Background Accurate prediction of thermo-mechanical responses in biological tissues is essential for thermal therapies such as hyperthermia. The Green–Naghdi (GN) theory provides a suitable framework for modeling non-Fourier heat conduction in biological media. Objective This study investigates the coupled thermo-mechanical behavior of viscoelastic biological media under transient thermal excitation using the Green–Naghdi type II (GN-II) theory. Methods A coupled thermo-viscoelastic model is formulated for a stress-free medium subjected to a time-dependent, exponentially attenuated thermal load. The governing equations are solved using the Laplace transform and an eigenvalue-based spectral approach. Temperature, displacement, and stress fields are evaluated numerically, followed by a parametric analysis. Results The results demonstrate significant coupling between thermal and mechanical fields. Thermal loading and material parameters strongly influence the distributions of temperature, displacement, and stress. Distinct responses are observed between dissipative and non-dissipative thermal models. Conclusion The proposed eigen-spectral approach effectively describes thermo-mechanical responses in viscoelastic biological media. The findings demonstrate the importance of non-Fourier heat conduction and viscoelastic effects in modeling thermal therapies and optimizing treatment conditions.
Background Bio-inspired high-entropy alloys (Bio-HEAs) are emerging as materials for orthopedic implants because of their high strength, corrosion resistance, compositional flexibility, and biocompatibility. Their tunable mechanical properties may reduce elastic mismatch with bone and mitigate stress shielding and implant loosening. Objective This review evaluates Bio-HEAs for orthopedic applications, emphasizing elastic modulus tailoring, stress-shielding mitigation, microstructural control, biological response, and mathematical modeling. Methods Literature on Bio-HEAs for biomedical applications was reviewed, focusing on composition–structure–property relationships, elastic modulus, phase stability, biological response, and computational approaches. Experimental findings were considered alongside molecular dynamics (MD), continuum elasticity, partial differential equation (PDE)-based approaches, and finite element method (FEM) simulations. Results Reported Bio-HEAs exhibit elastic moduli ranging approximately from 10 to 30 GPa, providing opportunities to reduce mechanical mismatch with cortical bone. Atomic size mismatch, lattice distortion, phase constitution, and microstructural features influence elastic behavior. MD, continuum models, and FEM provide complementary insights across length scales, while integrated multiscale approaches can improve implant-level predictions and support patient-specific design. Conclusion Bio-HEAs offer potential for mechanically compatible orthopedic implants. Integrating materials design with multiscale mathematical modeling may enable improved control of elastic behavior, stress distribution, and implant performance, although experimental validation and clinically relevant modeling are required.
BACKGROUND There are problems such as intimal hyperplasia leading to restenosis after artery bypass graft surgery. A detailed understanding of hemodynamics is very important for the treatment of arterial stenosis. OBJECTIVE The novel model of two-way artery bypass graft considering microcirculation function is proposed to investigate hemodynamic characteristics. METHODS The two-way artery bypass graft model with the interaction of blood-arterial wall-microcirculation is constructed. Different suture angles (20°, 30°, 45°) in the model are considered to compare the differences of hemodynamics. The fluid-structure interaction and a seepage condition are adopted. RESULTS The results show that almost all blood flows into the graft tubes when it comes to the bifurcation between the graft tubes and the host artery. The blood flow is symmetrically distributed in the upper and lower graft tubes. The peak pressures in the 20°, 30° and 45° models are about 370, 750 and 500 Pa respectively. Sequentially, the wall shear stresses of approximately 3, 0.4 and 2 Pa in the three models are generated in the post-stenotic region. The more suitable distributions and levels of pressure and wall shear stress are generated in the 45° model in contrast to the 20° and 30° models. CONCLUSION It indicates that the addition of microcirculation could better simulate the physiological flow characteristics. Compared with the 20° and 30° models, the 45° model produces better hemodynamic effects. 45° may be the optimal bypass graft angle.
Background Critical-sized bone defects remain a major challenge in orthopedic practice. Biomimetic scaffolds are designed to support bone regeneration by reproducing the structural and functional characteristics of native bone. Objective To synthesize advances in multidimensional biomimetic bone scaffolds, examine their roles in bone regeneration, and identify key barriers to clinical translation. Methods This narrative review drew primarily on literature identified through PubMed and Google Scholar, with an emphasis on publications from the past five years. Representative original studies and reviews were selected based on their relevance to biomimetic scaffold design, regenerative mechanisms, pathological bone defects, and fabrication technologies. Earlier publications were included where needed to provide foundational context. The selected literature was synthesized thematically across complementary aspects of scaffold design and application. Results The synthesis integrates five interconnected design dimensions: composition, hierarchical structure, mechanical properties, biophysical signaling, and biological regulation. These dimensions link scaffold design to controlled drug delivery, reconstruction of a vascularized microenvironment, and neuro-osseous coupling. Preclinical studies report promising regenerative outcomes in models of infected, post-tumor-resection, and diabetic bone defects. Three-dimensional printing, electrospinning, and self-assembly offer complementary fabrication approaches for implementing these strategies across diverse material classes. However, limited clinical evidence and unresolved challenges in long-term biosafety, mechanical compatibility, functional stability, and reproducible, patient-specific manufacturing continue to hinder translation. Conclusion Multidimensional biomimetic design provides a framework for coordinating structural support with biological regulation during bone repair. Further progress requires validation of long-term safety and functional performance, alongside manufacturing approaches that balance functional complexity with clinical feasibility.
Background Magnesium-based alloys have emerged as promising biodegradable materials for temporary biomedical implants due to their biocompatibility, low density, and elastic modulus similar to natural bone. However, their rapid degradation in physiological environments limits their clinical application, making surface modification strategies necessary to improve corrosion resistance and mechanical performance. Objective The aim of this study was to evaluate the effect of ionic nitriding on the microstructure, corrosion resistance, mechanical properties, and cytocompatibility of Mg–Zn–Ca–Mn biodegradable alloys. Methods Mg–Zn–Ca–Mn quaternary alloys were synthesized by powder metallurgy and subsequently surface modified by ionic nitriding. The microstructure and phase composition were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Corrosion behavior was evaluated through electrochemical tests in Hank's solution, while mechanical properties were assessed using Vickers microhardness measurements. Cytocompatibility was analyzed by indirect cytotoxicity tests using fibroblast and keratinocyte cells. Results The nitrided alloys exhibited improved corrosion resistance, evidenced by lower corrosion current densities and more noble corrosion potentials compared with pure magnesium. In addition, ionic nitriding increased the Vickers microhardness by approximately 42–48%. Cytotoxicity assays showed that the Mg64–Zn30–Ca5–Mn1 alloy and its nitrided counterpart-maintained cell viability above 70%, indicating acceptable cytocompatibility. Conclusion Ionic nitriding is an effective surface modification technique to enhance the corrosion resistance, mechanical properties, and biological performance of Mg–Zn–Ca–Mn biodegradable alloys, demonstrating their potential for use as temporary biomedical implant materials.
