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1. Multimodule imaging of the hierarchical equine hoof wall porosity and structure

   Mahmoud A. Mahrous; Charul Chadha; Pei L. Robins; Christian Bonney; Kingsley A. Boateng; Marc Meyers' Iwona Jasiuk (June 2023, bioRxiv)

   The equine hoof wall has a complex, hierarchical structure that can inspire designs of impactresistant materials. In this study, we utilized micro-computed tomography (µ-CT) and serial blockface scanning electron microscopy (SBF-SEM) to image the microstructure and nanostructure of the hoof wall. We quantified the morphology of tubular medullary cavities by measuring equivalent diameter, surface area, volume, and sphericity. High-resolution µ-CT revealed that tubules are partially or fully filled with tissue near the exterior surface and become progressively empty towards the inner part of the hoof wall. Thin bridges were detected within the medullary cavity, starting in the middle section of the hoof wall and increasing in density and thickness towards the inner part. Porosity was measured using three-dimensional (3D) µ-CT, twodimensional (2D) µ-CT, and a helium pycnometer, with the highest porosity obtained using the helium pycnometer (8.07%), followed by 3D (3.47%) and 2D (2.98%) µ-CT. SBF-SEM captured the 3D structure of the hoof wall at the nanoscale, showing that the tubule wall is not solid, but has nano-sized pores, which explains the higher porosity obtained using the helium pycnometer. The results of this investigation provide morphological information on the hoof wall for the future development of hoof-inspired materials and offer a novel perspective on how various measurement methods can influence the quantification of porosity. 

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2. Viscoelastic properties of the equine hoof wall

   https://doi.org/10.1016/j.actbio.2024.06.022  

   Bonney, Christian; Pang, Siyuan; Meyers, Marc A; Jasiuk, Iwona (August 2024, Acta Biomaterialia)

   The equine hoof wall has outstanding impact resistance, which enables high-velocity gallop over hard terrain with minimum damage. To better understand its viscoelastic behavior, complex moduli were de- termined using two complementary techniques: conventional ( ∼5 mm length scale) and nano ( ∼1 μm length scale) dynamic mechanical analysis (DMA). The evolution of their magnitudes was measured for two hydration conditions: fully hydrated and ambient. The storage modulus of the ambient hoof wall was approximately 400 MPa in macro-scale experiments, decreasing to ∼250 MPa with hydration. In contrast, the loss tangent decreased for both hydrated ( ∼0.1–0.07) and ambient ( ∼0.04–0.01) conditions, over the frequency range of 1–10 Hz. Nano-DMA indentation tests conducted up to 200 Hz showed little frequency dependence beyond 10 Hz. The loss tangent of tubular regions showed more hydration sensitivity than in intertubular regions, but no significant difference in storage modulus was observed. Loss tangent and effective stiffness were higher in indentations for both hydration levels. This behavior is attributed to the hoof wall’s hierarchical structure, which has porosity, functionally graded aspects, and material interfaces that are not captured at the scale of indentation. The hoof wall’s viscoelasticity characterized in this work has implications for the design of bioinspired impact-resistant materials and structures. 

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3. Characterization of MXene‐Based Materials by X‐Ray Computed Tomography

   https://doi.org/10.1002/smtd.202500262  

   Soltan_Mohammadlou, Bita; Ippolito, Stefano; FitzPatrick, James; Upadhyay, Prastuti; Burnett, Tim L; Gogotsi, Yury (August 2025, Small Methods)

   Abstract MXenes are a class of 2D materials that have gained significant attention for their potential applications in energy storage, electromagnetic interference shielding, biomedicine, and (opto)electronics. Despite their broad range of applications, a detailed understanding of the internal architecture of MXene‐based materials remains limited due to the lack of effective 3D imaging techniques. This work demonstrates the application of X‐ray micro‐computed tomography (micro‐CT) to investigate various MXene systems, including nanocomposites, coated textiles, and aerogels. Micro‐CT enables high‐resolution, 3D visualization of the internal microstructure, MXene distribution, infiltration patterns, and defect formations, which significantly influence the material's performance. Moreover, the typical technical challenges and limitations encountered during sample preparation, scanning, and post‐processing of micro‐CT data are discussed. The information obtained from optical and electron microscopy is also compared with micro‐CT, highlighting the unique advantages of micro‐CT in providing comprehensive 3D imaging and quantitative data. This study highlights micro‐CT as a powerful and nondestructive imaging tool for characterizing MXene‐based materials, providing insights into material optimization and guidelines for developing future advanced applications. 

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4. Serial Block Face‐Scanning Electron Microscopy as a Burgeoning Technology

   https://doi.org/10.1002/adbi.202300139  

   Marshall, Andrea_G; Neikirk, Kit; Stephens, Dominique_C; Vang, Larry; Vue, Zer; Beasley, Heather_K; Crabtree, Amber; Scudese, Estevão; Lopez, Edgar_Garza; Shao, Bryanna; et al (May 2023, Advanced Biology)

   Abstract Serial block face scanning electron microscopy (SBF‐SEM), also referred to as serial block‐face electron microscopy, is an advanced ultrastructural imaging technique that enables three‐dimensional visualization that provides largerx‐ andy‐axis ranges than other volumetric EM techniques. While SEM is first introduced in the 1930s, SBF‐SEM is developed as a novel method to resolve the 3D architecture of neuronal networks across large volumes with nanometer resolution by Denk and Horstmann in 2004. Here, the authors provide an accessible overview of the advantages and challenges associated with SBF‐SEM. Beyond this, the applications of SBF‐SEM in biochemical domains as well as potential future clinical applications are briefly reviewed. Finally, the alternative forms of artificial intelligence‐based segmentation which may contribute to devising a feasible workflow involving SBF‐SEM, are also considered. 

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5. Equine Hoof Wall Deformation: Novel Aspects Revealed

   https://doi.org/10.1002/sstr.202200402  

   Lazarus, Benjamin S.; Luu, Rachel K.; Ruiz-Pérez, Samuel; Barbosa, Josiane D. V.; Jasiuk, Iwona; Meyers, Marc A. (May 2023, Small Structures)

   The equine hoof wall has a unique hierarchical structure that allows it to survive high‐impact scenarios. Previous authors have explored the compressive, viscoelastic, and fracture control properties of the hoof wall and suggested that this complex structure plays a vital role in the hoof's behavior. However, the link between the structure and the behavior of the hoof wall has been made primarily with the use of post‐fracture analysis. Here, periodic microcomputed tomography scans are used to observe the temporal behavior of the hoof's meso and microstructures during compression, fracture, and relaxation. These results shed light on the structural anisotropy of the hoof wall and how its hollow tubules behave when compressed in different directions, at different hydration levels, and in various locations within the hoof wall. The behavior of tubule bridges during compression is also reported for the first time. This study elucidates several fracture phenomena, including the way cracks are deflected at tubule interfaces and tubule bridging, tubule arresting, and fiber bridging. Finally, relaxation tests are used to show how the tubule cavities can regain their shape after compression. 

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