An Asymmetric Layer Structure Enables Robust Multifunctional Wearable Bacterial Cellulose Composite Film with Excellent Electrothermal/Photothermal and EMI Shielding Performance

Abstract Highly robust flexible multifunctional film with excellent electromagnetic interference shielding and electrothermal/photothermal characteristics are highly desirable for aerospace, military, and wearable devices. Herein, an asymmetric gradient multilayer structured bacterial cellulose@Fe 3 O 4 /carbon nanotube/Ti 3 C 2 T x (BC@Fe 3 O 4 /CNT/Ti 3 C 2 T x ) multifunctional composite film is fabricated with simultaneously demonstrating fast Joule response, excellent EMI shielding effectiveness (EMI SE) and photothermal conversion properties. The asymmetric gradient 6‐layer composite film with 40% of Ti 3 C 2 T x possesses excellent mechanical performance with exceptional tensile strength (76.1 MPa), large strain (14.7%), and good flexibility. This is attributed to the asymmetric gradient multilayer structure designed based on the hydrogen bonding self‐assembly strategy between Ti 3 C 2 T x and BC. It achieved an EMI SE of up to 71.3 dB, which is attributed to the gradient “absorption–reflection–reabsorption” mechanism. Furthermore, this composite film also exhibits excellent low‐voltage‐driven Joule heating (up to 80.3 °C at 2.5 V within 15 s) and fast‐response photothermal performance (up to 101.5 °C at 1.0 W cm −2 within 10 s), which is attributed to the synergistic effect of heterostructure. This work demonstrates the fabrication of multifunctional bacterial cellulose@Fe 3 O 4 /carbon nanotube/Ti 3 C 2 T x composite film has promising potentials for next‐generation wearable electronic devices in energy conversion, aerospace, and artificial intelligence.