4D printing is proposed based on the additive manufacturing of stimuli-responsive materials and structures,which can realize shape changing upon external stimuli.This article reviews the 4D printing methods and actuat...4D printing is proposed based on the additive manufacturing of stimuli-responsive materials and structures,which can realize shape changing upon external stimuli.This article reviews the 4D printing methods and actuating performances of 4D printing structures based on shape memory polymers,hydrogels,liquid crystal elastomers,and electroactive polymers.This article shows that the shape morphing properties of single materials are limited,while 4D printing of composites can integrate the various driving modes of different smart materials.In the end,challenges facing 4D printing such as broadening the scope of smart materials,improving printing processes,the compatibility of printing different materials have been discussed.展开更多
Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field,due to the electros...Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field,due to the electrostatic force between the two electrodes,the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value,the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases,which can be applied to design of actuators. Finally,this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.展开更多
Uncontrolled lithium dendrite growth hinders the practical application of lithium metal batteries(LMBs).Herein,we report a novel Li^(+) flux distributor achieved by placing an electroactive polyvinylidene fluoride/pol...Uncontrolled lithium dendrite growth hinders the practical application of lithium metal batteries(LMBs).Herein,we report a novel Li^(+) flux distributor achieved by placing an electroactive polyvinylidene fluoride/polymethyl methacrylate(PVDF/PMMA)composite nanofiber interlayer on a current collector,inducing uniform lithium deposition to mitigate the dendrite problem.Specifically,the released PMMA reacts with Liþto form abundant C–O–Li bonds and generate in situ a stable lithiophilic PMMA-Li solid electrolyte interphase layer.Theoretical calculations reveal that polar C–F groups in the PVDF framework and lithiophilic PMMA-Li provide homo-dispersed Li^(+) migration pathways with low energy barriers.Consequently,uniform Li nucleation is achieved at the molecular level,resulting in ultrahigh cycling stability with dendrite-free Li deposition at 5 mA cm^(-2) and 5 mAh cm^(-2)for over 500 h.The PVDF/PMMA||Li||LiFePO_(4)(LFP)full cell presents an increased rate capacity of 110 mAh g^(-1) at 10 C.In addition,a soft-package battery demonstrates a high energy density of 289 Wh kg^(-1).This work provides a facile design for stable lithium metal anodes to promote the practical use of LMBs and other alkali metal batteries.展开更多
The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the t...The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the two parameters indicates Arrhenius behavior. The polymer solventeffects on diffusion and electron transfer dynamics of ferrocene were discussed展开更多
Ionic electroactive polymers （IEAPs） are a category of intelligent soft materials exhibiting large displacement under electric excitation, based on inner ion or solvent transport. Due to their unique advantages such...Ionic electroactive polymers （IEAPs） are a category of intelligent soft materials exhibiting large displacement under electric excitation, based on inner ion or solvent transport. Due to their unique advantages such as flexibility, low driving voltage, large bending displacement and aquatic-environment adaptability, IEAPs have been documented as very promising actuators for the applications in bionic robots. This review presents an analysis to the current research status of IEAPs exploited in bionic robots. According to the specific bionic parts, those robots are divided into four classes： imitation of fins, limbs, joints and trunks. Their dimension, weight, voltage amplitude, frequency and maximum speed were summarized to show the optimum design range. The results show that the approach velocity of the current robots were higher （〉 35 mm· s-1） when the robot weighted 60 g - 180 g and the body was 90 mm - 130 mm long. For voltage from 1 V - 3 V and frequencies from 0.7 Hz - 1.2 Hz, the speed was relatively higher （〉 35 mm·s-1）.To some extent, the maximum speed decreases when the area of the IEAP material used in bionic robot increases. For underwater circumstances, IEAP materials are most suitable for designing bionic robots swimming with Body and/or Caudal Fin （BCF）. This review provides important guidance for the design of lEAP bionic robots.展开更多
In this study,we attempt to improve the electromechanical performance of ionic polymer–metal composites(IPMCs)by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness.With proper ...In this study,we attempt to improve the electromechanical performance of ionic polymer–metal composites(IPMCs)by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness.With proper electroless plating techniques,a high dispersion of palladium particles is achieved deep in the ionomer membrane,thereby increasing notably the interfacial surface area of electrodes.The membrane thickness is increased using 0.5 and 1 mm thick ionomer films.For comparison,IPMCs with the same ionomer membranes,but conventional Pt electrodes,are also prepared and studied.The electromechanical,mechanoelectrical,electrochemical and mechanical properties of different IPMCs are characterized and discussed.Scanning electron microscopy-energy dispersive X-ray(SEM-EDS)is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt IPMCs.Our experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt electrodes are superior in mechanoelectrical transduction,and show significantly higher blocking force compared to conventional type of IPMCs.The blocking forces of more than 0.3 N were measured at 4V DC input,exceeding the force output of typical Nafion®117-based Pt IPMCs more than two orders of magnitude.The newly designed Pd-Pt IPMCs can be useful in more demanding applications,e.g.,in biomimetic underwater robotics,where high stress and drag forces are encountered.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFB1105100,2018YFC2001300)the National Natural Science Foundation of China(Grant Nos.5167050531,51822504,91848204)+4 种基金the Joint Foundation for Equipment Pre-research of Ministry of Education(Grant No.2018G944J00084)Key Scientific and Technological Project of Jilin Province(Grant No.20180201051GX)the Program for JLU Science and Technology Innovative Research Team(Grant No.2017TD-04)the National Postdoctoral Program for Innovative Talents(Grant No.BX20180126)the China Postdoctoral Science Foundation(Grant No.2018M641769)。
文摘4D printing is proposed based on the additive manufacturing of stimuli-responsive materials and structures,which can realize shape changing upon external stimuli.This article reviews the 4D printing methods and actuating performances of 4D printing structures based on shape memory polymers,hydrogels,liquid crystal elastomers,and electroactive polymers.This article shows that the shape morphing properties of single materials are limited,while 4D printing of composites can integrate the various driving modes of different smart materials.In the end,challenges facing 4D printing such as broadening the scope of smart materials,improving printing processes,the compatibility of printing different materials have been discussed.
文摘Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field,due to the electrostatic force between the two electrodes,the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value,the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases,which can be applied to design of actuators. Finally,this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.
基金support from the National Natural Science Foundation of China(22075042)the Natural Science Foundation of Shanghai(20ZR1401400)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Donghua University(DHU)Distinguished Young Professor Program(LZB2021002).
文摘Uncontrolled lithium dendrite growth hinders the practical application of lithium metal batteries(LMBs).Herein,we report a novel Li^(+) flux distributor achieved by placing an electroactive polyvinylidene fluoride/polymethyl methacrylate(PVDF/PMMA)composite nanofiber interlayer on a current collector,inducing uniform lithium deposition to mitigate the dendrite problem.Specifically,the released PMMA reacts with Liþto form abundant C–O–Li bonds and generate in situ a stable lithiophilic PMMA-Li solid electrolyte interphase layer.Theoretical calculations reveal that polar C–F groups in the PVDF framework and lithiophilic PMMA-Li provide homo-dispersed Li^(+) migration pathways with low energy barriers.Consequently,uniform Li nucleation is achieved at the molecular level,resulting in ultrahigh cycling stability with dendrite-free Li deposition at 5 mA cm^(-2) and 5 mAh cm^(-2)for over 500 h.The PVDF/PMMA||Li||LiFePO_(4)(LFP)full cell presents an increased rate capacity of 110 mAh g^(-1) at 10 C.In addition,a soft-package battery demonstrates a high energy density of 289 Wh kg^(-1).This work provides a facile design for stable lithium metal anodes to promote the practical use of LMBs and other alkali metal batteries.
文摘The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the two parameters indicates Arrhenius behavior. The polymer solventeffects on diffusion and electron transfer dynamics of ferrocene were discussed
基金The authors acknowledge the financial support from the National Natural Science Foundation of China （No. 51605131）, National Natural Science Foundation of China （No. 11674354）, Natural Science Foundation of Anhui Province, China （No. 1608085QE100）, and Fundamental Research Funds for the Central Universities （No. JZ2016HGTB0711）.
文摘Ionic electroactive polymers （IEAPs） are a category of intelligent soft materials exhibiting large displacement under electric excitation, based on inner ion or solvent transport. Due to their unique advantages such as flexibility, low driving voltage, large bending displacement and aquatic-environment adaptability, IEAPs have been documented as very promising actuators for the applications in bionic robots. This review presents an analysis to the current research status of IEAPs exploited in bionic robots. According to the specific bionic parts, those robots are divided into four classes： imitation of fins, limbs, joints and trunks. Their dimension, weight, voltage amplitude, frequency and maximum speed were summarized to show the optimum design range. The results show that the approach velocity of the current robots were higher （〉 35 mm· s-1） when the robot weighted 60 g - 180 g and the body was 90 mm - 130 mm long. For voltage from 1 V - 3 V and frequencies from 0.7 Hz - 1.2 Hz, the speed was relatively higher （〉 35 mm·s-1）.To some extent, the maximum speed decreases when the area of the IEAP material used in bionic robot increases. For underwater circumstances, IEAP materials are most suitable for designing bionic robots swimming with Body and/or Caudal Fin （BCF）. This review provides important guidance for the design of lEAP bionic robots.
基金supported in part by the Office of Naval Research under Grant N000140910218 and N000141310274.
文摘In this study,we attempt to improve the electromechanical performance of ionic polymer–metal composites(IPMCs)by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness.With proper electroless plating techniques,a high dispersion of palladium particles is achieved deep in the ionomer membrane,thereby increasing notably the interfacial surface area of electrodes.The membrane thickness is increased using 0.5 and 1 mm thick ionomer films.For comparison,IPMCs with the same ionomer membranes,but conventional Pt electrodes,are also prepared and studied.The electromechanical,mechanoelectrical,electrochemical and mechanical properties of different IPMCs are characterized and discussed.Scanning electron microscopy-energy dispersive X-ray(SEM-EDS)is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt IPMCs.Our experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt electrodes are superior in mechanoelectrical transduction,and show significantly higher blocking force compared to conventional type of IPMCs.The blocking forces of more than 0.3 N were measured at 4V DC input,exceeding the force output of typical Nafion®117-based Pt IPMCs more than two orders of magnitude.The newly designed Pd-Pt IPMCs can be useful in more demanding applications,e.g.,in biomimetic underwater robotics,where high stress and drag forces are encountered.
