With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted structures developed through natural s...With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted structures developed through natural selection, which inspired us for the design of biomimetic materials or devices. Particularl3 human fingertip skin, where many epidermal ridges amplify external stimulations, might be a good example to imitate for highly sensitive sensors. In this work, based on unique chemical vapor depositions （CVD）-grown three-dimensional （3D） graphene films that mimic the morphology of fingertip skin, we fabricated flexible pressure sensing membranes, which simultaneously showed a high sensitivity of 110 （kPa）-1 for 0-0.2 kPa and wide workable pressure range （up to 75 kPa）. Hierarchical structured polydimethylsiloxane （PDMS） films molded from natural leaves were used as the supporting elastic films for the graphene films, which also contribute to the superior performance of the pressure sensors. The pressure sensor showed a low detection limit （0.2 Pa）, fast response （〈 30 ms）, and excellent stability for more than 10,000 loading/unloading cycles. Based on these features, we demonstrated its applications in detecting tiny objects, sound, and human physiological signals, showing its potential in wearable electronics for health monitoring and human/machine interfaces.展开更多
A flexible 3D N-doped reduced graphene oxide(N-RGO)/carbon nanotube(CNT)eMnO_(2) hybrid film was constructed with outstanding supercapacitor,excellent oxygen reduction reaction(ORR)and good sensing performances.The re...A flexible 3D N-doped reduced graphene oxide(N-RGO)/carbon nanotube(CNT)eMnO_(2) hybrid film was constructed with outstanding supercapacitor,excellent oxygen reduction reaction(ORR)and good sensing performances.The resultant hybrid film possessed large specific capacitances of 418 F g^(-1) and 209 mF cm^(-2) in aqueous and solid electrolytes,and outstanding capacitance retentions of 95% and 94% were obtained for both electrolytes after experiencing 5000 cycles.A simple supercapacitor based on the resultant flexible hybrid film was further fabricated with a much smaller time constant τ0(0.38 s)than that of typical activated-carbon supercapacitors,suggesting a quick response frequency.Moreover,the assembled supercapacitor device showed high energy densities of 45.72 and 92.13 Wh kg^(-1) and simultaneously sustained large power densities of 12,526 and 15873 W kg^(-1) under a scan rate of 50 mV s^(-1) in aqueous and solid electrolytes,respectively.Furthermore,the resultant flexible film showed excellent performance in the ORR and can also be used to assemble a strain sensor with an excellent sensing performance for bending strain.展开更多
Wearable devices have great application potential in the next generation of smart portable electronics,especially in the fields of medical monitoring,soft robotics,artificial intelligence,and human-machine interfaces....Wearable devices have great application potential in the next generation of smart portable electronics,especially in the fields of medical monitoring,soft robotics,artificial intelligence,and human-machine interfaces.Piezoelectric flexible strain sensors are key components of wearable devices.However,existing piezoelectric flexible strain sensors have certain limitations in weak signal monitoring due to their large modulus and low sensitivity.To solve this problem,the concept of Kirigami(paper-cutting)was introduced in this study to design the sensor structure.By comparing the Kirigami structures of different basic structures,the serpentine structure was determined as the basic configuration of the sensor.The serpentine structure not only provides excellent tensile properties,but also significantly improves the sensitivity of the sensor,which performs well in monitoring weak signals.On this basis,the adhesion properties of the flexible sensor were analyzed and tested,and the optimal ratio of the substrate was selected for preparation.In addition,a low-cost and rapid prototyping process for stretchable patches was established in this study.Using this technology,we prepared the sensor device and tested its performance.Finally,we successfully developed a flexible sensor with a sensitivity of 0.128 mV/μɛand verified its feasibility for wrist joint motion monitoring applications.This result opens up new avenues for the recovery care of tenosynovitis patients after surgery.展开更多
A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates,which hinders the development of flexible electronics.Proposed here is an electron-cyclotron-...A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates,which hinders the development of flexible electronics.Proposed here is an electron-cyclotron-resonance sputtering system that can batch-fabricate devices directly on flexible substrates under a low temperature by virtue of the polariton energy transfer between the plasma and the material.Flexible graphene nanosheet-embedded carbon(F-GNEC)films are manufactured directly on polyimide,polyethylene terephthalate,and polydimethylsiloxane,and how the substrate bias(electron energy),microwave power(plasma flux and energy),and magnetic field(electron flux)affect the nanostructure of the F-GNEC films is investigated,indicating that electron energy and flux contribute to the formation of standing graphene nanosheets in the film.The films have good uniformity of distribution in a large size(17 mm×17 mm),and tensile and angle sensors with a high gauge factor(0.92)and fast response(50 ms)for a machine hand are obtained by virtue of the unique nanostructure of the F-GNEC film.This work sheds light on the quantum manufacturing of carbon sensors and its applications for intelligent machine hands and virtual-reality technology.展开更多
针对固体火箭发动机柔性接头组件室温粘接、加压固化成型工艺过程中存在的加压压力分布参数难以在线监测等问题,建立了采用薄膜压力传感器阵列的柔性接头成型压力测试系统,用于监测成型过程中柔性接头组件所受压力的大小和分布。研究了...针对固体火箭发动机柔性接头组件室温粘接、加压固化成型工艺过程中存在的加压压力分布参数难以在线监测等问题,建立了采用薄膜压力传感器阵列的柔性接头成型压力测试系统,用于监测成型过程中柔性接头组件所受压力的大小和分布。研究了压力测试系统在柔性接头成型工艺条件下的在线监测适用性,分析了柔性接头组件受压变化及结构误差的影响。结果表明,该研究建立的压力测试系统具有1%左右的测试线性度和10 k Hz以上的动态响应特性,能够有效测试1.5 MPa以下曲面压力场,最大压差为0.03 MPa,所测压力分布反映了成型过程中的变化,满足接头成型工艺测试要求。测试结果对于理解柔性接头成型工艺过程中的粘接剂流动等,为通过进一步优化工艺参数和减少结构误差、实现对柔性接头成型质量的有效控制有所帮助。展开更多
Hydrogen has been recently attracted much attention with respect to high energy-conversion efficiency and low environmental burden. However, hydrogen gas is dangerous due to an explosive gas and a fast combustion rate...Hydrogen has been recently attracted much attention with respect to high energy-conversion efficiency and low environmental burden. However, hydrogen gas is dangerous due to an explosive gas and a fast combustion rate. Therefore, the development of hydrogen sensor with high accuracy and reliability that can detect hydrogen easily is required. Especially, a flexible hydrogen sensor is useful because it has a high degree of freedom with respect to the shape of location in which the sensor is to be located. A flexible hydrogen sensor—namely, a WO3 thin film formed on a PET film by the sol-gel method using photo irradiation—based on gasochromism of WO3 was developed. By irradiating a thin film, which was prepared by using WO3 precursor solution synthesized by the sol-gel method, with ultraviolet rays, a high-purity WO3 film could be prepared on PET at low temperature. The sensor was structured as a polystyrene (PS) film containing palladium (Pd) laminated on a WO3 film. The WO3 layer was porous, so the PS containing Pd atoms solution penetrated the WO3 layer. WO3 reacted with hydrogen gas and instantly turned blue as the transmittance of the WO3 layer changed. The sensor showed high reactivity even for hydrogen concentration below 4% (1%, 0.5%, 0.25%, and 0.1%), which was the lower limit of hydrogen ignition, and a linear relationship between hydrogen concentration and change in transmittance was found. Moreover, the resistance of the WO3 film significantly and instantaneously changed due to hydrogen-gas exposure, and the hydrogen concentration and resistance change showed a linear relationship. It is therefore possible to quantitatively detect low concentrations of hydrogen by using changes in transmittance and resistance as indices. Since these changes occur selectively under hydrogen at room temperature and normal pressure, they form the basis of a highly sensitive hydrogen sensor. Since the developed sensor is flexible, it has a high degree of freedom with respect to the shape of location in which the sensor 展开更多
A novel instrument named Micro-Electro-Mechanical System(MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the...A novel instrument named Micro-Electro-Mechanical System(MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the mean sidewall shear stress distribution along the meandering channel, and the lateral boundary shear stress distribution in the typical cross-section of the meandering channel was analysed. Based on the measurement of the boundary shear stress, a semi-empirical semi-theoretical computing approach of the boundary shear stress was derived including the effects of the secondary flow, sidewall roughness factor, eddy viscosity and the additional Reynolds stress, and more importantly, for the first time, it combined the effects of the cross-section central angle and the Reynolds number into the expressions. Afterwards, a comparison between the previous research and this study was developed. Following the result, we found that the semi-empirical semi-theoretical boundary shear stress distribution algorithm can predict the boundary shear stress distribution precisely. Finally, a single factor analysis was conducted on the relationship between the average sidewall shear stress on the convex and concave bank and the flow rate, water depth, slope ratio,or the cross-section central angle of the open channel bend. The functional relationship with each of the above factors was established, and then the distance from the location of the extreme sidewall shear stress to the bottom of the open channel was deduced based on the statistical theory.展开更多
文摘With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted structures developed through natural selection, which inspired us for the design of biomimetic materials or devices. Particularl3 human fingertip skin, where many epidermal ridges amplify external stimulations, might be a good example to imitate for highly sensitive sensors. In this work, based on unique chemical vapor depositions （CVD）-grown three-dimensional （3D） graphene films that mimic the morphology of fingertip skin, we fabricated flexible pressure sensing membranes, which simultaneously showed a high sensitivity of 110 （kPa）-1 for 0-0.2 kPa and wide workable pressure range （up to 75 kPa）. Hierarchical structured polydimethylsiloxane （PDMS） films molded from natural leaves were used as the supporting elastic films for the graphene films, which also contribute to the superior performance of the pressure sensors. The pressure sensor showed a low detection limit （0.2 Pa）, fast response （〈 30 ms）, and excellent stability for more than 10,000 loading/unloading cycles. Based on these features, we demonstrated its applications in detecting tiny objects, sound, and human physiological signals, showing its potential in wearable electronics for health monitoring and human/machine interfaces.
基金supported by the fund of the China Postdoctoral Science Foundation(2019M653853XB)State Key Laboratory of Solidification Processing in NWPU(SKLSP201815)+4 种基金Opening Project of Guangxi Key Laboratory of Clean Pulp&Papermaking and Pollution Control(2019KF21)Natural science advance research foundation of Shaanxi University of Science and Technology(2018QNBJ-03)National Demonstration Center for Experimental Light Chemistry Engineering Education(Shaanxi University of Science&Technology)High-level Foreign Experts Project(GDT20186100425)and Biomass Chemistry and Materials Academician Workstation Project in SUST(134090002).
文摘A flexible 3D N-doped reduced graphene oxide(N-RGO)/carbon nanotube(CNT)eMnO_(2) hybrid film was constructed with outstanding supercapacitor,excellent oxygen reduction reaction(ORR)and good sensing performances.The resultant hybrid film possessed large specific capacitances of 418 F g^(-1) and 209 mF cm^(-2) in aqueous and solid electrolytes,and outstanding capacitance retentions of 95% and 94% were obtained for both electrolytes after experiencing 5000 cycles.A simple supercapacitor based on the resultant flexible hybrid film was further fabricated with a much smaller time constant τ0(0.38 s)than that of typical activated-carbon supercapacitors,suggesting a quick response frequency.Moreover,the assembled supercapacitor device showed high energy densities of 45.72 and 92.13 Wh kg^(-1) and simultaneously sustained large power densities of 12,526 and 15873 W kg^(-1) under a scan rate of 50 mV s^(-1) in aqueous and solid electrolytes,respectively.Furthermore,the resultant flexible film showed excellent performance in the ORR and can also be used to assemble a strain sensor with an excellent sensing performance for bending strain.
基金supported by National Natural Science Foundation of China(Nos.62301509,62304209)Key Research and Development Program of Shanxi Province(No.202302030201001)Fundamental Research Program of Shanxi Province(Nos.202203021222079,0210302123203,202103021223185).
文摘Wearable devices have great application potential in the next generation of smart portable electronics,especially in the fields of medical monitoring,soft robotics,artificial intelligence,and human-machine interfaces.Piezoelectric flexible strain sensors are key components of wearable devices.However,existing piezoelectric flexible strain sensors have certain limitations in weak signal monitoring due to their large modulus and low sensitivity.To solve this problem,the concept of Kirigami(paper-cutting)was introduced in this study to design the sensor structure.By comparing the Kirigami structures of different basic structures,the serpentine structure was determined as the basic configuration of the sensor.The serpentine structure not only provides excellent tensile properties,but also significantly improves the sensitivity of the sensor,which performs well in monitoring weak signals.On this basis,the adhesion properties of the flexible sensor were analyzed and tested,and the optimal ratio of the substrate was selected for preparation.In addition,a low-cost and rapid prototyping process for stretchable patches was established in this study.Using this technology,we prepared the sensor device and tested its performance.Finally,we successfully developed a flexible sensor with a sensitivity of 0.128 mV/μɛand verified its feasibility for wrist joint motion monitoring applications.This result opens up new avenues for the recovery care of tenosynovitis patients after surgery.
基金support of the National Natural Science Foundation of China(Grant Nos.52275565,NSFC-JSPS:52011540005,and 62104155)the Natural Science Foundation of Guangdong Province(Grant No.2022A1515011667)the Guangdong Kangyi Special Fund(Grant No.2020KZDZX1173).
文摘A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates,which hinders the development of flexible electronics.Proposed here is an electron-cyclotron-resonance sputtering system that can batch-fabricate devices directly on flexible substrates under a low temperature by virtue of the polariton energy transfer between the plasma and the material.Flexible graphene nanosheet-embedded carbon(F-GNEC)films are manufactured directly on polyimide,polyethylene terephthalate,and polydimethylsiloxane,and how the substrate bias(electron energy),microwave power(plasma flux and energy),and magnetic field(electron flux)affect the nanostructure of the F-GNEC films is investigated,indicating that electron energy and flux contribute to the formation of standing graphene nanosheets in the film.The films have good uniformity of distribution in a large size(17 mm×17 mm),and tensile and angle sensors with a high gauge factor(0.92)and fast response(50 ms)for a machine hand are obtained by virtue of the unique nanostructure of the F-GNEC film.This work sheds light on the quantum manufacturing of carbon sensors and its applications for intelligent machine hands and virtual-reality technology.
文摘针对固体火箭发动机柔性接头组件室温粘接、加压固化成型工艺过程中存在的加压压力分布参数难以在线监测等问题,建立了采用薄膜压力传感器阵列的柔性接头成型压力测试系统,用于监测成型过程中柔性接头组件所受压力的大小和分布。研究了压力测试系统在柔性接头成型工艺条件下的在线监测适用性,分析了柔性接头组件受压变化及结构误差的影响。结果表明,该研究建立的压力测试系统具有1%左右的测试线性度和10 k Hz以上的动态响应特性,能够有效测试1.5 MPa以下曲面压力场,最大压差为0.03 MPa,所测压力分布反映了成型过程中的变化,满足接头成型工艺测试要求。测试结果对于理解柔性接头成型工艺过程中的粘接剂流动等,为通过进一步优化工艺参数和减少结构误差、实现对柔性接头成型质量的有效控制有所帮助。
文摘Hydrogen has been recently attracted much attention with respect to high energy-conversion efficiency and low environmental burden. However, hydrogen gas is dangerous due to an explosive gas and a fast combustion rate. Therefore, the development of hydrogen sensor with high accuracy and reliability that can detect hydrogen easily is required. Especially, a flexible hydrogen sensor is useful because it has a high degree of freedom with respect to the shape of location in which the sensor is to be located. A flexible hydrogen sensor—namely, a WO3 thin film formed on a PET film by the sol-gel method using photo irradiation—based on gasochromism of WO3 was developed. By irradiating a thin film, which was prepared by using WO3 precursor solution synthesized by the sol-gel method, with ultraviolet rays, a high-purity WO3 film could be prepared on PET at low temperature. The sensor was structured as a polystyrene (PS) film containing palladium (Pd) laminated on a WO3 film. The WO3 layer was porous, so the PS containing Pd atoms solution penetrated the WO3 layer. WO3 reacted with hydrogen gas and instantly turned blue as the transmittance of the WO3 layer changed. The sensor showed high reactivity even for hydrogen concentration below 4% (1%, 0.5%, 0.25%, and 0.1%), which was the lower limit of hydrogen ignition, and a linear relationship between hydrogen concentration and change in transmittance was found. Moreover, the resistance of the WO3 film significantly and instantaneously changed due to hydrogen-gas exposure, and the hydrogen concentration and resistance change showed a linear relationship. It is therefore possible to quantitatively detect low concentrations of hydrogen by using changes in transmittance and resistance as indices. Since these changes occur selectively under hydrogen at room temperature and normal pressure, they form the basis of a highly sensitive hydrogen sensor. Since the developed sensor is flexible, it has a high degree of freedom with respect to the shape of location in which the sensor
基金financially supported by the National Key R&D Program of China(Grant No.2016YFC0402306)the National Natural Science Foundation of China(Grant No.51779149)
文摘A novel instrument named Micro-Electro-Mechanical System(MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the mean sidewall shear stress distribution along the meandering channel, and the lateral boundary shear stress distribution in the typical cross-section of the meandering channel was analysed. Based on the measurement of the boundary shear stress, a semi-empirical semi-theoretical computing approach of the boundary shear stress was derived including the effects of the secondary flow, sidewall roughness factor, eddy viscosity and the additional Reynolds stress, and more importantly, for the first time, it combined the effects of the cross-section central angle and the Reynolds number into the expressions. Afterwards, a comparison between the previous research and this study was developed. Following the result, we found that the semi-empirical semi-theoretical boundary shear stress distribution algorithm can predict the boundary shear stress distribution precisely. Finally, a single factor analysis was conducted on the relationship between the average sidewall shear stress on the convex and concave bank and the flow rate, water depth, slope ratio,or the cross-section central angle of the open channel bend. The functional relationship with each of the above factors was established, and then the distance from the location of the extreme sidewall shear stress to the bottom of the open channel was deduced based on the statistical theory.
