Simplifying the bonding technique used to package power devices is crucial for electric vehicles and 5G communication. Herein, a transparent liquid Ag-based complex was employed to simplify the Ag sintering process. The complex can directly fabricate Ag nanostructures on substrates and dies by thermal decomposition at 180 °C for 30 min. These nanostructures consisted of linked nanoparticles with a wide size distribution and exhibited remarkable compressibility, indicating an excellent potential for sintering. Unlike traditional Ag paste, the Ag-based complex presented a single phase, and the obtained Ag nanostructures could be directly sintered at a low temperature. Robust sintered Ag joints with a high average shear strength of 45.4 MPa and a low porosity of 9.3% were successfully achieved by sintering at 300 °C and 5 MPa for 40 min. Such joint properties can be attributed to the frame–filler structure generated during sintering. This structure, which featured large Ag particles acting as frames and small Ag particles acting as bridges linking the frames, was beneficial for improving the sintering performance of the Ag nanostructures. The Ag-based complex could be used for the facile preparation of robust sintered Ag joints, creating possibilities for die attachment while reducing manufacturing costs.
Integrating stretchable and rigid electric units presents a significant challenge in manufacturing stretchable electronics. Their surface property differences prevented reliable stretching-tolerant connections. Here, we report a universal method to construct stretchable connections based on interfacial covalent reactions. It enables robust and conductive bonding among various soft/rigid electronics through simple surface modification and interfacial reaction. The bonding between SEBS rubber and metals reached stretchability over 250% with interfacial toughness over 200 N/m. The ultrathin connection layer provided conductive pathways, achieving an electrical stretchability of 60% between Au-deposited SEBS and Cu sheets. Connections between liquid metal-based stretchable conductors could withstand more than 10,000 stretching cycles to 60% strain while maintaining their high conductivity. The versatility and stability of this method were further proved by fabricating electronic devices that integrated soft and rigid units, including circuits on papers and a gesture-visualizing glove with LEDs, highlighting the robustness of the stretchable connections.
Emerging demand in soft bioelectronic systems poses critical challenges in stiffness control and end-to-end connections due to huge modulus difference in various components. Here, a bidirectionally electrical interface of hydrogel and metal electrodes to bridge soft skin/issue and data collection circuits is enabled by coordination interactions. The dual-mode chelation including internal chelation and surface chelation effectively configures the crosslinking structure of hydrogel as well as enhances the binding interface of metal-hydrogel complex surfaces. Internally, strong chelation competes with esterification, yielding tissue-like softness of hydrogel with an ultra-low modulus of ∼339.9 Pa. Externally, the hydrogel passivates the combined metal surfaces, promoting the formation of interlocked structures between metal oxide nanoislands, achieving a high binding strength of ∼1.95 MPa without compromising electrical conductivity. The stable electrical interconnections via hybrid interfacial bonding enable high signal-to-noise ratio signal recordings from the skin, neural surfaces, and brain, maintaining reliable performance even under mechanical disturbances. This work provides an effective strategy for achieving mechanically and electrically robust hybrid bioelectronic interfaces, advancing their applications in capturing both in vitro and in vivo electrical signals.
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