BN Nanosheets‐Regulated Elastic Carbon Aerogel Microwave Absorber: Strain‐Driven Broadband Frequency Shifting over S‐Ku Bands with Sustained Large Bandwidth at High Strains

To address the demand for dynamically tunable microwave absorbers, an elastic carbon aerogel is developed by integrating hexagonal boron nitride nanosheets (h‐BNNS) and cellulose nanocrystals into chitosan‐derived lamellar architectures. The unique “pit/protrusion” structure formed by h‐BNNS optimizes dielectric properties and mechanical compliance of the aerogel, enabling strain‐driven broadband frequency shifting over S‐Ku bands (2–18 GHz). Crucially, the aerogel achieves an ultrawide adjustable effective absorption bandwidth (EAB) of 15.2 GHz under 0–75% compressive strains–the broadest reported tunable range–while maintaining >8 GHz EAB even at 75% strain. This performance stems from h‐BNNS that suppresses excessive conductivity enhancement and ensures optimal impedance matching under high deformation. The work pioneers a strategy for high‐performance, strain‐adaptive microwave absorbers with applications in smart wearable devices and radar stealth.