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Natural metal-organic complexes have gained much attention due to their self-assembly behaviors and photochemical properties. They perform various biological processes, including catalysis, anti-oxidation, molecular transport, and structural organization. Recently, the bio-inspired metal-phenolic complexes have been widely adopted as molecular scaffolds and redox-active molecules for the fabrication of functional materials. This review focuses on recent studies on the applications of metal-polyphenol complexes as bioinspired materials to build functional biomaterials possessing unique physical and chemical properties. Metal-phenolic coordination provides a simple fabrication route to complex and hierarchical structures as found in metal-ligand complexes in nature, leading to assembled supramolecular materials and robust interfaces of metal species with polyphenols. Furthermore, the metal-polyphenol chemistry features the versatile biochemical and structural functions of metal species through complexation with polyphenols as biocompatible ligands. This article is concluded with a discussion on the redox properties of metal-phenolic coordination potentially useful for biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: The repeated-bending properties of Sn-0.7Cu, Sn-0.3Ag-0.7Cu (SAC0307), and Sn-3.0Ag-0.5Cu (SAC305) solders mounted on flexible substrates were studied using highly accelerated stress testing (HAST), followed by repeated-bending testing. In the Sn-0.7Cu joints, the Cu6Sn5 intermetallic compound (IMC) coarsened as the HAST time increased. For the SAC0307 and SAC305 joints, the Ag3Sn and Cu6Sn5 IMCs coarsened mainly along the grain boundary as the HAST time increased. The Sn-0.7Cu solder had a high contact angle, compared to the SAC0307 and SAC305 solders; consequently, the SAC0307 and SAC305 solder joints displayed smoother fillet shapes than the Sn-0.7Cu solder joint. The repeated-bending for the Sn-0.7Cu solder produced the crack initiated from the interface between the Cu lead wire and the solder, and that for the SAC solders indicated the cracks initiated at the surface, but away from the interface between the Cu lead wire and the solder. Furthermore, the oxide layer was thickest for Sn-0.7Cu and thinnest for SAC305, regardless of the HAST time. For the SAC solders, the crack initiation rate increased as the oxide layer thickened and roughened. Cu6Sn5 precipitated and grew along the grain and subgrain boundaries as the HAST time increased, embrittling the grain boundary at the crack propagation site.Graphical Abstract: [ABSTRACT FROM AUTHOR]