We report strong chiral coupling between magnons and photons in microwave waveguides that contain chains of small magnets on special lines. Large magnon accumulations at one edge of the chain emerge when exciting the magnets by a phased antenna array. This mechanism holds the promise of new functionalities in nonlinear and quantum magnonics.

Recent advances in additive manufacturing (AM) have enabled the fabrication of functionally graded porous biomaterials (FGPBs) for application as orthopedic implants and bone substitutes. Here, we present a step-wise topological design of FGPB based on diamond unit cells to mimic the structure of the femoral diaphysis. The FGPB was manufactured from Ti-6Al-4V powder using the selective laser melting (SLM) technique. The morphological parameters, permeability and mechanical properties of FGPB samples were measured and compared with those of the biomaterials with uniform porous structures based on the same type of the unit cell. The FGPB exhibited a low density (1.9 g/cm³), a moderate Young's modulus (10.44 GPa), a high yield stress (170.6 MPa), a high maximum stress (201 MPa) and favorable ductility, being superior to the biomaterials with uniform porous structures in comprehensive mechanical properties. In addition, digital image correlation (DIC) and finite element (FE) simulation were used to unravel the mechanisms governing the deformation and yielding behavior of these biomaterials particularly at the strut junctions. Both DIC and FE simulations confirmed that the deformation and yielding of the FGPB occurred largely in the load-bearing layers but not at the interfaces between layers. Defect-coupled FE models based on solid elements provided further insights into the mechanical responses of the FGPB to compressive loads at both macro- and micro-scales. With the defect-coupled representative volume element model for the FGPB, the Young's modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The study clearly demonstrated the capabilities of combined experimental and computational methods to resolve the uncertainties of the mechanical behavior of FGPBs, which would open up the possibilities of applying various porosity variation strategies for the design of biomimetic AM porous biomaterials. Statement of Significance: Functionally graded bone scaffolds significantly promote the recovery of segmental bone defect. In the present study, we present a step-wise topological design of functionally graded porous biomaterial (FGPB) to mimic the structure of the femoral diaphysis. The Ti-6Al-4V FGPB exhibited a superior combination of low density, moderate Young's modulus, high yield stress and maximum stress as well as favorable ductility. The biomechanical performance of FGPB was studied in both macro and micro perspectives. The defect-coupled model revealed the significant yielding in the load-bearing parts and the Young's modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The superiority of combined experimental and computational methods has been confirmed.

Functionally graded scaffold (FGS) is designed to mimic the morphology, mechanical and biological properties of natural bone closely. Porosity variation strategy between different regions in FGS plays a crucial role in influencing its mechanical and biological performance. A combination of modeling tool and scripting language can effectively enhance the ability to optimize FGS design. This study was aimed at determining the effect of porosity variation strategy on the mechanical performance and permeability of the as-built and as-heat-treated FGSs. Ti-6Al-4V FGSs with sizes of 10 × 10 × 15 mm and diamond lattice structures were designed and fabricated by means of selective laser melting. A wide range of porosities in the FGSs (38–75%) were achieved by applying six different porosity variation strategies. The elastic modulus (3.7–5.7 GPa) and yield strength (27.1–84.7 MPa) of the as-built FGSs were found to vary between the corresponding mechanical properties of cancellous bone and cortical bone. Heat treatment reduced the strengths by 13–56%. Porosity variation strategy strongly affected the deformation behavior and failure mechanisms of the FGSs. The sigmoid function-controlled FGSs showed gradual failure behavior and sample Sigk0.5b8 showed superior overall performance. The results demonstrated that porosity variation strategy is a feasible means for tailor design of FGS.