For advanced conductive hydrogels,adaptable mechanical properties and high conductivity are essential requirements for practical application,e.g.,soft electronic devices.Here,a straightforward strategy to develop a me...For advanced conductive hydrogels,adaptable mechanical properties and high conductivity are essential requirements for practical application,e.g.,soft electronic devices.Here,a straightforward strategy to develop a mechanically robust hydrogel with high conductivity by constructing complicated 3D structures composed of covalently cross-linked polymer network and two nanofillers with distinguishing dimensions is reported.The combination of one-dimensional quaternized cellulose nanofibrils(QACNF)and two-dimensional MXene nanosheets not only provides prominent and tunable mechanical properties modulated by materials composition,but results in electronically conductive path with high conductivity(1281 mS m^(-1)).Owing to the uniform interconnectivity of network structure attributed to the strong macro-molecular interaction and nano-reinforced effect,the resultant hydrogel exhibits a balanced mechanical feature,i.e.,high tensile strength(449 kPa),remarkable stretchability(>1700%),and ultra-high toughness(5.46 MJ m^(-3)),outperforming those of virgin one.Additionally,the enhanced conductive characteristic with the aid of QACNF enables hydrogels with impressive electromechanical behavior,containing high sensitivity(maximum gauge factor:2.24),wide working range(0-1465%),and fast response performance(response time:141 ms,recover time:140 ms).Benefiting from the excellent mechanical performance,a flexible strain sensor based on such conductive hydrogel can deliver an appealing sensing performance of monitoring multi-scale deformations,from large and monotonous mechanical deformation to tiny and complex physiological motions(e.g.,joint movement and signature/vocal recognition).Together,the hydrogel material in this work opens up opportunities in the design and fabrication of advanced gel-based materials for emerging wearable electronics.展开更多
To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performan...To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performances of sensor devices and the data processing capabilities of the device’s software.Significant research efforts have been devoted to improving materials,sensing mechanism,and configurations of flexible sensing systems in a quest to fulfill the requirements of future technology.Meanwhile,advanced data analysis methods are being developed to extract useful information from increasingly complicated data collected by a single sensor or network of sensors.Machine learning(ML)as an important branch of artificial intelligence can efficiently handle such complex data,which can be multi-dimensional and multi-faceted,thus providing a powerful tool for easy interpretation of sensing data.In this review,the fundamental working mechanisms and common types of flexible mechanical sensors are firstly presented.Then how ML-assisted data interpretation improves the applications of flexible mechanical sensors and other closely-related sensors in various areas is elaborated,which includes health monitoring,human-machine interfaces,object/surface recognition,pressure prediction,and human posture/motion identification.Finally,the advantages,challenges,and future perspectives associated with the fusion of flexible mechanical sensing technology and ML algorithms are discussed.These will give significant insights to enable the advancement of next-generation artificial flexible mechanical sensing.展开更多
Wound healing has been recognized as a complex and dynamic regeneration process and attracted increasing interests on its management.For effective wound healing management,a continuous monitoring on the wound healing ...Wound healing has been recognized as a complex and dynamic regeneration process and attracted increasing interests on its management.For effective wound healing management,a continuous monitoring on the wound healing based on sensors is essential.Since pH has been found to play an important role on wound healing process,a variety of pH sensors systems for wound healing monitoring have been greatly developed in recent years.Among these pH sensors,flexible and wearable pH sensors which can be incorporated with wound dressing have gained much attention.In this review,the recent advances in the development of flexible and wearable pH sensors for wound healing monitoring have been comprehensive summarized from the range of optical and electrochemical bases.展开更多
Flexible mechanical sensors offer extensive application prospects in the field of smart wearables.However,developing highly sensitive,flexible mechanical sensors that can simultaneously detect strain and pressure rema...Flexible mechanical sensors offer extensive application prospects in the field of smart wearables.However,developing highly sensitive,flexible mechanical sensors that can simultaneously detect strain and pressure remains a significant challenge.Herein,we present a flexible mechanical sensor based on AgNPs/MWCNTsCOOH/PDA/PU/PVB nanofiber-covered yarn(AMPPPNY)featuring a DNA-like double-helix wrinkled structure.The sensor is fabricated by electrospraying polyvinyl butyral(PVB)onto a pre-stretched double-helix elastic yarn,followed by electrospinning a polyurethane(PU)nanofiber membrane and inducing the self-polymerization of dopamine(DA)to create an adhesive layer.Then,one-dimensional carboxylated multi-walled carbon nanotubes(MWCNTs-COOH)and zero-dimensional silver nanoparticles(AgNPs)are dispersed onto the structure,synergistically forming a stable conductive network for efficient signal transmission.The integration of conductive fillers with different dimensionalities and DNA-like double-helix wrinkled structure endows the sensor with high strain sensitivity(gauge factor of 11,977)in the strain range of 0-310%and high pressure sensitivity(0.475 kPa^(-1))in the pressure range of 0-2 kPa.Moreover,the fabricated sensor exhibits rapid response and recovery times(130 ms/135 ms)and outstanding cyclic stability(over 10,000 cycles of both strain and pressure).Next,the fibrous sensor is weaved into a large-area fabric,and the developed smart textiles demonstrate impressive performance in detecting both subtle and large human movements.The proposed sensor is a promising candidate for flexible wearable applications.展开更多
Compared with traditional rain gauges and weather radars,hydrogel flexible electronic sensor capable of responding directly to rainfall events with promptness and authenticity,shows great prospects in real-time rainfa...Compared with traditional rain gauges and weather radars,hydrogel flexible electronic sensor capable of responding directly to rainfall events with promptness and authenticity,shows great prospects in real-time rainfall monitoring.Aluminum coordination hydrogel(Al-HG),one of the most qualified sensors suitable for rainfall monitoring,however,is currently impeded from widespread application by its weak mechanical properties due to the low binding strength between Al^(3+)and functional ligands.Herein,inspired by the antifreeze proteins(AFPs)that protect those Patagonian toothfishes by strongly binding to ice crystals at freezing temperatures,a low temperature-induced strategy is introduced to promote more and stronger ligand carboxyls firm combination with Al^(3+),thus forming a high-coordinated structure to deal with this challenge.Expectedly,the whole mechanical performance of the product Al-HG_(F1/F2) obtained by the low temperature-induced strategy is improved.For example,the tensile fracture toughness and the maximum compressive stress of Al-HG_(F1/F2) are 1.66 MJ·m^(-3) and 12.01 MPa,approximately twice those of the sample Al-HGF3/F0 obtained by traditional soaking method(0.86 MJ·m^(-3) and 7.38 MPa,respectively).Coupled with its good biocompatibility,ionic conductivity,and sensing ability,Al-HG_(F1/F2) demonstrates promising application for real-time rainfall monitoring in discrepant rainfall intensities,different zones,and even under extreme environments.This work aims to offer a stride toward mechanically robust aluminum coordination hydrogel sensors for real-time rainfall monitoring as well as provide insights into flood prevention and disaster mitigation.展开更多
Hydrogel-based electronic skins or triboelectric nanogenerator(TENG)are considered ideal candidates for flexible electronics.However,current hydrogels face limitations that lead to suboptimal performance,and their rel...Hydrogel-based electronic skins or triboelectric nanogenerator(TENG)are considered ideal candidates for flexible electronics.However,current hydrogels face limitations that lead to suboptimal performance,and their reliance on external power sources hampers their practical application.A two-step washing approach comprising of“salt soaking”and“salt washing”is introduced to fabricate the multifunctional hydrogel.Initially,the hydrogel framework(SAC_(2)Z)-acrylamide(AM)and silk fibroin(SF)hydrogel is formed via salt soaking.Subsequently,the crosslinking degree is fine-tuned by adjusting the salt ion concentration through salt washing.The obtained hydrogel SAC_(2)ZC possesses excellent mechanical properties(a 15-fold increase in fracture strength to 320 kPa)and excellent cold resistance up to-80℃.Compared to conventional water-dispersible hydrogels,strain sensors based on SAC_(2)ZC are capable of sensing up to-30℃.The flexible antifreeze battery based on SAC_(2)ZC has excellent dendrite resistance and could supply power under high pressure(30 MPa)and severe bending(180°).The SAC_(2)ZC-based TENG(C-TENG)enables energy harvesting,eliminating reliance on external power sources.This innovation paves the way for flexible sensing systems that integrate energy collection and storage,facilitating all-weather human-smartphone signal interaction.This research provides a new strategy to develop multifunctional SAC_(2)ZC hydrogel for flexible wearable devices,especially in extremely cold complex environments.展开更多
Two-dimensional(2D)materials have great potential in the fields of flexible electronics and photoelectronic devices due to their unique properties derived by special structures.The study of the mechanical properties o...Two-dimensional(2D)materials have great potential in the fields of flexible electronics and photoelectronic devices due to their unique properties derived by special structures.The study of the mechanical properties of 2D materials plays an important role in next-generation flexible mechanical electronic device applications.Unfortunately,traditional experiment models and measurement methods are not suitable for 2D materials due to their atomically ultrathin thickness,which limits both the theoretical research and practical value of the 2D materials.In this review,we briefly summarize the characterization of mechanical properties of 2D materials by in situ probe nanoindentation experiments,and discuss the effect of thickness,grain boundary,and interlayer interactions.We introduce the strain-induced effect on electrical properties and optical properties of 2D materials.Then,we generalize the mechanical sensors based on various 2D materials and their future potential applications in flexible and wearable electronic devices.Finally,we discuss the state of the art for the mechanical properties of 2D materials and their opportunities and challenges in both basic research and practical applications.展开更多
The development of electronic skin,soft robots,and smart wearables has significantly driven advances in flexible pressure sensing technology.However,traditional multilayer solid-structure flexible pressure sensors enc...The development of electronic skin,soft robots,and smart wearables has significantly driven advances in flexible pressure sensing technology.However,traditional multilayer solid-structure flexible pressure sensors encounter challenges at temperatures between 100°C and 150°C due to high-temperature modal distortion.Changes in the conductivity of the sensor’s conductive components interfere with accurate pressure measurement.In this research,a flexible pressure sensor with a convective liquid metal sensitive layer is proposed.The sensor uses a cyclic self-cooling mechanism to lower the temperature of its conductive components,reducing the impact of external high temperatures on the pressure measurement accuracy.At a 2.8 W thermal load,the flexible sensor,with liquid metal circulating at 2.0 mL/min,exhibits a sensitivity of 0.11 kPa⁻¹within the pressure range from 0 to 12.5 kPa,and its maximum measurable pressure is 30 kPa.In addition,the resistance of the sensor is 18.5 mΩless than that of a stationary liquid metal sensor,representing a 38.1%reduction.The sensor proposed in this research introduces a novel strategy for pressure measurement in high-temperature applications,extending the application scope to aircraft,special robots,and hydraulic oil circuits.展开更多
Flexible humidity sensors are widely used in many fields,such as environmental monitoring,agricultural soil moisture content determination,food quality monitoring and healthcare services.Therefore,it is essential to m...Flexible humidity sensors are widely used in many fields,such as environmental monitoring,agricultural soil moisture content determination,food quality monitoring and healthcare services.Therefore,it is essential to measure humidity accurately and reliably in different conditions.Flexible materials have been the focusing substrates of humidity sensors because of their rich surface chemical properties and structural designability.In addition,flexible materials have superior ductility for different conditions.In this review,we have summarized several sensing mechanisms,processing techniques,sensing layers and substrates for specific humidity sensing requirements.Aadditionally,we have sorted out some cases of flexible humidity sensors based on different functional materials.We hope this paper can contribute to the development of flexible humidity sensors in the future.展开更多
Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction...Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction interfaces.Among the various flexible sensor types,those with microstructure designs are considered promising for strain sensing due to their simple structure,high sensitivity,extensive operational range,rapid response time,and robust stability.This review provides a concise overview of recent advancements in flexible piezoresistive sensors based on microstructure design for enhanced strain sensing performance,including the impact of microstructure on sensing mechanisms,classification of microstructure designs,fabrication methods,and practical applications.Initially,this review delves into the analysis of piezoresistive sensor sensing mechanisms and performance parameters,exploring the relationship between microstructure design and performance enhancement.Subsequently,an in-depth discussion is presented,focusing on the primary themes of microstructure design classification,process selection,performance characteristics,and specific applications.This review employs mathematical modeling and hierarchical analysis to emphasize the directionality of different microstructures on performance enhancement and to highlight the performance advantages and applicable features of various microstructure types.In conclusion,this review examines the multifunctionality of flexible piezoresistive sensors based on microstructure design and addresses the challenges that still need to be overcome and improved,such as achieving a wide range of stretchability,high sensitivity,and robust stability.This review summarizes the research directions for enhancing sensing performance through microstructure design,aiming to assist in the advancement of flexible piezoresistive sensors.展开更多
Flexible pressure sensors play an important role in the field of monitoring, owing to their inherent safety and the fact that they are embedded at the material level. Capacitive pressure sensors have been proven to be...Flexible pressure sensors play an important role in the field of monitoring, owing to their inherent safety and the fact that they are embedded at the material level. Capacitive pressure sensors have been proven to be quite versatile, with the ability to change the sensitivity and monitoring range by modifying the pore structure of the dielectric layer(elastic modulus). In this paper, capacitive pressure sensors are devised, comprising hierarchical porous polydimethylsiloxane. Due to the inherent hollow and hierarchical micropore structure, the capacitive pressure sensor allows operation at a wider pressure range(~1000 kPa) while maintaining sensitivity(6.33 MPa-1) in the range of 0–300 k Pa. Subsequently, the capacitance output model of the sensor is optimized, which provides an overall approximation of the experimental values for the sensor performance. Additionally, the signal response of the“break up the whole into parts”(by analysis of the whole sensor in parts) is simulated and outputted by the finite element analysis. The simplified analysis model provides a good understanding of the relationship between the local pressure and the signal response of the pressure sensor. For practical applications, seal monitoring and rubber wheel pressure array system are tested, and the proposed sensor shows sufficient potential for application in large deformation elastomer products.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52203148,51973047,and 12002113)the Research Foundation of Talented Scholars of Zhejiang A&F University(Nos.2020FR070 and 2021FR024)+1 种基金the Zhejiang A&F University Scientific Research Training Program for Undergraduates(No.S202210341186)the Key Research and Development Program of Shaanxi(No.2022-JBGS3-09).
文摘For advanced conductive hydrogels,adaptable mechanical properties and high conductivity are essential requirements for practical application,e.g.,soft electronic devices.Here,a straightforward strategy to develop a mechanically robust hydrogel with high conductivity by constructing complicated 3D structures composed of covalently cross-linked polymer network and two nanofillers with distinguishing dimensions is reported.The combination of one-dimensional quaternized cellulose nanofibrils(QACNF)and two-dimensional MXene nanosheets not only provides prominent and tunable mechanical properties modulated by materials composition,but results in electronically conductive path with high conductivity(1281 mS m^(-1)).Owing to the uniform interconnectivity of network structure attributed to the strong macro-molecular interaction and nano-reinforced effect,the resultant hydrogel exhibits a balanced mechanical feature,i.e.,high tensile strength(449 kPa),remarkable stretchability(>1700%),and ultra-high toughness(5.46 MJ m^(-3)),outperforming those of virgin one.Additionally,the enhanced conductive characteristic with the aid of QACNF enables hydrogels with impressive electromechanical behavior,containing high sensitivity(maximum gauge factor:2.24),wide working range(0-1465%),and fast response performance(response time:141 ms,recover time:140 ms).Benefiting from the excellent mechanical performance,a flexible strain sensor based on such conductive hydrogel can deliver an appealing sensing performance of monitoring multi-scale deformations,from large and monotonous mechanical deformation to tiny and complex physiological motions(e.g.,joint movement and signature/vocal recognition).Together,the hydrogel material in this work opens up opportunities in the design and fabrication of advanced gel-based materials for emerging wearable electronics.
基金support from National Natural Science Foundation of China(Nos.62274140,61904141,52173234)the State Key Laboratory of Mechanics and Control of Mechanical Structures(Nanjing University of Aeronautics and Astronautics)(Grant No.MCMS-E-0422G03)the Shenzhen-Hong Kong-Macao Technology Research Program(Type C,202011033000145,SGDX2020110309300301).
文摘To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performances of sensor devices and the data processing capabilities of the device’s software.Significant research efforts have been devoted to improving materials,sensing mechanism,and configurations of flexible sensing systems in a quest to fulfill the requirements of future technology.Meanwhile,advanced data analysis methods are being developed to extract useful information from increasingly complicated data collected by a single sensor or network of sensors.Machine learning(ML)as an important branch of artificial intelligence can efficiently handle such complex data,which can be multi-dimensional and multi-faceted,thus providing a powerful tool for easy interpretation of sensing data.In this review,the fundamental working mechanisms and common types of flexible mechanical sensors are firstly presented.Then how ML-assisted data interpretation improves the applications of flexible mechanical sensors and other closely-related sensors in various areas is elaborated,which includes health monitoring,human-machine interfaces,object/surface recognition,pressure prediction,and human posture/motion identification.Finally,the advantages,challenges,and future perspectives associated with the fusion of flexible mechanical sensing technology and ML algorithms are discussed.These will give significant insights to enable the advancement of next-generation artificial flexible mechanical sensing.
基金supported by the National Natural Science Foundation of China (No. 51703102)the Innovation and Entrepreneurship Training Program for College Students of Qingdao University (2019)
文摘Wound healing has been recognized as a complex and dynamic regeneration process and attracted increasing interests on its management.For effective wound healing management,a continuous monitoring on the wound healing based on sensors is essential.Since pH has been found to play an important role on wound healing process,a variety of pH sensors systems for wound healing monitoring have been greatly developed in recent years.Among these pH sensors,flexible and wearable pH sensors which can be incorporated with wound dressing have gained much attention.In this review,the recent advances in the development of flexible and wearable pH sensors for wound healing monitoring have been comprehensive summarized from the range of optical and electrochemical bases.
基金National Natural Science Foundation of China,51503168,Chengkun LiuTaishan Scholar Foundation of Shandong Province,tsqn201909100,Chengkun LiuInnovation Capability Support Plan of Shaanxi,China,2020PT-043,Chengkun Liu。
文摘Flexible mechanical sensors offer extensive application prospects in the field of smart wearables.However,developing highly sensitive,flexible mechanical sensors that can simultaneously detect strain and pressure remains a significant challenge.Herein,we present a flexible mechanical sensor based on AgNPs/MWCNTsCOOH/PDA/PU/PVB nanofiber-covered yarn(AMPPPNY)featuring a DNA-like double-helix wrinkled structure.The sensor is fabricated by electrospraying polyvinyl butyral(PVB)onto a pre-stretched double-helix elastic yarn,followed by electrospinning a polyurethane(PU)nanofiber membrane and inducing the self-polymerization of dopamine(DA)to create an adhesive layer.Then,one-dimensional carboxylated multi-walled carbon nanotubes(MWCNTs-COOH)and zero-dimensional silver nanoparticles(AgNPs)are dispersed onto the structure,synergistically forming a stable conductive network for efficient signal transmission.The integration of conductive fillers with different dimensionalities and DNA-like double-helix wrinkled structure endows the sensor with high strain sensitivity(gauge factor of 11,977)in the strain range of 0-310%and high pressure sensitivity(0.475 kPa^(-1))in the pressure range of 0-2 kPa.Moreover,the fabricated sensor exhibits rapid response and recovery times(130 ms/135 ms)and outstanding cyclic stability(over 10,000 cycles of both strain and pressure).Next,the fibrous sensor is weaved into a large-area fabric,and the developed smart textiles demonstrate impressive performance in detecting both subtle and large human movements.The proposed sensor is a promising candidate for flexible wearable applications.
基金supported by the National Natural Science Foundation of China(22308210)the Young Talent Fund of the Association for Science and Technology in Shaanxi of China(20240412)+1 种基金the RIKEN-MOST Project between the Ministry of Science and Technology of the People’s Republic of China(MOST)and RIKEN,the China Scholarship Council(202108610127)the Natural Science Foundation of Shaanxi University of Science&Technology(2019BT-44).
文摘Compared with traditional rain gauges and weather radars,hydrogel flexible electronic sensor capable of responding directly to rainfall events with promptness and authenticity,shows great prospects in real-time rainfall monitoring.Aluminum coordination hydrogel(Al-HG),one of the most qualified sensors suitable for rainfall monitoring,however,is currently impeded from widespread application by its weak mechanical properties due to the low binding strength between Al^(3+)and functional ligands.Herein,inspired by the antifreeze proteins(AFPs)that protect those Patagonian toothfishes by strongly binding to ice crystals at freezing temperatures,a low temperature-induced strategy is introduced to promote more and stronger ligand carboxyls firm combination with Al^(3+),thus forming a high-coordinated structure to deal with this challenge.Expectedly,the whole mechanical performance of the product Al-HG_(F1/F2) obtained by the low temperature-induced strategy is improved.For example,the tensile fracture toughness and the maximum compressive stress of Al-HG_(F1/F2) are 1.66 MJ·m^(-3) and 12.01 MPa,approximately twice those of the sample Al-HGF3/F0 obtained by traditional soaking method(0.86 MJ·m^(-3) and 7.38 MPa,respectively).Coupled with its good biocompatibility,ionic conductivity,and sensing ability,Al-HG_(F1/F2) demonstrates promising application for real-time rainfall monitoring in discrepant rainfall intensities,different zones,and even under extreme environments.This work aims to offer a stride toward mechanically robust aluminum coordination hydrogel sensors for real-time rainfall monitoring as well as provide insights into flood prevention and disaster mitigation.
基金supported by the National Natural Science Foundation of China(52273095)the Outstanding Youth Project of Zhejiang Provincial Natural Science Foundation(LR22E030002)+2 种基金the Key Research and Development Program of Zhejiang Province(2022C01049)the Open Fund of State Key Laboratory of Biobased Fiber Manufacturing Technology(SKL202301)the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials(KF2314)。
文摘Hydrogel-based electronic skins or triboelectric nanogenerator(TENG)are considered ideal candidates for flexible electronics.However,current hydrogels face limitations that lead to suboptimal performance,and their reliance on external power sources hampers their practical application.A two-step washing approach comprising of“salt soaking”and“salt washing”is introduced to fabricate the multifunctional hydrogel.Initially,the hydrogel framework(SAC_(2)Z)-acrylamide(AM)and silk fibroin(SF)hydrogel is formed via salt soaking.Subsequently,the crosslinking degree is fine-tuned by adjusting the salt ion concentration through salt washing.The obtained hydrogel SAC_(2)ZC possesses excellent mechanical properties(a 15-fold increase in fracture strength to 320 kPa)and excellent cold resistance up to-80℃.Compared to conventional water-dispersible hydrogels,strain sensors based on SAC_(2)ZC are capable of sensing up to-30℃.The flexible antifreeze battery based on SAC_(2)ZC has excellent dendrite resistance and could supply power under high pressure(30 MPa)and severe bending(180°).The SAC_(2)ZC-based TENG(C-TENG)enables energy harvesting,eliminating reliance on external power sources.This innovation paves the way for flexible sensing systems that integrate energy collection and storage,facilitating all-weather human-smartphone signal interaction.This research provides a new strategy to develop multifunctional SAC_(2)ZC hydrogel for flexible wearable devices,especially in extremely cold complex environments.
基金Fundamental Research Funds for the Central Universities,Grant/Award Numbers:31020190QD010,3102019PY004,3102019JC004Ministry of Education-Singapore,Grant/Award Numbers:MOE2015-T2-2-043,MOE2017-T2-2-136,Tier 1 RG7/18+2 种基金National Natural Science Foundation of China,Grant/Award Number:11904289Natural Science Foundation of Shaanxi Province,Grant/Award Number:2019JQ-613Start-up funds from Northwestern Polytechnical University,Grant/Award Numbers:19SH020159,19SH020123。
文摘Two-dimensional(2D)materials have great potential in the fields of flexible electronics and photoelectronic devices due to their unique properties derived by special structures.The study of the mechanical properties of 2D materials plays an important role in next-generation flexible mechanical electronic device applications.Unfortunately,traditional experiment models and measurement methods are not suitable for 2D materials due to their atomically ultrathin thickness,which limits both the theoretical research and practical value of the 2D materials.In this review,we briefly summarize the characterization of mechanical properties of 2D materials by in situ probe nanoindentation experiments,and discuss the effect of thickness,grain boundary,and interlayer interactions.We introduce the strain-induced effect on electrical properties and optical properties of 2D materials.Then,we generalize the mechanical sensors based on various 2D materials and their future potential applications in flexible and wearable electronic devices.Finally,we discuss the state of the art for the mechanical properties of 2D materials and their opportunities and challenges in both basic research and practical applications.
基金the support of the Natural Science Foundation of Anhui Province(2108085QE226)Anhui Future Technology Research Institute Industry Guidance Fund Project(2023ccyd01)+1 种基金National Natural Science Foundation of China(No.12472257)National Key Research and Development Program of China Stem Cell and Translational Research(2022YFB4600600).
文摘The development of electronic skin,soft robots,and smart wearables has significantly driven advances in flexible pressure sensing technology.However,traditional multilayer solid-structure flexible pressure sensors encounter challenges at temperatures between 100°C and 150°C due to high-temperature modal distortion.Changes in the conductivity of the sensor’s conductive components interfere with accurate pressure measurement.In this research,a flexible pressure sensor with a convective liquid metal sensitive layer is proposed.The sensor uses a cyclic self-cooling mechanism to lower the temperature of its conductive components,reducing the impact of external high temperatures on the pressure measurement accuracy.At a 2.8 W thermal load,the flexible sensor,with liquid metal circulating at 2.0 mL/min,exhibits a sensitivity of 0.11 kPa⁻¹within the pressure range from 0 to 12.5 kPa,and its maximum measurable pressure is 30 kPa.In addition,the resistance of the sensor is 18.5 mΩless than that of a stationary liquid metal sensor,representing a 38.1%reduction.The sensor proposed in this research introduces a novel strategy for pressure measurement in high-temperature applications,extending the application scope to aircraft,special robots,and hydraulic oil circuits.
基金the National Natural Science Foundation of China(No.22008014)the Changzhou Young Scientific and Technological Talents Promotion Project,the Qing Lan Project of Jiangsu Province and China Scholarship Council(CSC).+1 种基金the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(20215710100170)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2023R1A2C200769911).
文摘Flexible humidity sensors are widely used in many fields,such as environmental monitoring,agricultural soil moisture content determination,food quality monitoring and healthcare services.Therefore,it is essential to measure humidity accurately and reliably in different conditions.Flexible materials have been the focusing substrates of humidity sensors because of their rich surface chemical properties and structural designability.In addition,flexible materials have superior ductility for different conditions.In this review,we have summarized several sensing mechanisms,processing techniques,sensing layers and substrates for specific humidity sensing requirements.Aadditionally,we have sorted out some cases of flexible humidity sensors based on different functional materials.We hope this paper can contribute to the development of flexible humidity sensors in the future.
基金supported by the National Natural Science Foundation of China(No.52204299)the Natural Science Foundation of Hunan Province(Nos.2022JJ40623 and 2022JJ30722)the Start-Up Funds for Outstanding Talents in Central South University(Nos.202045007 and 202044017).
文摘Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction interfaces.Among the various flexible sensor types,those with microstructure designs are considered promising for strain sensing due to their simple structure,high sensitivity,extensive operational range,rapid response time,and robust stability.This review provides a concise overview of recent advancements in flexible piezoresistive sensors based on microstructure design for enhanced strain sensing performance,including the impact of microstructure on sensing mechanisms,classification of microstructure designs,fabrication methods,and practical applications.Initially,this review delves into the analysis of piezoresistive sensor sensing mechanisms and performance parameters,exploring the relationship between microstructure design and performance enhancement.Subsequently,an in-depth discussion is presented,focusing on the primary themes of microstructure design classification,process selection,performance characteristics,and specific applications.This review employs mathematical modeling and hierarchical analysis to emphasize the directionality of different microstructures on performance enhancement and to highlight the performance advantages and applicable features of various microstructure types.In conclusion,this review examines the multifunctionality of flexible piezoresistive sensors based on microstructure design and addresses the challenges that still need to be overcome and improved,such as achieving a wide range of stretchability,high sensitivity,and robust stability.This review summarizes the research directions for enhancing sensing performance through microstructure design,aiming to assist in the advancement of flexible piezoresistive sensors.
基金supported by the National Natural Science Foundation of China(Grant No.52075119)。
文摘Flexible pressure sensors play an important role in the field of monitoring, owing to their inherent safety and the fact that they are embedded at the material level. Capacitive pressure sensors have been proven to be quite versatile, with the ability to change the sensitivity and monitoring range by modifying the pore structure of the dielectric layer(elastic modulus). In this paper, capacitive pressure sensors are devised, comprising hierarchical porous polydimethylsiloxane. Due to the inherent hollow and hierarchical micropore structure, the capacitive pressure sensor allows operation at a wider pressure range(~1000 kPa) while maintaining sensitivity(6.33 MPa-1) in the range of 0–300 k Pa. Subsequently, the capacitance output model of the sensor is optimized, which provides an overall approximation of the experimental values for the sensor performance. Additionally, the signal response of the“break up the whole into parts”(by analysis of the whole sensor in parts) is simulated and outputted by the finite element analysis. The simplified analysis model provides a good understanding of the relationship between the local pressure and the signal response of the pressure sensor. For practical applications, seal monitoring and rubber wheel pressure array system are tested, and the proposed sensor shows sufficient potential for application in large deformation elastomer products.
