The active development of space industry necessitates the cre-ation of novel materials with unique properties,including shape memory alloys(SMAs).The development of ultra-high temperature SMAs(UHTSMAs)with operating t...The active development of space industry necessitates the cre-ation of novel materials with unique properties,including shape memory alloys(SMAs).The development of ultra-high temperature SMAs(UHTSMAs)with operating temperatures above 400℃is a significant challenge[1-3].It is known that reversible thermoelas-tic martensitic transformation(MT)is the basis for shape mem-ory behavior[4].Currently,there are several systems in which MT temperatures meet the above requirements,for example,RuNb[5],HfPd[6],TiPd[7].展开更多
Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerfu...Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.展开更多
(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co co...(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co content on microstructure and mechanical properties were investigated.The results indicate that the grain size of the alloy decreases with increasing the Co content.In the as-cast state,the alloy consists primarily of the B19′phase,with a trace of B2 phase.The fracture morphology is predominantly composed of the B19′phase,whereas the B2 phase is nearly absent.Increasing the Co content or reducing the sample dimensions(d)markedly enhance the compressive strength and ductility of the alloy.When d=2 mm,the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy demonstrates the optimal mechanical properties,achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%.The compressive cyclic test shows that with increasing the compressive strain,the residual strain of the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy increases while the recovery ability declines.The superelastic recovery capability of the alloy is continuously enhanced.The superelastic recovery rate increases from 1.36%to 2.12%,the residual strain rate rises from 1.79%to 5.52%,the elastic recovery rate ascends from 3.86%to 7.36%,while the total recovery rate declines from 74.48%to 63.20%.展开更多
Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,exc...Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,excellent fatigue resistance,and the ability to undergo significant recoverable deformation,SMAs have found extensive applications in various fields,including biomedical devices,robotics,aerospace,automotive industries,and smart textiles.This paper provides a comprehensive overview of the phase transformation behavior and smart applications of SMAs,focusing on the underlying mechanisms,characteristics,and technological advancements in SMA-based devices.It explores the various phases involved in SMA behavior,including the martensitic and austenitic phases,thermoelastic transformations,and stress-induced phase transformations.Furthermore,this paper discusses the applications of SMAs in smart technologies,including their use in medical devices,actuators,sensors,and energy harvesting systems.By exploring the key factors influencing phase transformations,this study highlights the potential of SMAs in designing next-generation smart materials and systems.展开更多
The superelasticity and elastocaloric effect(eCE)in N-free Ti-Nb-Zr-Ta alloy and 0.6N(at.%)-doped Ti-Nb-Zr-Ta alloy were comparatively studied.It was found that nitrogen doping played roles in elevating β→α transit...The superelasticity and elastocaloric effect(eCE)in N-free Ti-Nb-Zr-Ta alloy and 0.6N(at.%)-doped Ti-Nb-Zr-Ta alloy were comparatively studied.It was found that nitrogen doping played roles in elevating β→α transition temperature,refining grain sizes,homogenizing microstructure and altering dominant texture index.The N-free Ti-Nb-Zr-Ta alloy exhibited a temperature change of +6.7/−6.5 K during load-ing/unloading processes in the first superelastic cycle,but gradually decreased to+5.7/−5.2 K in 200th cycle owing to the accumulation of newly codirectional dislocation lines and the following single-system dislocation slip during cyclic tests.By contrast,the N-doped alloy showed a lower initial temperature change of+3.7/−3.1 K but increased to+4.6/−4.1 K in 200th cycle due to the extra caloric effect generated from nanoscale O′phase to α″phase which experienced reorientation to favorable variants in early cycles.Residual α″phase laths derived from stress-induced martensitic transformation(SIMT)appeared in both alloys after tensile cycles.The phase interface between β and α″phase was determined to behave a terraced shape,a type of interface compromising the reversible martensitic transformation(MT)and stabilization of martensite phase.The amount of nanodomains(O′phase)in regions situated at a distance from martensite significantly increased after cycles in both alloys,which accounted for the quickly reached stable superelastic deformation and much narrower hysteresis after the first cycle.Therefore,in light of the reproducibility and reversibility of elastocaloric performance in practical application,N-doped β-Ti shape memory alloys(SMAs)are promising candidate materials.展开更多
The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory e...The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory effect,which hinder its widespread application.Heat treatment has been identified as a method to enhance the performance of metallic materials in the realm of additive manufacturing.This process eliminates residual stress and enhances performance through precipitation strengthening.This study conducted a comprehensive annealing investigation on NiTi alloys to explore the impact of annealing time and temperature on the phase transformation behavior and shape memory performance.The mechanism underlying the performance enhancement was analyzed using scanning electron microscopy,energy-dispersive X-ray spectroscopy,electron backscatter diffraction,and transmission electron microscopy.The findings revealed that different annealing conditions resulted in multistep phase transformation behavior,with the 500℃-5 h sample exhibiting the best mechanical properties owing to the formation of nanoscale dispersed precipitates like Ni_(4)Ti_(3).However,higher temperatures led to larger precipitates,significantly weakening the properties of the NiTi alloy.Additionally,the annealing treatment did not have a notable impact on the grain size,texture strength,or direction.This study provides valuable insights for optimizing the heat treatment process of LPBF-NiTi alloys.展开更多
This paper introduces an innovative approach to the deployment of folding wings on cruise missiles,aiming to overcome the issues associated with explosive devices.The proposed solution involves employing NiTi shape me...This paper introduces an innovative approach to the deployment of folding wings on cruise missiles,aiming to overcome the issues associated with explosive devices.The proposed solution involves employing NiTi shape memory wires for a nonexplosive self-deploying wing mechanism.The fundamental concept of the design revolves around the utilization of NiTi wires,which contract upon electric heating.This contraction action severs the shear pin,consequently releasing the folded wings.The operational performance of the NiTi wire is thoroughly examined through a series of electro-thermo-mechanical tests,offering valuable insights for selecting the appropriate wire material.Moreover,the mechanical dynamics involved in the self-deploying process are elucidated through finite element simulations.The simulations highlight that the thermally-induced phase transformation within the NiTi wires generates substantial actuation forces,exceeding 700 N,and strokes of over 6 mm.These forces are deemed sufficient for breaking the aluminum shear pin and effecting wing deployment.The proposed mechanism’s practical viability is substantiated through prototype tests,which conclusively establish the superiority of the nonexplosive self-deploying wing mechanism when compared to conventional methods.The experimental outcomes underscore the mechanism’s capability to markedly reduce overload stress while remaining compliant with the designated requirements and constraints.展开更多
Shape Memory Polymers(SMPs)need to be given a temporary shape in advance to realize the shape memory process,but the manual shaping process is cumbersome and has low precision.Here,we propose a universal applicable me...Shape Memory Polymers(SMPs)need to be given a temporary shape in advance to realize the shape memory process,but the manual shaping process is cumbersome and has low precision.Here,we propose a universal applicable method for 4D printing self-folding SMPs by pre-stretching extruded filaments during 3D printing,the temporary shape of the SMPs were designed and fixed during 3D printing.Prepared samples can automatically perform shape memory process under stimulation without manual temporary shape programming process.Furthermore,using carbon ink as a photothermal conversion agent enables the 4D printing SMPs to have thermal and light response characteristics.In addition,some bionic applications of self-folding SMPs were demonstrated,such as self-morphing grasper,DNA double helix structures,programmable sequential switching mimosa,self-folding box and human hand.The combination of SMP and 3D printing fully takes advantage of 4D printing technology,and the self-folding SMPs show great potential applications in the fields of tissue engineering scaffold,self-folding robots,self-assembly system and so on.展开更多
This paper presents the development of a thermoplastic shape memory rubber that can be programmed at human body temperature for comfortable fitting applications.We hybridized commercially available thermoplastic rubbe...This paper presents the development of a thermoplastic shape memory rubber that can be programmed at human body temperature for comfortable fitting applications.We hybridized commercially available thermoplastic rubber(TPR)used in the footwear industry with un-crosslinked polycaprolactone(PCL)to create two samples,namely TP6040 and TP7030.The shape memory behavior,elasticity,and thermo-mechanical response of these rubbers were systematically investigated.The experimental results demonstrated outstanding shape memory performance,with both samples achieving shape fixity ratios(Rf)and shape recovery ratios(R_(r))exceeding 94%.TP6040 exhibited a fitting time of 80 s at body temperature(37℃),indicating a rapid response for shape fixing.The materials also showed good elasticity before and after programming,which is crucial for comfort fitting.These findings suggest that the developed shape memory thermoplastic rubber has potential applications in personalized comfort fitting products,offering advantages over traditional customization techniques in terms of efficiency and cost-effectiveness.展开更多
An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual cry...An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual crystallinity of the EUG matrix synergistically interacted with the dual cross-linking networks to establish reversible deformation domains,providing EUG-SZIM-xs with quick shape memory capability at moderate temperatures.The damping properties were also investigated,and EUG-SZIM-xs displayed high tanδ values (>0.3) when the SZIM dosage was higher than 5.5 phr,which showed a positive correlation with SZIM concentration.Such good damping performance endowed the EUG-SZIM-xs with broadband low-frequency sound absorption.In addition,the dual cross-linking networks endowed the materials with reprocessability under different catalytic systems,and the 1,8-diazobicyclic[5.4.0]undeca-7-ene (DBU)-catalyzed samples exhibited better mechanical properties than EUG-SZIM-xs.展开更多
Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence ...Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.展开更多
Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this ...Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this study,novel poly(ε-caprolactone)(PCL)-poly(2-vinyl)ethylene glycol(PVEG)copolymers bearing multi-pendant vinyl groups is synthesized by branched-selective allylic etherification polymerization of vinylethylene carbonate(VEC)with linear and tetra-arm PCLs under a synergistic catalysis of palladium complex and boron reagent.Facile thiol-ene photo-click reaction of PCL-PVEG copolymers with multifunctional thiols can rapidly access a serious crosslinked SMPs with high shape memory performance.The thermal properties,mechanical properties and response temperature of the obtained SMPs are tunable by the variation of PCL prepolymers,vinyl contents and functionality of thiols.Moreover,high elastic modulus in the rubbery plateau region can be maintained effectively owing to high-density topological networks of the PCL materials.In addition,the utility of the present SMPs is further demonstrated by the post-functionalization via thiol-ene photo-click chemistry.展开更多
A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of sho...A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of short glass fiber-based SMPCs,this work explores the potential for programming below the glass transition temperature(Tg)for epoxy-based SMPCs.To mitigate the inherent brittleness of the SMPC during deformation,a linear polymer is incorporated,and a temperature between room temperature and Tg is chosen as the deformation temperature to study the shape memory properties.The findings demonstrate an enhancement in shape fixity and recovery stress,alongside a reduction in shape recovery,with the incorporation of short glass fibers.In addition to tensile properties,thermal properties such as thermal conductivity,specific heat capacity,and glass transition temperature are investigated for their dependence on fiber content.Microscopic properties,such as fiber-matrix adhesion and the dispersion of glass fibers,are examined through Scanning Electron Microscope imaging.The fiber length distribution and mean fiber lengths are also measured for different fiber fractions.展开更多
Reconfigurable metamaterials significantly expand the application scenarios and operating frequency range of metamaterials,making them promising candidates for use in smart tunable device.Here,we propose and experimen...Reconfigurable metamaterials significantly expand the application scenarios and operating frequency range of metamaterials,making them promising candidates for use in smart tunable device.Here,we propose and experimentally demonstrate that integrating metamaterial design principles with the intrinsic features of natural materials can engineer thermal smart metadevices.Tunable extraordinary optical transmission like(EOT-like)phenomena have been achieved in the microwave regime using shape memory alloy(SMA).The strongly localized fields generated by designed metadevices,combined with the intense interference of incident waves,enhance transmission through subwavelength apertures.Leveraging the temperature-responsive properties of SMA,the morphology of the metadevice can be recontructed,thereby modifying its response to electromagnetic waves.The experiments demonstrated control over the operating frequency and transmission amplitude of EOT-like behavior,achieving a maximum transmission enhancement factor of 126.Furthermore,the metadevices with modular design enable the realization of multiple functions with independent control have been demonstrated.The proposed SMA-based metamaterials offer advantages in terms of miniaturization,easy processing,and high design flexibility.They may have potential applications in microwave devices requiring temperature control,such as sensing and monitoring.展开更多
Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformab...Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformable wings inspired by the wing structures of birds.Shape Memory Alloy(SMA)is applied as a smart material to the deformable wing.Compared with other drive methods,SMA actuators have the advantages of high drive capacity and a simple structure for driving wing deformation.According to the shape memory effect,SMA actuators are classified as single-range and dual-range actuators.The wing structure designed for each SMA drive is unique.By comparing and analyzing the structures of airfoils,airfoils with similar drive forms and deformation structures are put together for review and discussion.The deformable wings are categorized into out-of-face deformation,in-face deformation,airfoil curvature deformation,and combined deformation with multiple degrees of freedom based on the structure and location of the wing that produces the deformation.An overview of the deformed wing is introduced by telling the bionic theory of seagulls.The principles of deformation of the wing,the mechanics of the SMA actuator mechanism,and the aerodynamic characteristics of the deformable wing are presented.The structure and working principle of SMA actuators for each type of deformable wing are explained in detail.Methods and approaches to study the deformability of deformable wings are analyzed and summarized.This work provides comprehensive insights and perspectives for future studies of SMA-driven deformable airfoils.展开更多
The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope ...The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope and image processing technology were employed to achieve a quantitative grain size distribution of NiTi alloys so as to provide experimental data for molecular dynamics modeling at the atomic scale.Considering the size effect of molecular dynamics model on material properties,a reasonable modeling size was provided by taking into account three characteristic dimensions from the perspective of macro,meso,and micro scales according to the Buckinghamπtheorem.Then,the corresponding MD simulation on deformation and fracture behavior was investigated to derive a parameterized traction-separation(T-S)law,and then it was embedded into cohesive elements of finite element software.Thus,the crack propagation behavior in NiTi alloys was reproduced by the finite element method(FEM).The experimental results show that the predicted initiation fracture toughness is in good agreement with experimental data.In addition,it is found that the dynamics initiation fracture toughness increases with decreasing grain size and increasing loading velocity.展开更多
In this work,a new strategy is proposed to improve the pseudoelasticity stability of NiTi SMAs under strains beyond the martensite transformation stress plateau by introducing homogeneous Ni_(4) Ti_(3) pre-cipitates,m...In this work,a new strategy is proposed to improve the pseudoelasticity stability of NiTi SMAs under strains beyond the martensite transformation stress plateau by introducing homogeneous Ni_(4) Ti_(3) pre-cipitates,multiple martensite variants,and high-density austenite twins.Our experimental results show that this new strategy achieves excellent and stable pseudoelasticity with a recoverable ratio up to 85.5%larger than the highest value ever reported of 63.4%after 40 cyclic loading under a fixed strain of 14%due to the introduction of high-density austenite twins.The mechanisms of this promising property are revealed with the aid of subregional(grain boundary and grain interior)EDS,TEM,and in-situ BSE anal-ysis.First,an appropriate forging and aging process introduces homogenous Ni_(4) Ti_(3) precipitates,which reduce the energy dissipation required for one pseudoelastic loop from 4.49 to 2.48 J g^(-1) by changing the phase transformation path and temperature.Second,the high-density austenite twins induced by de-formed martensite twins during cyclic loading enhance the strength of the matrix.The reduced energy dissipation and stronger matrix improve the pseudoelasticity and its stability.We attribute these bene-ficial microstructure features to the specially designed processing routes:forging and subsequent aging.On the one hand,the dislocations induced by forging provide homogeneous nucleation sites,leading to Ni_(4) Ti_(3) homogeneously precipitating during aging;on the other hand,the dense and homogeneously dis-tributed precipitates accelerate the martensite transformation and increase the elastic modulus of the martensite,resulting in the advancement of the second stress plateau from 38%to 12%,in which part of the martensite is reoriented to generate multiple martensite variants,resulting in the formation of de-formation{113}_(B19′)martensite twin.It transforms into(112)[111]_(B2) austenite twin after unloading.These findings pave a feasible avenue for tailoring the functional properties of SMAs.展开更多
4D-printable shape memory polymers(SMPs)hold great promise for fabricating shape morphing biomedical devices,but most existing printed polymers either require harsh activation conditions or lack sufficient mechanical ...4D-printable shape memory polymers(SMPs)hold great promise for fabricating shape morphing biomedical devices,but most existing printed polymers either require harsh activation conditions or lack sufficient mechanical strength for vascular implantation.Here,we report a dual-stimuli-responsive shape memory polymer system enhanced by acrylated Pluronic F127(PF127-DA)micelles,which can be fabricated using digital light processing(DLP)based 3D printing.The PF127-DA based nanoscale micelles,which are formed via self-assembly in the hydrogel ink for 3D printing,act as crosslinkers to improve mechanical strength,fatigue resistance and elastic recovery.After drying the printed hydrogel,the obtained SMPs exhibit excellent shape recovery behaviour under mild physiological conditions—specifically body temperature(37℃)and aqueous swelling—resulting in recovery stress up to about 150?k Pa.This swelling-assisted actuation enables effective radial support,making the printed constructs suitable for vascular use.In vitro cytocompatibility assays with NIH/3T3 fibroblasts confirmed the suitable biocompatibility.Furthermore,the self-expanding behavior of the printed stents was validated in an occluded vessel model under physiological conditions.These results demonstrate the feasibility of 4D printed micelle-enhanced SMP for patient-specific,minimally invasive vascular stents and other soft implantable devices requiring high recovery force under physiological stimulation.展开更多
The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved ...The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.展开更多
Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent ...Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52201207 and 52271169)the Fundamental Research Funds for the Central University(No.3072024LJ1002).
文摘The active development of space industry necessitates the cre-ation of novel materials with unique properties,including shape memory alloys(SMAs).The development of ultra-high temperature SMAs(UHTSMAs)with operating temperatures above 400℃is a significant challenge[1-3].It is known that reversible thermoelas-tic martensitic transformation(MT)is the basis for shape mem-ory behavior[4].Currently,there are several systems in which MT temperatures meet the above requirements,for example,RuNb[5],HfPd[6],TiPd[7].
基金supported by the National Natural Science Foundation of China(12202294)the Sichuan Science and Technology Program(2024NSFSC1346).
文摘Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.
基金National Natural Science Foundation of China(12404230,52061027)Science and Technology Program Project of Gansu Province(22YF7GA155)+1 种基金Lanzhou Youth Science and Technology Talent Innovation Project(2023-QN-91)Zhejiang Provincial Natural Science Foundation of China(LY23E010002)。
文摘(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co content on microstructure and mechanical properties were investigated.The results indicate that the grain size of the alloy decreases with increasing the Co content.In the as-cast state,the alloy consists primarily of the B19′phase,with a trace of B2 phase.The fracture morphology is predominantly composed of the B19′phase,whereas the B2 phase is nearly absent.Increasing the Co content or reducing the sample dimensions(d)markedly enhance the compressive strength and ductility of the alloy.When d=2 mm,the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy demonstrates the optimal mechanical properties,achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%.The compressive cyclic test shows that with increasing the compressive strain,the residual strain of the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy increases while the recovery ability declines.The superelastic recovery capability of the alloy is continuously enhanced.The superelastic recovery rate increases from 1.36%to 2.12%,the residual strain rate rises from 1.79%to 5.52%,the elastic recovery rate ascends from 3.86%to 7.36%,while the total recovery rate declines from 74.48%to 63.20%.
文摘Shape memory alloys(SMAs)are unique materials that exhibit the ability to recover their original shape upon heating after being deformed at low temperatures.Due to their remarkable properties,such as high strength,excellent fatigue resistance,and the ability to undergo significant recoverable deformation,SMAs have found extensive applications in various fields,including biomedical devices,robotics,aerospace,automotive industries,and smart textiles.This paper provides a comprehensive overview of the phase transformation behavior and smart applications of SMAs,focusing on the underlying mechanisms,characteristics,and technological advancements in SMA-based devices.It explores the various phases involved in SMA behavior,including the martensitic and austenitic phases,thermoelastic transformations,and stress-induced phase transformations.Furthermore,this paper discusses the applications of SMAs in smart technologies,including their use in medical devices,actuators,sensors,and energy harvesting systems.By exploring the key factors influencing phase transformations,this study highlights the potential of SMAs in designing next-generation smart materials and systems.
基金financially supported by the National Key R&D Program of China(No.2022YFB3805701)the National Natural Sci-ence Foundation of China(NSFC)(No.52371182)the Provincial Natural Science Foundation of China(Grant Number YQ2024E014).
文摘The superelasticity and elastocaloric effect(eCE)in N-free Ti-Nb-Zr-Ta alloy and 0.6N(at.%)-doped Ti-Nb-Zr-Ta alloy were comparatively studied.It was found that nitrogen doping played roles in elevating β→α transition temperature,refining grain sizes,homogenizing microstructure and altering dominant texture index.The N-free Ti-Nb-Zr-Ta alloy exhibited a temperature change of +6.7/−6.5 K during load-ing/unloading processes in the first superelastic cycle,but gradually decreased to+5.7/−5.2 K in 200th cycle owing to the accumulation of newly codirectional dislocation lines and the following single-system dislocation slip during cyclic tests.By contrast,the N-doped alloy showed a lower initial temperature change of+3.7/−3.1 K but increased to+4.6/−4.1 K in 200th cycle due to the extra caloric effect generated from nanoscale O′phase to α″phase which experienced reorientation to favorable variants in early cycles.Residual α″phase laths derived from stress-induced martensitic transformation(SIMT)appeared in both alloys after tensile cycles.The phase interface between β and α″phase was determined to behave a terraced shape,a type of interface compromising the reversible martensitic transformation(MT)and stabilization of martensite phase.The amount of nanodomains(O′phase)in regions situated at a distance from martensite significantly increased after cycles in both alloys,which accounted for the quickly reached stable superelastic deformation and much narrower hysteresis after the first cycle.Therefore,in light of the reproducibility and reversibility of elastocaloric performance in practical application,N-doped β-Ti shape memory alloys(SMAs)are promising candidate materials.
基金supported by National Key R&D Program of China(Grant No.2022YFB4601701)74th Batch of General Funding from the China Postdoctoral Science Foundation(Grant No.2023M741341)+7 种基金5th Batch of Special Grants from the China Postdoctoral Science Foundation(before the station,Grant No.2023TQ0129)Postdoctoral Fellowship Program of CPSF(Grant No.GZB20230257)National Natural Science Foundation of China(Grant Nos.52375289,52205310)Natural Science Foundation of Shandong Province(Grant No.ZR2021QE263)Science and Technology Development Program of Jilin Province(Grant No.20230508045RC)Capital Construction Fund plan within the budget of Jilin Province(Grant No.2023C041-4)Chongqing Natural Science Foundation(Grant No.CSTB2022NSCQ-MSX0225)the Shandong Postdoctoral Science Foundation(Grant No.SDCX-ZG-202400238).
文摘The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory effect,which hinder its widespread application.Heat treatment has been identified as a method to enhance the performance of metallic materials in the realm of additive manufacturing.This process eliminates residual stress and enhances performance through precipitation strengthening.This study conducted a comprehensive annealing investigation on NiTi alloys to explore the impact of annealing time and temperature on the phase transformation behavior and shape memory performance.The mechanism underlying the performance enhancement was analyzed using scanning electron microscopy,energy-dispersive X-ray spectroscopy,electron backscatter diffraction,and transmission electron microscopy.The findings revealed that different annealing conditions resulted in multistep phase transformation behavior,with the 500℃-5 h sample exhibiting the best mechanical properties owing to the formation of nanoscale dispersed precipitates like Ni_(4)Ti_(3).However,higher temperatures led to larger precipitates,significantly weakening the properties of the NiTi alloy.Additionally,the annealing treatment did not have a notable impact on the grain size,texture strength,or direction.This study provides valuable insights for optimizing the heat treatment process of LPBF-NiTi alloys.
基金Supported by National Natural Science Foundation of China(Grant No.12372156).
文摘This paper introduces an innovative approach to the deployment of folding wings on cruise missiles,aiming to overcome the issues associated with explosive devices.The proposed solution involves employing NiTi shape memory wires for a nonexplosive self-deploying wing mechanism.The fundamental concept of the design revolves around the utilization of NiTi wires,which contract upon electric heating.This contraction action severs the shear pin,consequently releasing the folded wings.The operational performance of the NiTi wire is thoroughly examined through a series of electro-thermo-mechanical tests,offering valuable insights for selecting the appropriate wire material.Moreover,the mechanical dynamics involved in the self-deploying process are elucidated through finite element simulations.The simulations highlight that the thermally-induced phase transformation within the NiTi wires generates substantial actuation forces,exceeding 700 N,and strokes of over 6 mm.These forces are deemed sufficient for breaking the aluminum shear pin and effecting wing deployment.The proposed mechanism’s practical viability is substantiated through prototype tests,which conclusively establish the superiority of the nonexplosive self-deploying wing mechanism when compared to conventional methods.The experimental outcomes underscore the mechanism’s capability to markedly reduce overload stress while remaining compliant with the designated requirements and constraints.
基金supported by the National Natural Science Foundation of China(52175271,52021003,52375287)Science and Technology Development Plan Project of Jilin Province(20210509047RQ,20230508041RC).
文摘Shape Memory Polymers(SMPs)need to be given a temporary shape in advance to realize the shape memory process,but the manual shaping process is cumbersome and has low precision.Here,we propose a universal applicable method for 4D printing self-folding SMPs by pre-stretching extruded filaments during 3D printing,the temporary shape of the SMPs were designed and fixed during 3D printing.Prepared samples can automatically perform shape memory process under stimulation without manual temporary shape programming process.Furthermore,using carbon ink as a photothermal conversion agent enables the 4D printing SMPs to have thermal and light response characteristics.In addition,some bionic applications of self-folding SMPs were demonstrated,such as self-morphing grasper,DNA double helix structures,programmable sequential switching mimosa,self-folding box and human hand.The combination of SMP and 3D printing fully takes advantage of 4D printing technology,and the self-folding SMPs show great potential applications in the fields of tissue engineering scaffold,self-folding robots,self-assembly system and so on.
基金supported by the Aeronautical Science Foundation of China(Grant Nos.2024Z009052003,20230038052001 and 20230015052002)the Third Batch of Science and Technology Plan Projects in Changzhou City in 2023(Applied Basic Research,Grant No.CJ20230080).
文摘This paper presents the development of a thermoplastic shape memory rubber that can be programmed at human body temperature for comfortable fitting applications.We hybridized commercially available thermoplastic rubber(TPR)used in the footwear industry with un-crosslinked polycaprolactone(PCL)to create two samples,namely TP6040 and TP7030.The shape memory behavior,elasticity,and thermo-mechanical response of these rubbers were systematically investigated.The experimental results demonstrated outstanding shape memory performance,with both samples achieving shape fixity ratios(Rf)and shape recovery ratios(R_(r))exceeding 94%.TP6040 exhibited a fitting time of 80 s at body temperature(37℃),indicating a rapid response for shape fixing.The materials also showed good elasticity before and after programming,which is crucial for comfort fitting.These findings suggest that the developed shape memory thermoplastic rubber has potential applications in personalized comfort fitting products,offering advantages over traditional customization techniques in terms of efficiency and cost-effectiveness.
基金supported by the Natural Science Foundation of Hunan Province(No.2024JJ7392)the National Natural Science Foundation of China(No.52463002)+1 种基金Educational Commission of Hunan Province(No.22A0383)Special Funds for Construction of Innovative Provinces in Hunan Province(No.2020SK2028).
文摘An inverse vulcanized polymer,SZIM combining Zn2+-imidazole coordination bonds and polysulfide bonds was synthesized and incorporated into bio-based Eucommia ulmoides gum (EUG) to generate EUG-SZIM-xs.The residual crystallinity of the EUG matrix synergistically interacted with the dual cross-linking networks to establish reversible deformation domains,providing EUG-SZIM-xs with quick shape memory capability at moderate temperatures.The damping properties were also investigated,and EUG-SZIM-xs displayed high tanδ values (>0.3) when the SZIM dosage was higher than 5.5 phr,which showed a positive correlation with SZIM concentration.Such good damping performance endowed the EUG-SZIM-xs with broadband low-frequency sound absorption.In addition,the dual cross-linking networks endowed the materials with reprocessability under different catalytic systems,and the 1,8-diazobicyclic[5.4.0]undeca-7-ene (DBU)-catalyzed samples exhibited better mechanical properties than EUG-SZIM-xs.
基金support from the National Key Research and Development Program of China(Grant No.2021YFB3501402)the National Natural Science Foundation of China(Grant Nos.52250313 and 52121001)Yang Liu and Chen Si acknowledge financial support from the National Natural Science Foundation of China(Grant No.12274013).
文摘Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.
基金financially supported by the National Natural Science Foundation of China(No.22171182)Sichuan Tianfu Emei Plan.
文摘Control crosslink network and chain connectivity are essential to develop shape memory polymers(SMPs)with high shape memory capabilities,adjustable response temperature,and satisfying mechanistical properties.In this study,novel poly(ε-caprolactone)(PCL)-poly(2-vinyl)ethylene glycol(PVEG)copolymers bearing multi-pendant vinyl groups is synthesized by branched-selective allylic etherification polymerization of vinylethylene carbonate(VEC)with linear and tetra-arm PCLs under a synergistic catalysis of palladium complex and boron reagent.Facile thiol-ene photo-click reaction of PCL-PVEG copolymers with multifunctional thiols can rapidly access a serious crosslinked SMPs with high shape memory performance.The thermal properties,mechanical properties and response temperature of the obtained SMPs are tunable by the variation of PCL prepolymers,vinyl contents and functionality of thiols.Moreover,high elastic modulus in the rubbery plateau region can be maintained effectively owing to high-density topological networks of the PCL materials.In addition,the utility of the present SMPs is further demonstrated by the post-functionalization via thiol-ene photo-click chemistry.
文摘A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of short glass fiber-based SMPCs,this work explores the potential for programming below the glass transition temperature(Tg)for epoxy-based SMPCs.To mitigate the inherent brittleness of the SMPC during deformation,a linear polymer is incorporated,and a temperature between room temperature and Tg is chosen as the deformation temperature to study the shape memory properties.The findings demonstrate an enhancement in shape fixity and recovery stress,alongside a reduction in shape recovery,with the incorporation of short glass fibers.In addition to tensile properties,thermal properties such as thermal conductivity,specific heat capacity,and glass transition temperature are investigated for their dependence on fiber content.Microscopic properties,such as fiber-matrix adhesion and the dispersion of glass fibers,are examined through Scanning Electron Microscope imaging.The fiber length distribution and mean fiber lengths are also measured for different fiber fractions.
基金the financial support from the National Key R&D Program of China (Nos. 2023YFB3811400, 2022YFB3806000)the National Natural Science Foundation of China (Nos. 12074314, 52202370, 52332006)+3 种基金the Aeronautical Science Foundation of China (No. 20230018053007)the Science and Technology New Star Program of Shaanxi Province (No. 2023KJXX-148)the Fundamental Research Funds for the Central UniversitiesChina Postdoctoral Science Foundation (No. 2023T160359)
文摘Reconfigurable metamaterials significantly expand the application scenarios and operating frequency range of metamaterials,making them promising candidates for use in smart tunable device.Here,we propose and experimentally demonstrate that integrating metamaterial design principles with the intrinsic features of natural materials can engineer thermal smart metadevices.Tunable extraordinary optical transmission like(EOT-like)phenomena have been achieved in the microwave regime using shape memory alloy(SMA).The strongly localized fields generated by designed metadevices,combined with the intense interference of incident waves,enhance transmission through subwavelength apertures.Leveraging the temperature-responsive properties of SMA,the morphology of the metadevice can be recontructed,thereby modifying its response to electromagnetic waves.The experiments demonstrated control over the operating frequency and transmission amplitude of EOT-like behavior,achieving a maximum transmission enhancement factor of 126.Furthermore,the metadevices with modular design enable the realization of multiple functions with independent control have been demonstrated.The proposed SMA-based metamaterials offer advantages in terms of miniaturization,easy processing,and high design flexibility.They may have potential applications in microwave devices requiring temperature control,such as sensing and monitoring.
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025053)National Natural Science Foundation of China(No.52305302)+1 种基金the Natural Science Foundation of Jilin Province(No.20220101216JC)the asterisk indicates the corresponding authors.
文摘Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformable wings inspired by the wing structures of birds.Shape Memory Alloy(SMA)is applied as a smart material to the deformable wing.Compared with other drive methods,SMA actuators have the advantages of high drive capacity and a simple structure for driving wing deformation.According to the shape memory effect,SMA actuators are classified as single-range and dual-range actuators.The wing structure designed for each SMA drive is unique.By comparing and analyzing the structures of airfoils,airfoils with similar drive forms and deformation structures are put together for review and discussion.The deformable wings are categorized into out-of-face deformation,in-face deformation,airfoil curvature deformation,and combined deformation with multiple degrees of freedom based on the structure and location of the wing that produces the deformation.An overview of the deformed wing is introduced by telling the bionic theory of seagulls.The principles of deformation of the wing,the mechanics of the SMA actuator mechanism,and the aerodynamic characteristics of the deformable wing are presented.The structure and working principle of SMA actuators for each type of deformable wing are explained in detail.Methods and approaches to study the deformability of deformable wings are analyzed and summarized.This work provides comprehensive insights and perspectives for future studies of SMA-driven deformable airfoils.
基金Funded by the National Natural Science Foundation of China Academy of Engineering Physics and Jointly Setup"NSAF"Joint Fund(No.U1430119)。
文摘The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope and image processing technology were employed to achieve a quantitative grain size distribution of NiTi alloys so as to provide experimental data for molecular dynamics modeling at the atomic scale.Considering the size effect of molecular dynamics model on material properties,a reasonable modeling size was provided by taking into account three characteristic dimensions from the perspective of macro,meso,and micro scales according to the Buckinghamπtheorem.Then,the corresponding MD simulation on deformation and fracture behavior was investigated to derive a parameterized traction-separation(T-S)law,and then it was embedded into cohesive elements of finite element software.Thus,the crack propagation behavior in NiTi alloys was reproduced by the finite element method(FEM).The experimental results show that the predicted initiation fracture toughness is in good agreement with experimental data.In addition,it is found that the dynamics initiation fracture toughness increases with decreasing grain size and increasing loading velocity.
基金support from the National Natural Science Foundation of China(No.52475406)the National Key R&D Program of China(No.2022YFB3707201)+1 种基金the Key R&D Program of Shaanxi Province(No.2024CY2-GJHX-32)Ye Qisun Science Foundation of National Natural Science Foundation of China(No.U2341254)。
文摘In this work,a new strategy is proposed to improve the pseudoelasticity stability of NiTi SMAs under strains beyond the martensite transformation stress plateau by introducing homogeneous Ni_(4) Ti_(3) pre-cipitates,multiple martensite variants,and high-density austenite twins.Our experimental results show that this new strategy achieves excellent and stable pseudoelasticity with a recoverable ratio up to 85.5%larger than the highest value ever reported of 63.4%after 40 cyclic loading under a fixed strain of 14%due to the introduction of high-density austenite twins.The mechanisms of this promising property are revealed with the aid of subregional(grain boundary and grain interior)EDS,TEM,and in-situ BSE anal-ysis.First,an appropriate forging and aging process introduces homogenous Ni_(4) Ti_(3) precipitates,which reduce the energy dissipation required for one pseudoelastic loop from 4.49 to 2.48 J g^(-1) by changing the phase transformation path and temperature.Second,the high-density austenite twins induced by de-formed martensite twins during cyclic loading enhance the strength of the matrix.The reduced energy dissipation and stronger matrix improve the pseudoelasticity and its stability.We attribute these bene-ficial microstructure features to the specially designed processing routes:forging and subsequent aging.On the one hand,the dislocations induced by forging provide homogeneous nucleation sites,leading to Ni_(4) Ti_(3) homogeneously precipitating during aging;on the other hand,the dense and homogeneously dis-tributed precipitates accelerate the martensite transformation and increase the elastic modulus of the martensite,resulting in the advancement of the second stress plateau from 38%to 12%,in which part of the martensite is reoriented to generate multiple martensite variants,resulting in the formation of de-formation{113}_(B19′)martensite twin.It transforms into(112)[111]_(B2) austenite twin after unloading.These findings pave a feasible avenue for tailoring the functional properties of SMAs.
基金Natural Science Basic Research Program of Shaanxi(No.2025JC-YBMS-358)the Fundamental Research Funds for the Central Universities(No.D5000250307)。
文摘4D-printable shape memory polymers(SMPs)hold great promise for fabricating shape morphing biomedical devices,but most existing printed polymers either require harsh activation conditions or lack sufficient mechanical strength for vascular implantation.Here,we report a dual-stimuli-responsive shape memory polymer system enhanced by acrylated Pluronic F127(PF127-DA)micelles,which can be fabricated using digital light processing(DLP)based 3D printing.The PF127-DA based nanoscale micelles,which are formed via self-assembly in the hydrogel ink for 3D printing,act as crosslinkers to improve mechanical strength,fatigue resistance and elastic recovery.After drying the printed hydrogel,the obtained SMPs exhibit excellent shape recovery behaviour under mild physiological conditions—specifically body temperature(37℃)and aqueous swelling—resulting in recovery stress up to about 150?k Pa.This swelling-assisted actuation enables effective radial support,making the printed constructs suitable for vascular use.In vitro cytocompatibility assays with NIH/3T3 fibroblasts confirmed the suitable biocompatibility.Furthermore,the self-expanding behavior of the printed stents was validated in an occluded vessel model under physiological conditions.These results demonstrate the feasibility of 4D printed micelle-enhanced SMP for patient-specific,minimally invasive vascular stents and other soft implantable devices requiring high recovery force under physiological stimulation.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoalde Nível Superior-Brasil(CAPES)-Finance Code 001.
文摘The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.
基金supported by the National Natural Science Foundation of China(No.52305262)the Aeronautical Science Foundation of China(No.20230015052002)the Fundamental Research Funds for the Central Universities(No.NT2024001)。
文摘Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.
