“Life”represents a distinctive attribute inherent to organisms in nature,evident in their capacity to actively adapt to changes in their environment.In contrast to the static and intricate constructs of additive man...“Life”represents a distinctive attribute inherent to organisms in nature,evident in their capacity to actively adapt to changes in their environment.In contrast to the static and intricate constructs of additive manufacturing(AM),the dynamic structure of 4D printing(4DP)adeptly integrates AM technology,responsive mechanisms,and external stimuli,imbuing it with a semblance of“life.”This fusion significantly broadens its functional applica-tions across biomedicine,actuators,and metamaterials.The escalating demand across diverse fields necessitates heightened criteria for 4DP,encompassing rapid response,multi-stimulus response,large shape change,and specific mechanical properties(e.g.,high strength,high modulus)capable of accommodating varying environ-mental conditions.In recent years,shape memory polymers(SMPs)have garnered increasing attention among 4DP researchers due to their ease of design and preprogramming at the molecular level,facilitating controlled transformations along predictable pathways.However,4DP of high-strength SMPs,as an indispensable part of the high-performance field,is full of challenges because the intrinsic properties of the raw materials are not well compatible with the printing principle and the printed configuration is not flexible enough.Consequently,this paper provides a concise overview of the response mechanisms and applications of five prominent high-strength SMPs utilized in 4DP:epoxy resin,poly(ether-ether-ketone),polyimide,polylactic acid,and polyurethane.Ad-ditionally,it delves into the associated challenges and prospects,offering researchers valuable insights into the potential value of high-strength SMPs within the domain of 4DP.展开更多
Shape memory polymers （SMPs） as one type of the most important smart materials have attracted increasing attention due to their promising application in the field of biomedicine, textiles, aerospace et al. Following...Shape memory polymers （SMPs） as one type of the most important smart materials have attracted increasing attention due to their promising application in the field of biomedicine, textiles, aerospace et al. Following a brief intoduction of the conception and classification of SMPs, this review is focused on the progress of shape memory polymers for biomedical applications. The progress includes the early researches based on thermo-induced SMPs, the improvement of the stimulus, the development of shape recovery ways and the expansion of the applications in biomedical field. In addition, future perspectives of SMPs in the field of biomedicine are also discussed.展开更多
This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SMPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables...This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SMPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables and rational thermodynamics.This method is developed for the finite bending of multilayers in a dual-shape memory effect(SME) cycle.The layer number and layering order are investigated for two different SMPs and a hyperelastic material.In addition to the semi-analytical solution,the finite element simulation is performed to verify the predicted results,where the outcomes demonstrate the excellent accuracy of the proposed solution for predicting the behavior of the multilayer SMPs.Since this method has a much lower computational cost than the finite element method(FEM),it can be used as an effective tool to analyze the SMP behavior under different conditions,including different materials,different geometries,different layer numbers,and different layer arrangements.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
Thermo-induced Shape Memory Polymers(TSMPs)and their corresponding 4D printing technology are at the forefront of current research.In this work,we review the progress from TSMPs to 4D printing and their corresponding ...Thermo-induced Shape Memory Polymers(TSMPs)and their corresponding 4D printing technology are at the forefront of current research.In this work,we review the progress from TSMPs to 4D printing and their corresponding applications.Firstly,taking thermally activated TSMPs as an example,the shape memory behavior is explained,and various shape memory experiments and mechanisms,as well as constitutive models,are discussed.This comprehensive information is designed to provide a solid understanding of TSMPs.Moreover,the history of 4D printing and various technologies used in 4D printing are introduced,and potential printing methods are summarized.These insights can guide researchers in selecting appropriate techniques for practical applications.The applications of 4D printed TSMPs are then outlined,with a focus on metamaterials and various industry cases that provide a clear understanding of what 4D printing can achieve.This knowledge will open new doors for innovative applications.Finally,the current research status is summarized,and the existing research gaps and future development directions are pointed out.Through this review,we aim to offer a comprehensive understanding of the journey from TSMPs to 4D printing and their applications so as to support further research and the promotion of 4D printing of TSMPs in the field of smart materials.展开更多
Smart dry adhesives,a rapidly growing class of intelligent materials and structures,are engineered to provide strong,robust adhesion when needed while also allowing for controlled,easy detachment in response to specif...Smart dry adhesives,a rapidly growing class of intelligent materials and structures,are engineered to provide strong,robust adhesion when needed while also allowing for controlled,easy detachment in response to specific stimuli.Traditional smart adhesives,often exemplified by fibrillar structures made of elastomers,face a number of challenges.These include limitations on maximum adhesion strength imposed by microstructural dimensions,restricted adaptability to surfaces with varying degrees of roughness,and an inherent trade-off between adhesion strength and switchability.This review explores how shape memory polymers(SMPs)can address these challenges and,through their rubber-to-glass(R2G)transition capability,provide a powerful foundation for the next generation of smart dry adhesives.Specifically,we summarize and elucidate the mechanisms by which SMPs enhance adhesion strength and switchability through material characteristics such as tunable stiffness,shape-locking,and shape-memory effects.Additionally,we discuss a wide range of innovative designs and applications of SMP adhesives,offering insights into the ongoing challenges and emerging opportunities in this rapidly evolving field.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
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
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
Controlled and switchable adhesion is commonly observed in biological systems.In recent years,many scholars have focused on making switchable bio-inspired adhesives.However,making a bio-inspired adhesive with high adh...Controlled and switchable adhesion is commonly observed in biological systems.In recent years,many scholars have focused on making switchable bio-inspired adhesives.However,making a bio-inspired adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge.A Shape Memory Polymer Bio-inspired Adhesive(SMPBA)was successfully developed,well realizing high adhesion(about 337 kPa),relatively low preload(about90 kPa),high adhesion-to-preload ratio(about 3.74),high switching ratio(about 6.74),and easy detachment,which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect(SME).Furthermore,SMPBA exhibits adhesion strength of80–337 kPa on various surfaces(silicon,iron,and aluminum)with different roughness(Ra=0.021–10.280)because of the conformal contact,reflecting outstanding surface adaptability.The finite element analysis verifies the bending ability under different temperatures,while the adhesion model analyzes the influence of preload on contact area and adhesion.Furthermore,an Unmanned Aerial Vehicle(UAV)landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces.This study provides a novel switchable bio-inspired adhesive and UAV landing method.展开更多
Although various shape memory polymers(SMPs)or diverse applications have been widely reported,the SMPs based on rubbers have been rarely realized due to the low triggering temperature of rubbers.In another aspect,the ...Although various shape memory polymers(SMPs)or diverse applications have been widely reported,the SMPs based on rubbers have been rarely realized due to the low triggering temperature of rubbers.In another aspect,the SMPs based on sustainable substances are highly desired for the growing shortage in fossil resources.In the present study,we accordingly developed the sustainable SMPs with tunable triggering temperature,based on natural rubber(NR)and ferulic acid(FA)as the raw materials.Specifically,the SMPs are based on a crosslinked network of epoxidized natural rubber(ENR)crosslinked by in situ formed zinc ferulate(ZDF)via oxa-Michael reaction.The excellent shape memory effect(SME)is found in these SMPs,as evidenced by the high fixity/recovery ratio and the tunable triggering temperature.With the incorpora-tion of natural halloysite nanotubes(HNTs),the stress and recovery rate of the SMPs are found to be tunable,which widens the application of this kind of SMPs.The combination of adoption of sustainable raw materials,and the excellent and tunable SME makes these SMPs potentially useful in many applications,such as various actuators and heat-shrinkable package materials.展开更多
This paper proposes a new thermoviscoelastic finite deformation model incorporating dual relaxation mechanisms to predict the complete thermo-mechanical response of amorphous shape memory polymers.The model is underpi...This paper proposes a new thermoviscoelastic finite deformation model incorporating dual relaxation mechanisms to predict the complete thermo-mechanical response of amorphous shape memory polymers.The model is underpinned by the detailed microscopic molecular mechanism and effectively reflects the current understanding of the glass transition phenomenon.Novel evolution rules are obtained from the model to characterize the viscous flow,and a new theory named an internal stress model is introduced and combined with the dual relaxation mechanisms to capture the stress recovery.The rationality of the constitutive model is verified as the theoretical results agree well with the experimental data.Moreover,the constitutive model is further simplified to facilitate engineering applications,and it can roughly capture the characteristics of shape memory polymers.展开更多
Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering.However,most of the reported platforms designed for the manipulation of water droplets cannot thoroughly sol...Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering.However,most of the reported platforms designed for the manipulation of water droplets cannot thoroughly solve the problem of droplet evaporation.Herein,we report a shape-reconfigurable micropillar array chip for the manipulation of water droplets,oil droplets and water-in-oil droplets.Water-in-oil droplets provide an enclosed space for water droplets,preventing the evaporation in an open environment.Perfluoropolyether coated on the surface of the chip effectively reduces the droplet movement resistance.The micropillar array chip has light and magnetic dual-response due to the Fe3O4 nanoparticles and the reduced iron powder mixed in the shape-memory polymer.The micropillars irradiated by a near-infrared laser bend under the magnetic force,while the unirradiated micropillars still keep their original shape.In the absence of a magnetic field,when the micropillars in a temporary shape are irradiated by the near-infrared laser to the transition temperature,the micropillars return to their initial shape.In this process,the surface morphology gradient caused by the deformation of the micropillars and the surface tension gradient caused by the temperature change jointly produce the driving force of droplet movement.展开更多
Shape memory polymers （SMPs） are smart materials that can change their shape in a pre-defined manner under a stimulus. The shape memory functionality has gained considerable interest for biomedical applications, whi...Shape memory polymers （SMPs） are smart materials that can change their shape in a pre-defined manner under a stimulus. The shape memory functionality has gained considerable interest for biomedical applications, which require materials that are biocompatible and sometimes biodegradable. There is a need for SMPs that are prepared from renewable sources to be used as substitutes for conventional SMPs. In this paper, advances in SMPs based on synthetic monomers and bio-compounds are discussed. Materials designed for biomedical applica- tions are highlighted.展开更多
Multi-wall carbon nanotube filled shape memory polymer composite(MWCNT/SMC)possessed enhanced modulus,strength,and electric conductivity,as well as excellent electrothermal shape memory properties,showing wide design ...Multi-wall carbon nanotube filled shape memory polymer composite(MWCNT/SMC)possessed enhanced modulus,strength,and electric conductivity,as well as excellent electrothermal shape memory properties,showing wide design scenarios and engineering application prospects.The thermoelectrically triggered shape memory process contains complex multi-physical mechanisms,especially when coupled with finite deformation rooted on micro-mechanisms.A multi-physical finite deformation model is necessary to get a deep understanding on the coupled electro-thermomechanical properties of electrothermal shape memory composites(ESMCs),beneficial to its design and wide application.Taking into consideration of micro-physical mechanisms of the MWCNTs interacting with double-chain networks,a finite deformation theoretical model is developed in this work based on two superimposed network chains of physically crosslinked network formed among MWCNTs and the chemically crosslinked network.An intact crosslinked chemical network is considered featuring with entropic-hyperelastic properties,superimposed with a physically crosslinked network where percolation theory is based on electric conductivity and electric-heating mechanisms.The model is calibrated by experiments and used for shape recoveries triggered by heating and electric fields.It captures the coupled electro-thermomechanical behavior of ESMCs and provides design guidelines for MWCNTs filled shape memory polymers.展开更多
Following deformation, thermally induced shape memory polymers(SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behavi...Following deformation, thermally induced shape memory polymers(SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behaviors of three types of epoxy SMPs with varying curing agent contents were investigated using a molecular dynamics(MD) method. The mechanical properties under uniaxial tension at different temperatures were obtained, and the simulation results compared reasonably with experimental data. In addition, in a thermomechanical cycle, ideal shape memory effects for the three types of SMPs were revealed through the shape frozen and shape recovery responses at low and high temperatures, respectively, indicating that the recovery time is strongly influenced by the ratio of E-51 to 4,4'-Methylenedianiline.展开更多
The nano-carbon powders are often used as fillers to endow the shape memory polymers(SMPs)with electroconductivity.It has been found that the shape memory effects(SMEs)of SMPs filled with nano-carbon powder can be tri...The nano-carbon powders are often used as fillers to endow the shape memory polymers(SMPs)with electroconductivity.It has been found that the shape memory effects(SMEs)of SMPs filled with nano-carbon powder can be triggered both by temperature and by water.To reveal the driving mechanism of SMEs,a constitutive model for describing the thermally activated and moisture activated SMEs of these shape memory polymer composite(SMPCs)is developed here.Because both of the SMEs share the same driving mechanism,the variable moisture is incorporated into the framework of a thermo-mechanical modeling approach to disclose the effect of moisture on the thermoviscoelastic properties.The SMPCs are regarded as isotropic materials and the effect of carbon powder on the mechanical properties of the matrix is also considered in the paper.Because the complete recovery may not be reached even they are exposed to the stimulus environment long enough,the blocking mechanism is also considered here.This is the mainly new contribution compared to the early work.Using the method of parameter determination presented here,the effectiveness of the proposed hygro-thermo-mechanical constitutive model is confirmed by comparing the model results with the test data of uniaxial deformation from the literature.展开更多
The mismatch in thermal expansion coefficients between the fiber-rich and resin-rich regions of a shape memory polymer composite(SMPC)laminate,along with the residual strain during SMPC fabrication,results in buckling...The mismatch in thermal expansion coefficients between the fiber-rich and resin-rich regions of a shape memory polymer composite(SMPC)laminate,along with the residual strain during SMPC fabrication,results in buckling deformation of the inhomogeneous laminate.This paper presents a macroscopic model for buckling of an inhomogeneous SMPC laminate under initial biaxial prestrains.Both linear and nonlinear buckling analyses are carried out using the energy method.The influences of prestrain biaxiality,temperature,and ply angle on the buckling wavelength,critical buckling prestrain,and buckling amplitude are calculated.The results demonstrate that the critical buckling wavelength of the SMPC laminate is independent of the prestrain,while the amplitude is almost independent of temperature.In addition,the optimal fiber stacking configuration with the maximum critical buckling prestrains of inhomogeneous SMPC laminates is determined by a genetic algorithm.展开更多
Metamaterials,owing to their exceptional physical characteristics that are absent in natural materials,have emerged as a crucial constituent of intelligent devices and systems.However,there are still significant chall...Metamaterials,owing to their exceptional physical characteristics that are absent in natural materials,have emerged as a crucial constituent of intelligent devices and systems.However,there are still significant challenges that necessitate immediate attention,as they have considerably constrained the applicability of metamaterials,including fixed mechanical properties post-fabrication and restricted design freedom.Here,thermo-responsive,photo-responsive,electro-responsive,and magneto-responsive shape memory polymer nano-composites were developed,and shape memory gradient metamaterials were fabricated using multi-material 4D printing technology.The correlation mechanism between the design parameters and the mechanical properties of multi-responsive gradient metamaterials was systematically analyzed,and the highly designable and programmable configuration and mechanical properties of the gradient metamaterials were realized.More importantly,4D printed multi-responsive shape memory polymer gradient metamaterials can be programmed in situ without additional infrastructure for multi-functional mechanical functions,paving the way for the realization of multiple functions of a single structure.Based on the multi-responsive gradient metamaterials,4D printed digital pixel metamaterial intelligent information carriers were fabricated,featuring customizable encryption and decryption protocols,exceptional scalability,and reusability.Additionally,4D printed gradient metamaterial logic gate electronic devices were developed,which were anticipated to contribute to the development of smart,adaptable robotic systems that combine sensing,actuation,and decision-making capabilities.展开更多
Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two l...Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two layers are SMPs with different thermal transition temperatures.By designing specific thermomechanical processes,the mismatched deformation between the two layers leads to a morphology change of ring-shaped bilayer structures from a smooth ring to a gear-like buckling shape under cooling and a reversible recovery to the smooth shape under heating.Such a morphology change is ascribed to occurrence and recovery of thermoelastic buckling.This method was validated by finite element simulation.We experimentally investigated the influence of pre-strain on buckling,and it was found that both the buckling occurrence and recovery temperature vary with pre-strain.Furthermore,considering a ring-shaped SMP-SMP bilayer structure,finite element analysis was conducted to study the influence of film thickness and modulus ratio of two layers on buckling behavior.The results showed that the critical buckling wavelength was greatly influenced by film thickness and modulus ratio.W e made a theoretical analysis that accorded well with the numerical results.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.51935012,52005481)LICP Cooperation Foundation for Young Scholars(Grant No.HZJJ22-11)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0470303)Major Program of the Lanzhou Institute of Chemical Physics,CAS(Grant No.ZYFZFX-7).
文摘“Life”represents a distinctive attribute inherent to organisms in nature,evident in their capacity to actively adapt to changes in their environment.In contrast to the static and intricate constructs of additive manufacturing(AM),the dynamic structure of 4D printing(4DP)adeptly integrates AM technology,responsive mechanisms,and external stimuli,imbuing it with a semblance of“life.”This fusion significantly broadens its functional applica-tions across biomedicine,actuators,and metamaterials.The escalating demand across diverse fields necessitates heightened criteria for 4DP,encompassing rapid response,multi-stimulus response,large shape change,and specific mechanical properties(e.g.,high strength,high modulus)capable of accommodating varying environ-mental conditions.In recent years,shape memory polymers(SMPs)have garnered increasing attention among 4DP researchers due to their ease of design and preprogramming at the molecular level,facilitating controlled transformations along predictable pathways.However,4DP of high-strength SMPs,as an indispensable part of the high-performance field,is full of challenges because the intrinsic properties of the raw materials are not well compatible with the printing principle and the printed configuration is not flexible enough.Consequently,this paper provides a concise overview of the response mechanisms and applications of five prominent high-strength SMPs utilized in 4DP:epoxy resin,poly(ether-ether-ketone),polyimide,polylactic acid,and polyurethane.Ad-ditionally,it delves into the associated challenges and prospects,offering researchers valuable insights into the potential value of high-strength SMPs within the domain of 4DP.
基金partially supported by the National Natural Science Foundation of China (Nos.21574105 and 51725303)the Sichuan Province Youth Science and Technology Innovation Team (No.2016TD0026)
文摘Shape memory polymers （SMPs） as one type of the most important smart materials have attracted increasing attention due to their promising application in the field of biomedicine, textiles, aerospace et al. Following a brief intoduction of the conception and classification of SMPs, this review is focused on the progress of shape memory polymers for biomedical applications. The progress includes the early researches based on thermo-induced SMPs, the improvement of the stimulus, the development of shape recovery ways and the expansion of the applications in biomedical field. In addition, future perspectives of SMPs in the field of biomedicine are also discussed.
基金Project supported by the Iran National Science Foundation (INSF)(No.98027408)。
文摘This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SMPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables and rational thermodynamics.This method is developed for the finite bending of multilayers in a dual-shape memory effect(SME) cycle.The layer number and layering order are investigated for two different SMPs and a hyperelastic material.In addition to the semi-analytical solution,the finite element simulation is performed to verify the predicted results,where the outcomes demonstrate the excellent accuracy of the proposed solution for predicting the behavior of the multilayer SMPs.Since this method has a much lower computational cost than the finite element method(FEM),it can be used as an effective tool to analyze the SMP behavior under different conditions,including different materials,different geometries,different layer numbers,and different layer arrangements.
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.
基金Financial support by the National Natural Science Foundation of China(12102411,12072295)Central Government Guides Local Government-Free Exploration Project(2023ZYDF004)+1 种基金Research Funds from the China Academy of Engineering Physics(TCGH0414)Sichuan Provincial Natural Science Foundation(2025ZNSFSC0008)are acknowledged.
文摘Thermo-induced Shape Memory Polymers(TSMPs)and their corresponding 4D printing technology are at the forefront of current research.In this work,we review the progress from TSMPs to 4D printing and their corresponding applications.Firstly,taking thermally activated TSMPs as an example,the shape memory behavior is explained,and various shape memory experiments and mechanisms,as well as constitutive models,are discussed.This comprehensive information is designed to provide a solid understanding of TSMPs.Moreover,the history of 4D printing and various technologies used in 4D printing are introduced,and potential printing methods are summarized.These insights can guide researchers in selecting appropriate techniques for practical applications.The applications of 4D printed TSMPs are then outlined,with a focus on metamaterials and various industry cases that provide a clear understanding of what 4D printing can achieve.This knowledge will open new doors for innovative applications.Finally,the current research status is summarized,and the existing research gaps and future development directions are pointed out.Through this review,we aim to offer a comprehensive understanding of the journey from TSMPs to 4D printing and their applications so as to support further research and the promotion of 4D printing of TSMPs in the field of smart materials.
基金support from the Ministry of Education(MOE)of Singapore under the Academic Research Fund Tier 2[MOE-T2EP50122-0001]support from the National Key R&D Program of China[2022YFB3805700]+1 种基金support from the National Natural Science Foundation of China[U23A20412]support from the China Scholarship Council program[202406120073].
文摘Smart dry adhesives,a rapidly growing class of intelligent materials and structures,are engineered to provide strong,robust adhesion when needed while also allowing for controlled,easy detachment in response to specific stimuli.Traditional smart adhesives,often exemplified by fibrillar structures made of elastomers,face a number of challenges.These include limitations on maximum adhesion strength imposed by microstructural dimensions,restricted adaptability to surfaces with varying degrees of roughness,and an inherent trade-off between adhesion strength and switchability.This review explores how shape memory polymers(SMPs)can address these challenges and,through their rubber-to-glass(R2G)transition capability,provide a powerful foundation for the next generation of smart dry adhesives.Specifically,we summarize and elucidate the mechanisms by which SMPs enhance adhesion strength and switchability through material characteristics such as tunable stiffness,shape-locking,and shape-memory effects.Additionally,we discuss a wide range of innovative designs and applications of SMP adhesives,offering insights into the ongoing challenges and emerging opportunities in this rapidly evolving field.
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.
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financial support from the National Natural Science Foundation of China(No.51605220)the Jiangsu Province Natural Science Foundation,China(No.BK20160793)+1 种基金the Postgraduate Research and Practice Innovation Program of Nanjing University of Aeronautics and Astronautics,China(No.xcxjh20210514)the Fundamental Research Funds for the Central Universities,China(No.XCA2205406)。
文摘Controlled and switchable adhesion is commonly observed in biological systems.In recent years,many scholars have focused on making switchable bio-inspired adhesives.However,making a bio-inspired adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge.A Shape Memory Polymer Bio-inspired Adhesive(SMPBA)was successfully developed,well realizing high adhesion(about 337 kPa),relatively low preload(about90 kPa),high adhesion-to-preload ratio(about 3.74),high switching ratio(about 6.74),and easy detachment,which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect(SME).Furthermore,SMPBA exhibits adhesion strength of80–337 kPa on various surfaces(silicon,iron,and aluminum)with different roughness(Ra=0.021–10.280)because of the conformal contact,reflecting outstanding surface adaptability.The finite element analysis verifies the bending ability under different temperatures,while the adhesion model analyzes the influence of preload on contact area and adhesion.Furthermore,an Unmanned Aerial Vehicle(UAV)landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces.This study provides a novel switchable bio-inspired adhesive and UAV landing method.
基金This work was supported by the National Natural Science Foundation of China[grant number 51222301],[grant number 51473050],[grant number 51333003]Research Fund for the Doctoral Program of Higher Education of China[grant number 20130172110001]Fundamental Research Funds for the Central Universities[grant number 2014ZG0001].
文摘Although various shape memory polymers(SMPs)or diverse applications have been widely reported,the SMPs based on rubbers have been rarely realized due to the low triggering temperature of rubbers.In another aspect,the SMPs based on sustainable substances are highly desired for the growing shortage in fossil resources.In the present study,we accordingly developed the sustainable SMPs with tunable triggering temperature,based on natural rubber(NR)and ferulic acid(FA)as the raw materials.Specifically,the SMPs are based on a crosslinked network of epoxidized natural rubber(ENR)crosslinked by in situ formed zinc ferulate(ZDF)via oxa-Michael reaction.The excellent shape memory effect(SME)is found in these SMPs,as evidenced by the high fixity/recovery ratio and the tunable triggering temperature.With the incorpora-tion of natural halloysite nanotubes(HNTs),the stress and recovery rate of the SMPs are found to be tunable,which widens the application of this kind of SMPs.The combination of adoption of sustainable raw materials,and the excellent and tunable SME makes these SMPs potentially useful in many applications,such as various actuators and heat-shrinkable package materials.
基金This work is supported by the National Natural Science Foundation of China(Grant No.:12202181)the Natural Science Foundation of Jiangsu Province of China(Grant No.:BK20220325)the Fund of Prospective Layout of Scientific Research for Nanjing University of Aeronautics and Astronautics.
文摘This paper proposes a new thermoviscoelastic finite deformation model incorporating dual relaxation mechanisms to predict the complete thermo-mechanical response of amorphous shape memory polymers.The model is underpinned by the detailed microscopic molecular mechanism and effectively reflects the current understanding of the glass transition phenomenon.Novel evolution rules are obtained from the model to characterize the viscous flow,and a new theory named an internal stress model is introduced and combined with the dual relaxation mechanisms to capture the stress recovery.The rationality of the constitutive model is verified as the theoretical results agree well with the experimental data.Moreover,the constitutive model is further simplified to facilitate engineering applications,and it can roughly capture the characteristics of shape memory polymers.
基金the Natural Science Foundation of China(No.21874015)the Fundamental Research Funds for the Central Universities(No.N2005024).
文摘Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering.However,most of the reported platforms designed for the manipulation of water droplets cannot thoroughly solve the problem of droplet evaporation.Herein,we report a shape-reconfigurable micropillar array chip for the manipulation of water droplets,oil droplets and water-in-oil droplets.Water-in-oil droplets provide an enclosed space for water droplets,preventing the evaporation in an open environment.Perfluoropolyether coated on the surface of the chip effectively reduces the droplet movement resistance.The micropillar array chip has light and magnetic dual-response due to the Fe3O4 nanoparticles and the reduced iron powder mixed in the shape-memory polymer.The micropillars irradiated by a near-infrared laser bend under the magnetic force,while the unirradiated micropillars still keep their original shape.In the absence of a magnetic field,when the micropillars in a temporary shape are irradiated by the near-infrared laser to the transition temperature,the micropillars return to their initial shape.In this process,the surface morphology gradient caused by the deformation of the micropillars and the surface tension gradient caused by the temperature change jointly produce the driving force of droplet movement.
文摘Shape memory polymers （SMPs） are smart materials that can change their shape in a pre-defined manner under a stimulus. The shape memory functionality has gained considerable interest for biomedical applications, which require materials that are biocompatible and sometimes biodegradable. There is a need for SMPs that are prepared from renewable sources to be used as substitutes for conventional SMPs. In this paper, advances in SMPs based on synthetic monomers and bio-compounds are discussed. Materials designed for biomedical applica- tions are highlighted.
基金supported by the National Natural Science Foundation of China(Grant No.12172125)the Science Foundation of Hunan Province(Grant No.2022JJ30119).
文摘Multi-wall carbon nanotube filled shape memory polymer composite(MWCNT/SMC)possessed enhanced modulus,strength,and electric conductivity,as well as excellent electrothermal shape memory properties,showing wide design scenarios and engineering application prospects.The thermoelectrically triggered shape memory process contains complex multi-physical mechanisms,especially when coupled with finite deformation rooted on micro-mechanisms.A multi-physical finite deformation model is necessary to get a deep understanding on the coupled electro-thermomechanical properties of electrothermal shape memory composites(ESMCs),beneficial to its design and wide application.Taking into consideration of micro-physical mechanisms of the MWCNTs interacting with double-chain networks,a finite deformation theoretical model is developed in this work based on two superimposed network chains of physically crosslinked network formed among MWCNTs and the chemically crosslinked network.An intact crosslinked chemical network is considered featuring with entropic-hyperelastic properties,superimposed with a physically crosslinked network where percolation theory is based on electric conductivity and electric-heating mechanisms.The model is calibrated by experiments and used for shape recoveries triggered by heating and electric fields.It captures the coupled electro-thermomechanical behavior of ESMCs and provides design guidelines for MWCNTs filled shape memory polymers.
基金the National Natural Science Foundation of China(Grant Nos.11272044 and 11023001)
文摘Following deformation, thermally induced shape memory polymers(SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behaviors of three types of epoxy SMPs with varying curing agent contents were investigated using a molecular dynamics(MD) method. The mechanical properties under uniaxial tension at different temperatures were obtained, and the simulation results compared reasonably with experimental data. In addition, in a thermomechanical cycle, ideal shape memory effects for the three types of SMPs were revealed through the shape frozen and shape recovery responses at low and high temperatures, respectively, indicating that the recovery time is strongly influenced by the ratio of E-51 to 4,4'-Methylenedianiline.
基金This work was supported by the Natural Science Foundation of Jiangsu Province[BK20170759].
文摘The nano-carbon powders are often used as fillers to endow the shape memory polymers(SMPs)with electroconductivity.It has been found that the shape memory effects(SMEs)of SMPs filled with nano-carbon powder can be triggered both by temperature and by water.To reveal the driving mechanism of SMEs,a constitutive model for describing the thermally activated and moisture activated SMEs of these shape memory polymer composite(SMPCs)is developed here.Because both of the SMEs share the same driving mechanism,the variable moisture is incorporated into the framework of a thermo-mechanical modeling approach to disclose the effect of moisture on the thermoviscoelastic properties.The SMPCs are regarded as isotropic materials and the effect of carbon powder on the mechanical properties of the matrix is also considered in the paper.Because the complete recovery may not be reached even they are exposed to the stimulus environment long enough,the blocking mechanism is also considered here.This is the mainly new contribution compared to the early work.Using the method of parameter determination presented here,the effectiveness of the proposed hygro-thermo-mechanical constitutive model is confirmed by comparing the model results with the test data of uniaxial deformation from the literature.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102107 and 12272113)China National Postdoctoral Program for Innovative Talents(No.BX2021090).
文摘The mismatch in thermal expansion coefficients between the fiber-rich and resin-rich regions of a shape memory polymer composite(SMPC)laminate,along with the residual strain during SMPC fabrication,results in buckling deformation of the inhomogeneous laminate.This paper presents a macroscopic model for buckling of an inhomogeneous SMPC laminate under initial biaxial prestrains.Both linear and nonlinear buckling analyses are carried out using the energy method.The influences of prestrain biaxiality,temperature,and ply angle on the buckling wavelength,critical buckling prestrain,and buckling amplitude are calculated.The results demonstrate that the critical buckling wavelength of the SMPC laminate is independent of the prestrain,while the amplitude is almost independent of temperature.In addition,the optimal fiber stacking configuration with the maximum critical buckling prestrains of inhomogeneous SMPC laminates is determined by a genetic algorithm.
基金supported by the National Key R&D Program of China(2022YFB3805700)the National Natural Science Foundation of China(Grant No.12302198)+2 种基金China Postdoctoral Science Foundation(2022M720042)Heilongjiang Postdoctoral Science Foundation(LBH-Z22016)Key Project of Heilongjiang Provincial Department of Science and Technology(2022ZX02C25).
文摘Metamaterials,owing to their exceptional physical characteristics that are absent in natural materials,have emerged as a crucial constituent of intelligent devices and systems.However,there are still significant challenges that necessitate immediate attention,as they have considerably constrained the applicability of metamaterials,including fixed mechanical properties post-fabrication and restricted design freedom.Here,thermo-responsive,photo-responsive,electro-responsive,and magneto-responsive shape memory polymer nano-composites were developed,and shape memory gradient metamaterials were fabricated using multi-material 4D printing technology.The correlation mechanism between the design parameters and the mechanical properties of multi-responsive gradient metamaterials was systematically analyzed,and the highly designable and programmable configuration and mechanical properties of the gradient metamaterials were realized.More importantly,4D printed multi-responsive shape memory polymer gradient metamaterials can be programmed in situ without additional infrastructure for multi-functional mechanical functions,paving the way for the realization of multiple functions of a single structure.Based on the multi-responsive gradient metamaterials,4D printed digital pixel metamaterial intelligent information carriers were fabricated,featuring customizable encryption and decryption protocols,exceptional scalability,and reusability.Additionally,4D printed gradient metamaterial logic gate electronic devices were developed,which were anticipated to contribute to the development of smart,adaptable robotic systems that combine sensing,actuation,and decision-making capabilities.
基金This work was supported by the National Natural Science Foundations of China(Grant 11272044)the Fundamental Research Funds for the Central Universities(Grant 2018JBM305).
文摘Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two layers are SMPs with different thermal transition temperatures.By designing specific thermomechanical processes,the mismatched deformation between the two layers leads to a morphology change of ring-shaped bilayer structures from a smooth ring to a gear-like buckling shape under cooling and a reversible recovery to the smooth shape under heating.Such a morphology change is ascribed to occurrence and recovery of thermoelastic buckling.This method was validated by finite element simulation.We experimentally investigated the influence of pre-strain on buckling,and it was found that both the buckling occurrence and recovery temperature vary with pre-strain.Furthermore,considering a ring-shaped SMP-SMP bilayer structure,finite element analysis was conducted to study the influence of film thickness and modulus ratio of two layers on buckling behavior.The results showed that the critical buckling wavelength was greatly influenced by film thickness and modulus ratio.W e made a theoretical analysis that accorded well with the numerical results.
