Foaming ink for 3D-printing of ultralight and hyperelastic graphene architectures: Multiscale design and...

Extrusion-based printing of macroscopic architectures layer-by-layer offers new opportunities for constructing customized electromagnetic interference (EMI) shielding materials. However, current research primarily focuses on improving the printability of material inks by increasing contents and adding various modifiers, controllable construction of ultralight and robust macro-architectures with structural design at both macro- and micro-scales is still challenging. Herein, we develop a graphene oxide foaming ink enriched with air bubbles for direct-ink writing, enabling the creation of macroscopic graphene architectures with arbitrary geometries. Meanwhile, air bubbles guide the self-assembly of nanosheets into a unique closed-cellular structure, which plays a critical role in enhancing EMI shielding performance. The resulting bubble-derived graphene aerogels (BGAs), fabricated through lyophilization and reduction of the foaming inks, exhibit ultralow densities of 0.0033-0.0045 g·cm^-3, superior resilience even at cryogenic temperatures (-196 °C in liquid nitrogen), high compressive strength, and a negative Poisson's ratio. Remarkably, these BGAs achieve exceptionally high EMI shielding effectiveness (SE), reaching 103.2 dB with a low SE reflection of merely 4.8 dB. The specific SE (SSE/t), an absolute measure considering density and thickness, reaches an impressive value of 52,252 dB·cm²·g^-1, ranking among the highest reported for synthetic foams. The desirable nanosheets-wrapped closed bubble-shaped cells, well-connected porous and conductive networks, and abundant interfaces in the BGAs collectively contribute to the intense interference and multireflection of electromagnetic waves, driving their outstanding shielding performance. This study presents a straightforward and practical approach to construct ultralight and resilient graphene architectures with multiscale designs, offering a promising solution for advanced EMI shielding applications.