To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properti...To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.展开更多
Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequ...Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequate strength limit their applicability.To overcome this,the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium(Zr)content.This approach presents a promising strategy for simultaneously improving corrosion resistance,maintaining biocompatibility,and enhancing strength without compromising osseointegration.By leveraging Mg’s inherent biodegradability,it has the potential to minimize the need for secondary surgeries,thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings,denoted Mg-xZr(x=0–5 at.%).Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content.XRD analysis confirmed the presence of the Mg(00.2)basal plane,shifting towards higher angles(1.15°)with 5 at.%Zr doping due to lattice parameter changes(i.e.,decrease and increase of“c”and“a”lattice parameters,respectively).Mg–Zr coatings exhibited“liquidphilic”behavior,while Young’s modulus retained a steady value around 80 GPa across all samples.However,the hardness has significantly improved across all samples’coating,reaching the highest value of(2.2±0.3)GPa for 5 at.%Zr.Electrochemical testing in simulated body fluid(SBF)at 37℃ revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.%Zr.Compared with the 5 at.%Zr coating which exhibited a corrosion rate of 32 mm/year,these coatings displayed lower corrosion rates,ranging from 1 to 12 mm/year.This synergistic enhancement in mechanical properties and corrosion resistance,achieved with 2.0–3.4 at.%Zr,suggests potential ability for reducing stress shielding and controlled degradation performance,and consequently,promising functional biodegradable materials for temporary bone implants.展开更多
This paper investigates the effects of the physical properties on the microstructure and weldability of explosive welding by joining two metals with a significant contrast in thermophysical properties:stainless steel ...This paper investigates the effects of the physical properties on the microstructure and weldability of explosive welding by joining two metals with a significant contrast in thermophysical properties:stainless steel and copper.Sound welds between stainless steel and copper were obtained,and the interfacial morphology was wavy,regardless of the position of the materials.The weldability of dissimilar pairs was found to be more dependent on the relationship between the physical properties of the base materials than on the absolute value of the material property.When there is a significant difference in thermal conductivity between the flyer and the base plate,together with a material with a low melting temperature,the weldability of the pair is often poor.The relative position of the plates affects the interfacial microstructure even when similar morphologies are found.For the metallic pairs studied,the wave size was bigger for the configuration in which the ratio between the density of the flyer and the density of the base plate is smaller.The same phenomenon was observed for the impedance:bigger waves were found for a smaller ratio between the impedance of the flyer and the impedance of the base plate.展开更多
Commercial pure aluminum and galvanized carbon steel were lap-welded using the weld-brazing(WB)technique.Three types of aluminum filler materials(4043,4047,and 5356) were used for WB.The joint strength and intermetall...Commercial pure aluminum and galvanized carbon steel were lap-welded using the weld-brazing(WB)technique.Three types of aluminum filler materials(4043,4047,and 5356) were used for WB.The joint strength and intermetallic compounds at the interface of three series of samples were analyzed and compared.Depending on the Si content,a variety of ternary Al-Fe-Si intermetallic compounds(IMCs) such as Fe_(4)(Al,Si)_(13),Fe_(2) Al_(8) Si(τ_(5)),and Fe_(2) Al_(9) Si_(2)(τ_(6)) were formed at the interface.Mg element in 5356 filler material cannot contribute to the formation of Al-Fe intermetallic phases due to the positive mixing enthalpy of Mg-Fe.The presence of Mg enhances the hot cracking phenomenon near the Al-Fe intermetallic compound at the interface.Zn coating does not participate in intermetallic formation due to its evaporation during WB.It was concluded that the softening of the base metal in the heat-affected zone rather than the IMCs determines the joint efficiency.展开更多
In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear pe...In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current(DC)reactive magnetron sputtering is investigated.The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings.In general,two layers are formed during the oxidation process:i)Ti(V)O_(2) on top,followed by a protective layer,which is subdivided into two layers,Cr_(2)O_(3) and Si-O.ii)The diffusion of V controls the oxidation of V-containing coatings.The addition of vanadium improves the wear resistance of coatings,and the wear rate decreases with increasing V content in the coatings;however,the friction coefficient is independent of the chemical composition of the coatings.The wear of the V-containing coatings is driven by polishing wear.展开更多
The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose ...The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air,water,and seawater.The results show that the addition of C into the TiN binary film induced a new amorphous phase,and the films exhibited a dual phase of fcc(face-centered cubic)-TiN and amorphous carbon.The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at%C.However,a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates.Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater,the negative abrasion state was detected for all Ti-C-N films due to the adhesion of the tribocorrosion debris on the wear track.展开更多
Polymeric coronary stents,like the ABSORB^(TM)are commonly used to treat atherosclerosis due to their bioresorbable and cell-compatible polymer structure.However,they face challenges such as high strut thickness,high ...Polymeric coronary stents,like the ABSORB^(TM)are commonly used to treat atherosclerosis due to their bioresorbable and cell-compatible polymer structure.However,they face challenges such as high strut thickness,high elastic recoil,and lack of radiopacity.This study aims to address these limitations by modifying degradable stents produced by additive manufacturing with poly(lactic acid)(PLA)and poly(ε-caprolactone)(PCL)with degradable metallic coatings,specifically zinc(Zn)and magnesium(Mg),deposited via radiofrequency(rf)magnetron sputtering.The characterisation included the evaluation of the degradation of the coatings,antibacterial,anti-thrombogenicity,radiopacity,and mechanical properties.The results showed that the metallic coatings inhibited bacterial growth,though Mg exhibited a high degradation rate.Thrombogenicity studies showed that Zn-coated stents had anticoagulant properties,while Mgcoated and controls were thrombogenic.Zn coatings significantly improved radiopacity,enhancing contrast by 43%.Mechanical testing revealed that metallic coatings reduced yield strength and,thus,diminished elastic recoil after stent expansion.Zn-coated stents improved cyclic compression resistance by 270%for PCL stents,with PLA-based stents showing smaller improvements.The coatings also enhanced crush resistance,particularly for Zn-coated PCL stents.Overall,Zn-coated polymers have emerged as the premier prototype due to their superior biological and mechanical performance,appropriate degradation during the stent life,and ability to provide the appropriate radiopacity to medical devices.展开更多
The inverse relationship between the tribological and mechanical properties of environmentally friendly selflubricant films,induced by the addition of soft lubricant agents that can diffuse quickly at elevated tempera...The inverse relationship between the tribological and mechanical properties of environmentally friendly selflubricant films,induced by the addition of soft lubricant agents that can diffuse quickly at elevated temperatures,has hindered the widespread use of these materials in industrial applications.This paper took this challenge to break through the above established relationship by developing novel nacrelike multilayered Mo_(2)N–SiN_(x)/Ag–SiN_(x)self-lubricant films via an radio frequency(RF)magnetron sputtering system for real applications where harsh conditions at elevated temperatures exist.The multilayered films,deposited by alternating deposition of Mo_(2)N–SiN_(x)and Ag–SiN_(x)modulation layers,exhibited three phases of face-centered cubic(fcc)Mo_(2)N,fcc Ag and SiN_(x),where SiN_(x)encapsulated the nano-crystalline Mo_(2)N and Ag phases in each layer to successfully induce a“brick and mortar”nacre-like microstructure(in the area without the coherent structure).The epitaxy growth of the Ag–SiN_(x)layers with thickness below 6 nm on the Mo_(2)N template resulted in an extraordinary increase in both the hardness and elastic modulus,which was able to prevent severe degradation of the mechanical properties caused by the addition of Ag.The room-temperature anti-friction property could be enhanced by increasing the Ag–SiN_(x)layer thickness due to the excellent lubricant nature of Ag,which acts in synergy with Mo_(2)N,while the wear rate below 4×10^(−8)mm^(3)/(N·mm)was due to the high mechanical strength.The tribological properties at 600℃also benefited from the interlocked multilayered architecture,which allowed an extreme low friction coefficient of~0.12 and a negligible wear rate(WR).This behavior was attributed to the synergism between the lubricant action of Ag and Mo_(2)N and the tribo-phase transformation from Ag_(2)Mo_(4)O_(13)to Ag_(2)MoO_(4).展开更多
Machines that mimic humans have inspired scientists for centuries.Bioinspired soft robotic hands are a good example of such an endeavor,featuring intrinsic material compliance and continuous motion to deal with uncert...Machines that mimic humans have inspired scientists for centuries.Bioinspired soft robotic hands are a good example of such an endeavor,featuring intrinsic material compliance and continuous motion to deal with uncertainty and adapt to unstructured environments.Recent research led to impactful achievements in functional designs,modeling,fabrication,and control of soft robots.Nevertheless,the full realization of life-like movements is still challenging to achieve,often based on trial-and-error considerations from design to fabrication,consuming time and resources.In this study,a soft robotic hand is proposed,composed of soft actuator cores and an exoskeleton,featuring a multimaterial design aided by finite element analysis(FEA)to define the hand geometry and promote finger’s bendability.The actuators are fabricated using molding,and the exoskeleton is 3D-printed in a single step.An ON-OFF controller keeps the set fingers’inner pressures related to specific bending angles,even in the presence of leaks.The FEA numerical results were validated by experimental tests,as well as the ability of the hand to grasp objects with different shapes,weights,and sizes.This integrated solution will make soft robotic hands more available to people,at a reduced cost,avoiding the time-consuming design-fabrication trial-and-error processes.展开更多
A multilayer film,composed by ZrN‒Ag(20 nm)and Mo‒S‒N(10 nm)layers,combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system,to promote lubrication in a wide-ra...A multilayer film,composed by ZrN‒Ag(20 nm)and Mo‒S‒N(10 nm)layers,combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system,to promote lubrication in a wide-range of temperatures.The results showed that the ZrN‒Ag/Mo‒S‒N multilayer film exhibited a sharp interface between the different layers.A face-centered cubic(fcc)dual-phases of ZrN and Ag co-existed in the ZrN‒Ag layers,whilst the Mo‒S‒N layers displayed a mixture of hexagonal close-packed MoS_(2)(hcp-MoS_(2))nano-particles and an amorphous phase.The multilayer film exhibited excellent room temperature(RT)triblogical behavior,as compared to the individual monolayer film,due to the combination of a relative high hardness with the low friction properties of both layers.The reorientation of MoS_(2)parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT.At 400℃,the reorientation of MoS_(2)as well as the formation of MoO_(3)phase were responsible for the lubrication,whilst the hard t-ZrO_(2)phase promoted abrasion and,consequently,led to increasing wear rate.At 600℃,the Ag_(2)MoO_(4)double-metal oxide was the responsible for the low friction and wear-resistance;furthermore,the observed transformation from t-ZrO_(2)to m-ZrO_(2),could also have contributed to the better tribological performance.展开更多
Bio-inspired soft robots have already shown the ability to handle uncertainty and adapt to unstructured environments.However,their availability is partially restricted by time-consuming,costly,and highly supervised de...Bio-inspired soft robots have already shown the ability to handle uncertainty and adapt to unstructured environments.However,their availability is partially restricted by time-consuming,costly,and highly supervised design-fabrication processes,often based on resource-intensive iterative workflows.Here,we propose an integrated approach targeting the design and fabrication of pneumatic soft actuators in a single casting step.Molds and sacrificial water-soluble hollow cores are printed using fused filament fabrication.A heated water circuit accelerates the dissolution of the core’s material and guarantees its complete removal from the actuator walls,while the actuator’s mechanical operability is defined through finite element analysis.This enables the fabrication of actuators with non-uniform cross-sections under minimal supervision,thereby reducing the number of iterations necessary during the design and fabrication processes.Three actuators capable of bending and linear motion were designed,fabricated,integrated,and demonstrated as 3 different bio-inspired soft robots,an earthworm-inspired robot,a 4-legged robot,and a robotic gripper.We demonstrate the availability,versatility,and effectiveness of the proposed methods,contributing to accelerating the design and fabrication of soft robots.This study represents a step toward increasing the accessibility of soft robots to people at a lower cost.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51801079,52001140)the National Funds Through FCT of Portugal–Fundacao para a Ciência e a Tecnologia,under a scientific contract of 2021.04115.CEECIND,and the Projects of UIDB/00285/2020,and LA/0112/2020。
文摘To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.
基金support by the project n°7225-ILLIANCE High Performing EnergyPro-jeto apoiado pelo PRR-Plano de Recuperação e Resiliência e pelos Fundos Europeus Next Generation EU,no sequência do AVISO N.°02/C05-i01/2022,Componente 5-Capital-ização e Inovação Empresarial-Agendas Mobilizadores para a Inovação Empresarialsupport by national funds through FCT-Fundação para a Ciência e a Tecnologia,under the project UID/EMS/00285/2020,ARISE-LA/P/0112/2020.
文摘Magnesium(Mg)alloys are widely used for temporary bone implants due to their favorable biodegradability,cytocompatibility,hemocompatibility,and close mechanical properties to bone.However,rapid degradation and inadequate strength limit their applicability.To overcome this,the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium(Zr)content.This approach presents a promising strategy for simultaneously improving corrosion resistance,maintaining biocompatibility,and enhancing strength without compromising osseointegration.By leveraging Mg’s inherent biodegradability,it has the potential to minimize the need for secondary surgeries,thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings,denoted Mg-xZr(x=0–5 at.%).Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content.XRD analysis confirmed the presence of the Mg(00.2)basal plane,shifting towards higher angles(1.15°)with 5 at.%Zr doping due to lattice parameter changes(i.e.,decrease and increase of“c”and“a”lattice parameters,respectively).Mg–Zr coatings exhibited“liquidphilic”behavior,while Young’s modulus retained a steady value around 80 GPa across all samples.However,the hardness has significantly improved across all samples’coating,reaching the highest value of(2.2±0.3)GPa for 5 at.%Zr.Electrochemical testing in simulated body fluid(SBF)at 37℃ revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.%Zr.Compared with the 5 at.%Zr coating which exhibited a corrosion rate of 32 mm/year,these coatings displayed lower corrosion rates,ranging from 1 to 12 mm/year.This synergistic enhancement in mechanical properties and corrosion resistance,achieved with 2.0–3.4 at.%Zr,suggests potential ability for reducing stress shielding and controlled degradation performance,and consequently,promising functional biodegradable materials for temporary bone implants.
基金sponsored by FEDER funds through the program COMPETE-Programa Operacional Factores de Competitividadeby national funds through FCT-Funda??o para a Ciência e a Tecnologia,under the project UIDB/00285/2020。
文摘This paper investigates the effects of the physical properties on the microstructure and weldability of explosive welding by joining two metals with a significant contrast in thermophysical properties:stainless steel and copper.Sound welds between stainless steel and copper were obtained,and the interfacial morphology was wavy,regardless of the position of the materials.The weldability of dissimilar pairs was found to be more dependent on the relationship between the physical properties of the base materials than on the absolute value of the material property.When there is a significant difference in thermal conductivity between the flyer and the base plate,together with a material with a low melting temperature,the weldability of the pair is often poor.The relative position of the plates affects the interfacial microstructure even when similar morphologies are found.For the metallic pairs studied,the wave size was bigger for the configuration in which the ratio between the density of the flyer and the density of the base plate is smaller.The same phenomenon was observed for the impedance:bigger waves were found for a smaller ratio between the impedance of the flyer and the impedance of the base plate.
基金Project(97.13966(97.11.15)) supported by the Deputy of Research and Technology of Arak University,Iran。
文摘Commercial pure aluminum and galvanized carbon steel were lap-welded using the weld-brazing(WB)technique.Three types of aluminum filler materials(4043,4047,and 5356) were used for WB.The joint strength and intermetallic compounds at the interface of three series of samples were analyzed and compared.Depending on the Si content,a variety of ternary Al-Fe-Si intermetallic compounds(IMCs) such as Fe_(4)(Al,Si)_(13),Fe_(2) Al_(8) Si(τ_(5)),and Fe_(2) Al_(9) Si_(2)(τ_(6)) were formed at the interface.Mg element in 5356 filler material cannot contribute to the formation of Al-Fe intermetallic phases due to the positive mixing enthalpy of Mg-Fe.The presence of Mg enhances the hot cracking phenomenon near the Al-Fe intermetallic compound at the interface.Zn coating does not participate in intermetallic formation due to its evaporation during WB.It was concluded that the softening of the base metal in the heat-affected zone rather than the IMCs determines the joint efficiency.
基金financially supported by the National Natural Science Foundation of China(Nos.51801081 and 52171071)national funds through FCT of Portugal-Fundacao para a Ciencia e a Tecnologia,under a scientific contract of 2021.04115,CEMMPRE-ref.“UIDB/00285/2020”and LA/P/0112/2020 projects+2 种基金FEDER funds through the COMPETE program-Operational Program on Competitiveness Factorsnational funds through FCT-Foundation for Science and Technology,Outstanding University Young Teachers of“Qing Lan Project”of Jiangsu Province of China,Excellent Talents of“Shenlan Project”of Jiangsu University of Science and Technology of ChinaA part of this study was supported by the Directorate-General of Scientific Research and Technological Development(Algeria)。
文摘In the last decades,vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties.In this work,the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current(DC)reactive magnetron sputtering is investigated.The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings.In general,two layers are formed during the oxidation process:i)Ti(V)O_(2) on top,followed by a protective layer,which is subdivided into two layers,Cr_(2)O_(3) and Si-O.ii)The diffusion of V controls the oxidation of V-containing coatings.The addition of vanadium improves the wear resistance of coatings,and the wear rate decreases with increasing V content in the coatings;however,the friction coefficient is independent of the chemical composition of the coatings.The wear of the V-containing coatings is driven by polishing wear.
基金financially supported by the National Natural Science Foundation of China (Nos. 52171071, 52172090, 52071159, and 51801081)Portugal National Funds through FCT project (No. 2021.04115)+4 种基金FEDER National funds FCT under the project CEMMPRE–UIDB/ 00285/2020Outstanding University Young Teachers of “Qing Lan Project” of Jiangsu ProvinceExcellent Talents of “Shenlan Project” of Jiangsu University of Science and Technologyand China Merchants Marine Scientific Research and Innovation FundFilipe Fernandes acknowledges the funding received in the aim of the projects: MCTool21– ref. “POCI-01-0247-FEDER-045940”, CEMMPRE–ref. “UIDB/00285/2020”, and SMARTLUB–ref. “POCI-010145-FEDER-031807”
文摘The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air,water,and seawater.The results show that the addition of C into the TiN binary film induced a new amorphous phase,and the films exhibited a dual phase of fcc(face-centered cubic)-TiN and amorphous carbon.The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at%C.However,a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates.Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater,the negative abrasion state was detected for all Ti-C-N films due to the adhesion of the tribocorrosion debris on the wear track.
基金The authors acknowledge Fundaçao para a Ciencia e Tecnologia(FCT),Portugal,for the support through the Research Centre CEMMPRE(UIDB/00285/2020).
文摘Polymeric coronary stents,like the ABSORB^(TM)are commonly used to treat atherosclerosis due to their bioresorbable and cell-compatible polymer structure.However,they face challenges such as high strut thickness,high elastic recoil,and lack of radiopacity.This study aims to address these limitations by modifying degradable stents produced by additive manufacturing with poly(lactic acid)(PLA)and poly(ε-caprolactone)(PCL)with degradable metallic coatings,specifically zinc(Zn)and magnesium(Mg),deposited via radiofrequency(rf)magnetron sputtering.The characterisation included the evaluation of the degradation of the coatings,antibacterial,anti-thrombogenicity,radiopacity,and mechanical properties.The results showed that the metallic coatings inhibited bacterial growth,though Mg exhibited a high degradation rate.Thrombogenicity studies showed that Zn-coated stents had anticoagulant properties,while Mgcoated and controls were thrombogenic.Zn coatings significantly improved radiopacity,enhancing contrast by 43%.Mechanical testing revealed that metallic coatings reduced yield strength and,thus,diminished elastic recoil after stent expansion.Zn-coated stents improved cyclic compression resistance by 270%for PCL stents,with PLA-based stents showing smaller improvements.The coatings also enhanced crush resistance,particularly for Zn-coated PCL stents.Overall,Zn-coated polymers have emerged as the premier prototype due to their superior biological and mechanical performance,appropriate degradation during the stent life,and ability to provide the appropriate radiopacity to medical devices.
基金supported by projects granted by the National Natural Science Foundation of China(Nos.52171071 and 51801081)national funds through FCT of Portugal-Fundação para a Ciência e a Tecnologia,under a scientific contract of 2021.04115.CEECIND,2023.06224.CEECIND+3 种基金the projects of UIDB/00285/2020,and LA/0112/2020,MCTool21-ref.“POCI-01-0247-FEDER-045940”co-financed via FEDER and FCTFundação para a Ciência e a Tecnologia(COMPETE)The projects of UIDB/00285/2020,and LA/0112/2020The Slovenian Research Agency ARIS under the Research Core Funding Programme No.P2-0231 and the project MSCA-COFUND-5100-237/2023-9supported by the Outstanding University Young Teachers of“Qing Lan Project”of Jiangsu Province of China and the Excellent Talents of“Shenlan Project”of Jiangsu University of Science of China.
文摘The inverse relationship between the tribological and mechanical properties of environmentally friendly selflubricant films,induced by the addition of soft lubricant agents that can diffuse quickly at elevated temperatures,has hindered the widespread use of these materials in industrial applications.This paper took this challenge to break through the above established relationship by developing novel nacrelike multilayered Mo_(2)N–SiN_(x)/Ag–SiN_(x)self-lubricant films via an radio frequency(RF)magnetron sputtering system for real applications where harsh conditions at elevated temperatures exist.The multilayered films,deposited by alternating deposition of Mo_(2)N–SiN_(x)and Ag–SiN_(x)modulation layers,exhibited three phases of face-centered cubic(fcc)Mo_(2)N,fcc Ag and SiN_(x),where SiN_(x)encapsulated the nano-crystalline Mo_(2)N and Ag phases in each layer to successfully induce a“brick and mortar”nacre-like microstructure(in the area without the coherent structure).The epitaxy growth of the Ag–SiN_(x)layers with thickness below 6 nm on the Mo_(2)N template resulted in an extraordinary increase in both the hardness and elastic modulus,which was able to prevent severe degradation of the mechanical properties caused by the addition of Ag.The room-temperature anti-friction property could be enhanced by increasing the Ag–SiN_(x)layer thickness due to the excellent lubricant nature of Ag,which acts in synergy with Mo_(2)N,while the wear rate below 4×10^(−8)mm^(3)/(N·mm)was due to the high mechanical strength.The tribological properties at 600℃also benefited from the interlocked multilayered architecture,which allowed an extreme low friction coefficient of~0.12 and a negligible wear rate(WR).This behavior was attributed to the synergism between the lubricant action of Ag and Mo_(2)N and the tribo-phase transformation from Ag_(2)Mo_(4)O_(13)to Ag_(2)MoO_(4).
基金supported by Portuguese national funds through FCT-Fundação para a Ciência e a Tecnologia(grant numbers UIDB/00285/2020,LA/P/0112/2020,and 2022.13512.BD).
文摘Machines that mimic humans have inspired scientists for centuries.Bioinspired soft robotic hands are a good example of such an endeavor,featuring intrinsic material compliance and continuous motion to deal with uncertainty and adapt to unstructured environments.Recent research led to impactful achievements in functional designs,modeling,fabrication,and control of soft robots.Nevertheless,the full realization of life-like movements is still challenging to achieve,often based on trial-and-error considerations from design to fabrication,consuming time and resources.In this study,a soft robotic hand is proposed,composed of soft actuator cores and an exoskeleton,featuring a multimaterial design aided by finite element analysis(FEA)to define the hand geometry and promote finger’s bendability.The actuators are fabricated using molding,and the exoskeleton is 3D-printed in a single step.An ON-OFF controller keeps the set fingers’inner pressures related to specific bending angles,even in the presence of leaks.The FEA numerical results were validated by experimental tests,as well as the ability of the hand to grasp objects with different shapes,weights,and sizes.This integrated solution will make soft robotic hands more available to people,at a reduced cost,avoiding the time-consuming design-fabrication trial-and-error processes.
基金supported by the National Natural Science Foundation of China(Nos.52171071,51801081,and 52071159)national funds through FCT of Portugal-Fundação para a Ciência e a Tecnologia,under a scientific contract of 2021.04115.CEECIND,and the project of UIDB/00285/2020,LA/0112/2020,MCTool21-ref.“POCI-01-0247-FEDER-045940”cofinanced via FEDER and FCT-Fundação para a Ciência e a Tecnologia(COMPETE),Outstanding University Young Teachers of“Qing Lan Project”of Jiangsu Province of China,Excellent Talents of“Shenlan Project”of Jiangsu University of Science of China.
文摘A multilayer film,composed by ZrN‒Ag(20 nm)and Mo‒S‒N(10 nm)layers,combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system,to promote lubrication in a wide-range of temperatures.The results showed that the ZrN‒Ag/Mo‒S‒N multilayer film exhibited a sharp interface between the different layers.A face-centered cubic(fcc)dual-phases of ZrN and Ag co-existed in the ZrN‒Ag layers,whilst the Mo‒S‒N layers displayed a mixture of hexagonal close-packed MoS_(2)(hcp-MoS_(2))nano-particles and an amorphous phase.The multilayer film exhibited excellent room temperature(RT)triblogical behavior,as compared to the individual monolayer film,due to the combination of a relative high hardness with the low friction properties of both layers.The reorientation of MoS_(2)parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT.At 400℃,the reorientation of MoS_(2)as well as the formation of MoO_(3)phase were responsible for the lubrication,whilst the hard t-ZrO_(2)phase promoted abrasion and,consequently,led to increasing wear rate.At 600℃,the Ag_(2)MoO_(4)double-metal oxide was the responsible for the low friction and wear-resistance;furthermore,the observed transformation from t-ZrO_(2)to m-ZrO_(2),could also have contributed to the better tribological performance.
基金supported by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia,[grant numbers UIDB/00285/2020,LA/P/0112/2020,and 2022.13512.BD].
文摘Bio-inspired soft robots have already shown the ability to handle uncertainty and adapt to unstructured environments.However,their availability is partially restricted by time-consuming,costly,and highly supervised design-fabrication processes,often based on resource-intensive iterative workflows.Here,we propose an integrated approach targeting the design and fabrication of pneumatic soft actuators in a single casting step.Molds and sacrificial water-soluble hollow cores are printed using fused filament fabrication.A heated water circuit accelerates the dissolution of the core’s material and guarantees its complete removal from the actuator walls,while the actuator’s mechanical operability is defined through finite element analysis.This enables the fabrication of actuators with non-uniform cross-sections under minimal supervision,thereby reducing the number of iterations necessary during the design and fabrication processes.Three actuators capable of bending and linear motion were designed,fabricated,integrated,and demonstrated as 3 different bio-inspired soft robots,an earthworm-inspired robot,a 4-legged robot,and a robotic gripper.We demonstrate the availability,versatility,and effectiveness of the proposed methods,contributing to accelerating the design and fabrication of soft robots.This study represents a step toward increasing the accessibility of soft robots to people at a lower cost.
