fulfil contact conditions, as spurious oscillations appear. To circumvent these difficulties, several approaches have been proposed. One of them relies on multiphase flow modelling of the numerically diffused zone and is based on extended hyperbolic systems with stiff mechanical relaxation (Saurel and Abgrall, 1999 [4], Saurel et al., 2009 [6]). This approach is very robust, accurate and flexible in the sense that many physical effects can be included: surface tension, phase transition, elastic-plastic materials, detonations, granular effects etc. It is also able to deal with dynamic appearance of interfaces. However it suffers from an important drawback when long time evolution is under interest as the interface becomes more and more diffused. The present paper addresses this issue and provides an efficient way to sharpen interfaces. A sharpening flow model is used to correct the solution after each time step. The sharpening process is based on a hyperbolic equation that produces a steady shock in finite time at the interface location. This equation is embedded in a “sharpening multiphase model” redistributing volume fractions, masses, momentum and energy in a consistent way. The method is conservative with respect to the masses, mixture momentum and mixture energy. It results in diffused interfaces sharpened in one or two mesh points. The method is validated on test problems having exact solutions.展开更多
Structures in nature are often multi-material,and their structures have afine bal-ance between segregation and aggregation(mixed,but not scrambled)that provides functionality.Chaotic fabrication,a technology that expl...Structures in nature are often multi-material,and their structures have afine bal-ance between segregation and aggregation(mixed,but not scrambled)that provides functionality.Chaotic fabrication,a technology that exploits the ability of chaotic advection to create predictable and reproducible multilayered structures,excels at producing materials where this balance can be achieved andfinely tuned.This method is based on the use of chaotic mixing systems,which can produce constructs with highly organized internal micro-architecture in a simple and cost-effective way.This manuscript provides a perspective on how chaotic printing can be a great enabler in the manufacture of advanced materials,including living tissues.Chaotic printing may overcome many of the critical hurdles that are currently faced in man-ufacturing and biofabrication(e.g.,creating a wide array of interfaces,reaching high resolutions rapidly and at low cost,and producing densely vascularized tissues).The manuscript introduces the technology,explains how the idea originated,presents a timeline that provides a recapitulation of the milestones achieved so far,describes the main characteristics,advantages,limitations,and challenges of the technology,and concludes with future perspectives on the evolution and use of this versatile method.展开更多
The ＂lab-on-fiber＂ concept envisions novel and highly functionalized technological platforms completely integrated in a single optical fiber that would allow the development of advanced devices, components and sub-s...The ＂lab-on-fiber＂ concept envisions novel and highly functionalized technological platforms completely integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems to be incorporated in modem optical systems for communication and sensing applications. The realization of integrated optical fiber devices requires that several structures and materials at nano- and micro-scale are constructed, embedded and connected all together to provide the necessary physical connections and light-matter interactions. This paper reviews the strategies, the main achievements and related devices in the lab-on-fiber roadmap discussing perspectives and challenges that lie ahead.展开更多
基金the National Natural Science Foundation of China (No. 12072142)the Key Talent Recruitment Program of Guangdong Province (No. 2019QN01Z438)the support by the Science, Technology and Innovation Commission of Shenzhen Municipality under Grant No. ZDSYS20210623092005017
文摘Multimaterial(MM)3D printing shows great potential for application in metamaterials,flexible electronics,biomedical devices and robots,since it can seamlessly integrate distinctive materials into one printed structure.Among numerous MM 3D printing technologies,digital light processing(DLP)MM 3D printing is compatible with a wide range of materials from hydrogels to ceramics,and can print MM 3D structures with high resolution,high complexity and fast speed.This paper introduces the fundamental mechanisms of DLP 3D printing,and reviews the recent advances of DLP MM 3D printing technologies with emphasis on material switching methods and material contamination issues.It also summarizes a number of typical examples of DLP MM 3D printing systems developed in the past decade,and introduces their system structures,working principles,material switching methods,residual resin removal methods,printing steps,as well as the representative structures and applications.Finally,we provide perspectives on the directions of the further development of DLP MM 3D printing technology.
基金the National Natural Science Foundation of China (Grants 11072009 and 11872080)Beijing Education Committee Development Project (Grant SQKM201610005001).
文摘A new topology optimization method is formulated for lightweight design of multimaterial structures, using the independent continuous mapping (ICM) method to minimize the weight with a prescribed nodal displacement constraint. Two types of independent topological variable are used to identify the presence of elements and select the material for each phase, to realize the interpolations of the element stiffness matrix and total weight. Furthermore, an explicit expression for the optimized formulation is derived, using approximations of the displacement and weight given by first- and second-order Taylor expansions. The optimization problem is thereby transformed into a standard quadratic programming problem that can be solved using a sequential quadratic programming approach. The feasibility and effectiveness of the proposed multimaterial topology optimization method are demonstrated by determining the best load transfer path for four numerical examples. The results reveal that the topologically optimized configuration of the multimaterial structure varies with the material properties, load conditions, and constraint. Firstly, the weight of the optimized multimaterial structure is found to be lower than that composed of a single material. Secondly, under the precondition of a displacement constraint, the weight of the topologically optimized multimaterial structure decreases as the displacement constraint value is increased. Finally, the topologically optimized multimaterial structures differ depending on the elastic modulus of the materials. Besides, the established optimization formulation is more reliable and suitable for use in practical engineering applications with structural performance parameters as constraint.
基金supports by National Natural Science Foundation of China(grant no.51902265)Fundamental Research Funds for the Central Universities,Key Research and Development Program of Shaanxi(no.2020KWZ-001)Project for graduate Innovation team of Northwestern Polytechnical University.
文摘The increasing energy requirements to power the modern world has driven active research into more advanced electrochemical energy storage devices(EESD)with both high energy densities and power densities.Wide range of newly discovered materials with promising electrochemical properties has shown great potential for next-generation devices,but their performance is normally associated with contradicting demands of thin electrodes and high mass loading that can be hardly achieved for practical applications.Design of three-dimensional(3D)porous electrodes can increase the mass loading while maintaining the effective charge transport even with thick electrodes,which has proven to be efficient to overcome the limitations.3D structures have also been demonstrated excellent structural stability to withstand strong strains and stresses generated during charge/discharge cycle.3D printing,which can fabricate various delicate and complex structural designs,thus offering brand-new opportunities for the rational design and facile construction of next-generation EESDs.The recent developments in 3D printing of next-generation EESDs with high performance are reviewed.Advanced/multiscale electrode structures,such as hierarchically porous structure that can be constructed via high-resolution 3D printing or with post-treatment,are further emphasized.The ability of current 3D printing techniques to fulfill multimaterial printing to fulfill simple packaging will be covered.
基金supported by the National KeyResearch and Development Program of China(2020YFB1312900)the National Natural Science Foundation of China(No.12072142)+1 种基金the Key Talent Recruitment Program of Guangdong Province(No.2019QN01Z438)the Science Technology and Innovation Commission of Shenzhen Municipality(ZDSYS20210623092005017).
文摘Origami structure has been employed in many engineering applications.However,there is currently no strategy that can systematically achieve stiffness-tunable origami(STO)structures through proper geometric design.Here,we report a strategy for designing and fabricating STO structures based on thick-panel origami using multimaterial 3D printing.By adjusting the soft hinge position,we tune the geometric parameterψto program the stiffness and strength of origami structures.We develop origami structures with graded stiffness and strength by stacking Kresling origami structures with differentψ.The printed structures show great cyclic characteristics and deformation ability.After optimizing combinations of structures with differentψ,the multi-layer Kresling STO structures can effectively reduce the peak impact,showing a good energy absorption effect.The proposed approach can be implemented in various origami patterns to design and tune the mechanical properties of origami structures for many potential applications.
基金supported by National Key R&D Program of China(Grant No.2022YFB4600103)National Youth Talent Support Program,China Postdoctoral Science Foundation(Grant No.2021M692555)+1 种基金Shaanxi Province Qinchuangyuan'Scientists+Engineers'Team Building Project(Grant No.2023KXJ-266)Fundamental Research Funds for the Central Universities(Grant No.xzy012023145)。
文摘Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping capabilities based on photopolymerization.However,owing to differences in the curing behavior and physical properties of different materials,multimaterial DLP 3D printing faces challenges such as insufficient interfacial bonding strength and unstable mechanical properties.In this study,two resins were integrated by multimaterial DLP 3D printing technology,and the effects of different layer thicknesses and exposure times on the interfacial bonding strength and morphology of the multimaterials were systematically investigated.The interfacial bonding mechanisms of the two resins was analyzed.It was found that increasing the exposure time can improve the interfacial bonding strength between materials,but certain limitations exist.A mathematical model relating the interfacial bonding strength to the exposure time and layer thickness was developed,and optimal process parameters were determined using optimization algorithms.A variable-parameter printing strategy for the interface was proposed to further improve the performance of printed parts.The maximum tensile strength of the multimaterial samples(44.43 MPa)using this strategy reached that of single-material parts(45 MPa),validating the feasibility of this strategy.This provides guidance for multimaterial DLP 3D printing processes and offers valuable insights for the future additive manufacturing of high-performance multimaterial components.
基金supported by National Natural Science Foundation of China(Grant No.52305398)Chengdu University of Information Technology Project(Grant No.KYTZ202145).
文摘Vat photopolymerization 3D printing creates structures by projecting patterns onto a photosensitive resin within a vat.However,the presence of resin vats limits the printing of multiscale multimaterial structures.In this context,a novel 3D printing process is presented in which a cured structure is produced from acoustically levitated droplets without a physical vat.This enables the printing process to achieve high flexibility in the printing orientation and material supply.In pursuit of the envisioned 3D acoustic levitation printing strategy,acoustic levitation technology was utilized to suspend a photosensitive resin.Objects with small features were successfully produced by projecting patterns onto levitated resin droplets.Transforming printing orientations allows the fabrication of multiscale structures.Levitating resin droplets on-demand enables the rapid replacement of materials,thereby realizing effortless multimaterial 3D printing.By exploiting the flexibility of printing on levitation resin droplets,the capability of 3D printing on existing objects was established.Finally,an interesting example was illustrated,in which an object integrating liquid,gas,and solid materials was fabricated using the proposed 3D printing strategy.The results show that 3D printing on levitated droplets is feasible for fabricating multiscale and multimaterial objects,which contributes to the development of new 3D printing methods and potential applications.
基金This work was supported by the National Key Research and Development Program of China[No.2020YFB1312900]National Natural Science Foundation of China[No.52105261]Guangdong Basic and Applied Basic Research Foundation[No.2022A1515010316].
文摘Smart structures have the advantages of high system integrity and diverse sensing capabilities.However,the labor-intensive and timeconsuming fabrication process hinders the large-scale adoption of smart structures.Despite recent attempts to develop sensorembedded structures using 3D printing technologies,the reported smart structures generally suffer from the complex fabrication process,constrained part size,and limited sensing modality.Herein,we propose a workflow to design and fabricate novel smart structures via multi-material fused deposition modeling(FDM)-based 3D printing.More specifically,conductive filaments with tailorable mechanical and elec-trical properties,e.g.piezoresistive effects,were developed.Additionally,the printing process was optimized for processing soft filaments with Young’s modulus around 2 MPa,resolving the issue of filament buckling.Furthermore,the potential applications of the proposed workflow were showcased using three design cases,i.e.biaxial strain sensor,smart tire,and cable-driven soft finger with multiple sensing capabilities.This workflow provides a cost-effective and rapid solution for developing novel smart structures with soft materials.
基金Guangdong Provincial Basic and Applied Basic Research Foundation of China(Grant Nos.2019B1515120094,2022B1515020064)National Natural Science Foundation of China(Grant No.52073105)Guangdong Provincial Key Field Research and Development Program of China(Grant No.2020B090922002).
文摘Laser powder bed fusion(LPBF)is an innovative method for manufacturing multimaterial components with high geometrical resolution.The LPBF-printing sequences of materials may be diverse in the actual design and application of multimaterial components.In this study,multimaterial copper(CuSn10)–steel(316 L)structures are printed using different building strategies(printing 316 L on CuSn10 and printing CuSn10 on 316 L)via LPBF,and the characteristics of two interfaces(the 316 L/CuSn10 or“L/C”and CuSn10/316 L or“C/L”interfaces)are investigated.Subsequently,the interfacial melting mode and formation mechanisms are discussed.At the L/C interface,the keyhole melting mode induced by the high volumetric energy density(EL/C=319.4 J/mm3)results in a large penetration depth in the pre-solidified layer and enhances laser energy absorption,thus promoting the extensive migration of materials and intense intermixing of elements to form a wide diffusion zone(∼400μm).At the C/L interface,the conduction mode induced by the low volumetric energy density(EC/L=74.1 J/mm3)results in a narrow diffusion zone(∼160μm).The interfacial defects observed are primarily cracks and pores.More cracks appeared at the C/L interface,which is attributable to the weak bonding strength of the narrow diffusion zone.This study provides guidance and reference for the design and manufacturing of multimaterial components via LPBF using different building strategies.
基金the National Natural Science Foundation of China(Grant No.52075184)the Open-funding Project of State Key Laboratory of Digital Manufacturing Equipment and Technology(Huazhong University of Science and Technology),China(Grant No.DMETKF2021020).
文摘This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring safety and facilitating the postprocessing of topological structures.The approach involves constructing a multimaterial interpolation model based on an ordered solid isotropic material with penalization(ordered-SIMP)that incorporates failsafe considerations.To reduce the computational burden of finite element analysis,we adopt a much coarser analysis mesh and finer density mesh to discretize the design domain,in which the density field is described by the B-spline function.The B-spline can efficiently and accurately convert optimized FSSs into computer-aided design models.The 2D and 3D numerical examples demonstrate the significantly enhanced computational efficiency of the proposed method compared with the traditional SIMP approach,and the multimaterial TO provides a superior structural design scheme for FSSs.Furthermore,the postprocessing procedures are significantly streamlined.
基金This work was funded by the Natural Science Foundation of China under Grant Nos.11772065 and 11702028the Science Challenge Project(Grant No.TZ2016001)The work of the first author was supported by the Postdoctoral Science Foundation of China(Grant No.2020M670226).
文摘This paper presents an Eulerian diffuse-interface method using a high-order compact difference scheme for simulating elastic-plastic flows with the Mie–Gruneisen(MG)equation of state(EoS).For simulations of multimaterial problems,numerical errors were generated in the material discontinuities owing to inconsistent treatment of the convective terms.Based on the normal-stress-based mechanical equilibrium assumption for elastic-plastic solids,we introduce an improved form of the consistent localized artificial diffusivity(LAD)method to ensure an oscillation-free interface for velocity and normal stress.The proposed algorithm uses a hyperelastic model.A mixture type of the model system was formed by combining the conservation equations for the basic conserved variables,an equation of a unified deviatoric tensor describing solid deformation,and an additional set of equations for solving the material quantities in the MG EoS.Several one-and two-dimensional problems with various discontinuities,including the elastic-plastic Richtmyer–Meshkov instability,were considered for testing the proposed method.
基金Supported by the National Natural Science Foundation of China(10476011)~~
文摘Numerical simulations are performed on the interface with large deformation induced by the interaction between a moving shock and two consecutive bubbles. The high performance of the level set method for multi-material interfaces is demonstrated. Discontinuous Galerkin finite element method is used to solve Euleri- an equations. And the fifth-order weighted essentially non-oscillatory （WENO） scheme is used to solve the level set equation for capturing multi-material interfaces. The ghost fluid method is used to deal with the interfacial boundary condition. Results are obtained for two bubble interacting with a moving shock. The contours of the constant density and the pressure at different time are given. In the computational domain, three different cases are considered, i.e. two helium bubbles, a helium bubble followed by an R22 bubble in the direction of the moving shock, and an R22 bubble followed by a helium bubble. Computational results indicate that multi-mate- rial interfaces can be properly captured by the level set method. Therefore, for problems involving the flow of three different materials with two different interfaces, each interface separating two different materials can be similarly handled.
基金supported by FCT through the grants PD/BD/140202/2018,SFRH/BD/140191/2018 and SFRH/BD/128657/2017the projects PTDC/EMS-TEC/5422/2014 and NORTE-01-0145-FEDER-000018-HAMa BICo+1 种基金supported by FCT with the reference project UID/EEA/04436/2019the financial support through the M-ERA-NET/0001/2015 project(FCT)
文摘Ti6Al4V cellular structures were produced by selective laser melting(SLM)and then filled either with beta-tricalcium phosphate(β-TCP)or PEEK(poly-ether-ether-ketone)through powder metallurgy techniques,to improve osteoconductivity and wear resistance.The corrosion behavior of these structures was explored considering its importance for the long-term performance of implants.Results revealed that the incorporation of open cellular pores induced higher electrochemical kinetics when being compared with dense structures.The impregnation ofβ-TCP and PEEK led to the creation of voids or gaps between the metallic matrix and the impregnated material which also influenced the corrosion behavior of the cellular structures.
基金the National Natural Science Foundation of China(51420105009).
文摘Projection micro stereolithography(PμSL)is a high-resolution(up to 0.6μm)3D printing technology based on area projection triggered photopolymerization,and capable of fabricating complex 3D architectures covering multiple scales and with multiple materials.This paper reviews the recent development of the PμSL based 3D printing technologies,together with the related applications.It introduces the working principle,the commercialized products,and the recent multiscale,multimaterial printing capability of PμSL as well as some functional photopolymers that are suitable to PμSL.This review paper also summarizes a few typical applications of PμSL including mechanical metamaterials,optical components,4D printing,bioinspired materials and biomedical applications,and offers perspectives on the directions of the further development of PμSL based 3D printing technology.
基金funding for this project by the Temasek Research Fellowship(No.9016100729)。
文摘The feasibility of using selective heat melting(SHM) to fabricate composite materials and functionally graded structures was investigated.We report,for the first time,the successful 3 D printing of copper(Cu)-polyethylene(PE) composite,iron(Fe)-polyethylene(PE) composite and functionally graded CuO foams using the SHM technique.It was found that a low feed rate,high airflow rate and high airflow temperature were required for efficient delivery of heat from the emitted hot air to the powder bed,so that the PE binder particles can melt and form dense composites with smooth surfaces.The best mechanical properties were exhibited by composites with 80 vol.% PE,as lower PE concentrations led to deficient binding of the metal particles,while higher PE concentrations meant that very few metal particles were available to strengthen the composite.The strength exhibited by Cu-PE composites was comparable to engineering plastics such as polycarbonate,with the added advantage of being electrically conductive.The average conductivity of the samples,0.152±0.28 S/m,was on par with physically crosslinked graphene assemblies.By subjecting a Cu-PE composite,with Cu concentration graded from 10 vol.% to 30 vol.%,to a high temperature debinding and sintering treatment in air,CuO foam with graded porosity can be obtained.This CuO foam was observed to fail in a layer-by-layer manner under mechanical compression,which is a characteristic of functionally graded materials.Our study shows that,compared to existing 3 D printing techniques,SHM can be cheaper,have wider material compatibility,occupy a smaller footprint and potentially induce less residual stresses in the fabricated parts.Therefore,it could be a valuable complement to current additive manufacturing techniques for fabricating mechanically strong composite materials and functionally graded structures.
基金Open access funding provided by Shanghai Jiao Tong University。
文摘Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures.However,the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir,which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle.Here,we propose a dielectrophoresis(DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork(QTF)-atomic force microscope(AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions.We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation,which confirmed the surfaceenhanced Raman spectroscopy(SERS).To validate the scheme,we also performed a simulation for the system and found qualitative agreement with the experimental results.The method that combines DEP,pipette-based AFM,and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning,materials sorting,and diverse advanced applications.
文摘Diffuse interfaces appear with any Eulerian discontinuity capturing compressible flow solver. When dealing with multifluid and multimaterial computations, interfaces smearing results in serious difficulties to fulfil contact conditions, as spurious oscillations appear. To circumvent these difficulties, several approaches have been proposed. One of them relies on multiphase flow modelling of the numerically diffused zone and is based on extended hyperbolic systems with stiff mechanical relaxation (Saurel and Abgrall, 1999 [4], Saurel et al., 2009 [6]). This approach is very robust, accurate and flexible in the sense that many physical effects can be included: surface tension, phase transition, elastic-plastic materials, detonations, granular effects etc. It is also able to deal with dynamic appearance of interfaces. However it suffers from an important drawback when long time evolution is under interest as the interface becomes more and more diffused. The present paper addresses this issue and provides an efficient way to sharpen interfaces. A sharpening flow model is used to correct the solution after each time step. The sharpening process is based on a hyperbolic equation that produces a steady shock in finite time at the interface location. This equation is embedded in a “sharpening multiphase model” redistributing volume fractions, masses, momentum and energy in a consistent way. The method is conservative with respect to the masses, mixture momentum and mixture energy. It results in diffused interfaces sharpened in one or two mesh points. The method is validated on test problems having exact solutions.
基金CONAHCyT,Grant/Award Numbers:SNI 26048,SNI 256730Baur ChairChallenge-Based Research Funding Program。
文摘Structures in nature are often multi-material,and their structures have afine bal-ance between segregation and aggregation(mixed,but not scrambled)that provides functionality.Chaotic fabrication,a technology that exploits the ability of chaotic advection to create predictable and reproducible multilayered structures,excels at producing materials where this balance can be achieved andfinely tuned.This method is based on the use of chaotic mixing systems,which can produce constructs with highly organized internal micro-architecture in a simple and cost-effective way.This manuscript provides a perspective on how chaotic printing can be a great enabler in the manufacture of advanced materials,including living tissues.Chaotic printing may overcome many of the critical hurdles that are currently faced in man-ufacturing and biofabrication(e.g.,creating a wide array of interfaces,reaching high resolutions rapidly and at low cost,and producing densely vascularized tissues).The manuscript introduces the technology,explains how the idea originated,presents a timeline that provides a recapitulation of the milestones achieved so far,describes the main characteristics,advantages,limitations,and challenges of the technology,and concludes with future perspectives on the evolution and use of this versatile method.
文摘The ＂lab-on-fiber＂ concept envisions novel and highly functionalized technological platforms completely integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems to be incorporated in modem optical systems for communication and sensing applications. The realization of integrated optical fiber devices requires that several structures and materials at nano- and micro-scale are constructed, embedded and connected all together to provide the necessary physical connections and light-matter interactions. This paper reviews the strategies, the main achievements and related devices in the lab-on-fiber roadmap discussing perspectives and challenges that lie ahead.
