Due to its superior nanoscale properties, cobalt (Co) is highly desirable for ultrahigh-density 3D integration into materials through metal/dielectric hybrid bonding. However, this process is very challenging through Co/SiO₂ hybrid bonding, as very hydrophilic SiO₂ surfaces are needed for bonding during dehydration reactions and oxidation of the Co surfaces must be avoided. Additionally, the substantial coefficient of thermal expansion mismatch between the robust capping layers (Co and SiO₂ layers) necessitates hybrid bonding with minimal thermal input and compression. In this study, we introduce a ternary plasma activation strategy employing an Ar/NH₃/H₂O gas mixture to facilitate Co/SiO₂ hybrid bonding at temperatures as low as ~200 ℃, which is markedly lower than the melting point of Co (~1500 ℃). Intriguingly, non-oxide metallization at the Co–Co interface can be realized without the hindrance of a bonding barrier, thereby reducing the electrical resistance by over 40% and compression force requirements. Moreover, the enhancement in the SiO₂ surface energy through active group terminations fosters extensive interfacial hydration and strengthens the mechanical properties. This research paves the way for fine-tuning bonding surfaces using a material-selective strategy, which should advance metal/dielectric hybrid bonding for future integration applications.

Biomimetic bone-active coatings composed of inorganic nano-hydroxyapatite (i.e., nHA) and organic silk fibroin (i.e., SF) are layer-by-layer deposited on Mg-Zn-Ca alloy by a controllable ultrasonic spray method. Meanwhile, plasma activation is developed as a promising strategy to pretreat magnesium surfaces, which facilitates the direct adhesion of coatings with enhanced bonding interfaces. In this work, we engineer the nHA/SF composite coatings with excellent mechanical properties and adhesion force. The optimized parameters of ultrasonic spray bring significant influence on the surface morphologies of coatings. Assisted by hybrid plasma of oxygen and nitrogen (i.e., O₂/N₂ plasma), the activated Mg-Zn-Ca surfaces are uniformly covered by a robust and compact nHA/SF composite coating, establishing a multifunctional system with superior corrosion resistance and biological performance. Interestingly, secondary oxygen plasma treatment of nHA/SF coatings (A-nHA/SF) promotes the hydrophilicity, leading to a rapid self-repair effect from surface damage. The improvement of anti-corrosion and self-repair provides a dependable platform for better cell adhesion, proliferation, spreading and differentiation. These favorable factors contribute to the preferable in vivo biocompatibility and the promotion of newly formed bones for the A-nHA/SF-coated Mg implants. This study lays important foundations for coating strategy on biomedical magnesium alloy as multifunctional osteogenic system in bioactive implantable applications.