Penguin feather-inspired flexible aerogel composite films featuring ultra-low thermal conductivity and dielectric constant

Given extremely high porosity, aerogels have demonstrated remarkable advantages in serving as thermal insulation and wave-transparent materials. Unfortunately, their practical applications are greatly confined by their inherent fragility. The recent emergence of polymer aerogels presents an ideal platform for the development of flexible aerogel films. However, additional cross-linking agents are necessitated for constructing a robust structure, complicating the production process. Herein, we report a flexible aerogel film based on <i>meta</i>-aramid composites, inspired by the porous structure of penguin feathers. The intermolecular hydrogen bonds function as natural cross-linking agents. Their disruption results in the dissolution of <i>meta</i>-aramid fibers, while their reconstruction facilitates localized rearrangement of <i>meta</i>-aramid chains during the sol-gel process, generating closed nanopores. Furthermore, fluorinated hollow glass microspheres are filled, compressing the nanopores situated near the interface to 75-150 nm. This meets the critical threshold required by the Knudsen effect, decreasing the thermal conductivity to levels below that of ambient air. At an optimized doping ratio of 3 wt%, the thermal conductivity is 21.6 mW m^-1 K^-1, while achieving a low dielectric constant of 1.43. Simultaneously, aerogel films exhibit enhanced mechanical properties, and also show benefits of hydrophobicity, colorability, ultralightness, and flame retardancy, making themselves multifunctional materials suitable for practical applications.