The undesirable dendrite growth induced by non-planar zinc(Zn)deposition and low Coulombic efficiency resulting from severe side reactions have been long-standing challenges for metallic Zn anodes and substantially im...The undesirable dendrite growth induced by non-planar zinc(Zn)deposition and low Coulombic efficiency resulting from severe side reactions have been long-standing challenges for metallic Zn anodes and substantially impede the practical application of rechargeable aqueous Zn metal batteries(ZMBs).Herein,we present a strategy for achieving a high-rate and long-cycle-life Zn metal anode by patterning Zn foil surfaces and endowing a Zn-Indium(Zn-In)interface in the microchannels.The accumulation of electrons in the microchannel and the zincophilicity of the Zn-In interface promote preferential heteroepitaxial Zn deposition in the microchannel region and enhance the tolerance of the electrode at high current densities.Meanwhile,electron aggregation accelerates the dissolution of non-(002)plane Zn atoms on the array surface,thereby directing the subsequent homoepitaxial Zn deposition on the array surface.Consequently,the planar dendrite-free Zn deposition and long-term cycling stability are achieved(5,050 h at 10.0 mA cm^(−2) and 27,000 cycles at 20.0 mA cm^(−2)).Furthermore,a Zn/I_(2) full cell assembled by pairing with such an anode can maintain good stability for 3,500 cycles at 5.0 C,demonstrating the application potential of the as-prepared ZnIn anode for high-performance aqueous ZMBs.展开更多
Based on our continuum hydrodynamic model for immiscible two-phaseflows at solid surfaces, the stick-slip motion has been predicted for moving contactline at chemically patterned surfaces [Wang et al., J. Fluid Mech.,...Based on our continuum hydrodynamic model for immiscible two-phaseflows at solid surfaces, the stick-slip motion has been predicted for moving contactline at chemically patterned surfaces [Wang et al., J. Fluid Mech., 605 (2008), pp. 59-78].In this paper we show that the continuum predictions can be quantitatively verifiedby molecular dynamics (MD) simulations. Our MD simulations are carried out fortwo immiscible Lennard-Jones fluids confined by two planar solid walls in Poiseuilleflow geometry. In particular, one solid surface is chemically patterned with alternating stripes. For comparison, the continuum model is numerically solved using material parameters directly measured in MD simulations. From oscillatory fluid-fluidinterface to intermittent stick-slip motion of moving contact line, we have quantitativeagreement between the continuum and MD results. This agreement is attributed tothe accurate description down to molecular scale by the generalized Navier boundary condition in our continuum model. Numerical results are also presented for therelaxational dynamics of fluid-fluid interface, in agreement with a theoretical analysisbased on the Onsager principle of minimum energy dissipation.展开更多
A radar-infrared compatible stealth surface is designed and analyzed.Without modifying the radar absorbing material(RAM),the design can theoretically achieve radar-infrared compatibility and broadband radar absorption...A radar-infrared compatible stealth surface is designed and analyzed.Without modifying the radar absorbing material(RAM),the design can theoretically achieve radar-infrared compatibility and broadband radar absorption through surface patterns and structures.A transmission-line-based model(TLM)is developed to analyze the radar absorbing performance of the surface.Optimization of the structure geometries is conducted aiming to maximize the-10 d B absorption bandwidth in 2–18 GHz.Surface with optimized structure geometries exhibits a superior absorption bandwidth,more than twice the bandwidth of the original 1.5 mm RAM slab,while maintaining a relatively low infrared emissivity.展开更多
Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various ...Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various plasma parameters. The radiation patterns are shown. Results show that the radiation patterns are controllable by flexibly changing the plasma length and other parameters in comparison to the metal monopole antenna. It is meaningful and instructional for the optimization of the plasma antenna design.展开更多
Dominant statistical patterns of winter Arctic surface wind (WASW) variability and their impacts on Arctic sea ice motion are investigated using the complex vector empirical orthogonal function (CVEOF) method. The...Dominant statistical patterns of winter Arctic surface wind (WASW) variability and their impacts on Arctic sea ice motion are investigated using the complex vector empirical orthogonal function (CVEOF) method. The results indicate that the leading CVEOF of Arctic surface wind variability, which accounts for 33% of the covariance, is characterized by two different and alternating spatial patterns (WASWP1 and WASWP2). Both WASWP1 and WASWP2 show strong interannual and decadal variations, superposed on their declining trends over past decades. Atmospheric circulation anomalies associated with WASWPI and WASWP2 exhibit, respectively, equivalent barotropic and some baroclinic characteristics, differing from the Arctic dipole anomaly and the seesaw structure anomaly between the Barents Sea and the Beaufort Sea. On decadal time scales, the decline trend of WASWP2 can be attributed to persistent warming of sea surface temperature in the Greenland--Barents--Kara seas from autunm to winter, reflecting the effect of the Arctic warming. The second CVEOF, which accounts for 18% of the covariance, also contains two different spatial patterns (WASWP3 and WASWP4). Their time evolutions are significantly correlated with the North Atlantic Oscillation (NAO) index and the central Arctic Pattern, respectively, measured by the leading EOF of winter sea level pressure (SLP) north of 70~N. Thus, winter anomalous surface wind pattern associated with the NAO is not the most important surface wind pattern. WASWP3 and WASWP4 primarily reflect natural variability of winter surface wind and neither exhibits an apparent trend that differs from WASWP1 or WASWP2. These dominant surface wind patterns strongly influence Arctic sea ice motion and sea ice exchange between the western and eastern Arctic. Furthermore, the Fram Strait sea ice volume flux is only significantly correlated with WASWP3. The results demonstrate that surface and geostrophic winds are not interchangeable in terms of describing wind field variability over the Arctic Ocean. The results have important implications for understanding and investigating Arctic sea ice variations: Dominant patterns of Arctic surface wind variability, rather than simply whether there are the Arctic dipole anomaly and the Arctic Oscillation (or NAO), effectively affect the spatial distribution of Arctic sea ice anomalies.展开更多
In this work a new nanoscale surface marking technique,namely electron beam damage induced surface marking(EBDISM),is developed and tested for the first time on a fine-grained pure Mg surface.This technique utilizes f...In this work a new nanoscale surface marking technique,namely electron beam damage induced surface marking(EBDISM),is developed and tested for the first time on a fine-grained pure Mg surface.This technique utilizes focused high-energy electron beam of a scanning electron microscope to“burn”dense arrays of nano-scale grid patterns on the sample surface,and it is proved to be very effective for identifying and measuring localised deformation behaviours.However,the surface marking deposited by EBDISM is not permanent and it tends to deteriorate overtime.Cheap,easy to use and versatile,the EBDISM technique has a huge potential for quantitative measurement of strain field and nano-scale deformation analysis.展开更多
With sol-gel method, nanometer La-Ti composite oxide was successfully prepared at a low temperature (750~800C) using polyethylene glycol as dispersant. By means of atomic force microscope, the surface pattern, partic...With sol-gel method, nanometer La-Ti composite oxide was successfully prepared at a low temperature (750~800C) using polyethylene glycol as dispersant. By means of atomic force microscope, the surface pattern, particle size distribution, and specific surface area were studied. The compound particle surface appears as a smooth sheet, the mean size of the compound is 25.38 nm. On the specific surface, the particle erects at a height of 4.69 nm. The surface area is 58.90 nm2. The La-Ti composite oxide nanocrystal prefers to narrow and even particle size distribution and the homogeneity of surface topography.展开更多
The hollow hexagonal pattern involved in surface discharges is firstly investigated in a?dielectric barrier discharge system. The spatiotemporal structures of the pattern are studied using an intensified charge-coupl...The hollow hexagonal pattern involved in surface discharges is firstly investigated in a?dielectric barrier discharge system. The spatiotemporal structures of the pattern are studied using an intensified charge-coupled device and photomultiplier. Instantaneous images taken by an intensified charge-coupled device and optical correlation measurements show that the surface discharges are induced by volume discharges. The optical signals indicate that the discharge filaments constituting the hexagonal frame discharge randomly at the first current pulse or the second pulse, once?or twice. There is no?interleaving of several sub-lattices, which indicates that the ‘memory' effect is no longer in force due to surface discharges. By using the emission spectrum method, both the molecule vibration temperature?and electron density of the surface discharges are larger than that of the volume discharges.展开更多
Carbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern's recessions act as lubricant-retaining reservoirs.This study investigates the influenc...Carbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern's recessions act as lubricant-retaining reservoirs.This study investigates the influence of the structural depth of line patterns coated with multi-walled carbon nanotubes(CNTs)and carbon onions(COs)on their respective potential to reduce friction and wear.Direct laser interference patterning(DLIP)with a pulse duration of 12 ps is used to create line patterns with three different structural depths at a periodicity of 3.5μm on AISI 304 steel platelets.Subsequently,electrophoretic deposition(EPD)is applied to form homogeneous carbon nanoparticle coatings on the patterned platelets.Tribological ball-on-disc experiments are conducted on the as-described surfaces with an alumina counter body at a load of 100 mN.The results show that the shallower the coated structure,the lower its coefficient of friction(COF),regardless of the particle type.Thereby,with a minimum of just below 0.20,CNTs reach lower COF values than COs over most of the testing period.The resulting wear tracks are characterized by scanning electron microscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy.During friction testing,the CNTs remain in contact,and the immediate proximity,whereas the CO coating is largely removed.Regardless of structural depth,no oxidation occurs on CNT-coated surfaces,whereas minor oxidation is detected on CO-coated wear tracks.展开更多
In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strate...In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strategy to obtain highly ordered arrays of biological objects. To this purpose we fabricated a patterned surface wetted in the Cassie state, where we deposited a droplet containing genomic DNA. We observed that, when the droplet wets the surface in the Cassie state, an array of DNA filaments pinned on the top edges between pillars is formed. Conversely, when the Cassie-to-Wenzel transition occurs, DNA can be pinned at different height between pillars. These results open the way to the realization of tridimensional arrays of biological objects.展开更多
An appropriate cell microenvironment is key to tissue engineering and regenerative medicine.Revealing the factors that influence the cell microenvironment is a fundamental research topic in the fields of cell biology,...An appropriate cell microenvironment is key to tissue engineering and regenerative medicine.Revealing the factors that influence the cell microenvironment is a fundamental research topic in the fields of cell biology,biomaterials,tissue engineering,and regenerative medicine.The cell microenvironment consists of not only its surrounding cells and soluble factors,but also its extracellular matrix(ECM)or nearby external biomaterials in tissue engineering and regeneration.This review focuses on six aspects of bioma-terial-related cell microenvironments:①chemical composition of materials,②material dimensions and architecture,③material-controlled cell geometry,④effects of material charges on cells,⑤matrix stiff-ness and biomechanical microenvironment,and⑥surface modification of materials.The present chal-lenges in tissue engineering are also mentioned,and eight perspectives are predicted.展开更多
Microcutting is a precision technology that offers flexible fabrication of microfeatures or complex three-dimensional components with high machining accuracy and superior surface quality.This technology may offer grea...Microcutting is a precision technology that offers flexible fabrication of microfeatures or complex three-dimensional components with high machining accuracy and superior surface quality.This technology may offer great potential as well as advantageous process capabilities for the machining of hard-to-cut materials,such as tungsten carbide.The geometrical design and dimension of the tool cutting edge is a key factor that determines the size and form accuracy possible in the machined workpiece.Currently,the majority of commercial microtools are scaled-down versions of conventional macrotool designs.This approach does not impart optimal performance due to size effects and associated phenomena.Consequently,in-depth analysis and implementation of microcutting mechanics and fundamentals are required to enable successful industrial adaptation in microtool design and fabrication methods.This paper serves as a review of recent microtool designs,materials,and fabrication methods.Analysis of tool performance is discussed,and new approaches and techniques are examined.Of particular focus is tool wear suppression in the machining of hard materials and associated process parameters,including internal cooling and surface patterning techniques.The review concludes with suggestions for an integrated design and fabrication process chain which can aid industrial microtool manufacture.展开更多
In this paper,the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide(TMAH) solution with isopropyl alcohol(IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A s...In this paper,the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide(TMAH) solution with isopropyl alcohol(IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A series of experiments are performed by changing TMAH concentration,IPA concentration,etching temperature and etching time. The structure of inverted trapezoidal patterns and roughness of the bottom surface are characterized by scanning electron microscopy(SEM) and atomic force microscopy(AFM). The results show that with TMAH concentration increases,the roughness of bottom surface will decrease. The addition of IPA into TMAH solution improves the morphology of the bottom surface significantly. Low temperature is beneficial to get a smooth bottom surface. Furthermore,etching time can change the bottom surface roughness. A model is proposed to explain the etching processes. The hillock area ratio of the bottom surface has the same tendency as the etching area ratio. Finally,smooth silicon inverted trapezoidal patterns are obtained for epitaxial growth of Ga N-based light emitting diode(LED) devices.展开更多
Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patte...Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patterns,capable of controlling wrinkling time and independently modulating different information in both wrinkled and fluorescent states,remains a tremendous challenge.These limit DSPs to further enhance tamper-proofing capacity and extend the information storage density.Here,a rationally designed patterning strategy based on controllable elastic modulus was demonstrated to fabricate self-erasable dynamic surface patterns(S-DSPs)that increase information storage density.These novel S-DSPs strategically integrated amino co-oligomers(ACOs)with the 9-anthracenemethanol(9-AM)as skin layers,designing a bilayer multi-encoding system which could carry several different types of information with wrinkled and fluorescent patterns.The ACOs with relatively low molecular weight can endow the elastic modulus of skin layers with a wide range of regulation.As a result,the difference between the compressive strain and the critical wrinkle strain in the bilayer system would be precisely modulated by photo-dimerization to form quick-response(minimum<1 min)and self-erasable(3 min–8 days)wrinkled patterns for S-DSPs.Meanwhile,the fluorescence pattern could be independently erased and reprogrammed without affecting the change in the wrinkle pattern under modulus-controlled conditions.Moreover,controllable self-erasure in S-DSPs significantly develops tamper-proof capabilities in a supply chain.This original strategy could provide a new approach to the tamper-proof,high-density,and multi-encoded information storage in the product security or inkless printing.展开更多
Exact doubly periodic standing wave patterns of the Davey-Stewartson (DS) equations are derived in terms of rational expressions of elliptic functions.In fluid mechanics,DS equations govern the evolution of weakly n...Exact doubly periodic standing wave patterns of the Davey-Stewartson (DS) equations are derived in terms of rational expressions of elliptic functions.In fluid mechanics,DS equations govern the evolution of weakly nonlinear,free surface wave packets when long wavelength modulations in two mutually perpendicular,horizontal directions are incorporated.Elliptic functions with two different moduli (periods) are necessary in the two directions.The relation between the moduli and the wave numbers constitutes the dispersion relation of such waves.In the long wave limit,localized pulses are recovered.展开更多
We demonstrate a process to achieve selective surface metallization of ZrO_(2)ceramics using ultrasound technology in atmospheric environments at 350℃,which bestows good weldability of ZrO_(2)to achieve rapid and rel...We demonstrate a process to achieve selective surface metallization of ZrO_(2)ceramics using ultrasound technology in atmospheric environments at 350℃,which bestows good weldability of ZrO_(2)to achieve rapid and reliable connections with other metals as well as ceramic materials.The challenge is that brazing or diffusion welding processes to accomplish metallurgical connections for ZrO_(2) typically require holding at elevated temperatures for minutes to hours,while the selective ultrasonic metallization process requires only a few seconds of processing without the application of covering films or solder resists.In this study,the selected Sn-2Ti alloy could effectively wet and spread on ZrO_(2)substrate under ultrasonication,and continuous interphase layers were rapidly formed in situ between ZrO_(2)and Sn-2Ti.The bonding strength for the ZrO_(2)/Sn-2Ti interface was well established with the highest shear strength of 37.1 MPa,and the fracture location occurred at the filler metal.The interfacial reaction layer thickened remarkably with the prolongation of sonication,accompanied by the partial crystallization of amorphous TiO and the formation of irregularly striped Ti_(11.31)Sn_(3)O_(10)nanocrystals.展开更多
Adverse impact of icing,on either infrastructures or facilities,is the great impulsion for seeking anti-icing coatings with high performance.In this work,durable icephobic coatings with self-regulated surface patterns...Adverse impact of icing,on either infrastructures or facilities,is the great impulsion for seeking anti-icing coatings with high performance.In this work,durable icephobic coatings with self-regulated surface patterns were developed from branched polydimethylsiloxane(PDMS)co-crosslinked with fluorinated polyhedral oligomeric silsesquioxane(POSS)through a breath figure method.The prepared coatings with patterned microstructures on the surfaces exhibited excellent anti-icing performance ascribed to micro-crack generation between ice and coating surface under a small external force.The stable cross-linked network composed of branched PDMS and fluorinated POSS endowed the coatings with durability and abrasion resistance.Low ice shear strength was achieved at approximate 19.7±2.5 kPa on coating surface with self-regulated honeycomb pattern.After experiencing 30 icing/deicing cycles,the ice shear strength of the coating varied slightly.Additionally,owing to dedication of fluorinated POSS,the coating showed merely a little increase in ice shear strength after more than 1600 abrasion cycles,which was still in the icephobic range below 50 kPa.Hence,the prepared coatings with remarkably enhanced anti-icing performance and superior mechanical stability would be promising for the practical applications.展开更多
Patterning diversified properties and surface structure of polymer materials are of great importance toward their potential in biology,optics,and electronics.However,achieving both the patternability of stiffness and ...Patterning diversified properties and surface structure of polymer materials are of great importance toward their potential in biology,optics,and electronics.However,achieving both the patternability of stiffness and microstructure in a reconfigurable manner remains challenging.Here,we prepare amphigels crosslinked by dynamic disulfide bonds,which can be reversibly swollen by immiscible water or liquid paraffin.In the paraffingel form,the materials exhibited a high modulus of 130 MPa due to densified hydrogen bonds.Whereas swollen by water,the modulus fell over two orders of magnitude owing to the destruction of the hydrogen bonds.Via regionalized swelling of the solvents,well-controlled and rewritable soft/stiff mechanical patterns can be created.On the other hand,the dynamic exchange of the disulfide crosslinking enables mechanophoto patterning to fabricate sophisticated macrogeometries and microstructures.The reconfigurable stiffness-structure patterning can be manipulated orthogonally,which will create more application opportunities beyond conventional hydrogels and organogels.展开更多
Bacterial adhesion and biofilm formation impose a heavy burden on the medical system. Bacterial adhesion on implant materials would induce inflammation and result in implant failure. The adhesion of bacteria on food-p...Bacterial adhesion and biofilm formation impose a heavy burden on the medical system. Bacterial adhesion on implant materials would induce inflammation and result in implant failure. The adhesion of bacteria on food-processing and handling equipment may lead to food-borne illness. To reduce and even prevent bacterial adhesion, some bacterial anti-adhesion surface designs have been developed. However,the effect of some surface properties(including surface patterning, roughness and wettability) on bacterial adhesion has not been systematically summarized. In this review, a comprehensive overview of bacterial anti-adhesion surface design is presented. Modifying the surface pattern and roughness could reduce the contact area between bacteria and surfaces to weaken the initial adhesion force. Fabricating superhydrophobic surface or modifying hydrophilic functional groups could hinder the bacterial adhesion. The analysis and discussion about influencing factors of bacterial anti-adhesion surfaces provide basic guidelines on antibacterial surface design for future researches.展开更多
基金supported by the National Research Foundation of Korea Grant funded by the Korean government(MSIP)(No.2018R1A6A1A03025708).
文摘The undesirable dendrite growth induced by non-planar zinc(Zn)deposition and low Coulombic efficiency resulting from severe side reactions have been long-standing challenges for metallic Zn anodes and substantially impede the practical application of rechargeable aqueous Zn metal batteries(ZMBs).Herein,we present a strategy for achieving a high-rate and long-cycle-life Zn metal anode by patterning Zn foil surfaces and endowing a Zn-Indium(Zn-In)interface in the microchannels.The accumulation of electrons in the microchannel and the zincophilicity of the Zn-In interface promote preferential heteroepitaxial Zn deposition in the microchannel region and enhance the tolerance of the electrode at high current densities.Meanwhile,electron aggregation accelerates the dissolution of non-(002)plane Zn atoms on the array surface,thereby directing the subsequent homoepitaxial Zn deposition on the array surface.Consequently,the planar dendrite-free Zn deposition and long-term cycling stability are achieved(5,050 h at 10.0 mA cm^(−2) and 27,000 cycles at 20.0 mA cm^(−2)).Furthermore,a Zn/I_(2) full cell assembled by pairing with such an anode can maintain good stability for 3,500 cycles at 5.0 C,demonstrating the application potential of the as-prepared ZnIn anode for high-performance aqueous ZMBs.
基金This publication is based on work partially supported by Award No.SA-C0040/UKC0016made by King Abdullah University of Science and Technology(KAUST),Hong Kong RGC grant CA05/06.SC01the Croucher Foundation Grant Z0138.T.Qian was also supported by Hong Kong RGC grant No.602007.
文摘Based on our continuum hydrodynamic model for immiscible two-phaseflows at solid surfaces, the stick-slip motion has been predicted for moving contactline at chemically patterned surfaces [Wang et al., J. Fluid Mech., 605 (2008), pp. 59-78].In this paper we show that the continuum predictions can be quantitatively verifiedby molecular dynamics (MD) simulations. Our MD simulations are carried out fortwo immiscible Lennard-Jones fluids confined by two planar solid walls in Poiseuilleflow geometry. In particular, one solid surface is chemically patterned with alternating stripes. For comparison, the continuum model is numerically solved using material parameters directly measured in MD simulations. From oscillatory fluid-fluidinterface to intermittent stick-slip motion of moving contact line, we have quantitativeagreement between the continuum and MD results. This agreement is attributed tothe accurate description down to molecular scale by the generalized Navier boundary condition in our continuum model. Numerical results are also presented for therelaxational dynamics of fluid-fluid interface, in agreement with a theoretical analysisbased on the Onsager principle of minimum energy dissipation.
基金the Science&Technology Innovation Fund of AVIC Manufacturing Technology Institute,China(Grant No.KS91007113)。
文摘A radar-infrared compatible stealth surface is designed and analyzed.Without modifying the radar absorbing material(RAM),the design can theoretically achieve radar-infrared compatibility and broadband radar absorption through surface patterns and structures.A transmission-line-based model(TLM)is developed to analyze the radar absorbing performance of the surface.Optimization of the structure geometries is conducted aiming to maximize the-10 d B absorption bandwidth in 2–18 GHz.Surface with optimized structure geometries exhibits a superior absorption bandwidth,more than twice the bandwidth of the original 1.5 mm RAM slab,while maintaining a relatively low infrared emissivity.
文摘Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various plasma parameters. The radiation patterns are shown. Results show that the radiation patterns are controllable by flexibly changing the plasma length and other parameters in comparison to the metal monopole antenna. It is meaningful and instructional for the optimization of the plasma antenna design.
基金supported by the National Key Basic Research Project of China (Grant nos.2013CBA01804,2015CB453200)the National Natural Science Foundation of China (Grant nos.41475080,41221064)the Ocean Public Welfare Scientific Research Project of China (Grant no.201205007)
文摘Dominant statistical patterns of winter Arctic surface wind (WASW) variability and their impacts on Arctic sea ice motion are investigated using the complex vector empirical orthogonal function (CVEOF) method. The results indicate that the leading CVEOF of Arctic surface wind variability, which accounts for 33% of the covariance, is characterized by two different and alternating spatial patterns (WASWP1 and WASWP2). Both WASWP1 and WASWP2 show strong interannual and decadal variations, superposed on their declining trends over past decades. Atmospheric circulation anomalies associated with WASWPI and WASWP2 exhibit, respectively, equivalent barotropic and some baroclinic characteristics, differing from the Arctic dipole anomaly and the seesaw structure anomaly between the Barents Sea and the Beaufort Sea. On decadal time scales, the decline trend of WASWP2 can be attributed to persistent warming of sea surface temperature in the Greenland--Barents--Kara seas from autunm to winter, reflecting the effect of the Arctic warming. The second CVEOF, which accounts for 18% of the covariance, also contains two different spatial patterns (WASWP3 and WASWP4). Their time evolutions are significantly correlated with the North Atlantic Oscillation (NAO) index and the central Arctic Pattern, respectively, measured by the leading EOF of winter sea level pressure (SLP) north of 70~N. Thus, winter anomalous surface wind pattern associated with the NAO is not the most important surface wind pattern. WASWP3 and WASWP4 primarily reflect natural variability of winter surface wind and neither exhibits an apparent trend that differs from WASWP1 or WASWP2. These dominant surface wind patterns strongly influence Arctic sea ice motion and sea ice exchange between the western and eastern Arctic. Furthermore, the Fram Strait sea ice volume flux is only significantly correlated with WASWP3. The results demonstrate that surface and geostrophic winds are not interchangeable in terms of describing wind field variability over the Arctic Ocean. The results have important implications for understanding and investigating Arctic sea ice variations: Dominant patterns of Arctic surface wind variability, rather than simply whether there are the Arctic dipole anomaly and the Arctic Oscillation (or NAO), effectively affect the spatial distribution of Arctic sea ice anomalies.
基金support from the Australian Research Council(LP180100048)Baosteel Company。
文摘In this work a new nanoscale surface marking technique,namely electron beam damage induced surface marking(EBDISM),is developed and tested for the first time on a fine-grained pure Mg surface.This technique utilizes focused high-energy electron beam of a scanning electron microscope to“burn”dense arrays of nano-scale grid patterns on the sample surface,and it is proved to be very effective for identifying and measuring localised deformation behaviours.However,the surface marking deposited by EBDISM is not permanent and it tends to deteriorate overtime.Cheap,easy to use and versatile,the EBDISM technique has a huge potential for quantitative measurement of strain field and nano-scale deformation analysis.
基金This project was supported by the National Natural Science Foundation of China (1972003).
文摘With sol-gel method, nanometer La-Ti composite oxide was successfully prepared at a low temperature (750~800C) using polyethylene glycol as dispersant. By means of atomic force microscope, the surface pattern, particle size distribution, and specific surface area were studied. The compound particle surface appears as a smooth sheet, the mean size of the compound is 25.38 nm. On the specific surface, the particle erects at a height of 4.69 nm. The surface area is 58.90 nm2. The La-Ti composite oxide nanocrystal prefers to narrow and even particle size distribution and the homogeneity of surface topography.
基金supported by National Natural Science Foundation of China(Nos.11375051 and 11505044)Key Basic Research Project in the application basic research plan of Hebei Province(No.15961105D)the Research Foundation of Education Bureau of Hebei Province,China(No.LJRC011)
文摘The hollow hexagonal pattern involved in surface discharges is firstly investigated in a?dielectric barrier discharge system. The spatiotemporal structures of the pattern are studied using an intensified charge-coupled device and photomultiplier. Instantaneous images taken by an intensified charge-coupled device and optical correlation measurements show that the surface discharges are induced by volume discharges. The optical signals indicate that the discharge filaments constituting the hexagonal frame discharge randomly at the first current pulse or the second pulse, once?or twice. There is no?interleaving of several sub-lattices, which indicates that the ‘memory' effect is no longer in force due to surface discharges. By using the emission spectrum method, both the molecule vibration temperature?and electron density of the surface discharges are larger than that of the volume discharges.
基金financial support by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)within the project MU 959/47-1Furthermore,the authors gratefully acknowledge funding in the ZuMat projectsupported by the State of Saarland from the European Regional Development Fund(Europäischer Fonds für Regionale Entwicklung,EFRE).P.Grützmacher and C.Gachot would like to thank the Government of Lower Austria(WST3)for financially supporting the endowed professorship tribology at the TU Wien.V.Presser thanks Eduard Arzt(INM)for his continuing support.
文摘Carbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern's recessions act as lubricant-retaining reservoirs.This study investigates the influence of the structural depth of line patterns coated with multi-walled carbon nanotubes(CNTs)and carbon onions(COs)on their respective potential to reduce friction and wear.Direct laser interference patterning(DLIP)with a pulse duration of 12 ps is used to create line patterns with three different structural depths at a periodicity of 3.5μm on AISI 304 steel platelets.Subsequently,electrophoretic deposition(EPD)is applied to form homogeneous carbon nanoparticle coatings on the patterned platelets.Tribological ball-on-disc experiments are conducted on the as-described surfaces with an alumina counter body at a load of 100 mN.The results show that the shallower the coated structure,the lower its coefficient of friction(COF),regardless of the particle type.Thereby,with a minimum of just below 0.20,CNTs reach lower COF values than COs over most of the testing period.The resulting wear tracks are characterized by scanning electron microscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy.During friction testing,the CNTs remain in contact,and the immediate proximity,whereas the CO coating is largely removed.Regardless of structural depth,no oxidation occurs on CNT-coated surfaces,whereas minor oxidation is detected on CO-coated wear tracks.
文摘In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strategy to obtain highly ordered arrays of biological objects. To this purpose we fabricated a patterned surface wetted in the Cassie state, where we deposited a droplet containing genomic DNA. We observed that, when the droplet wets the surface in the Cassie state, an array of DNA filaments pinned on the top edges between pillars is formed. Conversely, when the Cassie-to-Wenzel transition occurs, DNA can be pinned at different height between pillars. These results open the way to the realization of tridimensional arrays of biological objects.
基金the financial support from the National Natural Science Foundation of China (21961160721 and 52130302)the National Key Research and Development Program of China(2016YFC1100300)
文摘An appropriate cell microenvironment is key to tissue engineering and regenerative medicine.Revealing the factors that influence the cell microenvironment is a fundamental research topic in the fields of cell biology,biomaterials,tissue engineering,and regenerative medicine.The cell microenvironment consists of not only its surrounding cells and soluble factors,but also its extracellular matrix(ECM)or nearby external biomaterials in tissue engineering and regeneration.This review focuses on six aspects of bioma-terial-related cell microenvironments:①chemical composition of materials,②material dimensions and architecture,③material-controlled cell geometry,④effects of material charges on cells,⑤matrix stiff-ness and biomechanical microenvironment,and⑥surface modification of materials.The present chal-lenges in tissue engineering are also mentioned,and eight perspectives are predicted.
基金supported by Science Foundation Ireland(No.15/RP/B3208)the National Natural Science Foundation of China(Nos.51320105009&61635008)the‘111’Project by the State Administration of Foreign Experts Affairs and the Ministry of Education of China(Grant No.B07014).
文摘Microcutting is a precision technology that offers flexible fabrication of microfeatures or complex three-dimensional components with high machining accuracy and superior surface quality.This technology may offer great potential as well as advantageous process capabilities for the machining of hard-to-cut materials,such as tungsten carbide.The geometrical design and dimension of the tool cutting edge is a key factor that determines the size and form accuracy possible in the machined workpiece.Currently,the majority of commercial microtools are scaled-down versions of conventional macrotool designs.This approach does not impart optimal performance due to size effects and associated phenomena.Consequently,in-depth analysis and implementation of microcutting mechanics and fundamentals are required to enable successful industrial adaptation in microtool design and fabrication methods.This paper serves as a review of recent microtool designs,materials,and fabrication methods.Analysis of tool performance is discussed,and new approaches and techniques are examined.Of particular focus is tool wear suppression in the machining of hard materials and associated process parameters,including internal cooling and surface patterning techniques.The review concludes with suggestions for an integrated design and fabrication process chain which can aid industrial microtool manufacture.
基金supported by the National Natural Science Foundation of China(Nos.51472229,61422405,51202238,61306051 and 61474109)the “100 Talent Program” of Chinese Academy of Sciencesthe Opening Funding of State Key Lab of Silicon Materials(No.SKL2014-4)
文摘In this paper,the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide(TMAH) solution with isopropyl alcohol(IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A series of experiments are performed by changing TMAH concentration,IPA concentration,etching temperature and etching time. The structure of inverted trapezoidal patterns and roughness of the bottom surface are characterized by scanning electron microscopy(SEM) and atomic force microscopy(AFM). The results show that with TMAH concentration increases,the roughness of bottom surface will decrease. The addition of IPA into TMAH solution improves the morphology of the bottom surface significantly. Low temperature is beneficial to get a smooth bottom surface. Furthermore,etching time can change the bottom surface roughness. A model is proposed to explain the etching processes. The hillock area ratio of the bottom surface has the same tendency as the etching area ratio. Finally,smooth silicon inverted trapezoidal patterns are obtained for epitaxial growth of Ga N-based light emitting diode(LED) devices.
基金This work was supported by the National Natural Science Foundations of China(Nos.51903058,51873042,and 51833011)Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education(No.PCFM-2922A02)Guangzhou Basic and Applied Basic Research Foundation(No.202201010382).
文摘Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patterns,capable of controlling wrinkling time and independently modulating different information in both wrinkled and fluorescent states,remains a tremendous challenge.These limit DSPs to further enhance tamper-proofing capacity and extend the information storage density.Here,a rationally designed patterning strategy based on controllable elastic modulus was demonstrated to fabricate self-erasable dynamic surface patterns(S-DSPs)that increase information storage density.These novel S-DSPs strategically integrated amino co-oligomers(ACOs)with the 9-anthracenemethanol(9-AM)as skin layers,designing a bilayer multi-encoding system which could carry several different types of information with wrinkled and fluorescent patterns.The ACOs with relatively low molecular weight can endow the elastic modulus of skin layers with a wide range of regulation.As a result,the difference between the compressive strain and the critical wrinkle strain in the bilayer system would be precisely modulated by photo-dimerization to form quick-response(minimum<1 min)and self-erasable(3 min–8 days)wrinkled patterns for S-DSPs.Meanwhile,the fluorescence pattern could be independently erased and reprogrammed without affecting the change in the wrinkle pattern under modulus-controlled conditions.Moreover,controllable self-erasure in S-DSPs significantly develops tamper-proof capabilities in a supply chain.This original strategy could provide a new approach to the tamper-proof,high-density,and multi-encoded information storage in the product security or inkless printing.
基金support of the Hong Kong Research Grants Council through contracts 711807E and 712008E
文摘Exact doubly periodic standing wave patterns of the Davey-Stewartson (DS) equations are derived in terms of rational expressions of elliptic functions.In fluid mechanics,DS equations govern the evolution of weakly nonlinear,free surface wave packets when long wavelength modulations in two mutually perpendicular,horizontal directions are incorporated.Elliptic functions with two different moduli (periods) are necessary in the two directions.The relation between the moduli and the wave numbers constitutes the dispersion relation of such waves.In the long wave limit,localized pulses are recovered.
基金financially supported by the National Natural Science Foundation of China(No.51805111).
文摘We demonstrate a process to achieve selective surface metallization of ZrO_(2)ceramics using ultrasound technology in atmospheric environments at 350℃,which bestows good weldability of ZrO_(2)to achieve rapid and reliable connections with other metals as well as ceramic materials.The challenge is that brazing or diffusion welding processes to accomplish metallurgical connections for ZrO_(2) typically require holding at elevated temperatures for minutes to hours,while the selective ultrasonic metallization process requires only a few seconds of processing without the application of covering films or solder resists.In this study,the selected Sn-2Ti alloy could effectively wet and spread on ZrO_(2)substrate under ultrasonication,and continuous interphase layers were rapidly formed in situ between ZrO_(2)and Sn-2Ti.The bonding strength for the ZrO_(2)/Sn-2Ti interface was well established with the highest shear strength of 37.1 MPa,and the fracture location occurred at the filler metal.The interfacial reaction layer thickened remarkably with the prolongation of sonication,accompanied by the partial crystallization of amorphous TiO and the formation of irregularly striped Ti_(11.31)Sn_(3)O_(10)nanocrystals.
基金supported by the Natural Science Foundation of Tianjin,China(Grant Nos.18JCQNJC03800,14ZCZDGX00008)the National Natural Science Foundation of China(Grant No.51273146)。
文摘Adverse impact of icing,on either infrastructures or facilities,is the great impulsion for seeking anti-icing coatings with high performance.In this work,durable icephobic coatings with self-regulated surface patterns were developed from branched polydimethylsiloxane(PDMS)co-crosslinked with fluorinated polyhedral oligomeric silsesquioxane(POSS)through a breath figure method.The prepared coatings with patterned microstructures on the surfaces exhibited excellent anti-icing performance ascribed to micro-crack generation between ice and coating surface under a small external force.The stable cross-linked network composed of branched PDMS and fluorinated POSS endowed the coatings with durability and abrasion resistance.Low ice shear strength was achieved at approximate 19.7±2.5 kPa on coating surface with self-regulated honeycomb pattern.After experiencing 30 icing/deicing cycles,the ice shear strength of the coating varied slightly.Additionally,owing to dedication of fluorinated POSS,the coating showed merely a little increase in ice shear strength after more than 1600 abrasion cycles,which was still in the icephobic range below 50 kPa.Hence,the prepared coatings with remarkably enhanced anti-icing performance and superior mechanical stability would be promising for the practical applications.
基金supported by the National Natural Science Foundation of China (Nos.22105167,U20A6001,and 52273112).
文摘Patterning diversified properties and surface structure of polymer materials are of great importance toward their potential in biology,optics,and electronics.However,achieving both the patternability of stiffness and microstructure in a reconfigurable manner remains challenging.Here,we prepare amphigels crosslinked by dynamic disulfide bonds,which can be reversibly swollen by immiscible water or liquid paraffin.In the paraffingel form,the materials exhibited a high modulus of 130 MPa due to densified hydrogen bonds.Whereas swollen by water,the modulus fell over two orders of magnitude owing to the destruction of the hydrogen bonds.Via regionalized swelling of the solvents,well-controlled and rewritable soft/stiff mechanical patterns can be created.On the other hand,the dynamic exchange of the disulfide crosslinking enables mechanophoto patterning to fabricate sophisticated macrogeometries and microstructures.The reconfigurable stiffness-structure patterning can be manipulated orthogonally,which will create more application opportunities beyond conventional hydrogels and organogels.
基金supported by the National Natural Science Foundation of China (52003028)Fundamental Research Funds for the Central Universities (FRF-GF-20-06B)
文摘Bacterial adhesion and biofilm formation impose a heavy burden on the medical system. Bacterial adhesion on implant materials would induce inflammation and result in implant failure. The adhesion of bacteria on food-processing and handling equipment may lead to food-borne illness. To reduce and even prevent bacterial adhesion, some bacterial anti-adhesion surface designs have been developed. However,the effect of some surface properties(including surface patterning, roughness and wettability) on bacterial adhesion has not been systematically summarized. In this review, a comprehensive overview of bacterial anti-adhesion surface design is presented. Modifying the surface pattern and roughness could reduce the contact area between bacteria and surfaces to weaken the initial adhesion force. Fabricating superhydrophobic surface or modifying hydrophilic functional groups could hinder the bacterial adhesion. The analysis and discussion about influencing factors of bacterial anti-adhesion surfaces provide basic guidelines on antibacterial surface design for future researches.