Unleashing multifunctionality: Janus-structured flexible CNT-based composite film with enduring superhydrophobicity and excellent electromagnetic interference shielding

Abstract

Versatile electromagnetic interference (EMI) shielding films are crucial for electronics and wearables. We acid-functionalize CNTs and load them with Fe3O4, and then fabricate Janus-structured Fe3O4@CNTs/ bacterial cellulose (BC)/ silver nanowires (AgNWs) composite films using layer-by-layer vacuum filtration and hot pressing. Benefiting from the rational regulation of component proportions and the design of a Janus structure, the composite film with a thickness of only 90 μm exhibits outstanding shielding effectiveness (SE) of 68.68 dB in the X-band, owing to the mechanism of absorption-reflection-reabsorption. Moreover, 1H,1H,2H,2H-Perfluorodecyltrimethoxysilane, and ethyl orthosilicate are utilized to synthesize fluoroalkyl-grafted silica nanoparticles (F-SiO2) and coated onto the film’s upper surface using spray technique, rendering it superhydrophobicity (150° <WCA < 160°), oleophobicity (CA ≈110°), and self-cleaning. Excitingly, the highly efficient Joule heating properties (rise to 107.2 °C within 30 s with 1.0 V) of the film (Fe3O4@CNTs/ BC/ F-SiO2/ AgNWs), combine with its superhydrophobicity, provide additional de-icing capabilities. The practical significance lies in the robust interlayer adhesion and intralayer entanglement, which endow the film with remarkable flexibility and sufficient tensile strength (33.5 MPa), ensuring its applicability in complex scenarios. This research presents an innovative and intriguing material combination and offers an efficient manufacturing strategy for EMI shielding films. It is highly suitable for outdoor portable or wearable devices and holds remarkable application potential in damp/ freezing environments.