This paper aims to reveal the multi-optimal mechanisms for dynamic control in drag- onfly wings. By combining the Arnold circulation with such micro/nano structures as the hollow inside constructions of the pterostigm...This paper aims to reveal the multi-optimal mechanisms for dynamic control in drag- onfly wings. By combining the Arnold circulation with such micro/nano structures as the hollow inside constructions of the pterostigma, veins and spikes, dragonfly wings can create variable mass, variable rotating inertia and variable natural frequency. This marvelous ability enables dragonflies to overcome the contradictory requirements of both light-weight-wing and heavy-weight-wing, and displays the multi-optimal mechanisms for the excellent flying ability and dynamic control capac- ity of dragonflies. These results provide new perspectives for understanding the wings＇ functions and new inspirations for bionic manufactures.展开更多
Nowadays, the importance of identifying the flight mechanisms of the dragonfly, as an inspiration for designing flapping wing vehicles, is well known. An experimental approach to understanding the complexities of inse...Nowadays, the importance of identifying the flight mechanisms of the dragonfly, as an inspiration for designing flapping wing vehicles, is well known. An experimental approach to understanding the complexities of insect wings as organs of flight could provide significant outcomes for design purposes. In this paper, a comprehensive investigation is carried out on the morphological and microstructural features of dragonfly wings. Scanning electron microscopy （SEM） and tensile testing are used to experimentally verify the functional roles of different parts of the wings. A number of SEM images of the elements of the wings, such as the nodus, leading edge, trailing edge, and vein sections, which play dominant roles in strengthening the whole structure, are presented. The results from the tensile tests indicate that the nodus might be the critical region of the wing that is subjected to high tensile stresses. Considering the patterns of the longitudinal corrugations of the wings obtained in this paper, it can be supposed that they increase the load-bearing capacity, giving the wings an ability to tolerate dynamic loading conditions. In addition, it is suggested that the longitudinal veins, along with the leading and trailing edges, are structural mechanisms that further improve fatigue resistance by providing higher fracture toughness, preventing crack propagation, and allowing the wings to sustain a significant amount of damage without loss of strength.展开更多
Dragonfly is one of the most excellent nature flyers,and its wings exhibit excellent functional characteristics through the coupling and synergy of morphology,configuration,structure and material.The functional charac...Dragonfly is one of the most excellent nature flyers,and its wings exhibit excellent functional characteristics through the coupling and synergy of morphology,configuration,structure and material.The functional characteristics presented by dragonfly wings provide an biological inspiration for the investigation and development of aerospace vehicles and bionics flapping aerocraft flapping-wing micro air vehicles.In resent years,some progresses have been achieved in the researches on the wings' geometric structure,material characteristics,flying mechanism and the controlling mode.In this paper,the functional characteristics of the dragonfly wings including flying,self-cleaning,anti-fatigue,vibration elimination and noise reduction are introduced and the effects of their morphology,configuration,structure and material on the functional characteristics are described.Moreover,the current state of the bionic study on the functional characteristics of dragonfly wings is analyzed and its application prospect is depicted.展开更多
To reveal the resonance suppression mechanism of the blood circulation in dragonfly wings,a numerical modeling method of dragonfly wings based on Voronoi diagrams is proposed,and the changes in mass,aerodynamic dampin...To reveal the resonance suppression mechanism of the blood circulation in dragonfly wings,a numerical modeling method of dragonfly wings based on Voronoi diagrams is proposed,and the changes in mass,aerodynamic damping,and natural frequencies caused by blood circulation in veins are investigated.The equivalent mass of blood,boundary conditions,and aerodynamic damping are calculated theoretically.Modal analysis and harmonic response analysis of wing models with different blood circulation paths are performed using the finite-element method(FEM).The vibration reduction ratioδis introduced to compare the damping efficiency of different mass regions.Finally,a natural frequency testing device is constructed to measure the natural frequencies of dragonfly wings.The results indicate that the shape,mass,and natural frequencies of the dragonfly wing model constructed by numerical method agree well with reality.The mass distribution on the wing can be altered by blood circulation,thereby adjusting the natural frequencies and achieving resonance suppression.The highestδof 1.013 is observed in the C region when blood circulates solely in secondary veins,but it is still lower than theδof 1.017 when blood circulates in complete veins.The aerodynamic damping ratio(1.19–1.79%)should not be neglected in the vibration analysis of the beating wing.展开更多
Aiming at exploring the excellent structural performance of the vein-stiffening membrane structure of dragonfly hind wings,we analyzed two planar computational models and three 3D computational models with cambered co...Aiming at exploring the excellent structural performance of the vein-stiffening membrane structure of dragonfly hind wings,we analyzed two planar computational models and three 3D computational models with cambered corrugation based on the finite element method.It is shown that the vein size in different zones is proportional to the magnitude of the vein internal force when the wing structure is subjected to uniform out-of-plane transverse loading.The membrane contributes little to the flexural stiffness of the planar wing models,while exerting an immense impact upon the stiffness of the 3D wing models with cambered corrugation.If a lumped mass of 10% of the wing is fixed on the leading edge close to the wing tip,the wing fundamental fre-quency decreases by 10.7%～13.2%;if a lumped mass is connected to the wing via multiple springs,the wing fundamental fre-quency decreases by 16.0%～18.0%.Such decrease in fundamental frequency explains the special function of the wing pterostigma in alleviating the wing quivering effect.These particular features of dragonfly wings can be mimicked in the design of new-style reticulately stiffening thin-walled roof systems and flapping wings in novel intelligent aerial vehicles.展开更多
Noble metal nanorough surfaces that support strong surface-enhanced Raman scattering （SERS） is widely applied in the practical detection of organic molecules. A low-cost, large-area, and environment-friendly SERS-ac...Noble metal nanorough surfaces that support strong surface-enhanced Raman scattering （SERS） is widely applied in the practical detection of organic molecules. A low-cost, large-area, and environment-friendly SERS-active substrate was acquired by sputtering inexpensive copper （Cu） on natural dragonfly wing （DW） with an easily controlled way of magnetron sputtering. By controlling the sputtering time of the fabrication of Cu on the DW, the performance of the SERS substrates was greatly improved. The SERS-active substrates, obtained at the optimal sputtering time （50 min）, showed a low detection limit （10-6M ） to 4-aminothiophenol （4-ATP）, a high average enhancement factor （EF, 1.98 x10^4）, excellent signal uniformity, and good reproducibility. In addition, the results of the 3D finite-difference time-domain （3D- FDTD） simulation illustrated that the SERS-active substrates provided high-density ＂hot spots＂, leading to a large SERS enhancement.展开更多
The ability of dragonflies to fly in the rain without being wetted by raindrops has motivated researchers to investigate the impact behavior of a drop on the superhydrophobic wings of dragonflies.This superhydrophobic...The ability of dragonflies to fly in the rain without being wetted by raindrops has motivated researchers to investigate the impact behavior of a drop on the superhydrophobic wings of dragonflies.This superhydrophobic surface is used as a reference for the design of directional surfaces and has attracted extensive attention owing to its wide applicability in microfluidics,self-cleaning,and other fields.In this study,the static contact angle and rebound process of a drop impacting a dragonfly wing surface are investigated experimentally,whereas the wetting pressure,Gibbs free energy,and Stokes number vs.coefficient of restitution are theoretically calculated to examine the dynamic and unidirectional transport behaviors of the drop.Results show that the initial inclination angle of the dragonfly wing is similar to the sliding angles along with the drop sliding.The water drop bounces from the bottom of the dragonfly wing to the distal position,demonstrating directional migration.The drop impacts the dragonfly wing surface,and the drop exhibits compression,recovery,and separation phases;in these three phases,the drop morphology evolves.As the Gibbs free energy and cross-sectional area evolve,the coefficient of restitution decreases as the drop continues to bounce,and the Stokes number increases.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 11102138 and 11272175)the Fundamental Research Funds for the Central Universities
文摘This paper aims to reveal the multi-optimal mechanisms for dynamic control in drag- onfly wings. By combining the Arnold circulation with such micro/nano structures as the hollow inside constructions of the pterostigma, veins and spikes, dragonfly wings can create variable mass, variable rotating inertia and variable natural frequency. This marvelous ability enables dragonflies to overcome the contradictory requirements of both light-weight-wing and heavy-weight-wing, and displays the multi-optimal mechanisms for the excellent flying ability and dynamic control capac- ity of dragonflies. These results provide new perspectives for understanding the wings＇ functions and new inspirations for bionic manufactures.
文摘Nowadays, the importance of identifying the flight mechanisms of the dragonfly, as an inspiration for designing flapping wing vehicles, is well known. An experimental approach to understanding the complexities of insect wings as organs of flight could provide significant outcomes for design purposes. In this paper, a comprehensive investigation is carried out on the morphological and microstructural features of dragonfly wings. Scanning electron microscopy （SEM） and tensile testing are used to experimentally verify the functional roles of different parts of the wings. A number of SEM images of the elements of the wings, such as the nodus, leading edge, trailing edge, and vein sections, which play dominant roles in strengthening the whole structure, are presented. The results from the tensile tests indicate that the nodus might be the critical region of the wing that is subjected to high tensile stresses. Considering the patterns of the longitudinal corrugations of the wings obtained in this paper, it can be supposed that they increase the load-bearing capacity, giving the wings an ability to tolerate dynamic loading conditions. In addition, it is suggested that the longitudinal veins, along with the leading and trailing edges, are structural mechanisms that further improve fatigue resistance by providing higher fracture toughness, preventing crack propagation, and allowing the wings to sustain a significant amount of damage without loss of strength.
基金supported by the National Natural Science Foundation of China (Major Project of International Cooperation) (Grant No.50920105504)the National Natural Science Fundation for Youths (GrantNos. 51005097 and 51205160)+1 种基金the Science and Technology Development Project of Jilin Province (Grant No. 201201025)the Fundamental Science Research Funds for Key Laboratory of Ministry Education (GrantNo. 450060326061)
文摘Dragonfly is one of the most excellent nature flyers,and its wings exhibit excellent functional characteristics through the coupling and synergy of morphology,configuration,structure and material.The functional characteristics presented by dragonfly wings provide an biological inspiration for the investigation and development of aerospace vehicles and bionics flapping aerocraft flapping-wing micro air vehicles.In resent years,some progresses have been achieved in the researches on the wings' geometric structure,material characteristics,flying mechanism and the controlling mode.In this paper,the functional characteristics of the dragonfly wings including flying,self-cleaning,anti-fatigue,vibration elimination and noise reduction are introduced and the effects of their morphology,configuration,structure and material on the functional characteristics are described.Moreover,the current state of the bionic study on the functional characteristics of dragonfly wings is analyzed and its application prospect is depicted.
基金sponsored by the Shandong Natural Science Foundation of the People's Republic of China(No.ZR2022ME213,ZR2023ME081).
文摘To reveal the resonance suppression mechanism of the blood circulation in dragonfly wings,a numerical modeling method of dragonfly wings based on Voronoi diagrams is proposed,and the changes in mass,aerodynamic damping,and natural frequencies caused by blood circulation in veins are investigated.The equivalent mass of blood,boundary conditions,and aerodynamic damping are calculated theoretically.Modal analysis and harmonic response analysis of wing models with different blood circulation paths are performed using the finite-element method(FEM).The vibration reduction ratioδis introduced to compare the damping efficiency of different mass regions.Finally,a natural frequency testing device is constructed to measure the natural frequencies of dragonfly wings.The results indicate that the shape,mass,and natural frequencies of the dragonfly wing model constructed by numerical method agree well with reality.The mass distribution on the wing can be altered by blood circulation,thereby adjusting the natural frequencies and achieving resonance suppression.The highestδof 1.013 is observed in the C region when blood circulates solely in secondary veins,but it is still lower than theδof 1.017 when blood circulates in complete veins.The aerodynamic damping ratio(1.19–1.79%)should not be neglected in the vibration analysis of the beating wing.
基金Project supported by the National Natural Science Foundation of China(No. 50408022)the Visiting Scholarship from the Future Academic Star Project of Zhejiang Universitythe Scientific Research Foundation for the Returned Overseas Chinese Scholars,MOE and Zhejiang Province,China
文摘Aiming at exploring the excellent structural performance of the vein-stiffening membrane structure of dragonfly hind wings,we analyzed two planar computational models and three 3D computational models with cambered corrugation based on the finite element method.It is shown that the vein size in different zones is proportional to the magnitude of the vein internal force when the wing structure is subjected to uniform out-of-plane transverse loading.The membrane contributes little to the flexural stiffness of the planar wing models,while exerting an immense impact upon the stiffness of the 3D wing models with cambered corrugation.If a lumped mass of 10% of the wing is fixed on the leading edge close to the wing tip,the wing fundamental fre-quency decreases by 10.7%～13.2%;if a lumped mass is connected to the wing via multiple springs,the wing fundamental fre-quency decreases by 16.0%～18.0%.Such decrease in fundamental frequency explains the special function of the wing pterostigma in alleviating the wing quivering effect.These particular features of dragonfly wings can be mimicked in the design of new-style reticulately stiffening thin-walled roof systems and flapping wings in novel intelligent aerial vehicles.
基金Project supported by the Youth Fund Project of University Science and Technology Plan of Hebei Provincial Department of Education,China(Grant No.QN2015004)the Doctoral Fund of Yanshan University,China(Grant No.B924)
文摘Noble metal nanorough surfaces that support strong surface-enhanced Raman scattering （SERS） is widely applied in the practical detection of organic molecules. A low-cost, large-area, and environment-friendly SERS-active substrate was acquired by sputtering inexpensive copper （Cu） on natural dragonfly wing （DW） with an easily controlled way of magnetron sputtering. By controlling the sputtering time of the fabrication of Cu on the DW, the performance of the SERS substrates was greatly improved. The SERS-active substrates, obtained at the optimal sputtering time （50 min）, showed a low detection limit （10-6M ） to 4-aminothiophenol （4-ATP）, a high average enhancement factor （EF, 1.98 x10^4）, excellent signal uniformity, and good reproducibility. In addition, the results of the 3D finite-difference time-domain （3D- FDTD） simulation illustrated that the SERS-active substrates provided high-density ＂hot spots＂, leading to a large SERS enhancement.
基金supported by the Fundamental Research Funds for the National Natural Science Foundation of China(No.52275182)Provincial Universities of Zhejiang,China(No.GK229909299001-14).
文摘The ability of dragonflies to fly in the rain without being wetted by raindrops has motivated researchers to investigate the impact behavior of a drop on the superhydrophobic wings of dragonflies.This superhydrophobic surface is used as a reference for the design of directional surfaces and has attracted extensive attention owing to its wide applicability in microfluidics,self-cleaning,and other fields.In this study,the static contact angle and rebound process of a drop impacting a dragonfly wing surface are investigated experimentally,whereas the wetting pressure,Gibbs free energy,and Stokes number vs.coefficient of restitution are theoretically calculated to examine the dynamic and unidirectional transport behaviors of the drop.Results show that the initial inclination angle of the dragonfly wing is similar to the sliding angles along with the drop sliding.The water drop bounces from the bottom of the dragonfly wing to the distal position,demonstrating directional migration.The drop impacts the dragonfly wing surface,and the drop exhibits compression,recovery,and separation phases;in these three phases,the drop morphology evolves.As the Gibbs free energy and cross-sectional area evolve,the coefficient of restitution decreases as the drop continues to bounce,and the Stokes number increases.
