Multifunctional carbon foam with hollow microspheres and a concave–convex microstructure for adjustable electromagnetic wave absorption and wearable applications

Rational design of the microstructure of a multifunctional electromagnetic wave absorber is a greatly promising route to establish convenient performance regulation and to satisfy complex application conditions. In this work, the proposed material for the absorber is a compressible carbonated reduced graphene oxide/Fe3O4 (C-rGO/Fe3O4) carbon foam with hollow microspheres and a concave–convex microstructure. Its unique porous structure can strengthen the multiple reflections of electromagnetic waves and improve the system's mechanical properties. The C-rGO/Fe3O4 carbon foam possesses excellent comprehensive electromagnetic wave absorption performance (reflection loss (RL) value of −57.50 dB and effective bandwidth of 6.72 GHz) and exhibits convenient RL value regulation (when varying compressive strains). The RL value of the carbon foam can be adjusted within the absorption range of RL ≤ −20 dB or switched between ≤−20 dB and RL ≤ −10 dB, exhibiting a smart function-tunable or function-switchable feature. Moreover, the compressible carbon foam also exhibits excellent fatigue durability and can be used to monitor human physiological signals. This provides a promising platform for practical applications in adjustable electromagnetic wave absorption; the material can also be used for wearable electronics.