Orientation adaptive heterogeneous CNT/Fe₃O₄ composite membrane with excellent Joule heating and enhanced electromagnetic shielding properties

Next-generation wearable electronics demand lightweight membranes integrated with multiple functionalities. Here, heterogeneous composite membranes of carbon nanotubes (CNTs) from vertical orientation to spreading are developed with a simple method to address this challenge. Magnetite (Fe₃O₄) nanoparticles with polydopamine ligands were uniformly adsorbed on acidified CNTs, resulting in magnetic responsive CNTs. Applying a magnet above the filtration membrane yielded a freestanding CNT/Fe₃O₄ heterogeneous membrane with an adaptive gradient structure of CNTs transitioning from vertically aligned to horizontally spread. The heterogeneous surfaces of the magnetically aligned CNT/Fe₃O₄ composite membranes displayed distinct differences in water contact angle, electrical conductivity, and thermal conductivity. Based on the adaptive alignment of CNTs, the fabricated freestanding heterogeneous composite membranes exhibited remarkable Joule heating effect and enhanced electromagnetic shielding effect.