3D Microstructures Research Articles

Ni-YSZ Electrode Stability in Solid Oxide Electrolysis Cells Operated in 90-98% Steam

Ni-YSZ electrode-supported SOECs were tested at 750 and 800oC using extremely high steam concentrations, 90, 95, and 98%. The performance was compared to SOECs tested in 50% steam with 50% hydrogen. Multiple cells were tested simultaneously with several repeats, all cells configured into a single furnace for each test to ensure a reasonable side-by-side comparison and results reproducibility. The Ni/YSZ electrodes was reduced by hydrogen in situ at each operating temperature and then 50-98% steam was added. Cells were tested at a fixed current or voltage for 1000-3000 hours. The electrochemical impedance data was periodically collected followed by the DRT analyses to identify any changes in polarization losses in time. Minimal to no changes in cell performance in time was observed when compared cell operation in 90+% steam vs 50% steam. Slightly higher degradation was seen for cells tested at 800oC vs those tested at 750oC during the initial 500 hours. After the initial break-in period, the degradation rates for all cells in the following >1000 hours remained the same.A separate set of tests was performed to characterize break-in period and to understand how the initial Ni thermal aging at different temperatures affects the time to a pseudo steady-state, i.e., if the Ni aging/conditioning could be used to accelerate the initial degradation and shorten break-in. Symmetrical cells with two Ni-YSZ electrodes on each side of 10 micron YSZ electrolyte were also tested.The extensive SEM/EDS analyses were performed on all cells to quantify the Ni particle size and describe any microstructural changes. The 2-dimensional SEM images were reconstructed into the 3D microstructures to calculate the triple phase boundary density, species transport paths tortuosity, and particle/pore size distribution.

Size Effect in the Compression of 3D Polymerized Micro-Structures

Abstract Micro/nanoscale additive manufacturing provides a powerful tool for advanced materials and structures with complex and precise features. For instance, the feature resolution of two-photon polymerization (2PP) can reach 200 nm. At this scale, materials properties can change, and the influence of the size effect cannot be ignored. Therefore, it is necessary to assess changes in the material mechanical properties considering size effects. In this work, several micrometric polymeric specimens are printed via 2PP, and their mechanical properties are assessed using compression tests. Detailed printing and testing procedures and the effects of parameter settings are provided. The experimental results show that the changes in the microstructures’ size have a direct effect on Young’s modulus. In particular, a large surface-volume ratio results in a higher Young’s modulus. In other words, the smaller the structure size, the higher the stiffness. The reported findings play a significant role in the development of fabrication strategies for polymeric microstructures where high stiffness accuracy is fundamental.

Wet Chemical and Plasma Etching of Photosensitive Glass

Photosensitive glasses for radiation-induced 3D microstructuring, due to their optical transparency and thermal, mechanical, and chemical resistance, enable the use of new strategies for numerous microscale applications, ranging from optics to biomedical systems. In this context, we investigated the plasma etching of photosensitive glasses after their exposure and compared it to the established wet chemical etching method, which offers new degrees of freedom in microstructuring control and microsystem fabrication. A CF4/H2 etching gas mixture with a constant volumetric flow of 30 sccm and a variable H2 concentration from 0% to 40% was utilized for plasma-based etching, while for wet chemical etching, diluted hydrofluoric acid (1% ≤ cHF ≤ 20%) was used. Therefore, both etching processes are based on a chemical etching attack involving fluorine ions. A key result is the observed reversion of the etch selectivity between the initial glassy and partially crystallized parts that evolve after UV exposure and thermal treatment. The crystallized parts were found to be 27 times more soluble than the unexposed glass parts during wet chemical etching. During the plasma etching process, the glassy components dissolve approximately 2.5 times faster than the partially crystalline components. Unlike wet chemical etching, the surfaces of plasma etched photostructured samples showed cone- and truncated-cone-shaped topographies, which supposedly resulted from self-masking effects during plasma etching, as well as a distinct physical contribution from the plasma etching process. The influences of various water species on the etching behaviors of the homogeneous glass and partially crystallized material are discussed based on FTIR-ATR and in relation to the respective etch rates and SNMS measurements.

Very High-Aspect-Ratio Polymeric Micropillars Made by Two-Photon Polymerization.

Polymeric micropillars with a high-aspect-ratio (HAR) are of interest for a wide range of applications, including drug delivery and the micro-electro-mechanical field. While molding is the most common method for fabricating HAR microstructures, it is affected by challenges related to demolding the final structure. In this study, we present very HAR micropillars using two-photon polymerization (TPP), an established technique for creating complex 3D microstructures. Polymeric micropillars with HARs fabricated by TPP often shrink and collapse during the development process. This is due to the lack of mechanical stability of micropillars against capillary forces primarily acting during the fabrication process when the solvent evaporates. Here, we report different parameters that have been optimized to overcome the capillary force. These include surface modification of the substrate, fabrication parameters such as laser power, exposure time, the pitch distance between the pillars, and the length of the pillars. On account of adopting these techniques, we were able to fabricate micropillars with a very HAR up to 80.

Magneto-optical engineering by plasmonic and dielectric metasurfaces in a CoFeB perforated microstructure

We have investigated theoretically and experimentally the effect of plasmonic and all-dielectric metasurfaces on the magneto-optical response of the 2D periodic structure. For this purpose, we fabricate polydimethylsiloxane-based 2D microstructures. So, we coated them with a gold layer and a TiO2 dielectric layer as plasmonic and dielectric metasurfaces, respectively, CoFeB as the prominent magneto-optical thin films. We record the spectral magneto-optical longitudinal Kerr effect under 40 mT, and the spectrometer’s response in all visible regions. Our results show that the electric and magnetic dipole moments enhance the magneto-optical response by factors of one and two in two closer channels in 650 and 660 nm in an all-dielectric structure, respectively. The plasmonic hot spot-based magneto-optical enhancement is also confirmed in two other media with an enhancement factor of two.

3D Printing Hierarchically Nano-Ordered Structures.

Natural materials are composed of a limited number of molecular building blocks and their exceptional properties are governed by their hierarchical structure. However, this level of precision is unattainable with current state-of-the-art materials for 3D printing. Herein, new self-assembled printable materials based on block copolymers (BCPs) enabling precise control of the nanostructure in 3D are presented. In particular, well-defined BCPs consisting of poly(styrene) (PS) and a polymethacrylate-based copolymer decorated with printable units are selected as suitable self-assembled materials and synthesized using controlled radical polymerization. The synthesized library of BCPs are utilized as printable formulations for the fabrication of complex 3D microstructures using two-photon laser printing. By fine-tuning the BCP composition and solvent in the formulations, the fabrication of precise 3D nano-ordered structures is demonstrated for the first time. A key point of this work is the achievement of controlled nano-order within the entire 3D structures. Thus, imaging of the cross-sections of the 3D printed samples is performed, enabling the visualization also from the inside. The presented versatile approach is expected to create new avenues for the precise design of functional polymer materials suitable for high-resolution 3D printing exhibiting tailor-made nanostructures.

Improvement of 3D printing performance of pea protein isolate Pickering emulsion gels by regulating electrostatic interaction between protein and polysaccharide

3D food printing had attracted wide attention for its multiple advantages such as being able to customize food according to individual needs. In this study, plant-based edible inks suitable for 3D food printing applications were formulated using Pickering emulsion gels containing pea protein isolate (PPI) and flaxseed gum (FG). The effect of different electrostatic interaction between PPI and FG on the 3D printing performance, rheology properties and microstructure of emulsion gel inks were investigated in acidic (pH 3) and neutral (pH 7) environments, respectively. At pH 3, the inks showed good printing performance with the addition of FG at 0.5%, 0.7% and 0.9%, respectively. At pH 7, the inks at 0.5% had the best 3D printing performance. They demonstrated printing performance with precise shape, smooth surface and clear texture. The inks produced were soft matter solids with a storage modulus (G′) greater than the loss modulus (G″). According to Lissajous plots analysis, the addition of FG significantly improved the viscoelasticity, which was beneficial to improve the 3D printing performance of inks. These inks also exhibited good thermal stability. In addition, Cryo-SEM analysis showed that the inks had a striated structure at pH 3 but a honeycomb structure at pH 7 due to the difference in electrostatic interaction. And the honeycomb structure is more stable compared to the striated structure. This study showed that edible inks can be formulated from plant-derived ingredients, which may increase their application in the development of plant-based foods with improved properties using additive manufacturing processes.

Fabrication of n-shaped micro copper structures through localized electrochemical deposition

Localized electrochemical deposition is a cost-effective technique for fabricating 3D microstructures. In this study, to fabricate a complete n-shaped micro copper structure, multi-layer deposition was adopted, and the v-groove was removed by an asymmetric trajectory. Thereafter, the merging mechanism of the n-shaped structure was analyzed using COMSOL simulations. The results demonstrated that multilayer deposition was suitable for connecting the copper column in different directions; the optimized layer was 15 layers with a height of 15 μm. The simulation showed that the v-groove was caused by the speed difference between the column and bumps, and an asymmetric trajectory with a height difference of 55 μm could suppress vertical deposition and remove the v-groove.

3D Multi-Ion Corrosion Model in Hierarchically Structured Cementitious Materials Obtained from Nano-XCT Data.

Corrosion of steel reinforcements in concrete constructions is a worldwide problem. To assess the degradation of rebars in reinforced concrete, an accurate description of electric current, potential and concentrations of various species present in the concrete matrix is necessary. Although the concrete matrix is a heterogeneous porous material with intricate microstructure, mass transport has been treated in a homogeneous material so far, modifying bulk transport coefficients by additional factors (porosity, constrictivity, tortuosity), which led to so-called effective coefficients (e.g., diffusivity). This study presents an approach where the real 3D microstructure of concrete is obtained from high-resolution X-ray computed tomography (XCT), processed to generate a mesh for finite element method (FEM) computations, and finally combined with a multi-species system of transport and electric potential equations. This methodology allows for a more realistic description of ion movements and reactions in the bulk concrete and on the rebar surface and, consequently, a better evaluation of anodic and cathodic currents, ultimately responsible for the loss of reinforcement mass and its location. The results of this study are compared with a state-of-the-art model and numerical calculations for 2D and 3D geometries.

3D surface microstructure of silicon modified by QDs to improve solar cell performance through down-conversion and anti-reflection mechanism

Improving the photoelectric conversion efficiency (PCE) of solar cells is an important subject for a wide range of photovoltaic research. One of the main reasons for low PCE is the mismatch between solar spectrum and solar cells. The use of down-conversion and anti-reflection mechanisms is a reasonable method to increase PCE. Down-conversion can convert low-absorbance photons in silicon solar cells into high-absorbance photons while the special 3D surface structure formed by the down-conversion material produces an anti-reflection effect to increase the PCE of the solar cell. In this study, cadmium selenide (CdSe) quantum dots (QDs) coating hybrid structure of monocrystalline silicon solar cells was proposed to increase the utilization. Here, the CdSe QDs were synthesized with a high absorption strength in the 300–500 nm and a photoluminescence (PL) peak at 628 nm. Benefiting from the larger absorption cross-section and weaker electron-phonon coupling characteristics of CdSe QDs, the down-conversion was achieved successfully, and the reflectance test of the CdSe QDs covered silicon solar cells also shows an anti-reflection effect. Therefore, by using the dual mechanism of down-conversion and anti-reflection, the PCE of solar cells was improved by the proposed system. The results show that the PCE of the CdSe QDs coating hybrid structure based monocrystalline silicon solar cells is increased by 1.42% from 14.45% to 15.87%. Besides, by using finite element method, the reflection reduction mechanism for lower transition layer was also simulated to further explain the experiment results. Due to the low synthesis cost of QDs, this work can be well integrated into the photovoltaic industry, which provides a new technical route and guidance for improving the PCE of silicon cells.

Ultrafast and facile construction of programmable, multidimensional wrinkled-patterned polyacrylamide/sodium alginate hydrogels for human skin-like tactile perception

Customizable structures and patterns are becoming powerful tools for biomimetic design and application of soft materials. The construction of long-range ordered self-wrinkled structures on multi-dimensional and complex-shaped surfaces with facile, fast and efficient strategies still faces serious challenges. During the stretch-recovery process, the carboxyl groups in the polyacrylamide/sodium alginate dual network gel form robust coordination with Fe3+ to achieve a hard shell layer, resulting in a modulus mismatch between the inner soft layer and the outer hard layer, thereby forming a wrinkled surface. This flexible strategy allows simultaneous construction of complex topologies from 1D to 3D wits well-organized microstructure and controllable dimensions. The mechanism of the influence of ion treating time and pre-stretching ratio on wrinkle wavelength was explored in detail. The finite element simulations matched well with the experimental results. Due to the unique surface and dual crosslinking network, the self-wrinkled hydrogel maintains a high sensitivity of up to 67.47 kPa−1 in 1000 compression cycles. As a high-sensitivity pressure sensor integrated into the detection system, it can be efficiently applied to the contact dynamic tactile perception and monitoring of various movement behaviors of the human body.

High-frequency ultrasonic vibration-assisted sculpturing with a smoothed tool path for optical 3D micro-structured surfaces with sharp edges

The fabrication of complex 3D micro-structured surfaces on difficult-to-machine materials such as steel and tungsten carbide is the premise for mass production of glass components with functional surfaces by the glass moulding process. Ultrasonic vibration-assisted cutting (UVAC) is an effective method to machine 3D micro-structured surfaces on these difficult-to-machine materials. However, it is challenging and difficult for UVAC to machine microlens arrays with sharp edges, at which sudden acceleration of the z-axis slide is required to make the cutting tool follow the tool path. This could induce tool vibration and cause relative tool-work displacement, resulting in poor machining accuracy and surface finish of the machined 3D microstructure. In this paper, high-frequency ultrasonic vibration-assisted sculpturing (HFUVAS) with a smoothed tool trajectory is used to machine microlens array on steel mould for fine machining accuracy and surface quality. A comparison is made between the cutting performance of the circular microlens arrays machined by diamond turning and diamond sculpturing. The results found that relative tool-work displacement arising at sharp edge in diamond turning could be eliminated in HFUVAS with a smoothed tool path, demonstrating the effectiveness of a smoothed tool path in reducing relative tool-workpiece displacement in the fabrication of 3D micro-structured surfaces. Furthermore, a quadrilateral microlens array and hexagonal microlens array are also fabricated in order to extend the applications of HFUVAS, with a form error within 1 μm and surface roughness with an arithmetical mean height Sa of below 10 nm achieved.

Additive Manufacturing of SiOC, SiC, and Si3N4 Ceramic 3D Microstructures

Herein, the fabrication of hard ceramic SiOC 3D microstructures by precursor synthesis, laser lithography, and pyrolysis combination is proposed. Precursors are hybrid organosilicon materials prepared via sol–gel method using trimethoxymethylsilane and 3‐(trimethoxysilyl)propyl methacrylate, which has an acrylate functional group enabling laser photopolymerization process. Hard 3D ceramic structures (hardness up to ≈15 GPa, reduced elastic modulus ≈105 GPa) from soft organometallic derivatives are obtained after high‐temperature pyrolysis under nitrogen atmosphere. The advantage of the proposed method is the absence of shrinkage defects leading to a uniform repetitive decrease in the volume of printed microstructures. In contrast to slurry‐based printing technology, the proposed method is focused on homogeneous monolithic molecular resins resulting in visual smooth surfaces of prepared microstructures. Moreover, the printing resolution of the proposed method is substantially improved through the absence of predispersed ceramic microparticles in mixtures, which is a necessary element in a slurry‐based technology.

3D Multiscale Lithium‐Ion Cell Modeling for LiFePO4Freeze‐Casted Electrode Structures Using Synchrotron X‐Ray and FIB/SEM Tomography

AbstractThe performance of batteries and the associated operating areas depend, among other things, on the 3D microstructures of the electrode materials, and thus fundamental research is required in the field of electrode design. A multiscale microstructure‐resolved 3D model is developed that investigates two different LiFePO4freeze‐casted electrode structures, that is, cellular and lamellar. The microstructure is simulated directly from the X‐ray computed tomography data and the nanostructure is combined with the pseudo‐2D simulation approach, where the morphological parameters and the distribution of the binder, carbon, and LiFePO4are obtained from ex situ focused ion beam scanning electron microscopy measurements. The discharge performance shows that the lamellar structure exhibits a lower ohmic overvoltage and achieves a higher gravimetric capacity compared to the cellular structure, even though both electrode materials have the same porosity and amount of active material. The simulation reveals that the performance is not only directly influenced by the lithium‐ion transport through the porous structure but also by the current distribution through the active material. Based on these insights, lamellar electrode structures should be considered for next‐generation battery electrodes. The modeling approach can assist in electrode fabrication by identifying defects or suggesting better structural parameters.

Simple Electroosmotic Pump and Active Microfluidics with Asymmetrically Coated Microelectrodes

Electroosmotic pumps can deliver liquid without moving parts, making them suitable for microfluidic and lab‐on‐chip systems. Previously, alternating current electroosmotic pumps were constructed using pairs of coplanar asymmetrical interdigitated microelectrodes on the same substrate. In this work, a simpler micropumping system is developed, separating the electrodes on two substrates and breaking the symmetry by half‐depositing electrodes with 3D microstructures. Numerical simulation models of the pumping system and experimental velocity profiles are used to explain the fluid motion mechanism and structure‐dependent pumping performance. In addition to its efficiency and simplicity, this new pumping system also allows for the creation of a microvortex device and an active microfluidics device. This scalable micropumping system provides a way to pump liquids at microscopic or macroscopical scale in complex microfluidics systems.

Application of Image Processing in Evaluation of Hydraulic Fracturing with Liquid Nitrogen: A Case Study of Coal Samples from Karaganda Basin

Research of microstructure and permeability evolution of coal following LN2 treatment elucidate the process of cryogenic fracturing due to environmentally friendly behavior in comparison with conventional hydraulic fracturing. The evolution of the 2D microstructure of bituminous coal before and after LN2 treatment was examined using a high-resolution camera. The image processing was implemented using functions from the OpenCV Python library that are sequentially applied to digital images of original coal samples. The images were converted into binary pixel matrices to identify cracks and to evaluate the number of cracks, crack density, total crack area, and average crack length. Results were visualized using Seaborn and Matplotlib Python libraries. There were calculations of total crack area (TCA), total number of cracks (TNC), crack density (CD), the average length of cracks (Q2), first (Q1) and third (Q3) quartiles in fracture length statistics. Our findings demonstrate a progressive increase in the Total Crack Area (δTCA) with longer freezing times and an increased number of freezing–thawing cycles. In contrast, the change in crack density (δCD) was generally unaffected by freezing time alone but exhibited a significant increase after several freezing–thawing cycles. Among the freezing times investigated, the highest crack density (CD) value of 300 m−1 was achieved in FT60, while the lowest CD value of 31.25 m−1 was observed in FT90 after liquid nitrogen (LN2) treatment. Additionally, the FTC4 process resulted in a 50% augmentation in the number of cracks, whereas the FTC5 process tripled the number of small cracks.

A novel approach for quantitative characterization of aqueous in-situ foam dynamic structure based on fractal theory

In this study, a quantitative characterization method of in-situ foam microstructure is proposed based on fractal theory and the captured two dimension(2D) microstructure image for the study of its fractal characteristic, evolution law, sensitivity of temperature and concentration, as well as the relationship between average particle size and fractal dimension of in-situ foam. The results demonstrate that in-situ aqueous foam in the bulk phase exhibits fractal characteristics with a box-counting fractal dimension ranging from 1.4 to 2.0. Distinct from the “exponential” evolution law of conventional foam, in-situ foam displays the “check mark” evolution law, which can be precisely described by two items with clear physical meaning in our proposed fitting model. Additionally, the in-situ foam's evolutionary characteristic exhibits high adaptability towards temperature and foaming agent concentration. Elevated temperatures accelerate coalescence, resulting in shorter effective times, while higher concentrations of foaming agents prolong the overall stability of in-situ foam. Besides, the variation of average particle size of in-situ foam correspond closely with the evolution of fractal dimension under different temperatures and foaming agent concentrations, providing the potential for predicting changes in microstructure of in-situ foam by fractal dimension.

Towards understanding the mechanism of 3D printing using protein: Femtosecond laser direct writing of microstructures made from homopeptides.

Femtosecond laser direct write (fs-LDW) is a promising technology for three-dimensional (3D) printing due to its high resolution, flexibility, and versatility. A protein solution can be used as a precursor to fabricate 3D proteinaceous microstructures that retain the protein's native function. The large diversity of protein molecules with different native functions allows diverse applications of this technology. However, our limited understanding of the mechanism of the printing process restricts the design and generation of 3D microstructures for biomedical applications. Therefore, we used eight commercially available homopeptides as precursors for fs-LDW of 3D structures. Our experimental results show that tyrosine, histidine, glutamic acid, and lysine contribute more to the fabrication process than do proline, threonine, phenylalanine, and alanine. In particular, we show that tyrosine is highly beneficial in the fabrication process. The beneficial effect of the charged amino acids glutamic acid and lysine suggests that the printing mechanism involves ions in addition to the previously proposed radical mechanism. Our results further suggest that the uneven electron density over larger amino acid molecules is key in aiding fs-LDW. The findings presented here will help generate more desired 3D proteinaceous microstructures by modifying protein precursors with beneficial amino acids. STATEMENT OF SIGNIFICANCE: Femtosecond laser direct write (fs-LDW) offers a three-dimensional (3D) printing capability for creating well-defined micro-and nanostructures. Applying this technology to proteins enables the manufacture of complex biomimetic 3D micro-and nanoarchitectures with retention of their original protein functions. To our knowledge, homopeptides themselves have never been used as precursor for fs-LDW so far. Our study gains several new insights into the 3D printing mechanism of pure protein for the first time. We believe that the experimental evidence presented greatly benefits the community of 3D printing of protein in particular and the biomaterial science community in general. With the gained insight, we aspire to expand the possibilities of biomaterial and biomedical applications of this technique.

Evaluation of the photocatalytic activity of ZnO nanorods and nanoflowers grown from seed layers deposited by spin coating

The increase in pollution, using photocatalytic materials to degrade organic pollutants remains in force. ZnO is the most used semiconductors for photocatalytic applications. The oriented growth of nanostructures on substrates or seed layers (SL) improves the physical and chemical properties compared to the bulk-grown material. In this work, the photocatalytic efficiency of ZnO nanorods and nanoflowers was evaluated, obtained by hydrothermal growth (HG) over SL deposited by the spin-coating technique (SCT). The characterizations results showed two types of growth: 1D nanostructures with a dimension in the range of 400–1000nm and diameters of 70–100nm, and 1D microstructures with approximate 5–11μm length and diameters of 1–2μm. However, in the 7 SL system, micro prisms were generated, which led to the formation of 3D nanostructures (micro flowers) of ZnO with a maximum of 6μm in diameter. The system with 1D and 3D ZnO nanostructures, grown in 7 SL, was the most efficient methylene blue degradation. Achieving 100% transformation in 120min, with a rate constant of 2.98×10−2min−1. The results show that the SCT deposit combined with the sol–gel method and HG produces 1D and 3D structures with high potential in photocatalytic degradation.

Non-destructive 3D characterization of the blood vessel wall microstructure in different species and blood vessel types using contrast-enhanced microCT and comparison with synthetic vascular grafts

To improve the current treatment for vascular diseases, such as vascular grafts, intravascular stents, and balloon angioplasty intervention, the evaluation of the native blood vessel microstructure in full 3D could be beneficial. For this purpose, we used contrast-enhanced X-ray microfocus computed tomography (CECT): a combination of X-ray microfocus computed tomography (microCT) and contrast-enhancing staining agents (CESAs) containing high atomic number elements. In this work, we performed a comparative study based on staining time and contrast-enhancement of 2 CESAs: Monolacunary and 1:2 Hafnium-substituted Wells-Dawson polyoxometalate (Mono-WD POM and Hf-WD POM, respectively) for imaging of the porcine aorta. After showing the advantages of Hf-WD POM in terms of contrast enhancement, we expanded our imaging to other species (rat, porcine, and human) and other types of blood vessels (porcine aorta, femoral artery, and vena cava), clearly indicating microstructural differences between different types of blood vessels and different species. We then showed the possibility to extract useful 3D quantitative information from the rat and porcine aortic wall, potentially to be used for computational modeling or for future design optimization of graft materials. Finally, a structural comparison with existing synthetic vascular grafts was made. This information will allow to better understand the in vivo functioning of native blood vessels and to improve the current disease treatments. STATEMENT OF SIGNIFICANCE: Synthetic vascular grafts, used as treatment for some cardiovascular diseases, still often fail clinically, potentially because of a mismatch in mechanical behaviour between the native blood vessel and the graft. To better understand the causes of this mismatch, we studied the full 3D microstructure of blood vessels. For this, we identified Hafnium-substituted Wells-Dawson polyoxometalate as contrast-enhancing staining agent to perform contrast-enhanced X-ray microfocus computed tomography. This technique allowed to show important differences in the microstructure of different types of blood vessels and in different species, as well as with that of synthetic grafts. This information can lead to a better understanding of the functioning of blood vessels and will allow to improve current disease treatments, such as vascular grafts.