Ultralight, Flexible, and Biomimetic Nanocellulose/Silver Nanowire Aerogels for Electromagnetic Interference Shielding

TLDR

Ultralight, flexible biopolymer aerogels composed of cellulose nanofibers and silver nanowires are fabricated by a simple freeze‑casting process. By tuning the freezing method, lamellar, honeycomb‑like, and random porous scaffolds are produced, linking microstructure to mechanical and EMI shielding performance. The optimized lamellar aerogels achieve EMI shielding effectiveness exceeding 70 dB in the X‑band at densities of 6.2 or 1.7 mg cm⁻³, with a normalized surface specific SE up to 178 235 dB·cm² g⁻¹, and also exhibit antibacterial and hydrophobic properties.

Abstract

Ultralight and highly flexible biopolymer aerogels, composed of biomimetic cellular microstructures formed from cellulose nanofibers and silver nanowires, are assembled via a convenient and facile freeze-casting method. The lamellar, honeycomb-like, and random porous scaffolds are successfully achieved by adjusting freezing approaches to modulate the relationships between microstructures and macroscopic mechanical and electromagnetic interference (EMI) shielding performances. Combining the shielding transformation arising from in situ compression and the controlled content of building units, the optimized lamellar porous biopolymer aerogels can show a very high EMI shielding effectiveness (SE), which exceeds 70 or 40 dB in the X-band while the density is merely 6.2 or 1.7 mg/cm3, respectively. The corresponding normalized surface specific SE (defined as the SE divided by the material density and thickness) is up to 178235 dB·cm2/g, far surpassing that of the so-far reported shielding materials. Antibacterial properties and hydrophobicity are also demonstrated extending the versatility and application potential of the biopolymer hybrid aerogels.