There is an urgent demand for polymer dielectrics in the rapidly growing fields of electric vehicles and energy exploration.However,the existing polymer dielectrics suffer from poor energy density due to the decrease ...There is an urgent demand for polymer dielectrics in the rapidly growing fields of electric vehicles and energy exploration.However,the existing polymer dielectrics suffer from poor energy density due to the decrease of breakdown strength at elevated temperatures,which limits their widespread application.Ultralow content inorganic fillers(<1 vol.%)with appropriate size have been reported to enhance the polarization of polymer matrix,while their influence on breakdown still lack attention.In this work,we developed the dilute polyetherimide(PEI)-Al_(2)O_(3) nanocomposites with different filler size(5,20,and 80 nm)and studied the size effect of nanofillers on the breakdown resistance and energy storage performances of nanocomposite dielectrics.Based on the results of multiscale simulations and tests,the dilute fillers with smaller size(5 nm)exhibit more remarkable enhancement on charge trapping and mechanical strengthening of polymer matrix,and thus yielding higher breakdown strength and a discharged energy density of 4.69 J·cm^(-3)(150℃)and 2.56 J·cm^(-3)(200℃)with a high efficiency of 90%.A long charge-discharge cycling stability up to 105 cycles was also achieved at 150℃.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
A biomimetic electrical microenvironment is known to facilitate bone defect repair.Nevertheless,precise and non-invasive modulation of the in situ electrical microenvironment poses a formidable challenge.This study de...A biomimetic electrical microenvironment is known to facilitate bone defect repair.Nevertheless,precise and non-invasive modulation of the in situ electrical microenvironment poses a formidable challenge.This study develops a poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))membrane with a precisely controlled porous structure.Ultrasonic stimulation is applied to induce acoustic-mechanic-electric(AcME)conversion and regulate the membrane’s surface potential to modulate the in situ electrical microenvironment.When the ultrasound frequency aligns with the membrane’s inherent frequency,maximal electrical energy conversion occurs via the resonance effect,which generates the highest possible surface potential.The maximal AcME conversion is achieved by a 12μm pore-sized P(VDF-TrFE)membrane with a resonance frequency of 40 kHz,resulting in the highest surface potential of-65.56 mV.Finite element modeling indicates that the deformation and stress of porous membranes are higher than that of non-porous membranes under the stimulation of ultrasound,yielding the highest surface potential.In vitro experiments and sequencing analysis show that the honeycomb sandwich-structured P(VDF-TrFE)membrane under the stimulation of the resonance ultrasound promoted osteogenic differentiation of rBMSCs through the PI3K-Akt signaling pathway.When the porous membranes are implanted to cover cranial defects,the bone defect repair is significantly enhanced under the stimulation of ultrasound compared with the non-porous membranes.This study establishes a new strategy for efficient AcME conversion on piezoelectric membranes and offers new insights into the applications of ultrasound-responsive piezoelectric materials for bone defect repair.展开更多
Mechanical stimuli are known to play critical roles in mediating tissue repair and regeneration. Recently, thisknowledge has led to a paradigm shift toward proactive programming of biological functionalities of biomat...Mechanical stimuli are known to play critical roles in mediating tissue repair and regeneration. Recently, thisknowledge has led to a paradigm shift toward proactive programming of biological functionalities of biomaterialsby leveraging mechanics–geometry–biofunction relationships, which are beginning to shape the newly emergingfield of mechanobiomaterials. To profile this emerging field, this article aims to elucidate the fundamentalprinciples in modulating biological responses with material–tissue mechanical interactions, illustrate recentfindings on the relationships between material properties and biological responses, discuss the importance ofmathematical/physical models and numerical simulations in optimizing material properties and geometry, andoutline design strategies for mechanobiomaterials and their potential for tissue repair and regeneration. Giventhat the field of mechanobiomaterials is still in its infancy, this article also discusses open questions and challengesthat need to be addressed.展开更多
基金supported by National Natural Science Foundation of China(Nos.52421001 and 524B2016).
文摘There is an urgent demand for polymer dielectrics in the rapidly growing fields of electric vehicles and energy exploration.However,the existing polymer dielectrics suffer from poor energy density due to the decrease of breakdown strength at elevated temperatures,which limits their widespread application.Ultralow content inorganic fillers(<1 vol.%)with appropriate size have been reported to enhance the polarization of polymer matrix,while their influence on breakdown still lack attention.In this work,we developed the dilute polyetherimide(PEI)-Al_(2)O_(3) nanocomposites with different filler size(5,20,and 80 nm)and studied the size effect of nanofillers on the breakdown resistance and energy storage performances of nanocomposite dielectrics.Based on the results of multiscale simulations and tests,the dilute fillers with smaller size(5 nm)exhibit more remarkable enhancement on charge trapping and mechanical strengthening of polymer matrix,and thus yielding higher breakdown strength and a discharged energy density of 4.69 J·cm^(-3)(150℃)and 2.56 J·cm^(-3)(200℃)with a high efficiency of 90%.A long charge-discharge cycling stability up to 105 cycles was also achieved at 150℃.
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 National Natural Science Foundation of China(Nos.82471029,U22A20314,and 81600905)the Peking University Medicine Fund of Fostering Young Scholars’Scentific&Technological Innovation supported by the Fundamental Research Funds for the Central Universities(No.BMU2018PY005)the National Key Research and Development Program of China(No.2018YFE0194400).
文摘A biomimetic electrical microenvironment is known to facilitate bone defect repair.Nevertheless,precise and non-invasive modulation of the in situ electrical microenvironment poses a formidable challenge.This study develops a poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))membrane with a precisely controlled porous structure.Ultrasonic stimulation is applied to induce acoustic-mechanic-electric(AcME)conversion and regulate the membrane’s surface potential to modulate the in situ electrical microenvironment.When the ultrasound frequency aligns with the membrane’s inherent frequency,maximal electrical energy conversion occurs via the resonance effect,which generates the highest possible surface potential.The maximal AcME conversion is achieved by a 12μm pore-sized P(VDF-TrFE)membrane with a resonance frequency of 40 kHz,resulting in the highest surface potential of-65.56 mV.Finite element modeling indicates that the deformation and stress of porous membranes are higher than that of non-porous membranes under the stimulation of ultrasound,yielding the highest surface potential.In vitro experiments and sequencing analysis show that the honeycomb sandwich-structured P(VDF-TrFE)membrane under the stimulation of the resonance ultrasound promoted osteogenic differentiation of rBMSCs through the PI3K-Akt signaling pathway.When the porous membranes are implanted to cover cranial defects,the bone defect repair is significantly enhanced under the stimulation of ultrasound compared with the non-porous membranes.This study establishes a new strategy for efficient AcME conversion on piezoelectric membranes and offers new insights into the applications of ultrasound-responsive piezoelectric materials for bone defect repair.
基金supported by the National Natural Science Foundation of China(grant numbers 82025025,U23A6008,32171321,32371385,81802155,51672184 and 81622032)National Key Research and Development Project of China(grant number 2023YFC2412300)+7 种基金Natural Science Foundation of Hebei Province of China(grant number H2022202007)Full-time Talents Program of Hebei Province of China(grant number 2020HBQZYC012)Natural Science Foundation of Tianjin of China(grant number 21JCZDJC01110,21JCYBJC01030)Academician Expert Workstation of Yunnan Province of China(202205AF150025)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)Key Laboratory of Orthopaedics of Suzhou(SZS2022017)Scientific Research Project of Tianjin Education Commission(2022KJ096)Science and Technology Innovation Project of Foshan City(1920001000025).
文摘Mechanical stimuli are known to play critical roles in mediating tissue repair and regeneration. Recently, thisknowledge has led to a paradigm shift toward proactive programming of biological functionalities of biomaterialsby leveraging mechanics–geometry–biofunction relationships, which are beginning to shape the newly emergingfield of mechanobiomaterials. To profile this emerging field, this article aims to elucidate the fundamentalprinciples in modulating biological responses with material–tissue mechanical interactions, illustrate recentfindings on the relationships between material properties and biological responses, discuss the importance ofmathematical/physical models and numerical simulations in optimizing material properties and geometry, andoutline design strategies for mechanobiomaterials and their potential for tissue repair and regeneration. Giventhat the field of mechanobiomaterials is still in its infancy, this article also discusses open questions and challengesthat need to be addressed.
