Graded polymer foams are emerging as transformative materials for structural applications, outperforming uniform foams due to their spatially tailored density and microstructural features. However, harnessing their full potential requires a deep understanding of how their macroscopic mechanical behavior relates to their complex microstructure evolution. In this study, we elucidate the uniaxial compressive response of graded foams using in-situ synchrotron X-ray microtomography, complemented by comparative experiments on uniform foams of varying densities. Our findings reveal that graded foams exhibit both qualitatively and quantitatively distinct mechanical behavior, driven by unique microscale deformation mechanisms. We evaluate and discuss their superior energy absorption performance and demonstrate how the density, cell size and circularity profile evolves under increasing macroscopic strain. Notably, the graded architecture enables precise control over the localization and progression of densification bands, offering unprecedented design flexibility for advanced structural applications.

Clay-rich rocks are commonly foreseen to be employed as hostrock for radioactive waste disposal due to their favourable properties, that is, high retention and low permeability. This study investigated the pore-related characteristics and drying pattern of Toarcian argillite using X-ray synchrotron imaging. Specimens at varying saturation levels exhibited consistent porosity across different radial locations, indicating limited drying heterogeneity which is crucial for sample preparation in laboratory material characterisation. Due to the imaging technique employed, most detected pores were on micron and submicron scales. Unconfined specimens showed greater porosity than those with axial confinement, and the presence of cracks inferred the influence of the swelling potential from the initial re-saturation process that disturbed the argillite integrity, especially in higher saturation conditions. The estimation of the air–water interface characteristic length was attempted based on theoretical insights from Laplace’s law. Computed tomography results suggest that the detected pores were mostly in the air phase, supporting a homogeneous drying pattern under imposed suctions. Correlation between porosity and suction further reinforced the hypothesis on this drying pattern. The findings offer critical insights, highlighting the significance of Synchrotron imaging techniques in understanding argillite behaviours in nuclear waste disposal environments.

Understanding and predicting the morphological changes of filler particles within composites under load is critical to design improved materials. Syntactic foams, consisting of microspheres embedded in a solid matrix, have recently emerged as an ultra-lightweight metamaterial with highly tuneable mechanical properties. Glass microspheres are commonly used in syntactic foams, but can fracture, leading to a loss in the bulk mechanical properties. It is thought that hollow thermoplastic microspheres instead buckle, inducing strong, reversible, constitutive nonlinearity in the syntactic foam. Here we demonstrate, in-situ, the buckling of embedded thermoplastic shells under uniaxial compression. The results validate several important predictions from theory; regardless of sphere size, equatorial buckling prevails whenever the shell walls are thin relative to their diameter. Furthermore, the buckling wavelength is shown to be tuneable via different mechanical and geometrical parameters for the microspheres and/or matrix. Now better understood, we anticipate that tuneable, controlled and coordinated microsphere buckling can be exploited in diverse applications including strain sensing. Glass microspheres are commonly used in syntactic foams but can fracture, leading to a loss in the bulk mechanical properties. Here we demonstrate in-situ the buckling of embedded thermoplastic shells under uniaxial compression.

Background The temporomandibular joint (TMJ) relies on a fibrocartilaginous disc for stabilization and load distribution. When the disc degenerates, current replacement options fail to restore native biomechanics. Developing effective implants requires detailed knowledge of the disc's structure. The present work provides a full-volume, three-dimensional characterization of collagen fiber architecture and anisotropy in a large animal model with anatomical and functional similarities to the human joint.Methods A multimodal 3D imaging workflow was implemented, combining cone-beam CT for anatomical context and synchrotron phase-contrast micro-CT for high-resolution visualization of the ovine temporomandibular joint disc, cartilage, ligament, and subchondral bone. Deep-learning segmentation enabled full-volume tissue segmentation. Fiber orientation and anisotropy were quantified using mean intercept length (Mean Intercept Length)-derived eigenvector fields, with analysis performed across anatomical axes and planes. Histological sections validated fiber segmentation and regional differences in extracellular matrix organization.Results The lamb TMJ disc displayed a heterogeneous but highly ordered collagen network. Strong lateromedial alignment formed frontal-plane reinforcement bands, while a craniocaudal tensile corridor dominated the sagittal plane, and mixed lateromedial-ventrodorsal orientations characterized the transverse plane. Anisotropy was highest in the peripheral rims and lower in the central zone, reflecting a functional division between stabilization and deformation. Quantitative analysis demonstrated an orthotropic organization, with distinct dominant fiber populations aligned along the lateral-medial, ventral-dorsal, and cranial-caudal axes. Subchondral bone beneath the disc exhibited a fine, highly anisotropic trabecular lattice with reduced spacing, complementing the disc's structural organization.Conclusion This study provides the first full-volume, plane-resolved 3D description of collagen anisotropy in the ovine TMJ disc. The orthotropic fiber architecture and regional anisotropy gradients identified here clarify direction-dependent mechanical behavior and offer quantitative benchmarks for the design of biomimetic scaffolds and regenerative TMJ disc replacements.

Bone tissue is highly complex and dynamic, capable of adapting to mechanical demands and repairing itself through remodeling processes. This remodeling results in a heterogeneous mineral distribution, with lower mineralization in younger bone regions and higher mineralization in older ones. Osteocytes - bone cells residing in small lacunae within the mineralized bone matrix - orchestrate this remodeling. Additionally, osteocytes actively modify their peri-lacunar mineralized tissue. These characteristics, combined with the high osteocyte density of several tens of thousands per mm³ , make the distribution, size, and shape of osteocyte lacunae highly relevant characteristics of bone tissue. To study osteocyte lacunar properties, synchrotron-based computed tomography (µCT) has become increasingly popular over the past decade due to its combination of high spatial resolution, sensitivity to mineral density variations, and rapid data acquisition. However, segmenting lacunae and quantifying their properties remains challenging. Osteocyte lacunae exhibit diverse shapes and sizes, and their surrounding mineral density can vary significantly between lacunae, even within the same tissue sample. Consequently, no global gray value threshold can provide an equally accurate segmentation across different tissue regions within the same sample. More advanced segmentation techniques, such as those based on top-hat transformations, require the definition of a structuring element whose size must be tailored to the feature size, in this case, the lacunae. In this study, we propose a novel approach to segmentation that adjusts the threshold value and the size of the structuring element for each lacuna individually. This method, referred to as the Kangaroo Segmentation Approach, involves an initial rough segmentation, followed by connected-component analysis and refinement steps applied to each component. The results of this Kangaroo Segmentation Approach are compared with conventional Otsu thresholding and thresholding methods based on top-hat transformations. Our findings demonstrate a significant improvement in segmentation accuracy with the proposed method.

Synchrotron radiation-based X-ray microtomography is uniquely suited for post-mortem 3D visualization of organs such as the mouse brain. Tomographic imaging of the entire mouse brain with isotropic cellular resolution requires an extended field-of-view and produces datasets of multiple terabytes in size. These data must be reconstructed, analyzed, and made accessible to domain experts who may have limited image processing knowledge. Extended-field X-ray microtomography is presented with 0.65 μ m $0.65 \,\umu \mathrm{m}$ voxel size covering an entire mouse brain. The 4495 projections from 8 × 8 offset acquisitions are stitched to reconstruct a volume of 150003 voxels. The microtomography volume was non-rigidly registered to the Allen Mouse Brain Common Coordinate Framework v3 based on a combination of image intensity and landmark pairs. The data were block-wise transformed and stored in a public repository with a hierarchical format for navigation and overlay with anatomical annotations in online viewers such as Neuroglancer or siibra-explorer. This study demonstrates X-ray imaging and data processing for a full mouse brain, augmenting current atlases by improving resolution in the third dimension by an order of magnitude. The 3.3-teravoxel dataset is publicly available and easily accessible for domain experts via browser-based viewers.

Efficient design strategies found in nature have led to innovative materials and technologies. One promising blueprint for lightweight applications is the hymenium of Fomes fomentarius, a cellular, hierarchically structured, light, strong, and failure‐resistant biological tissue. Phase‐contrast enhanced micro‐computed tomography is used to investigate deformation and failure during in situ compression testing of the tubular honeycomb structure. Specimens are loaded parallel or transverse to the long axis of the tubes , in wet or dry condition. Displacements are evaluated between defined loading steps with three‐dimensional optical flow and morphological image analysis is used to correlate the micro‐ and mesostructure with local strains and structural damage. Key findings include that displacements are about five times larger in transverse than parallel loading, with greater displacements in regions of lower density. Higher hyphae density is found in struts compared to vertices, which leads to uniform displacements without significant local strain concentration. While cracks are observed in both struts and vertices, surprisingly, fracture is more catastrophic in the struts. Parallel loading results in plastic buckling and delamination in dry samples, while their wet counterparts show telescopic shortening from the first loading step and fewer fatal cracks, probably due to greater hyphae elasticity.

Flax fiber reinforcements weaken with aging and microstructural changes, limiting their applications. Here, we examine the effects of microstructure and aging on flax fiber elements’ performance by using 4000-year-old and modern Egyptian flax as references through multi-scale numerical modeling. This study introduces a novel investigation into the tensile stress distribution behavior of archaeological and modern flax yarns. The finite element (FE) model is derived from 3D volumes obtained via X-ray microtomography and tensile testing in the elastic domain. At the microscale, fibers exhibit higher axial stress concentrations around surface defects and pores, particularly in regions with kink bands and lumens. At the mesoscale, fiber bundles show increased stress concentrations at inter-fiber voids and lumen, with larger bundles exhibiting greater stress heterogeneity, especially around pores and surface roughness. At the macroscale, yarns display significant stress heterogeneity, especially around microstructural defects like pores and fiber–fiber cohesion points. Aged fibers from ancient Egyptian cultural heritage in particular demonstrate large fiber discontinuities due to long-term degradation or aging. These numerical observations highlight how porosity, surface imperfections, and structural degradation increase stress concentration, leading to fiber rupture and mechanical failure. This insight reveals how aging and defects impact flax fiber performance and durability.

X-ray imaging techniques employing diffractive and refractive lenses face the challenge of chromatic aberration if X-ray beams with a broad photon energy range are used. Recent advances combining a compound refractive lens and a Fresnel zone plate have enabled the development of achromatic lenses for X-rays, which exhibit a constant focal length over a wider range of photon energies. However, in this first demonstration, the potential of the achromatic X-ray lens was limited by the challenging task of aligning the two individual separate components. In this investigation, we designed, fabricated, and characterized monolithic X-ray achromatic lenses by integrating a Fresnel zone plate and a compound refractive lens onto a single substrate. This innovative approach inherently achieves precise alignment during fabrication, greatly simplifying and stabilizing the alignment for the X-ray imaging setups. Benefiting from an increased numerical aperture, the reported monolithic lens demonstrated state-of-the-art achromatic focusing down to approximately 200 nm for photon energies ranging from 6.6 keV to 7.7 keV. With these advancements, we present the first successful application of an achromatic lens in scanning and full-field transmission X-ray microscopy, as well as fluorescence spectroscopy, highlighting its potential for broad adoption across diverse X-ray imaging applications.

In this study, we examined how printing temperature affects the microstructure and mechanical properties of polylactic acid (PLA) composite reinforced with iron oxide i.e., magnetite manufactured using a material extrusion technique. The composite was printed at temperatures from 185 °C to 215 °C. Microstructure analysis via synchrotron radiation X-ray microtomography revealed changes in both iron oxide and porosity contents within the printed structures. Mechanical testing results demonstrated a limited effect of the printing temperature on tensile performance. Finite element computation is considered to predict the elasticity behavior of the printed composite by converting 3D images into 3D structural meshes. When implementing a two-phase model, the predictions show a leading role of the iron oxide content, and an overestimation of the stiffness of the composite. A three-phase model demonstrates a better matching of the experimental results suggesting a limited load transfer across the PLA-iron oxide interface with Young’s moduli in the interphase zone as small as 10% of PLA Young’s modulus. Magnetic actuation demonstrates that experiments on PLA-iron oxide plates reveal a pronounced thickness-dependent limitation, with the maximum deflection observed in thin strips of 0.4 mm.

Pharmaceutical solid dosage forms are designed to control drug release timing and location in the body, ranging from immediate-release to delayed-release formulations such as enteric-coated tablets. Ensuring content uniformity, consistent dissolution, and intact excipients is vital for their efficacy and safety. Manufacturing flaws - like defective coatings, cracks, or porosity - can compromise performance, making precise quality control essential. X-ray computed microtomography (µCT) enables non-destructive assessment of internal morphology, coating thickness, porosity, active ingredient distribution, and density. However, conventional laboratory µCT systems may lack the resolution, sensitivity, or speed required for advanced dynamic structural analysis. Synchrotron radiation-based µCT (SR-µCT) addresses these limitations, offering significant improvements in spatial resolution and temporal performance. This paper highlights the capabilities of SR-µCT for (i) high-throughput structural analysis and (ii) time-resolved monitoring of the dissolution of solid dosage forms. A commercially available pantoprazole tablet serves as a case study to demonstrate the tradeoff between resolution and field-of-view. Structural analysis of this pantoprazole tablet includes porosity and coating thickness quantification, as well as detection of morphological defects at different voxel sizes. Additionally, a newly developed flow-through chamber which allows liquid from a 100 ml reservoir to circulate and renew during measurements is presented for dynamic disintegration studies under sink conditions. Fast dynamic time-resolved SR-µCT analysis shows the disintegration speed of multicomponent placebo formulation compacted tablets at rapid µCT tomogram recording times of 5 s, while (high-resolution) time-resolved SR-µCT captures swelling in sustained-release formulations (Beloc Zok), API (size) distribution as well as API shape distribution.

Microtomography enables the three-dimensional imaging of cellular details of the entire mouse choroid plexus (ChP). This anatomical structure is vital for regulating the fluid balance in the brain. During aging, its epithelial cells flatten while its stroma expands. Quantification of the thickness of the ChP epithelial cell layer is hampered by the folded nature of the layers. We have developed a method to automatically quantify the thickness of the ChP epithelial cell layer even in the presence of folds and cell clusters. Visual inspection and tests with a wide range of parameter settings showed that the method is robust and provides realistic results.

Additive Manufacturing by Molten material Extrusion (AM-ME) of biocompatible and edible parts based on natural biopolymers, such as zein, a protein extracted from corn, opens prospects for applications in the pharmaceutical field. Cohesion between deposited layers requires filament spreading and diffusion of macromolecules at the interface. Viscous sintering has to be characterized and modelled in the case of zein, to better control its processing in the molten state. Sintering kinetics of polymer melts is generally assessed in an instrumented furnace and modelled using the Frenkel-Eshelby approach. It is based on the evaluation of the growth rate of the bonding neck between two circular parts, linked to the melt's surface tension (Gamma), the driving force, and viscosity (eta). It was recently completed by the acquisition of 3D scans by dynamic X-ray tomography (5.2 mu m pixel size, 1 scan/s) on the ANATOMIX beamline of Synchrotron SOLEIL, to follow the hot-melt sintering of 4 filaments (L-Filament=5 mm, (sic)(Filament)=2 mm) disposed in two layers. The analysis of the reconstructed volumes leads to assess the decreasing size of the central pore during sintering. 2D modelling is carried out by FEM combined to Level Set with COMSOL Multiphysics (R). It requires a simplification of the geometry according to an axial symmetry and an adaptive time-stepping. At 120 degrees C, a typical temperature to process plasticized zein, simulated and experimental sintering are similar, with a decrease rate of the central pore at about 1%/s. Increasing sintering rates are obtained as the temperature and surface tension increase.

Flax fibre bundles possess a remarkable structure, mainly generated through intrusive growth, that can be likened to a unidirectional composite reinforced with discontinuous fibres, resulting in complex mechanical behaviour. The main objectives of the present work are to provide a detailed description of the microstructure and local mechanical properties of the bundle components to better explain their specific mechanical behaviour. Their tensile behaviour was examined using tensile testing and scanning electron microscopy, revealing disparities in the fracture phenomena. Micro-tomographic and multi-photon microscopy images revealed the presence of fibre ends (tips) with a high fraction of crystalline and oriented cellulose. Additional tests were conducted using atomic force microscopy to estimate the thickness and indentation modulus of the middle lamellae, the primary cell wall as well as the S1 and S2 layers. These observations elucidate the origin of the remarkable multi-scale structure of the flax bundles.

Bone is a living tissue in which communicating cells, osteocytes, are assumed to be vital for tissue turnover and adaptation. Interestingly however, most advanced teleost fish do not possess osteocyte‐mediated porosity, prompting intriguing questions about alternative material‐strategies for these bones to cope with damage. Using advanced imaging techniques, including phase‐contrast enhanced (PCE) microtomography (µCT) and nanotomography (nanoCT), X‐ray fluorescence (XRF), and diffraction (XRD) tomography, the micro‐ and nano‐architectures of osteocytic zebrafish are compared with anosteocytic medaka fishbone. PCE µCT and Zernike phase‐contrast nanoCT showed a lack of porosity in medaka bone and 0.75 – 2.26% osteocytic porosity in zebrafish. Both fish species have similar mineralized collagen fibril arrangements containing calcium (Ca) and traces of strontium (Sr) with increased zinc (Zn) localized on the outer bone regions. Medaka bones exhibit reduced apatite nanocrystal lattice spacings on the outer surfaces. Indeed we find higher compressive residual strains (‐0.100 ± 0.02) compared to zebrafish (‐0.071 ± 0.03). We propose that medaka bone evolved to replace the mechanosensitive osteocytic network by entrapping protective residual strains between collagen nanofibers and mineral crystals. These strains may enhance fracture toughness while making this nanocomposite well‐suited for sustaining repeated loading cycles, thus reducing the metabolic costs associated with housing a large network of cells.

Defects in flax fibres limit the use of more sustainable load bearing composites in industry, which highlights the need for a thorough understanding of their nature. In this work, X-ray micro-tomography of flax revealed pores in the cell wall of elementary fibres: kink-bands pores and longitudinal pores, a previously unseen defect. Their morphology and organisation are examined, highlighting fibre deterioration and locally increased porosity up to 14.86 %. Finite element modelling under a 1.5 % tensile strain reveals that kink-band pores concentrate stress up to 7.15 times, while longitudinal pores reach 2.35 times compared to defect-free areas. Under tension, cracks are thus likely to initiate at kink-band defects, may propagate through longitudinal pores to other kink-bands, and lead to fibre and composite failure as these defects are favoured zones for crack initiation and propagation. In situ peeling of fibres due to knot tightening under scanning electron microscopy suggests interlaminar decohesion between cellulose macrofibrils as the origin of the longitudinal pores. The study explores hypotheses on the origin of these weak interfaces related to fibre growth and extraction processes. It provides insights for improving flax fibre properties and widening the use of more sustainable composites.

This work explores how the morphology of kink-band zones in flax fibres impacts the mechanical properties of the elementary fibres. Kink-bands are structural defects and are particularly sensitive to physical and biological stresses, on isolated fibres or in bio-based composite materials. To this end, a panel of archaeological samples from different time periods and preserved under different environmental conditions were selected and studied using synchrotron micro-tomography. It is demonstrated that although kink-bands are generally more numerous in ancient fibres, their degree of severity is sometimes less. This underlines the importance of fibre extraction methods, which are principally responsible for kink-band formation. The results also show that kink-band are weaknesses points, allowing rapid development of internal porosity (up to 25 %) when the fibres are used or stored in extreme environments, and that this porosity can also extend to healthy areas of the fibres. However, in some cases, even after millennia of conservation, it appears that the fibres can present morphologies comparable to modern samples, probably due to their good initial quality. Thanks to the findings of the present work, simplified schemes of degradation in kink-band zones, useable on single fibres but also in composite materials, are proposed. These results confirm the importance of fibre extraction processes on fibre quality and durability, and subsequent use for sustainable and high-performance composite materials and textiles.

Bone material contains a hierarchical network of micro- and nano-cavities and channels, known as the lacuna-canalicular network (LCN), that is thought to play an important role in mechanobiology and turnover. The LCN comprises micrometer-sized lacunae, voids that house osteocytes, and submicrometer-sized canaliculi that connect bone cells. Characterization of this network in three dimensions is crucial for many bone studies. To quantify X-ray Zernike phase-contrast nanotomography data, deep learning is used to isolate and assess porosity in artifact-laden tomographies of zebrafish bones. A technical solution is proposed to overcome the halo and shade-off domains in order to reliably obtain the distribution and morphology of the LCN in the tomographic data. Convolutional neural network (CNN) models are utilized with increasing numbers of images, repeatedly validated by `error loss' and `accuracy' metrics. U-Net and Sensor3D CNN models were trained on data obtained from two different synchrotron Zernike phase-contrast transmission X-ray microscopes, the ANATOMIX beamline at SOLEIL (Paris, France) and the P05 beamline at PETRA III (Hamburg, Germany). The Sensor3D CNN model with a smaller batch size of 32 and a training data size of 70 images showed the best performance (accuracy 0.983 and error loss 0.032). The analysis procedures, validated by comparison with human-identified ground-truth images, correctly identified the voids within the bone matrix. This proposed approach may have further application to classify structures in volumetric images that contain non-linear artifacts that degrade image quality and hinder feature identification.

Flax fibers represent a valuable reinforcement in composite materials. However, the presence of defects known as kink-bands in flax fiber has the capacity to influence their mechanical properties. The primary objective of this research is to gain a comprehensive understanding of the damage mechanism in flax fiber bundles presenting a novel aspect due to the intricate structure of bundle fibers, which is more complex compared to elementary fibers. The study specifically explores flax fiber bundles under tensile loading and investigates the impact of kink-bands on their failure through a combined approach, utilizing both experimental and numerical methods. In the experimental part, X-ray microtomography in situ tensile testing is carried out, which reveals complex failure mechanisms. Furthermore, a 3D-Finite Elements (FE) model is implemented utilizing 3D reconstructed fiber and used for numerical tensile analysis. Our findings highlight that the kink-band region acts as prominent failure site in fiber bundles with significant stress concentration at the kink-band region, mainly induced by local porosity.