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
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
Transfer printing based on switchable adhesive is essential for developing unconventional systems,including flexible electronics,stretchable electronics,and micro light-emitting diode(LED)displays.Here we report a des...Transfer printing based on switchable adhesive is essential for developing unconventional systems,including flexible electronics,stretchable electronics,and micro light-emitting diode(LED)displays.Here we report a design of switchable dry adhesive based on shape memory polymer(SMP)with hemispherical indenters,which offers a continuously tunable and reversible adhesion through the combination of the preloading effect and the thermal actuation of SMP.Experimental and numerical studies reveal the fundamental aspects of design,fabrication,and operation of the switchable dry adhesive.Demonstrations of this adhesive concept in transfer printing of flat objects(e.g.,silicon wafers),three-dimensional(3D)objects(e.g.,stainless steel balls),and rough objects(e.g.,frosted glasses)in two-dimensional(2D)or 3D layouts illustrate its unusual manipulation capabilities in heterogeneous material integration applications.展开更多
With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstr...With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study o?ers a simple but effective approach to fabricate hybrid morphological features in micro-scale.With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study offers a simple but effective approach to fabricate hybrid morphological features in micro-scale.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
Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-pow...Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-power and low-cost space applications.In this study,a shape-memory polymer composite(SMPC)boom was designed,fabricated,and characterized for flexible reel-type solar arrays.The SMPC boom was fabricated from a smart material,a shape-memory polymer composite,whose mechanical properties were tested.Additionally,a mathematical model of the bending stiffness of the SMPC boom was developed,and the bending and buckling behaviors of the boom were further analyzed using the ABAQUS software.An SMPC boom was fabricated to demonstrate its shape memory characteristics,and the driving force of the booms with varying geometric parameters was investigated.We also designed and manufactured a reel-type solar array based on an SMPC boom and verified its self-deployment capability.The results indicated that the SMPC boom can be used as a deployable unit to roll out flexible solar arrays.展开更多
“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
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
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
As a kind of popular smart materials, shape memory polymers （SMPs） have a great potential for applications in deployable aerospace structures and other engineering struc- tures. However, the vibration analysis of sh...As a kind of popular smart materials, shape memory polymers （SMPs） have a great potential for applications in deployable aerospace structures and other engineering struc- tures. However, the vibration analysis of shape memory polymer structures, which would play an important role in engineering, has not gained much attention. In this study, we propose a dynamic model and establish the governing equations for characterizing the dynamic behavior of a shape memory polymer membrane subjected to time-dependent forces. The derivation of governing equations is based on a well-developed constitutive model of SMPs combined with the Euler-Lagrange equation. With the proposed model, two different loading cases are stud- ied： the equal-biaxial sinusoidal force and the uniaxial sinusoidal force. To analyze the dynamic response of a shape memory polymer membrane and find some effective ways to control vibra- tion, the isothermal amplitude-frequency response, the time-dependent behavior of vibration and the vibration in a variable temperature process are investigated in the numerical simulation. It is observed that temperature, mechanical force and heating rate have significant effects on the dynamic performances of a shape memory polymer membrane. We also investigate the shape memory behavior of SMP membrane involving the dynamic response. The influence of dynamics on shape fixation and shape recovery is discussed. These results and discussion may provide guidance for exploring the vibration and dynamic performances of shape memory polymer in deployable aerospace structures.展开更多
Stimuli-responsive polymers offer unprecedented control over drug release in implantable delivery systems.Shape memorypolymer fibers(SMPFs),with their large specific surface area and programmable properties,present pr...Stimuli-responsive polymers offer unprecedented control over drug release in implantable delivery systems.Shape memorypolymer fibers(SMPFs),with their large specific surface area and programmable properties,present promising alternativesfor triggerable drug delivery.However,the existing SMPFs face limitations in resolution,architecture,scalability,and functionality.We introduce thermal drawing as a materials and processing platform to fabricate microstructured,multimaterialSMPFs that are tens of meters long,with high resolution(10μm)and extreme aspect ratios(>105).These novel fibersachieve highly controlled,sequential drug release over tailored time periods of 6 months.Post thermal drawing photothermalcoatings enable accelerated,spatially precise drug release within 4 months and facilitate light-triggered,untethered shaperecovery.The fibers’fast self-tightening capability within 40 s shows their potential as smart sutures for minimally invasiveprocedures that deliver drugs simultaneously.In addition,the advanced multimaterial platform facilitates the integrationof optical and metallic elements within SMP systems,allowing highly integrated fibers with shape memory attributes andunprecedented functionalities.This versatile technology opens new avenues for diverse biomedical applications,includingimplantable drug delivery systems,smart sutures,wound dressings,stents,and functional textiles.It represents a significantadvancement in precise spatio-temporal control of drug delivery and adaptive medical devices.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
Smart photonic indicators(SPIs)offer a cost-effective and efficient way to monitor and control ethanol concentration,making them suitable for advanced digital informatics systems.The developed sensors can operate even...Smart photonic indicators(SPIs)offer a cost-effective and efficient way to monitor and control ethanol concentration,making them suitable for advanced digital informatics systems.The developed sensors can operate even after the removal of external stimuli,featuring exceptional optical memory and reconfigurable nanostructures,which will undoubtedly drive a revolution in colorimetric sensors.The SPI is prepared by polymerizing mixed monomers of poly(ethylene glycol)diacrylate(PEG600DA)and ethoxyethoxyethyl acrylate(EOEOEA)in a silica colloidal crystal template.SPIs contain periodically ordered interconnecting macropores via shape memory polymers(SMPs)that endow the films with structural colors.The evaporation of water can temporarily deform the initial periodic structure.The structure can then be restored by evaporating liquids with lower surface tension,such as water-ethanol solutions.The Laplace pressure generated during solvent evaporation competes with the elasticity of SMPs,driving nanoscale structural transformation.Consequently,the detection range of SPIs for ethanol con-centration in water depends on the balance between these two driving forces.Adjusting the size of the macropores expands the detection range allowing differentiation of alcohol concentrations from 5%to 100%.SPIs with selectivity and high sensitivity hold promise for various applications,including information technology,inkless writing,and anticounterfeiting,enhancing the versatility of photonic materials.展开更多
There is an increased risk of complications and even surgical failures for various types of medical devices due to difficult to control configurations and performances,incomplete deployments,etc.Shape memory polymers(...There is an increased risk of complications and even surgical failures for various types of medical devices due to difficult to control configurations and performances,incomplete deployments,etc.Shape memory polymers(SMPs)-based 4D printing technology offers the opportunity to create dynamic,personalized,and accurately controllable biomedical devices with complex configurations.SMPs,typical representatives of intelligent materials,are capable of programmable deformation in response to stimuli and dynamic remodeling on demand.4D printed SMP medical devices not only enable active control of configuration,performance and functionality,but also open the way for minimally invasive treatments and remote controllable deployment.Here,the shape memory mechanism,actuation methods,and printing strategies of active programmable SMPs are reviewed,and cutting-edge advances of 4D printed SMPs in the fields such as bone scaffolds,tracheal stents,cardiovascular stents,cell morphological regulation,and drug delivery are highlighted.In addition,promising and meaningful future research directions for 4D printed SMP biomedical devices are discussed.The development of 4D printed SMP medical devices is inseparable from the in-depth cooperation between doctors and engineers.The application of 4D printed SMP medical devices will facilitate the rapid realization of‘smart medical care’and accelerate the process of‘intelligentization’of medical devices.展开更多
With a 10%reversible compressive strain in more than 10 deformation cycles,the shape memory polymer composites(SMPCs)could be used for deployable structure and releasing mechanism.In this paper,without traditional ele...With a 10%reversible compressive strain in more than 10 deformation cycles,the shape memory polymer composites(SMPCs)could be used for deployable structure and releasing mechanism.In this paper,without traditional electro-explosive devices or motors/controllers,the deployable SMPC flexible solar array system(SMPC-FSAS)is studied,developed,ground-based tested,and finally on-orbit validated.The epoxy-based SMPC is used for the rolling-out variable-stiffness beams as a structural frame as well as an actuator for the flexible blanket solar array.The releasing mechanism is primarily made of the cyanate-based SMPC,which has a high locking stiffness to withstand 50 g gravitational acceleration and a large unlocking displacement of 10 mm.The systematical mechanical and thermal qualification tests of the SMPC-FSAS flight hardware were performed,including sinusoidal sweeping vibration,shocking,acceleration,thermal equilibrium,thermal vacuum cycling,and thermal cycling test.The locking function of the SMPC releasing mechanisms was in normal when launching aboard the SJ20 Geostationary Satellite on 27 Dec.,2019.The SMPC-FSAS flight hardware successfully unlocked and deployed on 5 Jan.,2020 on geostationary orbit.The triggering signal of limit switches returned to ground at the 139 s upon heating,which indicated the successful unlocking function of SMPC releasing mechanisms.A pair of epoxy-based SMPC rolled variable-stiffness tubes,which clapped the flexible blanket solar array,slowly deployed and finally approached an approximate 100%shape recovery ratio within 60 s upon heating.The study and on-orbit successful validation of the SMPC-FSAS flight hardware could accelerate the related study and associated productions to be used for the next-generation releasing mechanisms as well as space deployable structures,such as new releasing mechanisms with low-shocking,testability and reusability,and ultra-large space deployable solar arrays.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
Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and ...Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and feasible technique,has been used to prepare shape memory polymer fbers(SMPFs)and expand their structures.SMPFs show some advanced features and functions in many felds.In this review,we give a comprehensive overview of SMPFs,including materials,fabrication methods,structures,multifunction,and applications.Firstly,the mechanism and characteristics of SMP are introduced.We then discuss the electrospinning method to form various microstructures,like non-woven fbers,core/shell fbers,hollow fbers and oriented fbers.Afterward,the multiple functions of SMPFs are discussed,such as multi-shape memory efect,reversible shape memory efect and remote actuation of composites.We also focus on some typical applications of SMPFs,including biomedical scafolds,drug carriers,self-healing,smart textiles and sensors,as well as energy harvesting devices.At the end,the challenges and future development directions of SMPFs are proposed.展开更多
The epoxy shape memory polymer(SMP)with adjustable phase transition temperature is a kind of high-performance shape mem-ory polymer,which can change its phase transition temperature and improve its mechanical properti...The epoxy shape memory polymer(SMP)with adjustable phase transition temperature is a kind of high-performance shape mem-ory polymer,which can change its phase transition temperature and improve its mechanical properties through the process of photo curing.An epoxy SMP constitutive model combining phase transition and viscoelasticity is established by discretizing the epoxy SMP into several glass phase units and rubbery phase units in this paper.The model includes the viscoelastic constitutive equa-tions of glass phase units and rubber phase units,the parameter expression during shape memory process,and material parameter equation during photocuring process.And the stress relaxation behavior of epoxy SMP at different temperatures and the change of material parameters during the photo-curing process are simu-lated numerically,and the simulation results perform consistency with the experimental data.The model can not only relate shape memory effect and phase transformation in physics but also better characterize the viscoelastic properties of SMP and predict the shape memory response of SMP.展开更多
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The authors acknowledge the supports of the National Natural Science Foundation of China(Grant Nos.11872331 and U20A6001)Zhejiang University K.P.Chao’s High Technology Development Foundation.
文摘Transfer printing based on switchable adhesive is essential for developing unconventional systems,including flexible electronics,stretchable electronics,and micro light-emitting diode(LED)displays.Here we report a design of switchable dry adhesive based on shape memory polymer(SMP)with hemispherical indenters,which offers a continuously tunable and reversible adhesion through the combination of the preloading effect and the thermal actuation of SMP.Experimental and numerical studies reveal the fundamental aspects of design,fabrication,and operation of the switchable dry adhesive.Demonstrations of this adhesive concept in transfer printing of flat objects(e.g.,silicon wafers),three-dimensional(3D)objects(e.g.,stainless steel balls),and rough objects(e.g.,frosted glasses)in two-dimensional(2D)or 3D layouts illustrate its unusual manipulation capabilities in heterogeneous material integration applications.
基金The financial supports from NSF(CMMI-1405355)and ACS Petroleum Research Fund(53780-DNI7)are gratefully acknowledged.
文摘With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study o?ers a simple but effective approach to fabricate hybrid morphological features in micro-scale.With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study offers a simple but effective approach to fabricate hybrid morphological features in micro-scale.
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Supported by National Natural Science Foundation of China(Grant Nos.52105013 and 51835002)Self-Planned Task of State Key Laboratory of Robotics and System(HIT)of China(Grant No.SKLRS202202C)China Postdoctoral Science Foundation(Grant No.2020M681087).
文摘Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-power and low-cost space applications.In this study,a shape-memory polymer composite(SMPC)boom was designed,fabricated,and characterized for flexible reel-type solar arrays.The SMPC boom was fabricated from a smart material,a shape-memory polymer composite,whose mechanical properties were tested.Additionally,a mathematical model of the bending stiffness of the SMPC boom was developed,and the bending and buckling behaviors of the boom were further analyzed using the ABAQUS software.An SMPC boom was fabricated to demonstrate its shape memory characteristics,and the driving force of the booms with varying geometric parameters was investigated.We also designed and manufactured a reel-type solar array based on an SMPC boom and verified its self-deployment capability.The results indicated that the SMPC boom can be used as a deployable unit to roll out flexible solar arrays.
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Authors are grateful for the support from the National Natural Science Foundation of China through Grant numbers 11572236, 11372236.
文摘As a kind of popular smart materials, shape memory polymers （SMPs） have a great potential for applications in deployable aerospace structures and other engineering struc- tures. However, the vibration analysis of shape memory polymer structures, which would play an important role in engineering, has not gained much attention. In this study, we propose a dynamic model and establish the governing equations for characterizing the dynamic behavior of a shape memory polymer membrane subjected to time-dependent forces. The derivation of governing equations is based on a well-developed constitutive model of SMPs combined with the Euler-Lagrange equation. With the proposed model, two different loading cases are stud- ied： the equal-biaxial sinusoidal force and the uniaxial sinusoidal force. To analyze the dynamic response of a shape memory polymer membrane and find some effective ways to control vibra- tion, the isothermal amplitude-frequency response, the time-dependent behavior of vibration and the vibration in a variable temperature process are investigated in the numerical simulation. It is observed that temperature, mechanical force and heating rate have significant effects on the dynamic performances of a shape memory polymer membrane. We also investigate the shape memory behavior of SMP membrane involving the dynamic response. The influence of dynamics on shape fixation and shape recovery is discussed. These results and discussion may provide guidance for exploring the vibration and dynamic performances of shape memory polymer in deployable aerospace structures.
基金the Swiss National Science Foundation(SNSF project 200021_204579)The authors thank Dr.Shahrzad Shadman,Dr.Bastien Schyrr,Dr.Ines Richard,Dr.Andreas Leber,and Dr.Dong Yan for conducive discussion and experimental support+1 种基金the Laboratory for Processing of Advanced Composites(LPAC)at EPFL for the support in terms of equipment usagethe support from the China Scholarship Council.
文摘Stimuli-responsive polymers offer unprecedented control over drug release in implantable delivery systems.Shape memorypolymer fibers(SMPFs),with their large specific surface area and programmable properties,present promising alternativesfor triggerable drug delivery.However,the existing SMPFs face limitations in resolution,architecture,scalability,and functionality.We introduce thermal drawing as a materials and processing platform to fabricate microstructured,multimaterialSMPFs that are tens of meters long,with high resolution(10μm)and extreme aspect ratios(>105).These novel fibersachieve highly controlled,sequential drug release over tailored time periods of 6 months.Post thermal drawing photothermalcoatings enable accelerated,spatially precise drug release within 4 months and facilitate light-triggered,untethered shaperecovery.The fibers’fast self-tightening capability within 40 s shows their potential as smart sutures for minimally invasiveprocedures that deliver drugs simultaneously.In addition,the advanced multimaterial platform facilitates the integrationof optical and metallic elements within SMP systems,allowing highly integrated fibers with shape memory attributes andunprecedented functionalities.This versatile technology opens new avenues for diverse biomedical applications,includingimplantable drug delivery systems,smart sutures,wound dressings,stents,and functional textiles.It represents a significantadvancement in precise spatio-temporal control of drug delivery and adaptive medical devices.
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 Innovation Program for Quantum Science and Technology(2023ZD0300300)Foundation of China(XHD24A2401)+1 种基金Westlake University project(102510036022301)Key Laboratory for Quantum Materials of Zhejiang Province(10213004A092401).
文摘Smart photonic indicators(SPIs)offer a cost-effective and efficient way to monitor and control ethanol concentration,making them suitable for advanced digital informatics systems.The developed sensors can operate even after the removal of external stimuli,featuring exceptional optical memory and reconfigurable nanostructures,which will undoubtedly drive a revolution in colorimetric sensors.The SPI is prepared by polymerizing mixed monomers of poly(ethylene glycol)diacrylate(PEG600DA)and ethoxyethoxyethyl acrylate(EOEOEA)in a silica colloidal crystal template.SPIs contain periodically ordered interconnecting macropores via shape memory polymers(SMPs)that endow the films with structural colors.The evaporation of water can temporarily deform the initial periodic structure.The structure can then be restored by evaporating liquids with lower surface tension,such as water-ethanol solutions.The Laplace pressure generated during solvent evaporation competes with the elasticity of SMPs,driving nanoscale structural transformation.Consequently,the detection range of SPIs for ethanol con-centration in water depends on the balance between these two driving forces.Adjusting the size of the macropores expands the detection range allowing differentiation of alcohol concentrations from 5%to 100%.SPIs with selectivity and high sensitivity hold promise for various applications,including information technology,inkless writing,and anticounterfeiting,enhancing the versatility of photonic materials.
基金funded by the the National Key R&D Program of China(2022YFB3805700)Key R&D Program of Ningbo City(2023Z191)+2 种基金the National Natural Science Foundation of China(12302198)Heilongjiang Provincial Natural Science Foundation of China(LH2022A013)The project was also supported by the Interdisciplinary Research Foundation of HIT,and Key Project of Heilongjiang Provincial Department of Science,Technology(2022ZX02C25).
文摘There is an increased risk of complications and even surgical failures for various types of medical devices due to difficult to control configurations and performances,incomplete deployments,etc.Shape memory polymers(SMPs)-based 4D printing technology offers the opportunity to create dynamic,personalized,and accurately controllable biomedical devices with complex configurations.SMPs,typical representatives of intelligent materials,are capable of programmable deformation in response to stimuli and dynamic remodeling on demand.4D printed SMP medical devices not only enable active control of configuration,performance and functionality,but also open the way for minimally invasive treatments and remote controllable deployment.Here,the shape memory mechanism,actuation methods,and printing strategies of active programmable SMPs are reviewed,and cutting-edge advances of 4D printed SMPs in the fields such as bone scaffolds,tracheal stents,cardiovascular stents,cell morphological regulation,and drug delivery are highlighted.In addition,promising and meaningful future research directions for 4D printed SMP biomedical devices are discussed.The development of 4D printed SMP medical devices is inseparable from the in-depth cooperation between doctors and engineers.The application of 4D printed SMP medical devices will facilitate the rapid realization of‘smart medical care’and accelerate the process of‘intelligentization’of medical devices.
基金supported by the National Natural Science Foundation of China(Grant No.11632005)。
文摘With a 10%reversible compressive strain in more than 10 deformation cycles,the shape memory polymer composites(SMPCs)could be used for deployable structure and releasing mechanism.In this paper,without traditional electro-explosive devices or motors/controllers,the deployable SMPC flexible solar array system(SMPC-FSAS)is studied,developed,ground-based tested,and finally on-orbit validated.The epoxy-based SMPC is used for the rolling-out variable-stiffness beams as a structural frame as well as an actuator for the flexible blanket solar array.The releasing mechanism is primarily made of the cyanate-based SMPC,which has a high locking stiffness to withstand 50 g gravitational acceleration and a large unlocking displacement of 10 mm.The systematical mechanical and thermal qualification tests of the SMPC-FSAS flight hardware were performed,including sinusoidal sweeping vibration,shocking,acceleration,thermal equilibrium,thermal vacuum cycling,and thermal cycling test.The locking function of the SMPC releasing mechanisms was in normal when launching aboard the SJ20 Geostationary Satellite on 27 Dec.,2019.The SMPC-FSAS flight hardware successfully unlocked and deployed on 5 Jan.,2020 on geostationary orbit.The triggering signal of limit switches returned to ground at the 139 s upon heating,which indicated the successful unlocking function of SMPC releasing mechanisms.A pair of epoxy-based SMPC rolled variable-stiffness tubes,which clapped the flexible blanket solar array,slowly deployed and finally approached an approximate 100%shape recovery ratio within 60 s upon heating.The study and on-orbit successful validation of the SMPC-FSAS flight hardware could accelerate the related study and associated productions to be used for the next-generation releasing mechanisms as well as space deployable structures,such as new releasing mechanisms with low-shocking,testability and reusability,and ultra-large space deployable solar arrays.
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This work is funded by the National Natural Science Foundation of China(Grant No.11632005,11802075)This work was also supported by the China Postdoctoral Science Foundation funded project.
文摘Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and feasible technique,has been used to prepare shape memory polymer fbers(SMPFs)and expand their structures.SMPFs show some advanced features and functions in many felds.In this review,we give a comprehensive overview of SMPFs,including materials,fabrication methods,structures,multifunction,and applications.Firstly,the mechanism and characteristics of SMP are introduced.We then discuss the electrospinning method to form various microstructures,like non-woven fbers,core/shell fbers,hollow fbers and oriented fbers.Afterward,the multiple functions of SMPFs are discussed,such as multi-shape memory efect,reversible shape memory efect and remote actuation of composites.We also focus on some typical applications of SMPFs,including biomedical scafolds,drug carriers,self-healing,smart textiles and sensors,as well as energy harvesting devices.At the end,the challenges and future development directions of SMPFs are proposed.
基金This work was supported by the National Key Research and Development Program of China[2017YFC0307604].
文摘The epoxy shape memory polymer(SMP)with adjustable phase transition temperature is a kind of high-performance shape mem-ory polymer,which can change its phase transition temperature and improve its mechanical properties through the process of photo curing.An epoxy SMP constitutive model combining phase transition and viscoelasticity is established by discretizing the epoxy SMP into several glass phase units and rubbery phase units in this paper.The model includes the viscoelastic constitutive equa-tions of glass phase units and rubber phase units,the parameter expression during shape memory process,and material parameter equation during photocuring process.And the stress relaxation behavior of epoxy SMP at different temperatures and the change of material parameters during the photo-curing process are simu-lated numerically,and the simulation results perform consistency with the experimental data.The model can not only relate shape memory effect and phase transformation in physics but also better characterize the viscoelastic properties of SMP and predict the shape memory response of SMP.
