This PDF file contains the front matter associated with SPIE Proceedings Volume 10675, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Invited talk. See Abstract tect for online and/or printed programs.

3D printing, also called additive manufacturing, offers a new vision for optical fabrication in term of achievable optical quality and reduction of weight and cost. In this paper we describe two different ways to use this technique in the fabrication process. The first method makes use of 3D printing in the fabrication of warping harnesses for stress polishing, and we apply that to the fabrication of the WFIRST coronagraph off axis parabolas. The second method considers a proof of concept for 3D printing of lightweight X-Ray mirrors, targeting the next generation of X-rays telescopes. Stress polishing is well suited for the fabrication of the high quality off axis parabolas required by the coronagraph to image exoplanets.. Here we describe a new design of warping harness which can generate astigmatism and coma with only one actuator. The idea is to incorporate 3D printing in the manufacturing of the warping harness. The method depicted in this paper demonstrates that we reach the tight precision required at the mirrors surface. Moreover the error introduced by the warping harness fabricated by 3D printing does not impact the final error budget. Concerning the proof of concept project, we investigate 3D printing towards lightweight X-ray mirrors. We present the surface metrology of test samples fabricated by stereo lithography (SLA) and Selective Laser Sintering (SLS) with different materials. The lightweighting of the samples is composed of a series of arches. By complementing 3D printing with finite element analysis topology optimization we can simulate a specific optimum shape for the given input parameters and external boundary conditions. The next set of prototypes is designed taking to account the calculation of topology optimisation.

Component surfaces feature more and more complex functional properties and deterministic geometric structures. The result is that an areal characterization of surfaces is more often necessary. The increasing incidence of areal surface topography measuring instruments in geometrical product specification enables the acquisition of more information about a surface topography. However, also more complex calibration procedures are required as an increasing number of metrological characteristics need to be verified. This verification is achieved with areal material measures which are described in the standard ISO 25178-70. State of the art is a manufacturing of the proposed geometries with many different principles because there is a broad range of geometries whose structure size is usually in the micrometer-range. Typically applied principles include lithography, etching and ultra-precision cutting. The application of an ultra-precise 3D-printing technology, two-photon laser lithography alias direct laser writing, exhibits enormous potential for areal material measures as arbitrary 3D-freeform surfaces can be manufactured with a high repeatability in the nanometer-range. Hence, a feasibility study of the application of direct laser writing for the manufacturing of areal material measures is conducted. In doing so, different standardized material measures are manufactured and the resulting surface topographies are compared to their target geometries in order to qualify the manufacturing process. The measurements are performed with different surface topography measuring instruments in order to examine the overall suitability of the principle for the manufacturing of areal material measures. The standardized measurands of the ISO 25178-70 serve as evaluation criteria just as recently defined new parameters for the verification of surface topography measuring instruments. As a new resolution criterion, for example the small scale fidelity limit is evaluated. The enhancement of the resolution of the manufacturing process with stimulated emission depletion is examined and the resolution limits of the manufacturing and the measuring processes are compared. The samples that are manufactured with direct laser writing are further examined regarding their practical abilities. An important property of material measures is their stable provision of constant evaluation parameters. In order to examine this relevant characteristic of the samples, different studies which describe the aging behavior of varying coating materials are conducted. Based on the results, a suitable coating material with suitable optical characteristics can be chosen and the time-dependent behavior of the geometries can be evaluated. Because optical surface topography measuring instruments which are calibrated with the proposed material measures may feature varying magnifications and fields of view, in another study scaling effects are examined and material measures with different structure sizes are manufactured in order to evaluate the scalability of the different types of material measures. It can be concluded that almost any standardized areal material measure can be manufactured reliably with direct laser writing. Due to the scalability of the structures, a calibration of optical surface topography measuring instruments with varying fields of view can be ensured.

Applications in, e.g., optical communication, light routing, and emerging optical quantum technologies on a chip call for waveguide networks featuring tight control over the photons used. Quantum simulators on a chip harness this high level of control to guide and manipulate entangled photon states in sophisticated networks to gain insight into the role of entanglement in interacting many-body systems. We have recently shown direct laser written polymer waveguides fabricated from a low-fluorescent negative tone photoresist via two-photon lithography [1]. These waveguides feature bend radii down to 40 µm and loss coefficients smaller than 0.81 dB/mm, facilitating networks with high integration density. For coupling control, a novel three-dimensional coupler design was shown, giving optical access to all in- and outputs of the waveguide network simultaneously via one microscope objective. We present an in-depth analysis and optimization of these coupling structures in simulation and experiment. References: [1] A. Landowski et al., APL Photonics 2, 106102 (2017)

The ability to multiplex and demultiplex optical vortex beams using 3D-laser printed elements is investigated theoretically. This method of multiplexing and demultiplexing is based on two optical elements that serve as Log-polar transforming elements. The functionality of the structures is highly sensitive to the structures' surface roughness. Hence, various calculations and simulations are demonstrated to achieve ultimate vortex beams multiplexing and demultiplexing capabilities of the 3Dprinted elements. The beams spatial intensity and phase distributions are investigated during the transformations, along with surface roughness analysis that accompany the 3D-small scale fabrication process. Surface roughness effects are shown, as incoming beams of various orbital angular momentum values propagate inside the transforming optical elements of different surface roughness. The cross-talk between 11 incoming modes is demonstrated, in various systems of varied surface roughness, 1, 1.3 and 1.5 μm accordingly. In addition, the lateral intensity and phase distributions of the various incoming modes are shown, to provide a characterization tool to analyze the elements performance.

When printing microlens arrays with a Nanoscribe Photonics Professional machine, the object is typically split in many smaller hexagonal or square fields, which are written with high-precision galvo-scanning mirrors (or with a piezo-stage). Displacements between these sub-fields are performed with a mechanical stage, which has a lower precision (±1μm). This results in misalignments in the XY-plane. However, also differences in the Z-plane are present due to limitations of the interface finding method. If such a stitching seam goes through a microlens, its resolving power is affected. In the present contribution, we will present an adaptive stitching algorithm that automatically places the writing blocks in such a way so as to avoid cutting through the individual microlenses completely.

We demonstrate the fabrication of a 3D polymer/glass micromechanical sensor by combining two femtosecond laser direct writing processes: subtractive laser-assisted chemical etching combined with additive two-photon polymerization techniques. In the first step, the micromechanical sensor was fabricated from a single fused silica substrate by selective laser etching technique. The mechanical parameters of the glass are well-researched, thus it could be used to investigate unknown polymer mechanical properties through the concept of coupled-system. In the second step, we directly integrate polymeric beam via two-photon polymerization. This combination of additive and subtractive techniques allows investigation of reversible deformations of polymeric microstructures upon immersion in various solvents. Furthermore, we demonstrate that Young’s modulus of these laser fabricated structures could be altered by changing the writing laser exposure dose, also influenced by surrounding solvent.

An approach of synchronizing linear stages and galvo-scanners in order to eliminate inherent weaknesses of each device while capitalizing on their strengths and produce millimeter-sized highly complex meso-scale structures retaining small (~μm) features is presented. We concentrate on results and discussion about the structuring rate of 3D laser lithography (3DLL), investigating the interplay between translation velocity, feature size and structuring rate. These effects are uncovered by fabricating resolution bridge structures and 1 mm length gradient chain-mail structure with ring sizes from 5 μm to 100 μm. Provided results give an insight on current state- of-the-art manufacturing throughput of 3DLL systems using scanner-stage synchronization and allow to project the technological limit of this technique.

X-ray microscopy is advantageous over conventional optical microscopy because of its high resolution and capability to study the inner structure of materials opaque to visible light. Furthermore, this method does not require metallization and vacuum and therefore it can be used to visualize fragile biological samples that cannot be studied by scanning electron microscopy. Focusing X-ray optics may be roughly divided into three groups based on the physical principle of focusing: reflection, diffraction and refraction. The reflection optics includes curved mirrors, multilayers and capillaries; the diffractive optics includes Fresnel zone plates. Refractive optics comprises X-ray compound refractive lenses (CRLs) that are widely used nowadays because of their compactness and ease of fabrication. Focusing performance of the CRL is determined by the refractive index, absorption, the inner structure of the CRL material and the geometry of the lens. The optimal shape for the lens is parabolic with a small radius of curvature, because the smaller radius of the parabola leads to shorter focal distance and therefore allows to achieve higher resolution. The common choice of the CRL material is beryllium. However the resolution of Be lenses is far below theoretically predicted limits because of the parasitic scattering introduced by the grains in the material. Moreover the existing manufacturing technologies do not allow to achieve radius of curvature less than 50 μm. Polymer materials are also popular for the CRL microfabrication because of their amorphous nature, ease of structuring and low price. Among the advanced lithographic techniques the two-photon polymerization lithography (2PP) holds a special place. It is based on polymer solidification by means of two-photon absorption. Nonlinear character of two-photon absorption leads to the transparency of the out-of focus material, while presence of polymerization threshold reduces resolution far below diffraction limit. Therefore 2PP can be used for fabrication 3D structures of almost arbitrary shape including overhanging and self-intersecting structures. In this work we introduce the 3D X-ray CRL fabricated by 2PP from the commercially available photoresist ORMOCOMP. Hundred double concave individual lenses formed a CRL with the 60 μm distance between adjacent lenses. Radius of curvature of a single parabolic surface was 3 μm that is comparable to radius of 2D silicon nano-lens made by conventional lithography and much less than achievable radius of 3D Be lens. Physical aperture was 28 μm. The optimal processing parameters (power, incident on the sample, and velocity of the laser beam waist movement) were determined. The fabricated CRL was studied by scanning electron microscopy. It was shown that surface of the lens is smooth and the geometrical parameters do not deviate significantly from that of the model. Focusing performance of lenses was studied by the knife-edge technique. It was obtained that the focal distance is not larger than 2 cm at the energy of 9.25 keV. The radiation resistance of the CRL was tested at the synchrotron DESY: PETRA-III. The CRL was exposed at the non-focused X-ray radiation with the standard power and the energy of 12 keV for more than 10 hours without visible degradation.

Additive manufacturing is more and more used in optics to produce opto-mechanical components as well as light transmission mediums, either for prototype evaluation or for functional part generation. It was previously shown that optical systems can benefit from the geometrical accuracy of the printed parts. Intrinsic defects such as surface roughness or volume birefringence can also be exploited for optical component design. We here present such use of particular properties of an additive manufacturing process based on photopolymerization. The final goal of the work is the design of a force sensor for collaborative robotics. More precisely, the aim is to design an optical force sensor to control the contact force between a human body and a magnetic source controlled by a robot for medical purpose. Optical sensors are known to have major interests in harsh environments where classical electrical sensors cannot be used due to, like here, electromagnetic compatibility issues. Two 3D-printed designs of optical force sensors are compared. The first one, conceptually developed in a previous work, is using polarization modulation due to force-induced birefringence to modify optical transmission in a sensor based on a monolithic original geometry. For such a case, additive manufacturing appears as a powerful production technique as the 3D part must be transparent and at the same time obtained with an accurate complex geometry. The second design is based on the volume scattering properties of printed transparent parts. For the first time to our knowledge, we show that the optical system made out of a beam expander and a cylindrical lens, necessary to achieve an optical line, can be replaced by a simple prismatic 3D-printed element. Using the Polyjet technology developed by Stratasys Ltd, a line can simply be obtained using the 1D volume light scattering inside the printed medium. The variation of line properties is then related to the mechanical strain induced by the force to be measured. In other words, the optical properties we rely on are linked to the bulk liquid material, its photopolymerization during printing and finally the impact of mechanical stress on the printed component. The sensitive element in the force sensor can be seen as a metamaterial with properties which depend on its micrometric structuration. The micro-structuration size is not related to the standard minimum feature size as claimed by the manufacturer but to the additive manufacturing process itself. In our case, a Stratasys Connex 350 printer has been used with an acrylate transparent material. Opto-mechanical properties such as birefringence, surface roughness, elasto-optic coefficients have been measured. The ability to generate an optical line using natural 1D volume light scattering in a printed parallelepiped with polished surfaces is experimentally demonstrated. As potential application, the parallelepiped is used to replace a cylindrical lens in an amplitude modulation force sensor. The sensor response is measured. Thus, additive manufacturing appears to be a promising technique to achieve optical components and to integrate optical sensors in future 3D-printed mechatronic systems.

The new innovative Depth from Defocus (DFD) method was used to visual measurement of the stroke volume of the extracorporeal pneumatic heart assist pump. The heart pump developed in the framework of the Polish Artificial Heart is the object of the study. However, the current studies are conducted on its adequate model. Using this model is justified because of the significant costs of the original prosthesis. The model was equipped with an adapter to mount the camera. This makes it possible to observe the surface of the membrane from the pneumatic chamber side without obstructing its normal operation, in particular without affecting the blood chamber. The model was designed in CAD software then it was 3D printed. The momentary surface shape of the flaccid membrane affects the volume of the blood chamber. The difficulty of the accuracy verification of the shape mapping is that heart assist pump fitted with a flaccid membrane has only two membrane states with a known mathematical description. Using reverse engineering, the authors have invented new technique to 3D modeling of any surface shape of the flaccid membrane with well-known geometric dimensions. The rigid models of different membrane states were designed in CAD software and printed on a 3D printer. The process of modeling and 3D printing and ready prototypes were presented.

In the context of the fourth industrial revolution and the related development towards self-organizing processes, innovative and advanced production technologies with completely new approaches are required. Modern additive manufacturing (AM) technologies contribute to this with their advantages like freedom of design, cost-efficient product individualization, and functional integration. By using these technologies, the fabrication of the quantity of size one and also the manufacturing of problem adapted, demand driven or requirement adapted components are possible. One promising AM technology is the fused layer modeling technology (FLM). The desired components are produced by the direct solidification of an extruded and heated filament material. Modern FLM printers are able to use two or more nozzles and therefore enable the use of two or more different filament materials within one printing job. Applying simultaneously various materials, it is feasible to print components with additional functionalities. Currently, filament materials exist that are transparent within the wavelength of optical sensor systems and optical communication systems. Combining transparent and non-transparent materials or materials with different numerical indices, it is possible to manufacture light-guiding structures which inherit all of the above mentioned capabilities of AM. In this paper, the application of FLM technology to print light-guiding structures with a defined 3D trajectory is analyzed. At first different transparent filament materials are analyzed. Then first straight test structures consisting of one optical transparent material with a variation of the number of strands are defined and printed. The core cross-section, the fusion of different strands and the attenuation of these structures are analyzed. Based on the positive results of the latter different structures with embedded optical waveguides are printed. After this, the course of the trajectories, the core cross-section, and the attenuations are analyzed by measurement. Due to the promising results, the first prototype towards a sensor application is manufactured and analyzed by measurement.

Additive Manufacturing (AM) or additive layer manufacturing such as LMD-CLAD® has gained a lot of interest for industrial applications in aeronautics and medicine, taking advantage of the ability to build complex geometries and scale parts. However, due to the high cost of some manufactured parts and construction duration (eg: 155 hours for large part with 600mm*350mm*34mm in respectively diameter, height and thickness), parts must be successfully manufactured at the first try. For that reason, local residual stresses, strains, cracks and mismatch induced by the process in manufactured parts need to be handled before construction. In this work, thermal and distortion measurements on Titanium’TA6V’ material were used to understand the effects of the deposition strategies on the time cycle. Analysis show that time cycle has a great influence on the microstructure, residual stresses and distortions. A numerical model called ‘micro-meso’ is designed to model the LMD-CLAD ® process. This model helped analyzing the time cycle and construction strategies influences on small samples. Thermal and distortion comparison are done between numerical results and manufactured sample measurements. Micro-meso model was inserted in a ‘macro model’ which is a scale part. This simulation method helps to drastically reduce computation time of large parts. Then, the distortions trends were located and corrected before the scale part construction. Distortion trends of LMD-CLAD® can be studied through micro-meso-macro model in a short time ‘48h’ compared to 155h for large parts simulated with ordinary PC (core i5 8Gbs RAM). The numerical tool helped us optimizing the construction strategy and jigs. It was also used to reduce process setup, to design a distortion compensated part model, and modify the part design according to estimated trends.

Glass filters are often used in the field of medical technology and chemical analysis to separate particles of a defined size out of liquids. Depending on the application, different pore width from 1.6 μm to 500 μm are necessary. Glass materials are particularly suitable, because a high purity, the chemical resistance and a high thermal resistance of the filter are necessary. Traditionally, these glass filters are produced by conventional sintering. In the new investigations, selective laser sintering is investigated as an alternative method. The conventional sintering process allows defined pore sizes to be adjusted by varying the sintering time. The high purity of the glass filters can be achieved by a binder-free production. The material properties of the glass material, such as the chemical resistance or thermal stability is maintained by the sintering process. Typically, fused silica or borosilicate glasses are used as basis materials. High-temperature selective laser sintering (HT-SLS) is an additive manufacturing process for the production of silicate and porous components. This manufacturing technology allows complex and unconventional geometrics to be realized efficiently and flexibly. For this purpose, the volume model to be produced is first separated into the desired layer geometry and number of layers. In the subsequent specific process cycle, the glass powder is distributed by a squeegee on a building platform in a defined manner. A solid material layer is created by means of scanning CO₂ laser radiation. After lowering the building platform and transporting the powder again, the component can be generated layer by layer. For the production of the glass filters by HT-SLS, initial investigations are carried out with synthetic and natural fused silica glass powders with particle diameters in the range of 19... 78 μm in spheroidized and vitrified form. A laser sintering furnace has been specially designed for the HT-SLS, which achieves process temperatures up to T = 1000 °C as well as low contamination of the glass powder. In addition, material-specific scan and parameter concepts are developed. A high component quality can be achieved by combining a hull-and-core scan strategy with a 180° scan field rotation each sintered layer. Also a bidirectional beam guide and a material-specific parameter concept is needed. The absorption of CO₂ laser radiation and the heat-conduction of the powder are supported by the process-dependent plasma and the preheating of the building platform. The generated porous components are investigated with regard to the density and the bending strength. Component densities of ρ = 65 % and bending strengths of σ = 13.6 MPa are achieved. Basically, HT-SLS is an alternative method to the classical sintering process of glass powder to produce glass filters. In particular, an increase in efficiency with regard to the producible component geometry of the porous components can be achieved. This new technology offers a high degree of innovation, while at the same time requiring a high level of research.

It was verified that a lenticular lens array with a fine pitch of 100 μm was effective for improving resolution and clearness in switching of two images. Lenticular lens array patterns of negative resist SU-8 were fabricated on a 240-μm thin quartz plate, and they were directly used as lenticular lens arrays. The patterns were printed using 1:1 projection lithography under largely defocused conditions using a reticle with 50-μm line-and-space patterns. Because pattern images were made vague by the defocus, connected humpbacked patterns with a pitch of 100 μm were continuously formed without spaces. Cross section profiles of the patterns were almost circular, and the curvature radius was controllable in a range between 60 and 130 μm by adjusting exposure time. In the case of picture switching using conventional lenticular lens arrays with 40-100 lenses per inch, stitching lines appeared considerably clear between divided picture elements, and discontinuous steps were observed at inclined parts of figures. However, when the 100-μm pitch lens arrays were used, stitched steps became far finer and smoother, and scenes without notable stitching lines were obtained. Steps and discontinuities at inclined parts of figures were especially improved. Thus, fine pitch lenticular lens arrays are effective, and the new method for printing lenticular lens patterns would be useful for fabricating original molds of lenticular lens arrays.

We study the possibility of the fabrication of faceted structure with a standard additive fabrication technology using the 3D printer of Objet30 Prime series from Stratasys. The structure contains a small number of facets with size in millimeter: these facets are inclined in two directions. We use analytical expression to solve the tilt angles recorded into a matrix. After obtaining the desired illumination pattern, we try to fabricate the structure with a standard and commercial additive fabrication methods (3D printing) to make a master. We create the STL file usable for the 3D Printer. First tests were made with the printer of the Stratasys Model Objet30 Prime using the material of VeroWhite Plus FullCure 835 and the support model of FullCure 705 from FABLAB at INSA Strasbourg. The common dimension of the element is 6 × 6 facets, where one facet is in millimeter. As printing is conducted with the material of VeroWhite, the quality of the surface profile of the printed model is not sufficient for direct optical applications due to the porous property of the material. As a result, square silicon mirrors are cut and coated with a 100 nm aluminum layer in a second step. Professional adhesive of NHU series from Hart Kunststoff, Germany is used to glue the mirrors on the faceted structure with delicate operation. Then the surface profile of the glued mirrors on the faceted structure is measured with a Zygo Newview 7200 profilometer. A first optical test gives interesting results, but not sufficient for our applications, but this work is an innovation and can give new creativity at the frontier of design and optical applications.

Ceramics as advanced materials play an important role in science and technology as they are mechanically robust, can withstand immense heat, are chemically inert. Consequently, there is a direct end-user driven need to find ways for efficiently acquiring free-form 3D ceramic structures. Recently, stereo-lithographic 3D printing of hybrid organic-inorganic photo-polymer and subsequent heating was demonstrated to be capable of providing true 3D ceramic and glass structures. Up to now, this was limited to (sub-)millimeter scale and naturally the next step is to acquire functional glass-/ceramic-like 3D structures in micro-/nano-dimensions. In this paper, we explore a possibility to apply ultrafast 3D laser nanolithography followed by heating to acquire ceramic 3D structures down to micro-/nano-dimension. Laser fabrication is employed for the production of initial 3D structures with varying (ranging within hundreds of nm) feature sizes out of hybrid organic-inorganic material SZ2080. Then, a post-fabrication heating at different temperatures up to 1500 °C in an air atmosphere facilitates metal-organic framework decomposition, which results in the glass-ceramic hybrid material. Additionally, annealing procedure densifies the obtained objects providing an extra route for size control. As we show, this can be applied to bulk and free-form objects. We uncover that the geometric downscaling can reach up to 40%, while the aspect ratio of single features, as well as filling ratio of the whole object, remains the same regardless of volume/surface-area ratio. The structures proved to be qualitatively resistant to dry etching, hinting at significantly increased resiliency. Finally, Raman spectrum and X-ray diffraction (XRD) analysis were performed in order to uncover undergoing chemical processes during heat-treatment in order to determine the composition of material obtained. Revealed physical and chemical properties prove the proposed approach paving a route towards 3D opto-structuring of ceramics at the nanoscale for diverse photonic, microfluidic and biomedical applications.

In this work we reveal an influence of polarization of the laser beam on polymerization in direct laser writing. It was experimentally found that the width of suspended lines fabricated in SZ2080, OrmoComp and PETA (pentaerythritol triacrylate) pre-polymers directly depends on the incident polarization and is largest when the angle between the electric field vector and the sample translation direction is α = 90° and the smallest when α = 0°. The size of polymerized structures is consistent with theoretical simulations based on vectorial Debye theory. Experiments were performed by using average laser power corresponding to the middle value of the fabrication window. Polarization was found to be affecting feature sizes while structuring various widespread photoresists, the observed variation was material dependent and measured from 5 to 22% in the line-width. The performed study proves that polarization can be used as a variable parameter for fine tuning of the voxel's aspect ratio.

Laser metal deposition (LMD) by powder injection is an attractive and innovative additive manufacturing of metals. The key to predict material properties is the state of microstructure. In this paper, we develop a thermodynamically consistent temperature-displacement phase field model for grain growth during the LMD process. The governing equations that follow from the balance laws involve the phase variable, the displacement field, and the temperature field, with significant couplings between all equations. The model includes thermal expansion, transformation dilatation, strain dependency on phase transformation and local mechanical equilibrium conditions. Extensions to plastic models are discussed. Temperature dependencies of material properties (Young's modulus, Poisson's ratio, thermal expansion coefficient) are also included in the model formulation.

Two methods for correction of integrated optical circuits on lithium niobate via laser micro-trimming are proposed. The first method induces changes in the refractive index in waveguides, the second method causes and affects losses in them. The influence of both methods on waveguide elements of integrated intensity modulators is experimentally studied. Increases in the modulators extinction ratio by 17 dB (from 30 to 47 dB) for the first method and by 12 dB (from 28 to 40 dB) for the second method are obtained.

The technology of cell 3D scaffolds laser fabrication is developed. 3D scaffolds are designed to repair osteochondral defects, which are poorly restored during the organism’s life. The technology involves the use of an installation, the laser beam of which moves along a liquid nanomaterial and evaporates it layer by layer. Liquid nanomaterial consists of the water-protein (collagen, albumin) suspension with carbon nanoparticles (single-walled carbon nanotubes). During laser irradiation, the temperature in the region of nanotubes defects increases and nanotubes are combined into the scaffold. The main component of installation is a continuous laser operating at wavelengh of 810 nm. The laser beam moves along 3 coordinates, which makes it possible to obtain samples of the required geometric shape. The internal and surface structure of the samples at the micro- and nanoscale levels were studied using the X-ray microtomography and scanning electron microscopy. In vitro studies of cell growth during 48 and 72 hours demonstrated the ability of cell 3D scaffolds to support the proliferation of osteoblasts and chondroblasts. Using fluorescence and atomic force microscopy, it was found that the growth and development of cells on a sample with a larger concentration of nanotubes occurred faster compared to samples with a smaller concentration of nanotubes.

Results of the experimental study of the effect of the laser radiation on the jet of a gas-powder mixture are presented. The flow of the gas-powder mixture (GPM) was formed by the cone-slit nozzle of the set-up of laser metal deposition (LMD). Spatial-temporal distributions of the temperature of the powder phase of the GPM are obtained. Three granulometric compositions of stainless-steel powder Ch18N9 (PR-X18H9) was used apart in the experiment. The weight-average diameters d50 of powder particles of their compositions were 114, 63 and 36 μm, respectively. The characteristic distance of the temperature rise of particles in the gas-powder jet and the maximum temperature of particles are obtained experimentally and amount, respectively: 9.4 mm and 2200 K for the coarse powder; 6.3 mm and 2250 K for the medium-sized powder; 4.6 mm and 2700 K for the fine powder. The heating rate increased from 0.4*10^6 K/s for the coarse powder to 0.68*10^6 K/s for fine powder. The results of the study can be used to develop methods and tools for monitoring and control the LMD process. The revealed features of the dynamics of the temperature of the powder phase in the LMD process must be taken into account in modeling the processes of the effect of laser radiation on a gas-powder medium.

Selective laser melting (SLM) of the powder bed is one of the promising techniques for additive manufacturing of metals. Laser powder bed fusion is an inherently multiscale process and calls for an approach using multiple coupled models. In this work we developed the macroscopic thermodynamic model of SLM involving sequential deposition of powder layers on the plate followed by their melting. The accompanying processes of heat transfer, Marangoni convection and evolution of the melt free surface are included in the model. This model gives self-consistent consideration to the distributions of temperature and melt velocities during SLM. Modeling of the free surface evolution is performed by the VOF method. For numerical calculations the program software has been developed and tested. Its realization involved the C++ class library of numerical modeling OpenFOAM 2.4. Thermal flows, melt velocities and resulting profiles of sintered layers depending on the SLM parameters (beam power, scanning speed, powder layer) have been obtained. The calculated distributions demonstrate the development of widespread defects in SLM, e.g. residual porosity inside the solidified metal in the form of gas bubbles, incomplete penetration and bonding of the substrate metal and the particles. The results show that capillary effects play an important role in the liquid phase dynamics and, correspondingly, in the formation of final profile and structure of the deposed layer. The macro-level data (heat removal rate, cooling rate) can be used as the input parameters in boundary condition formulation for solving the microstructure evolution and the residual stress formation problems during SLM.

For a full-fledged application laser additive manufacturing technologies of parts from metal powder and for maximum disclosure of their potential, it is necessary to provide automated construction of an optimal synthesis strategy with determination of the process parameters to ensure the specified properties and geometry of the product. In this paper, in the framework of the thermo-hydrodynamic model, the influence of the geometric boundaries of the workpiece on the processes accompanying laser metal deposition is numerically investigated. The geometric characteristics of the melt pool and the forming bead are investigated: length, width, height and dilution, as well as features of the formation of the vortex structure of the flows in the molten pool caused by thermocapillary forces and injection of powder. Modeling of the process of formation of two adjacent tracks in the technology of selective laser melting is carried out. It is shown that in the case of scanning two adjacent tracks with alternating directions, the volume of the melt region increases. To maintain the parameters in the required range, a variation in the laser radiation power or the scanning speed can be used.

A numerical study of the influence of macroscopic processes of heat and mass transfer on the dendrites formation during laser metal deposition is carried out in the paper. The algorithm used to calculate the processes realizes the concept of multiscale modeling of crystallization and provides the interaction of models of different structural levels. Simulation of macro-level processes is carried out on the basis of 3D self-consistent equations for the dynamics of the free surface, temperature, and melt flow velocities. The microlevel problems are related to the modeling of the formation of dendrites during the crystallization of the melt and are solved using the phase field equation conjugate with the of heat conduction equation. The profiles of the phase field and the temperature gradient in different spatial regions of the object being formed are calculated. The orientation of the dendritic structures strongly depends on the thermal prehistory and the shape of the melt pool and varies in different areas. In the near-surface layers, the dendrites have a pronounced orientation along the plane of the part. In the process of depositing the material over the previously treated areas, the microstructural properties of the crystallized material change partially. After solidification in areas that have undergone repeated remelting, dendrites oriented vertically appear. With the growth of the temperature gradient, the morphology of the dendrites transforms with the formation of columnar structures.