Bioinspirational understanding of flexural performance in hedgehog spines

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

A Review of Image-Based Simulation Applications in High-Value Manufacturing

Image-Based Simulation (IBSim) is the process by which a digital representation of a real geometry is generated from image data for the purpose of performing a simulation with greater accuracy than with idealised Computer Aided Design (CAD) based simulations. Whilst IBSim originates in the biomedical field, the wider adoption of imaging for non-destructive testing and evaluation (NDT/NDE) within the High-Value Manufacturing (HVM) sector has allowed wider use of IBSim in recent years. IBSim is invaluable in scenarios where there exists a non-negligible variation between the 'as designed' and 'as manufactured' state of parts. It has also been used for characterisation of geometries too complex to accurately draw with CAD. IBSim simulations are unique to the geometry being imaged, therefore it is possible to perform part-specific virtual testing within batches of manufactured parts. This novel review presents the applications of IBSim within HVM, whereby HVM is the value provided by a manufactured part (or conversely the potential cost should the part fail) rather than the actual cost of manufacturing the part itself. Examples include fibre and aggregate composite materials, additive manufacturing, foams, and interface bonding such as welding. This review is divided into the following sections: Material Characterisation; Characterisation of Manufacturing Techniques; Impact of Deviations from Idealised Design Geometry on Product Design and Performance; Customisation and Personalisation of Products; IBSim in Biomimicry. Finally, conclusions are drawn, and observations made on future trends based on the current state of the literature.

Porous morphology and graded materials endow hedgehog spines with impact resistance and structural stability

Hedgehog spines with evolved unique structures are studied on account of their remarkable mechanical efficiency. However, because of limitations of existing knowledge, it remains unclear how spines work as a material with a balance of stiffness and toughness. By combining qualitative three-dimensional (3D) structural characterization, material composition analysis, biomechanical analysis, and parametric simulations, the relationship between microstructural characteristic and multifunctional features of hedgehog spines is revealed here. The result shows that the fibers transform from the outer cortex to the interior cellular structures by the "T" section composed of the "L" section and a deltoid. The outer cortex, however, shows an arrangement of a layered fibrous structure. An inward change in Young's moduli is observed. In addition, these spines are featured with a sandwich structure that combines an inner porous core with an outer dense cortex. This feature confirms that the hedgehog spines are a kind of biological functionally graded fiber-reinforced composite. Biomimetic models based on the spine are then built, and the corresponding mechanical performance is tested. The results confirm that the internal cellular structure of the spine effectively improve impact resistance. Furthermore, the transverse diaphragm can prevent ellipticity, which may delay buckling. The longitudinal stiffeners also contribute to promote buckling resistance. The design strategies of the spine proposed here provide inspirations for designing T-joint composites. It also exhibits potential applications in low-density, impact and buckling resistance artificial composites. STATEMENT OF SIGNIFICANCE: The spines of a hedgehog are its protective armor that combines strength and toughness. The animal can not only withstand longitudinal and radial forces that are 1 × 10⁶∼ 3 × 10⁶ times the gravity generated by its own weight, but it can also survive unscathed by elastic buckling while dropping to the ground at a speed of up to 15 m/s. Here, we first demonstrate that hedgehog spines are biological graded fiber-reinforced structural composites and reveal their superior impact and buckling resistance mechanism through simulation analysis. Our results broaden the understanding of the relationship among morphology, materials, and function of hedgehog spines. It is anticipated that the survival strategies of hedgehog revealed here could provide inspirations for the development of synthetic composites with impact resistance and structural stability.

Computed Tomography as a Characterization Tool for Engineered Scaffolds with Biomedical Applications

The ever-growing field of materials with applications in the biomedical field holds great promise regarding the design and fabrication of devices with specific characteristics, especially scaffolds with personalized geometry and architecture. The continuous technological development pushes the limits of innovation in obtaining adequate scaffolds and establishing their characteristics and performance. To this end, computed tomography (CT) proved to be a reliable, nondestructive, high-performance machine, enabling visualization and structure analysis at submicronic resolutions. CT allows both qualitative and quantitative data of the 3D model, offering an overall image of its specific architectural features and reliable numerical data for rigorous analyses. The precise engineering of scaffolds consists in the fabrication of objects with well-defined morphometric parameters (e.g., shape, porosity, wall thickness) and in their performance validation through thorough control over their behavior (in situ visualization, degradation, new tissue formation, wear, etc.). This review is focused on the use of CT in biomaterial science with the aim of qualitatively and quantitatively assessing the scaffolds’ features and monitoring their behavior following in vivo or in vitro experiments. Furthermore, the paper presents the benefits and limitations regarding the employment of this technique when engineering materials with applications in the biomedical field.

Engineering with keratin: A functional material and a source of bioinspiration

Keratin is a highly multifunctional biopolymer serving various roles in nature due to its diverse material properties, wide spectrum of structural designs, and impressive performance. Keratin-based materials are mechanically robust, thermally insulating, lightweight, capable of undergoing reversible adhesion through van der Waals forces, and exhibit structural coloration and hydrophobic surfaces. Thus, they have become templates for bioinspired designs and have even been applied as a functional material for biomedical applications and environmentally sustainable fiber-reinforced composites. This review aims to highlight keratin's remarkable capabilities as a biological component, a source of design inspiration, and an engineering material. We conclude with future directions for the exploration of keratinous materials.