It is well known that shark skin surface can effectively inhabit the occurrence of turbulence and reduce the wall friction, but in order to understand the mechanism of drag reduction, one has to solve the problem of t...It is well known that shark skin surface can effectively inhabit the occurrence of turbulence and reduce the wall friction, but in order to understand the mechanism of drag reduction, one has to solve the problem of the turbulent flow on grooved-scale surface, and in that respect, the direct numerical simulation is an important tool. In this article, based on the real biological shark skin, the model of real shark skin is built through high-accurate scanning and data processing. The turbulent flow on a real shark skin is comprehensively simulated, and based on the simulation, the drag reduction mechanism is discussed. In addition, in order to validate the drag-reducing effect of shark skin surface, actual experiments were carried out in water tunnel, and the experimental results are approximately consistent with the numerical simulation.展开更多
Plant of carnivorous genus Nepenthes alata has evolved specific pitchers to prey insects for survival in the barren habitat, especially its slippery zone. The excellent slippery function has received considerable inte...Plant of carnivorous genus Nepenthes alata has evolved specific pitchers to prey insects for survival in the barren habitat, especially its slippery zone. The excellent slippery function has received considerable interest because of its potential applica- tion in antifriction surface design. The surface morphologies of intact and de-waxed slippery zones were characterized using scanning electron microscope and scanning white-light interferometer. Hierarchical structures with anisotropic micro- lunate structure and nano- wax crystals were found on the slippery zone. Due to the hierarchical structures, the slippery zone is hy- drophobic. It shows a significant anisotropic wettability with static contact angles 153.3° and 140.1° in the directions perpen- dicular and parallel to the upward direction （toward the peristome）, respectively. The sliding angles are -3° and -10° in the downward and upward directions, respectively. Crawling experiments indicate that the microscopic surface roughness and the brittleness of the wax crystals may reduce insect attachment in different modes according to the insect mass differences. Moreover, artificial slippery surfaces inspired by the slippery zone of Nepenthes alata were fabricated. Traction experiments quantitatively verified that the friction force of replicated lunate structures with Ra-2.54 μm surface roughness was reduced by about 25% as compared to flat surface with Ra-0.56 μm surface roughness for cricket claws.展开更多
Birds have gradually formed various excellent structures such as streamlined shape and hollow shaft of feather to improve their flying performance by millions of years of natural selection. As typical property of bird...Birds have gradually formed various excellent structures such as streamlined shape and hollow shaft of feather to improve their flying performance by millions of years of natural selection. As typical property of bird feather, herringbone riblets align along the shaft of each feather, which is caused by perfect link of barbs, especially for the primary and secondary feathers of wings. Such herringbone riblets of feather are assumed to have great impact on drag reduction. In this paper, microstructures of secondary feathers of adult pigeons are investigated by SEM, and their structural parameters are statistically obtained. Based on quantitative analysis of feather structure, novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 16%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.展开更多
Direct replication of creatural scarfskins to form biomimetic surfaces with relatively vivid morphology is a new attempt of the bio-replicated forming technology at animal body. Taking shark skins as the replication t...Direct replication of creatural scarfskins to form biomimetic surfaces with relatively vivid morphology is a new attempt of the bio-replicated forming technology at animal body. Taking shark skins as the replication templates, and the micro-embossing and micro-molding as the material forming methods, the micro-replicating technology of the outward morphology on shark skins was demonstrated. The preliminary analysis on replication precision indicates that the bio-replicated forming technology can replicate the outward morphology of the shark scales with good precision, which validates the application of the bio-replicated forming technology in the direct morphology replication of the firm creatural scarfskins.展开更多
Learning from nature has traditionally and continuously provided important insights to drive a paradigm shift in technology.In particular,recent studies show that many biological organisms exhibit spectacular surface ...Learning from nature has traditionally and continuously provided important insights to drive a paradigm shift in technology.In particular,recent studies show that many biological organisms exhibit spectacular surface topography such as shape,size,spatial organization,periodicity,interconnectivity,and hierarchy to endow them with the capability to adapt dynamically and responsively to a wide range of environments.More excitingly,in a broader perspective,these normally neglected topological features have the potential to fundamentally change the way of how engineering surface works,such as how fluid flows,how heat is transported,and how energy is generated,saved,and converted,to name a few.Thus,the design of nature-inspired surface topography for unique functions will spur new thinking and provide paradigm shift in the development of the new engineering surfaces.In this review,we first present a brief introduction to some insights extracted from nature.Then,we highlight recent progress in designing new surface topographies and demonstrate their applications in emerging areas including thermal-fluid transport,anti-icing,water harvesting,power generation,adhesive control,and soft robotics.Finally,we offer our perspectives on this emerging field,with the aim to stimulate new thinking on the development of next-generation of new materials and devices,and dramatically extend the boundaries of traditional engineering.展开更多
背景:股骨头坏死出现新月征是病情进程的“分水岭”,修复和稳定骨-软骨界面对阻止病情继续进展和预防股骨头塌陷尤为重要。利用组织工程学同步修复、整合骨-软骨界面具有潜在优势。目的:综述探讨解决股骨头坏死软骨下分离的潜在适宜技...背景:股骨头坏死出现新月征是病情进程的“分水岭”,修复和稳定骨-软骨界面对阻止病情继续进展和预防股骨头塌陷尤为重要。利用组织工程学同步修复、整合骨-软骨界面具有潜在优势。目的:综述探讨解决股骨头坏死软骨下分离的潜在适宜技术。方法:检索1970年1月至2023年4月PubMed、Web of Science及中国知网、万方数据库中发表的相关文献,英文检索词:“Femoral head necrosis,Avascular necrosis of femoral head,Osteonecrosis of femoral head”等,中文检索词:“股骨头坏死,软骨下骨,软骨,软骨与软骨下骨整合”等,最终纳入114篇文献进行综述分析。结果与结论:①结构缺陷、缺血缺氧环境、炎症因素和应力集中可能造成股骨头坏死软骨下分离现象,软骨下骨分离会造成塌陷进展,并且可能与保髋手术失败相关,利用组织工程支架实现支架与骨-软骨界面的整合是治疗股骨头坏死软骨下分离的潜在方法之一。②目前的文献研究表明,多相、梯度支架和复合材料在促进骨、软骨细胞黏附与增殖,骨软骨基质的沉积方面均有提升,有助于支架与骨-软骨界面的整合,对治疗股骨头坏死软骨下分离有参考价值。③通过对支架表面进行修饰可以提高与界面整合的效率,但有各自不同的优缺点,提供不同环境的支架能够诱导同种间充质干细胞差异分化,有助于不同界面之间的整合。④未来有望应用于股骨头坏死软骨下分离的支架应为复合材料,具有梯度化和差异化的仿生结构,通过表面修饰和干细胞加载促进骨-软骨界面与支架的整合以实现治疗目的,但仍需进一步研究验证,而支架的降解速率与修复进度同步和不同界面之间的稳定性是未来需要解决的主要问题。展开更多
Superhydrophobic surfaces are often found in nature, such as plant leaves and insect wings. Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves, biomimetic hydrophnbic surfaces with high or...Superhydrophobic surfaces are often found in nature, such as plant leaves and insect wings. Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves, biomimetic hydrophnbic surfaces with high or low adhesion were prepared with a facile drop-coating approach in this paper. Poly（vinyl alcohol） （PVA） was used as adhesive and SiO2 nanoparticles were used to fabricate surface micro-structure. Stearic acid or dodecafluoroheptyl-propyl-trimethoxysilane （DFTMS） were used as low surface energy materials to modify the prepared PVA/SiO2 coating surfaces. The effects of size of SiO2 nanoparticles, concentration of SiO2 nanoparticle suspensions and the modifications on the wettability of the surface were investigated. The morphology of the PVA/SiO2 coating surfaces was observed by using scanning electron microscope. Water contact angle of the obtained superhydrophilic surface could reach to 3°. Stearic acid modified PVA/SiO2 coating surfaces showed hydrophobicity with high adhesion. By mixing the SiO2 nanoparticles with sizes of 40 nm and 200 nm and modifying with DFTMS, water contact angle of the obtained coating surface could be up to 155° and slide angle was only 5°. This work provides a facile and useful method to control surface wettability through changing the roughness and chemical composition of a surface.展开更多
Biomimetic surface is an effective ways to promote the performance grade and applied range of materials without alteringtheir substrate.Many improved properties such as resisting fatigue,enduring wear,etc,have been ac...Biomimetic surface is an effective ways to promote the performance grade and applied range of materials without alteringtheir substrate.Many improved properties such as resisting fatigue,enduring wear,etc,have been achieved by applyingbiomimetic morphology or structure to some engineering material surfaces.In this paper,aiming to reveal the relationshipbetween thermal cracking behavior and mechanical properties of engineering materials with biomimetic surface,biomimeticspecimens were fabricated using laser technique by imitating the heterogeneous structure on the surface of plant leaves.Theeffect of thermal fatigue cycling on the tensile properties of H13 die steel specimens with different surfaces (several types ofbiomimetic surfaces and a smooth surface) was compared and investigated.As a result,due to the coupling effects of themorphological features on the surface and the microstructure characteristics within unit zone,these specimens with biomimeticsurface exhibit remarkably enhanced Ultimate Tensile Strength (UTS) and 0.2% Yield Strength (YS) compared with referencespecimens while corresponding ductility remains largely unaffected even heightened,whether the thermal fatigue loads or not.The relative mechanisms leading to these improvements have been discussed.展开更多
Wedge-shaped microstructures have the ability to reproduce the excellent adhesive properties of geckos’feet because of their unique anisotropic structure.In particular,the controllability of the wedge-shaped microstr...Wedge-shaped microstructures have the ability to reproduce the excellent adhesive properties of geckos’feet because of their unique anisotropic structure.In particular,the controllability of the wedge-shaped microstructures on adhesion is beneficial to the undisturbed grasp or the capture of space targets.However,the problem currently remains of how to process it efficiently and with high quality.Here a strategy called ultraprecision multistep and layered scribing is proposed for the manufacture of the biomimetic controllable adhesive surface.The results show that the metal master mold prepared based on the manufacturing strategy has not only good surface topography but also high reliability and durability.Furthermore,the controllable adhesive surface of 1.96 cm2,fabricated by the proposed manufacturing strategy,has a normal adhesion of 1.012 N,and the corresponding shear friction and adhesion coefficient are 3.105 N and 4.82,respectively.Additionally,the controllable adhesive surface has been shown to be approximately superhydrophobic and also to possess the properties of controllable adhesion and dynamic adhesion.Also,after 250 adhesion-detachment cycles,the normal adhesion and shear friction only decrease by 5%and 3%,respectively.The research realizes an environmentally friendly and efficient method by which to manufacture a durable metal mold for fabricating a biomimetic controllable adhesive surface,laying a foundation for its effective application in the adherence of space-floating targets.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 50775006)the National High Technology Research and Development Program of China (863 Program, Grant No. 2009AA043802)
文摘It is well known that shark skin surface can effectively inhabit the occurrence of turbulence and reduce the wall friction, but in order to understand the mechanism of drag reduction, one has to solve the problem of the turbulent flow on grooved-scale surface, and in that respect, the direct numerical simulation is an important tool. In this article, based on the real biological shark skin, the model of real shark skin is built through high-accurate scanning and data processing. The turbulent flow on a real shark skin is comprehensively simulated, and based on the simulation, the drag reduction mechanism is discussed. In addition, in order to validate the drag-reducing effect of shark skin surface, actual experiments were carried out in water tunnel, and the experimental results are approximately consistent with the numerical simulation.
基金This work was supported by National Natural Science Foundation of China Major Program （Grant No.51290292）.
文摘Plant of carnivorous genus Nepenthes alata has evolved specific pitchers to prey insects for survival in the barren habitat, especially its slippery zone. The excellent slippery function has received considerable interest because of its potential applica- tion in antifriction surface design. The surface morphologies of intact and de-waxed slippery zones were characterized using scanning electron microscope and scanning white-light interferometer. Hierarchical structures with anisotropic micro- lunate structure and nano- wax crystals were found on the slippery zone. Due to the hierarchical structures, the slippery zone is hy- drophobic. It shows a significant anisotropic wettability with static contact angles 153.3° and 140.1° in the directions perpen- dicular and parallel to the upward direction （toward the peristome）, respectively. The sliding angles are -3° and -10° in the downward and upward directions, respectively. Crawling experiments indicate that the microscopic surface roughness and the brittleness of the wax crystals may reduce insect attachment in different modes according to the insect mass differences. Moreover, artificial slippery surfaces inspired by the slippery zone of Nepenthes alata were fabricated. Traction experiments quantitatively verified that the friction force of replicated lunate structures with Ra-2.54 μm surface roughness was reduced by about 25% as compared to flat surface with Ra-0.56 μm surface roughness for cricket claws.
文摘Birds have gradually formed various excellent structures such as streamlined shape and hollow shaft of feather to improve their flying performance by millions of years of natural selection. As typical property of bird feather, herringbone riblets align along the shaft of each feather, which is caused by perfect link of barbs, especially for the primary and secondary feathers of wings. Such herringbone riblets of feather are assumed to have great impact on drag reduction. In this paper, microstructures of secondary feathers of adult pigeons are investigated by SEM, and their structural parameters are statistically obtained. Based on quantitative analysis of feather structure, novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 16%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.
基金the National Defense Fundamental Research Foundation of China (Grant No. D2120060002)the National Natural Science Foundation of China (Grant No. 59975007)
文摘Direct replication of creatural scarfskins to form biomimetic surfaces with relatively vivid morphology is a new attempt of the bio-replicated forming technology at animal body. Taking shark skins as the replication templates, and the micro-embossing and micro-molding as the material forming methods, the micro-replicating technology of the outward morphology on shark skins was demonstrated. The preliminary analysis on replication precision indicates that the bio-replicated forming technology can replicate the outward morphology of the shark scales with good precision, which validates the application of the bio-replicated forming technology in the direct morphology replication of the firm creatural scarfskins.
基金supported by the National Key Research and Development Program of China(Grant No.2018YFA0209500)the Research Council of Hong Kong(Grant Nos.C1018-17G,and 11275216)+3 种基金the Shenzhen Science and Technology Innovation Council(Grant No.JCYJ20170413141208098)the National Natural Science Foundation of China(Grant No.51706100)the Natural Science Foundation of Jiangsu Province(Grant No.BK20180477)the City University of Hong Kong(Grant No.9360140)
文摘Learning from nature has traditionally and continuously provided important insights to drive a paradigm shift in technology.In particular,recent studies show that many biological organisms exhibit spectacular surface topography such as shape,size,spatial organization,periodicity,interconnectivity,and hierarchy to endow them with the capability to adapt dynamically and responsively to a wide range of environments.More excitingly,in a broader perspective,these normally neglected topological features have the potential to fundamentally change the way of how engineering surface works,such as how fluid flows,how heat is transported,and how energy is generated,saved,and converted,to name a few.Thus,the design of nature-inspired surface topography for unique functions will spur new thinking and provide paradigm shift in the development of the new engineering surfaces.In this review,we first present a brief introduction to some insights extracted from nature.Then,we highlight recent progress in designing new surface topographies and demonstrate their applications in emerging areas including thermal-fluid transport,anti-icing,water harvesting,power generation,adhesive control,and soft robotics.Finally,we offer our perspectives on this emerging field,with the aim to stimulate new thinking on the development of next-generation of new materials and devices,and dramatically extend the boundaries of traditional engineering.
文摘背景:股骨头坏死出现新月征是病情进程的“分水岭”,修复和稳定骨-软骨界面对阻止病情继续进展和预防股骨头塌陷尤为重要。利用组织工程学同步修复、整合骨-软骨界面具有潜在优势。目的:综述探讨解决股骨头坏死软骨下分离的潜在适宜技术。方法:检索1970年1月至2023年4月PubMed、Web of Science及中国知网、万方数据库中发表的相关文献,英文检索词:“Femoral head necrosis,Avascular necrosis of femoral head,Osteonecrosis of femoral head”等,中文检索词:“股骨头坏死,软骨下骨,软骨,软骨与软骨下骨整合”等,最终纳入114篇文献进行综述分析。结果与结论:①结构缺陷、缺血缺氧环境、炎症因素和应力集中可能造成股骨头坏死软骨下分离现象,软骨下骨分离会造成塌陷进展,并且可能与保髋手术失败相关,利用组织工程支架实现支架与骨-软骨界面的整合是治疗股骨头坏死软骨下分离的潜在方法之一。②目前的文献研究表明,多相、梯度支架和复合材料在促进骨、软骨细胞黏附与增殖,骨软骨基质的沉积方面均有提升,有助于支架与骨-软骨界面的整合,对治疗股骨头坏死软骨下分离有参考价值。③通过对支架表面进行修饰可以提高与界面整合的效率,但有各自不同的优缺点,提供不同环境的支架能够诱导同种间充质干细胞差异分化,有助于不同界面之间的整合。④未来有望应用于股骨头坏死软骨下分离的支架应为复合材料,具有梯度化和差异化的仿生结构,通过表面修饰和干细胞加载促进骨-软骨界面与支架的整合以实现治疗目的,但仍需进一步研究验证,而支架的降解速率与修复进度同步和不同界面之间的稳定性是未来需要解决的主要问题。
基金This work is supported by the National Natural Science Foundation of China （51273083 and 51405188） and China Postdoctoral Science Foundation （2015T80307）.
文摘Superhydrophobic surfaces are often found in nature, such as plant leaves and insect wings. Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves, biomimetic hydrophnbic surfaces with high or low adhesion were prepared with a facile drop-coating approach in this paper. Poly（vinyl alcohol） （PVA） was used as adhesive and SiO2 nanoparticles were used to fabricate surface micro-structure. Stearic acid or dodecafluoroheptyl-propyl-trimethoxysilane （DFTMS） were used as low surface energy materials to modify the prepared PVA/SiO2 coating surfaces. The effects of size of SiO2 nanoparticles, concentration of SiO2 nanoparticle suspensions and the modifications on the wettability of the surface were investigated. The morphology of the PVA/SiO2 coating surfaces was observed by using scanning electron microscope. Water contact angle of the obtained superhydrophilic surface could reach to 3°. Stearic acid modified PVA/SiO2 coating surfaces showed hydrophobicity with high adhesion. By mixing the SiO2 nanoparticles with sizes of 40 nm and 200 nm and modifying with DFTMS, water contact angle of the obtained coating surface could be up to 155° and slide angle was only 5°. This work provides a facile and useful method to control surface wettability through changing the roughness and chemical composition of a surface.
基金supported by the Key Program of National Natural Science Foundation of China (Grant No.50635030)the National Natural Science Foundation for Youths (No.51005097)+1 种基金the Major Program of the Science and Technology Development of Jilin Province (Grant No.09ZDGG001)the Fundamental Science Research Funds for the Central Universities (No.200903275)
文摘Biomimetic surface is an effective ways to promote the performance grade and applied range of materials without alteringtheir substrate.Many improved properties such as resisting fatigue,enduring wear,etc,have been achieved by applyingbiomimetic morphology or structure to some engineering material surfaces.In this paper,aiming to reveal the relationshipbetween thermal cracking behavior and mechanical properties of engineering materials with biomimetic surface,biomimeticspecimens were fabricated using laser technique by imitating the heterogeneous structure on the surface of plant leaves.Theeffect of thermal fatigue cycling on the tensile properties of H13 die steel specimens with different surfaces (several types ofbiomimetic surfaces and a smooth surface) was compared and investigated.As a result,due to the coupling effects of themorphological features on the surface and the microstructure characteristics within unit zone,these specimens with biomimeticsurface exhibit remarkably enhanced Ultimate Tensile Strength (UTS) and 0.2% Yield Strength (YS) compared with referencespecimens while corresponding ductility remains largely unaffected even heightened,whether the thermal fatigue loads or not.The relative mechanisms leading to these improvements have been discussed.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(Grant No.91848202)。
文摘Wedge-shaped microstructures have the ability to reproduce the excellent adhesive properties of geckos’feet because of their unique anisotropic structure.In particular,the controllability of the wedge-shaped microstructures on adhesion is beneficial to the undisturbed grasp or the capture of space targets.However,the problem currently remains of how to process it efficiently and with high quality.Here a strategy called ultraprecision multistep and layered scribing is proposed for the manufacture of the biomimetic controllable adhesive surface.The results show that the metal master mold prepared based on the manufacturing strategy has not only good surface topography but also high reliability and durability.Furthermore,the controllable adhesive surface of 1.96 cm2,fabricated by the proposed manufacturing strategy,has a normal adhesion of 1.012 N,and the corresponding shear friction and adhesion coefficient are 3.105 N and 4.82,respectively.Additionally,the controllable adhesive surface has been shown to be approximately superhydrophobic and also to possess the properties of controllable adhesion and dynamic adhesion.Also,after 250 adhesion-detachment cycles,the normal adhesion and shear friction only decrease by 5%and 3%,respectively.The research realizes an environmentally friendly and efficient method by which to manufacture a durable metal mold for fabricating a biomimetic controllable adhesive surface,laying a foundation for its effective application in the adherence of space-floating targets.
