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Versatile applications of three-dimensional objects fabricated by two-photon-initiated polymerization
摘要： In this topical review of two-photon stereolithography (TPS), we discuss novel materials and demonstrate applications of this technology. Two-photon-initiated chemical processes are used to fabricate arbitrary three-dimensional structures in TPS. In the first part of this article, the development of novel photoactive materials to fabricate pure inorganic or organic–inorganic hybrid microstructures is discussed. The second part discusses the fabrication of functional microstructures for highly specific applications to demonstrate the importance of TPS in different fields of science.
关键词： two-photon stereolithography,photoactive materials,functional microstructures,three-dimensional structures,TPS
更新于2025-09-23 15:21:01
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Microstructures Manufactured in Diamond by Use of Laser Micromachining
摘要： Different microstructures were created on the surface of a polycrystalline diamond plate (obtained by microwave plasma-enhanced chemical vapor deposition—MW PECVD process) by use of a nanosecond pulsed DPSS (diode pumped solid state) laser with a 355 nm wavelength and a galvanometer scanning system. Different average powers (5 to 11 W), scanning speeds (50 to 400 mm/s) and scan line spacings (“hatch spacing”) (5 to 20 μm) were applied. The microstructures were then examined using scanning electron microscopy, confocal microscopy and Raman spectroscopy techniques. Microstructures exhibiting excellent geometry were obtained. The precise geometries of the microstructures, exhibiting good perpendicularity, deep channels and smooth surfaces show that the laser microprocessing can be applied in manufacturing diamond microfluidic devices. Raman spectra show small differences depending on the process parameters used. In some cases, the diamond band (at 1332 cm?1) after laser modification of material is only slightly wider and shifted, but with no additional peaks, indicating that the diamond is almost not changed after laser interaction. Some parameters did show that the modification of material had occurred and additional peaks in Raman spectra (typical for low-quality chemical vapor deposition CVD diamond) appeared, indicating the growing disorder of material or manufacturing of the new carbon phase.
关键词： laser microprocessing,polycrystalline diamond,microstructures
更新于2025-09-23 15:19:57
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Application of Atom Probe Tomography to Complex Microstructures of Laser Additively Manufactured Samples
摘要： Additive Manufacturing (AM) technologies have gained increasing interest across multiple industrial sectors ranging from biomedical to aerospace. AM is not only used for prototyping, but also for tooling as well as for final part production. The computer-controlled, layer-by-layer building up process allows for increased design freedom enabling to produce almost any shape. Additional benefits are potential resource efficiency, increased product customization and lightweight design. Two prominent metal-based laser AM (LAM) techniques are laser powder bed fusion (LPBF) and laser metal deposition (LMD). In LPBF, a focused laser beam is scanned over a bed filled with metal powder to locally melt and fuse the powder to produce fully dense metal parts. The next layer of powder is then distributed and the laser scans again. LMD is a nozzle-based AM process in which a focused laser beam creates a melt pool in the build’s surface. Metallic powder is then injected into the melt pool through a nozzle. The 3D part is built by moving the nozzle/laser assembly forward track by track and layer by layer. Material produced by LAM exhibits a unique thermal history: initially, the material is cooled rapidly from the liquid state in the meltpool. Subsequently, the material experiences a cyclic reheating, the so-called intrinsic heat treatment (IHT), as neighboring tracks and further layers are deposited during the LAM process. Consequences of this thermal history are very complex, sometimes hierarchical microstructures with inhomogeneities at scales ranging from nanometers up millimeters. Fully understanding and characterizing these microstructures is challenging and requires the combination of methods spanning a similar range: from light optical microscopy (LOM) to electron microscopy to atom probe tomography (APT). Here we present examples how APT can deliver valuable information on complex microstructures to better understand the IHT, rapid solidification as well as phase separation in different metallic alloys. Here I will discuss examples in steel, Al- and Ni-based superalloys, and high entropy alloys (HEA).
关键词： Laser Additive Manufacturing,Additive Manufacturing,Phase Separation,Microstructures,Atom Probe Tomography,Rapid Solidification,Intrinsic Heat Treatment
更新于2025-09-23 15:19:57
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Formation of periodic superhydrophilic microstructures by infrared nanosecond laser processing of single-crystal silicon
摘要： The evolution of the morphology and composition of the single-crystal silicon surface irradiated by infrared and visible nanosecond laser pulses is investigated as a function of processing parameters (laser fluence, irradiation spot size, the number of pulses, background gas pressure and composition). Two types of periodic surface microstructures are obtained with IR (1064 nm) laser pulses in a narrow fluence range of 3-6 J/cm2. At a relatively low number of laser pulses applied, a grid of cleavage cracks is produced within the irradiation spot along the crystal orientation. With further Si irradiation, periodic microhillocks are formed in the nodes of the crack grid. Silicon surface with such microhillocks exhibits superhydrophilic properties which are retained during prolonged storage in air. The cracks are produced in any environment (including vacuum) but the microhillocks are observed only in the presence of oxygen. No periodic structures were observed with visible (532 nm) laser pulses. Mechanisms of nanosecond laser-induced periodic microstructure formation on silicon are discussed.
关键词： oxidation,superhydrophilicity,silicon,periodic microstructures,Nanosecond laser ablation,damage threshold
更新于2025-09-23 15:19:57
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FIB-SEM Investigation of Laser-Induced Periodic Surface Structures and Conical Surface Microstructures on D16T (AA2024-T4) Alloy
摘要： The use of aluminum alloy AA2024-T4 (Russian designation D16T) in applications requiring a high strength-to-weight ratio and fatigue resistance such as aircraft fuselage often demands the control and modification of surface properties. A promising route to surface conditioning of Al alloys is laser treatment. In the present work, the formation of ripples and conical microstructures under scanning with femtosecond (fs) laser pulses was investigated. Laser treatment was performed using 250 fs pulses of a 1033 nm Yb:YAG laser. The fluence of the pulses varied from 5 to 33 J/cm2. The scanning was repeated from 1 to 5 times for different areas of the sample. Treated areas were evaluated using focused ion beam (FIB)- scanning electron microscopy (SEM) imaging and sectioning, energy-dispersive X-ray (EDX) spectroscopy, atomic force microscopy (AFM), and confocal laser profilometry. The period of laser-induced periodic surface structures (LIPSS) and the average spacing of conical microstructures were deduced from SEM images by FFT. Unevenness of the treated areas was observed that is likely to have been caused by ablation debris. The structural and elemental changes of the material inside the conical microstructures was revealed by FIB-SEM and EDX. The underlying formation mechanisms of observed structures are discussed in this paper.
关键词： femtosecond laser,LIPSS,conical microstructures,aluminum alloy 2024
更新于2025-09-23 15:19:57
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Nanoscaled Fractal Superstructures via Laser Patterninga??A Versatile Route to Metallic Hierarchical Porous Materials
摘要： A laser-based procedure for the preparation of metallic hierarchical porous materials is introduced and exemplified on tin, copper, silicon, titanium, and tungsten surfaces to demonstrate its general applicability. The impact of suitably tuned nanosecond laser pulses triggers a process in which laser-induced metal ablation and instantaneous recondensation of partially oxidized metals lead to cauliflower-like superstructures comprising a hybrid micro-/nanopatterning. Repeated scanning with the intense focused beam over the surface creates microstructures of hierarchically tunable porosity in a layer-by-layer design. The 3D morphology of these superstructures is analyzed using tomographic data based on focused ion-beam scanning electron microscopy to return a fractal dimension of Df = 2.79—practically identical to a natural cauliflower (Df ≈ 2.8), even though the plant is four orders of magnitude larger than the superstructures generated through the laser process. The high Df value signifies a complex morphology that boasts a huge external surface. The introduced concept enables convenient access to a variety of metallic hierarchical porous materials, which are key to performance in environmentally and technologically relevant areas like energy generation, storage, and conversion, as well as sensing and catalysis.
关键词： fractal morphology,cauliflower-like superstructures,porous nanostructures,self-organizing microstructures,scalable patterning
更新于2025-09-23 15:19:57
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A fundamental investigation on threea??dimensional laser material deposition of AISI316L stainless steel
摘要： Laser material deposition (LMD), a direct laser deposition additive manufacturing technology, has been widely used to build full density metal parts. However, owing to the parallel deposition way which is universal used in LMD process, the staircase e?ect is presented even the collision occurs during the shape of target part is irregular and relatively complex. In this paper, the appropriate range of z-increment, which can assure the thin-walled part is perfectly fabricated, was veri?ed initially. Based on the e?ects of defocusing and z-increment on the deposited height, a novel three-dimensional laser material deposition process, which can provide new ways of avoiding the staircase e?ect and eluding the collision, was proposed. An experimental investigation, which contains the e?ects of deposition strategies (parallel and three-dimensional deposition way) and slope angle on the microstructures, hardness, and tensile properties of the fabricated slope thin-walled part, was conducted. The results showed that the grain size near the high side of slope thin-walled part increased with the increase of the slope angle regardless of the deposition way due to the increased accumulated heat. The average hardness of the parts with di?erent deposition way were basically the same, but the distributions of harness were quite di?erent. In addition, with the increase of the deposition height, the hardness increased until the distance to the substrate was about 25 mm and then decreased. The UTS and elongation of the LMD part in parallel deposition way were slightly higher than those of the part in three-dimensional deposition way. The UTS and elongation increased ?rstly and then decreased with the increase of the angle (β) between tensile loading direction and horizontal direction regardless of the deposition way. In the case of parallel and three-dimensional deposition way, the biggest UTS was presented during the β was 45° and 25° respectively because the direction of tensile loading was approximately perpendicular to the sliding surface that ensure the shearing force was smallest and the boundaries of molten pool could su?er from the highest tensile force. The smallest UTS showed when the β was 90°.
关键词： Mechanical properties,Z-increment,Microstructures,Three-dimensional deposition way,Laser material deposition
更新于2025-09-23 15:19:57
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Temperature Effect on Capillary Flow Dynamics in 1D Array of Open Nanotextured Microchannels Produced by Femtosecond Laser on Silicon
摘要： Capillary ?ow of water in an array of open nanotextured microgrooves fabricated by femtosecond laser processing of silicon is studied as a function of temperature using high-speed video recording. In a temperature range of 23–80°C, the produced wicking material provides extremely fast liquid ?ow with a maximum velocity of 37 cm/s in the initial spreading stage prior to visco-inertial regime. The capillary performance of the material enhances with increasing temperature in the inertial, visco-inertial, and partially in Washburn ?ow regimes. The classic universal Washburn’s regime is observed at all studied temperatures, giving the evidence of its universality at high temperatures as well. The obtained results are of great signi?cance for creating capillary materials for applications in cooling of electronics, energy harvesting, enhancing the critical heat ?ux of industrial boilers, and Maisotsenko cycle technologies.
关键词： Maisotsenko cycle,cooling of electronics,silicon,open capillary microchannels,microstructures,nanostructures,femtosecond laser processing,capillary flow
更新于2025-09-23 15:19:57
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Antia??Counterfeiting Microstructures Induced by Ultrashort Laser Pulses
摘要： Ultrashort pulsed laser enables selective ablation of metal films on glass substrates, ripple formation on metal surface, and defect generation inside functional glass, etc. Correspondingly, direct writing of computer-generated holograms (CGHs), ripple rendered structure color, and defect featured photostimulated luminescence can be realized. Due to the feature of small size or invisibility, these induced microstructures can be used for anti-counterfeiting.
关键词： ultrashort laser pulses,computer-generated holograms,defects,anti-counterfeiting microstructures,ripples
更新于2025-09-23 15:19:57
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Laser ablation of Ni in the presence of external magnetic field: Selection of microsized particles
摘要： The study presents results of nanosecond laser ablation of a Ni target in a liquid as a method of producing contamination-free micro- and nanosized colloidal structures. The ablation was performed in two liquids – double distilled water and ethanol, as their role on the characteristics of the ablated material is clarified. The laser ablation method in liquid was extended by applying an external magnetic field during the ablation process. A separation of micron and submicron particles from the nanoparticles in the colloidal solution is achieved by placing a substrate in the liquid, where the micron size structures are deposited under the action of the external magnetic field. At certain experimental conditions, the deposition of ordered one-dimensional microstructures on the substrate can be realized. The influence of different laser wavelengths on the features of the nanostructures dispersed in the liquid and microstructures deposited on the substrate was also investigated. On the basis of detailed analyses using Optical Microscopy, Scanning Electron Microscopy, Selected area electron diffraction, and Transmission Electron Microscopy the morphology, composition, and size distribution of the fabricated structures were studied. The presented method allows the fabrication of contamination-free micro- and nanostructures with potential applications in biotechnology, catalysis, and magneto-optics devices.
关键词： Laser ablation in liquid,Metal nanoparticles,Microstructures,Colloidal solution,External magnetic field
更新于2025-09-23 15:19:57