Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degr...Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass(MBG)with high pore volume(0.59 cc/g) and huge specific surface area(110.78 m^(2)/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+and HPO42-. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore,MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.展开更多
Hydroxyapatite(HA)nanoparticles and silver(Ag)nanoparticles are expected to enable desirable bioactivity and antibac-terial properties on biopolymer scaffolds.Nevertheless,interfacial adhesion between HA/Ag and the bi...Hydroxyapatite(HA)nanoparticles and silver(Ag)nanoparticles are expected to enable desirable bioactivity and antibac-terial properties on biopolymer scaffolds.Nevertheless,interfacial adhesion between HA/Ag and the biopolymer is poor due to the large physicochemical differences between these components.In this study,poly L-lactic acid(PLLA)powder was first surface-modified with bioactive polydopamine(PDA)in an alkaline environment.Next,HA and Ag nanoparticles were grown in situ on the PDA-coated PLLA powder,which was then adhered to the porous bone scaffold using a selective laser-sintering process.Results showed that HA and Ag nanoparticles were homogenously distributed in the matrix,with enhanced mechanical properties.Simulated body fluid bioactivity tests showed that the in situ grown HA-endowed scaffold shows excellent bioactivity.In vitro tests confirmed that the scaffold exhibits favorable biocompatibility with human umbilical cord mesenchymal stem cells,as well as strong antibacterial activity against Gram-negative Escherichia coli.Furthermore,in vivo assays indicated that the scaffold promoted bone generation,with a new bone area fraction of 71.8%after 8 weeks’implantation,without inflammation.展开更多
Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models.However,very few biomimetic robots can perform complex loc...Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models.However,very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and flying.Here,we describe an aerial–wall amphibious robot that is self-contained for flying and climbing,and that can seamlessly move between the air and wall.It adopts a flapping/rotor hybrid power layout,which realizes not only efficient and controllable flight in the air but also attachment to,and climbing on,the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion performance.On the basis of the attachment mechanism of insect foot pads,the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable climbing.The longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying–climbing transition,which has important implications in understanding the takeoff and landing of insects.Moreover,it enables the robot to cross the air–wall boundary in 0.4 s(landing),and cross the wall–air boundary in 0.7 s(taking off).The aerial–wall amphibious robot expands the working space of traditional flying and climbing robots,which can pave the way for future robots that can perform autonomous visual monitoring,human search and rescue,and tracking tasks in complex air–wall environments.展开更多
Biodegradable magnesium(Mg)alloy has been considered as a new generation of orthopedic implant ma-terial.Nevertheless,local corrosion usually occurs since the severe micro-galvanic behavior amongα-Mg and precipitates...Biodegradable magnesium(Mg)alloy has been considered as a new generation of orthopedic implant ma-terial.Nevertheless,local corrosion usually occurs since the severe micro-galvanic behavior amongα-Mg and precipitates,and results in too rapid degradation.In this study,porous Mg-Zn-Gd part was fabricated using laser additive manufacturing combined with solution heat treatment.During heat treatment,the precipitatedβ-(Mg,Zn)_(3) Gd phase dissolved inα-Mg,and reduced the energy threshold of stacking faults on basal planes,which finally triggered the formation of long period stacking ordered(LPSO)phase.The LPSO phases owned minor potential difference withα-Mg,thus causing less micro-galvanic corrosion ten-dency as compared toβ-(Mg,Zn)_(3) Gd phase.More importantly,they were uniformly distributed within theα-Mg grains and showed different orientations between adjacent grains.As a result,the LPSO-reinforced Mg-Zn-Gd tended to expand laterally during corrosion evolution,and achieved uniform degradation with a considerably reduced degradation rate of 0.34 mm/year.Moreover,in-vitro cell tests further proved its favorable biocompatibility.This work highlighted the additively manufactured Mg-Zn-Gd with LPSO structure showed great potential for orthopedic application.展开更多
Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstr...Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstructed via computed tomography had satisfactory biocompatibility. However, the reverse modeling scaffolds were inflexible for customized design. Therefore, a top-down designing biomimetic bone scaffold with favorable mechanical performances and cytocompatibility is urgently demanded for orthopedic implants. An emerging additive manufacturing technique, selective laser melting, was employed to fabricate the trabecular-like porous Ti-6Al-4 V scaffolds with varying irregularities(0.05-0.5) and porosities(48.83%–74.28%) designed through a novel Voronoi-Tessellation based method. Micro-computed tomography and scanning electron microscopy were used to characterize the scaffolds’ morphology.Quasi-static compression tests were performed to evaluate the scaffolds’ mechanical properties. The MG63 cells culture in vitro experiments, including adhesion, proliferation, and differentiation, were conducted to study the cytocompatibility of scaffolds. Compressive tests of scaffolds revealed an apparent elastic modulus range of 1.93–5.24 GPa and an ultimate strength ranging within 44.9–237.5 MPa, which were influenced by irregularity and porosity, and improved by heat treatment. Furthermore, the in vitro assay suggested that the original surface of the SLM-fabricated scaffolds was favorable for osteoblasts adhesion and migration because of micro scale pores and ravines. The trabecular-like porous scaffolds with full irregularity and higher porosity exhibited enhanced cells proliferation and osteoblast differentiation at earlier time, due to their preferable combination of small and large pores with various shapes. This study suggested that selective laser melting-derived Ti-6Al-4 V scaffold with the trabecular-like porous structure designed through Voronoi-Tessellation method, favorable mechanical performance, and good cytocompatibility was a potential biomaterial for orthopedic implants.展开更多
Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many ...Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many AM technologies,which decreases the precision of as-built parts.Like fusion welding,the local high-energy input generates residual stresses,which can adversely affect the fatigue performance of AM parts.To the best of the authors’knowledge,a comprehensive review does not exist regarding the distortion and residual stresses dedicated for AM,despite some work has explored the interrelationship between the two.The present review is aimed to fill in the identified knowledge gap,by first describing the evolution of distortion and residual stresses for a range of AM processes,and second assessing their influencing factors.This allows us to elucidate their formation mechanisms from both the micro-and macro-scales.Moreover,approaches which have been successfully adopted to mitigate both the distortion and residual stresses are reviewed.It is anticipated that this review paper opens many opportunities to increase the success rate of AM parts by improving the dimension precision and fatigue life.展开更多
基金National Natural Science Foundation of China (51935014,52165043, 82072084, 81871498)Jiang Xi Provincial Natural Science Foundation of China (20192ACB20005,2020ACB214004)+6 种基金The Provincial Key R&D Projects of Jiangxi (20201BBE51012)Guangdong Province Higher Vocational Colleges&Schools Pearl River Scholar Funded Scheme (2018)Shenzhen Science and Technology Plan Project (JCYJ20170817112445033)Innovation Team Project on University of Guangdong Province(2018GKCXTD001)Technology Innovation Platform Project of Shenzhen Institute of Information Technology 2020(PT2020E002)China Postdoctoral Science Foundation(2020M682114)Open Research Fund of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology。
文摘Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass(MBG)with high pore volume(0.59 cc/g) and huge specific surface area(110.78 m^(2)/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+and HPO42-. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore,MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.
基金This study was supported by the following funds:(1)National Natural Science Foundation of China(Nos.51935014,82072084,and 81871498)(2)Jiangxi Provincial Natural Science Foundation of China(Nos.20192ACB20005 and 2020ACB214004)+6 种基金(3)The Provincial Key R&D Projects of Jiangxi(No.20201BBE51012)(4)Guangdong Province Higher Vocational Colleges&Schools Pearl River Scholar Funded Scheme(2018)(5)Shenzhen Science and Technology Plan Project(No.JCYJ20170817112445033)(6)Innovation Team Project on University of Guangdong Province(No.2018GKCXTD001)(7)Technology Innovation Platform Project of Shenzhen Institute of Information Technology 2020(No.PT2020E002)(8)Open Research Fund of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(9)China Postdoctoral Science Foundation(No.2020M682114).
文摘Hydroxyapatite(HA)nanoparticles and silver(Ag)nanoparticles are expected to enable desirable bioactivity and antibac-terial properties on biopolymer scaffolds.Nevertheless,interfacial adhesion between HA/Ag and the biopolymer is poor due to the large physicochemical differences between these components.In this study,poly L-lactic acid(PLLA)powder was first surface-modified with bioactive polydopamine(PDA)in an alkaline environment.Next,HA and Ag nanoparticles were grown in situ on the PDA-coated PLLA powder,which was then adhered to the porous bone scaffold using a selective laser-sintering process.Results showed that HA and Ag nanoparticles were homogenously distributed in the matrix,with enhanced mechanical properties.Simulated body fluid bioactivity tests showed that the in situ grown HA-endowed scaffold shows excellent bioactivity.In vitro tests confirmed that the scaffold exhibits favorable biocompatibility with human umbilical cord mesenchymal stem cells,as well as strong antibacterial activity against Gram-negative Escherichia coli.Furthermore,in vivo assays indicated that the scaffold promoted bone generation,with a new bone area fraction of 71.8%after 8 weeks’implantation,without inflammation.
基金the National Key R&D Program of China grant no.2019YFB1309600the National Natural Science Foundation of China grant nos.51875281 and 51861135306.
文摘Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models.However,very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and flying.Here,we describe an aerial–wall amphibious robot that is self-contained for flying and climbing,and that can seamlessly move between the air and wall.It adopts a flapping/rotor hybrid power layout,which realizes not only efficient and controllable flight in the air but also attachment to,and climbing on,the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion performance.On the basis of the attachment mechanism of insect foot pads,the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable climbing.The longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying–climbing transition,which has important implications in understanding the takeoff and landing of insects.Moreover,it enables the robot to cross the air–wall boundary in 0.4 s(landing),and cross the wall–air boundary in 0.7 s(taking off).The aerial–wall amphibious robot expands the working space of traditional flying and climbing robots,which can pave the way for future robots that can perform autonomous visual monitoring,human search and rescue,and tracking tasks in complex air–wall environments.
基金National Natural Science Foundation of China (Nos.51935014,52165043,82072084)JiangXi Provincial Natural Science Foundation of China (No.20212BAB214026)Jiangsu Provincial Key Research and Development Program (No.BE2019002).
文摘Biodegradable magnesium(Mg)alloy has been considered as a new generation of orthopedic implant ma-terial.Nevertheless,local corrosion usually occurs since the severe micro-galvanic behavior amongα-Mg and precipitates,and results in too rapid degradation.In this study,porous Mg-Zn-Gd part was fabricated using laser additive manufacturing combined with solution heat treatment.During heat treatment,the precipitatedβ-(Mg,Zn)_(3) Gd phase dissolved inα-Mg,and reduced the energy threshold of stacking faults on basal planes,which finally triggered the formation of long period stacking ordered(LPSO)phase.The LPSO phases owned minor potential difference withα-Mg,thus causing less micro-galvanic corrosion ten-dency as compared toβ-(Mg,Zn)_(3) Gd phase.More importantly,they were uniformly distributed within theα-Mg grains and showed different orientations between adjacent grains.As a result,the LPSO-reinforced Mg-Zn-Gd tended to expand laterally during corrosion evolution,and achieved uniform degradation with a considerably reduced degradation rate of 0.34 mm/year.Moreover,in-vitro cell tests further proved its favorable biocompatibility.This work highlighted the additively manufactured Mg-Zn-Gd with LPSO structure showed great potential for orthopedic application.
基金financially supported by the Advanced Research Project of Army Equipment Development (No. 301020803)the Key Research and Development Program of Jiangsu (No. BE 2015161)+3 种基金the Young Scientists Fund of the National Natural Science Foundation of China (No. 51605473)the Jiangsu Provincial Research Foundation for Basic Research, China (No. BK 20161476)the Science and Technology Planning Project of Jiangsu Province of China (No. BE 2015029)the Science and Technology Support Program of Jiangsu (Nos. BE 2014009-1, BE 2014009-2 and BE 2016010-3)
文摘Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstructed via computed tomography had satisfactory biocompatibility. However, the reverse modeling scaffolds were inflexible for customized design. Therefore, a top-down designing biomimetic bone scaffold with favorable mechanical performances and cytocompatibility is urgently demanded for orthopedic implants. An emerging additive manufacturing technique, selective laser melting, was employed to fabricate the trabecular-like porous Ti-6Al-4 V scaffolds with varying irregularities(0.05-0.5) and porosities(48.83%–74.28%) designed through a novel Voronoi-Tessellation based method. Micro-computed tomography and scanning electron microscopy were used to characterize the scaffolds’ morphology.Quasi-static compression tests were performed to evaluate the scaffolds’ mechanical properties. The MG63 cells culture in vitro experiments, including adhesion, proliferation, and differentiation, were conducted to study the cytocompatibility of scaffolds. Compressive tests of scaffolds revealed an apparent elastic modulus range of 1.93–5.24 GPa and an ultimate strength ranging within 44.9–237.5 MPa, which were influenced by irregularity and porosity, and improved by heat treatment. Furthermore, the in vitro assay suggested that the original surface of the SLM-fabricated scaffolds was favorable for osteoblasts adhesion and migration because of micro scale pores and ravines. The trabecular-like porous scaffolds with full irregularity and higher porosity exhibited enhanced cells proliferation and osteoblast differentiation at earlier time, due to their preferable combination of small and large pores with various shapes. This study suggested that selective laser melting-derived Ti-6Al-4 V scaffold with the trabecular-like porous structure designed through Voronoi-Tessellation method, favorable mechanical performance, and good cytocompatibility was a potential biomaterial for orthopedic implants.
基金National Key Research and Development Program of China(Grant No.2018YFB1105400)National Natural Science Foundation of China(Grant No.51475238)+2 种基金Key Research and Development Program of Jiangsu Provincial Department of Science and Technology of China(Grant No.BE2019002)China Post-Doctoral Fund(Grant No.2020M671475)UK's Engineering and Physical Sciences Research Council,and EPSRC Early Career Fellowship Scheme[EP/R043973/1].
文摘Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many AM technologies,which decreases the precision of as-built parts.Like fusion welding,the local high-energy input generates residual stresses,which can adversely affect the fatigue performance of AM parts.To the best of the authors’knowledge,a comprehensive review does not exist regarding the distortion and residual stresses dedicated for AM,despite some work has explored the interrelationship between the two.The present review is aimed to fill in the identified knowledge gap,by first describing the evolution of distortion and residual stresses for a range of AM processes,and second assessing their influencing factors.This allows us to elucidate their formation mechanisms from both the micro-and macro-scales.Moreover,approaches which have been successfully adopted to mitigate both the distortion and residual stresses are reviewed.It is anticipated that this review paper opens many opportunities to increase the success rate of AM parts by improving the dimension precision and fatigue life.
