Laser-induced forward transfer(LIFT)is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer(LIDT)technique.To depo...Laser-induced forward transfer(LIFT)is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer(LIDT)technique.To deposit a single nanodot in a single shot of laser irradiation,a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid–liquid–solid(SLS)process.In conventional LIDT experiments,multi-shots with step scanning have been used to form array structures.However,interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot.In this study,a femtosecond laser interference pattern was first applied to LIDT,and an array of nanodots was successfully deposited in a single shot,producing the following unit structures:a single dot,adjoining dots,and stacking dots.The diameter of the smallest nanodot was 355 nm,and the narrowest gap between two adjoining nanodots was 17.2 nm.The LIDT technique produces high-purity,catalyst-free that do not require post-cleaning or alignment processes.Given these significant advantages,LIDT can expand the usability of nanodots in a wide range of fields.展开更多
We present a novel approach for tailoring the laser induced surface topography upon femtosecond(fs)pulsed laser irradiation.The method employs spatially controlled double fs laser pulses to actively regulate the hydro...We present a novel approach for tailoring the laser induced surface topography upon femtosecond(fs)pulsed laser irradiation.The method employs spatially controlled double fs laser pulses to actively regulate the hydrodynamic microfluidic motion of the melted layer that gives rise to the structures formation.The pulse train used,in particular,consists of a previously unexplored spatiotemporal intensity combination including one pulse with Gaussian and another with periodically modulated intensity distribution created by Direct Laser Interference Patterning(DLIP).The interpulse delay is appropriately chosen to reveal the contribution of the microfluidic melt flow,while it is found that the sequence of the Gaussian and DLIP pulses remarkably influences the surface profile attained.Results also demonstrate that both the spatial intensity of the double pulse and the effective number of pulses per irradiation spot can further be modulated to control the formation of complex surface morphologies.The underlying physical processes behind the complex patterns’generation were interpreted in terms of a multiscale model combining electron excitation with melt hydrodynamics.We believe that this work can constitute a significant step forward towards producing laser induced surface structures on demand by tailoring the melt microfluidic phenomena.展开更多
An absolute gravimeter is a precision instrument for measuring gravitational acceleration, which plays an important role in earthquake monitoring, crustal deformation, national defense construction, etc. The frequency...An absolute gravimeter is a precision instrument for measuring gravitational acceleration, which plays an important role in earthquake monitoring, crustal deformation, national defense construction, etc. The frequency of laser interference fringes of an absolute gravimeter gradually increases with the fall time. Data are sparse in the early stage and dense in the late stage. The fitting accuracy of gravitational acceleration will be affected by least-squares fitting according to the fixed number of zero-crossing groups. In response to this problem, a method based on Fourier series fitting is proposed in this paper to calculate the zero-crossing point. The whole falling process is divided into five frequency bands using the Hilbert transformation. The multiplicative auto-regressive moving average model is then trained according to the number of optimal zero-crossing groups obtained by the honey badger algorithm. Through this model, the number of optimal zero-crossing groups determined in each segment is predicted by the least-squares fitting. The mean value of gravitational acceleration in each segment is then obtained. The method can improve the accuracy of gravitational measurement by more than 25% compared to the fixed zero-crossing groups method. It provides a new way to improve the measuring accuracy of an absolute gravimeter.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
We report, for the first time to our knowledge, an on-chip mode-locked laser diode(OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCM...We report, for the first time to our knowledge, an on-chip mode-locked laser diode(OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCMLLD that does not require cleaved facets to operate, enabling us to locate this OCMLLD at any location within the photonic chip. This OCMLLD provides a simple source of optical pulses that can be inserted within a photonic integrated circuit chip for subsequent photonic signal processing operations within the chip(modulation, optical filtering, pulse rate multiplication, and so on). The device was designed using standardized building blocks of a generic active/passive In P technology platform, fabricated in a multi-project wafer run, and achieved mode-locking operation at its fundamental frequency, given the uncertainty at the design step of the optical length of these mirrors, critical to achieve colliding pulse mode-locked operation.展开更多
Laser surface texturing(LST)has been proven to improve the tribological performance of machine elements.The micro-scale patterns manufactured by LST may act as lubricant reservoirs,thus supplying oil when encountering...Laser surface texturing(LST)has been proven to improve the tribological performance of machine elements.The micro-scale patterns manufactured by LST may act as lubricant reservoirs,thus supplying oil when encountering insufficient lubrication.However,not many studies have investigated the use of LST in the boundary lubrication regime,likely due to concerns of higher contact stresses that can occur with the increasing surface roughness.This study aims to examine the influence of LST on the fatigue lifetime of thrust rolling bearings under boundary lubrication.A series of periodic patterns were produced on the thrust rolling bearings,using two geometrically different designs,namely cross and dimple patterns.Base oil ISO VG 100 mixed with 0.05 wt%P of zinc dialkyldithiophosphate(ZDDP)was supplied.The bearings with cross patterns reduce the wear loss by two orders of magnitude.The patterns not only retain lubricant in the textured pockets but also enhance the formation of an anti-wear tribofilm.The tribofilm generation may be improved by the higher contact stresses that occur when using the textured surface.Therefore,in contrast to the negative concerns,the ball bearings with cross patterns were instead found to increase the fatigue life by a factor of three.展开更多
The delamination of copper lead frames from epoxy molding compounds(EMC)is a severe problem for microelectronic devices,as it leads to reduced heat dissipation or circuit breakage.The micro/nanoscale surface structuri...The delamination of copper lead frames from epoxy molding compounds(EMC)is a severe problem for microelectronic devices,as it leads to reduced heat dissipation or circuit breakage.The micro/nanoscale surface structuring of copper is a promising method to improve the copper-EMC interfacial adhesion.In this study,the generation of micro/nano hybrid structures on copper surfaces through femtosecond pulsed laser irradiation is proposed to improve interfacial adhesion.The micro/nano hybrid structures were realized by generating nanoscale laser-induced periodic surface structures(LIPSS)on microscale parallel grooves.Several types of hybrid surface structures were generated by changing the laser polarization direction,fluence,and scanning speed.At a specific aspect ratio of microgrooves,a latticed structure was generated on the sides of microgrooves by combining LIPSS formation and direct laser interference patterning.This study provides an efficient method for the micro/nanoscale hybrid surface structure formation for interfacial adhesion improvement between copperand EMC.展开更多
基金the Japan Society for the Promotion of Science(JSPS)through a Grant-in-Aid for Scientific Research(B)(No.16H038850)Amada Foundation for Metal Work Technology(AF-2018212).
文摘Laser-induced forward transfer(LIFT)is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer(LIDT)technique.To deposit a single nanodot in a single shot of laser irradiation,a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid–liquid–solid(SLS)process.In conventional LIDT experiments,multi-shots with step scanning have been used to form array structures.However,interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot.In this study,a femtosecond laser interference pattern was first applied to LIDT,and an array of nanodots was successfully deposited in a single shot,producing the following unit structures:a single dot,adjoining dots,and stacking dots.The diameter of the smallest nanodot was 355 nm,and the narrowest gap between two adjoining nanodots was 17.2 nm.The LIDT technique produces high-purity,catalyst-free that do not require post-cleaning or alignment processes.Given these significant advantages,LIDT can expand the usability of nanodots in a wide range of fields.
基金support by the European Union’s Horizon 2020 research and innovation program through the project BioCombs4Nanofibres(Grant Agreement No.862016)。
文摘We present a novel approach for tailoring the laser induced surface topography upon femtosecond(fs)pulsed laser irradiation.The method employs spatially controlled double fs laser pulses to actively regulate the hydrodynamic microfluidic motion of the melted layer that gives rise to the structures formation.The pulse train used,in particular,consists of a previously unexplored spatiotemporal intensity combination including one pulse with Gaussian and another with periodically modulated intensity distribution created by Direct Laser Interference Patterning(DLIP).The interpulse delay is appropriately chosen to reveal the contribution of the microfluidic melt flow,while it is found that the sequence of the Gaussian and DLIP pulses remarkably influences the surface profile attained.Results also demonstrate that both the spatial intensity of the double pulse and the effective number of pulses per irradiation spot can further be modulated to control the formation of complex surface morphologies.The underlying physical processes behind the complex patterns’generation were interpreted in terms of a multiscale model combining electron excitation with melt hydrodynamics.We believe that this work can constitute a significant step forward towards producing laser induced surface structures on demand by tailoring the melt microfluidic phenomena.
基金Project supported by the National Key R&D Program of China (Grant No. 2022YFF0607504)。
文摘An absolute gravimeter is a precision instrument for measuring gravitational acceleration, which plays an important role in earthquake monitoring, crustal deformation, national defense construction, etc. The frequency of laser interference fringes of an absolute gravimeter gradually increases with the fall time. Data are sparse in the early stage and dense in the late stage. The fitting accuracy of gravitational acceleration will be affected by least-squares fitting according to the fixed number of zero-crossing groups. In response to this problem, a method based on Fourier series fitting is proposed in this paper to calculate the zero-crossing point. The whole falling process is divided into five frequency bands using the Hilbert transformation. The multiplicative auto-regressive moving average model is then trained according to the number of optimal zero-crossing groups obtained by the honey badger algorithm. Through this model, the number of optimal zero-crossing groups determined in each segment is predicted by the least-squares fitting. The mean value of gravitational acceleration in each segment is then obtained. The method can improve the accuracy of gravitational measurement by more than 25% compared to the fixed zero-crossing groups method. It provides a new way to improve the measuring accuracy of an absolute gravimeter.
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.
基金support from the Spanish Ministerio de Economia y Competitividad Di DACTIC project (TEC201347753-C3-3-R)financial support from SENESCYT (National Secretary of Science, Technology, and Innovation, Quito, Ecuador) for the Ph.D. stage at Universidad Carlos Ⅲ de Madrid
文摘We report, for the first time to our knowledge, an on-chip mode-locked laser diode(OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCMLLD that does not require cleaved facets to operate, enabling us to locate this OCMLLD at any location within the photonic chip. This OCMLLD provides a simple source of optical pulses that can be inserted within a photonic integrated circuit chip for subsequent photonic signal processing operations within the chip(modulation, optical filtering, pulse rate multiplication, and so on). The device was designed using standardized building blocks of a generic active/passive In P technology platform, fabricated in a multi-project wafer run, and achieved mode-locking operation at its fundamental frequency, given the uncertainty at the design step of the optical length of these mirrors, critical to achieve colliding pulse mode-locked operation.
基金The present work is supported by Deutsche Forschungsgemeinschaft(DFG)in the priority program SPP 1551“Resource efficient machine elements”(GA 1706/2-2,Ja1940/2-2)This work is also supported by the government of Lower Austria for the endowed professorship tribology at TU Vienna(No.WST3-F-5031370/001-2017)The authors also acknowledge the support by“Austrian COMET-Programme”(Project InTribology,No.872176)under the scope of K2 XTribology and were developed in collaboration with the“Excellence Centre of Tribology”(AC2T research GmbH).
文摘Laser surface texturing(LST)has been proven to improve the tribological performance of machine elements.The micro-scale patterns manufactured by LST may act as lubricant reservoirs,thus supplying oil when encountering insufficient lubrication.However,not many studies have investigated the use of LST in the boundary lubrication regime,likely due to concerns of higher contact stresses that can occur with the increasing surface roughness.This study aims to examine the influence of LST on the fatigue lifetime of thrust rolling bearings under boundary lubrication.A series of periodic patterns were produced on the thrust rolling bearings,using two geometrically different designs,namely cross and dimple patterns.Base oil ISO VG 100 mixed with 0.05 wt%P of zinc dialkyldithiophosphate(ZDDP)was supplied.The bearings with cross patterns reduce the wear loss by two orders of magnitude.The patterns not only retain lubricant in the textured pockets but also enhance the formation of an anti-wear tribofilm.The tribofilm generation may be improved by the higher contact stresses that occur when using the textured surface.Therefore,in contrast to the negative concerns,the ball bearings with cross patterns were instead found to increase the fatigue life by a factor of three.
文摘The delamination of copper lead frames from epoxy molding compounds(EMC)is a severe problem for microelectronic devices,as it leads to reduced heat dissipation or circuit breakage.The micro/nanoscale surface structuring of copper is a promising method to improve the copper-EMC interfacial adhesion.In this study,the generation of micro/nano hybrid structures on copper surfaces through femtosecond pulsed laser irradiation is proposed to improve interfacial adhesion.The micro/nano hybrid structures were realized by generating nanoscale laser-induced periodic surface structures(LIPSS)on microscale parallel grooves.Several types of hybrid surface structures were generated by changing the laser polarization direction,fluence,and scanning speed.At a specific aspect ratio of microgrooves,a latticed structure was generated on the sides of microgrooves by combining LIPSS formation and direct laser interference patterning.This study provides an efficient method for the micro/nanoscale hybrid surface structure formation for interfacial adhesion improvement between copperand EMC.