Cellulose‐Nanofiber‐Enabled 3D Printing of a Carbon‐Nanotube Microfiber Network

Abstract Highly conductive and mechanically strong microfibers are attractive in energy storage, thermal management, and wearable electronics. Here, a highly conductive and strong carbon nanotube/nanofibrillated cellulose (CNT–NFC) composite microfiber is developed via a fast and scalable 3D‐printing method. CNTs are successfully dispersed in an aqueous solution using 2,2,6,6‐tetramethylpiperidinyl‐1‐oxyl (TEMPO) oxidated NFCs, resulting in a mixture solution with an obvious shear‐thinning property. Both NFC and CNT fibers inside the all‐fiber‐based microfibers are well aligned, which helps to improve the interaction and percolation between these two building blocks, leading to a combination of high mechanical strength (247 ± 5 MPa) and electrical conductivity (216.7 ± 10 S cm −1 ). Molecular modeling is applied to offer further insights into the role of CNT–NFC fiber alignment for the excellent mechanical strength. The combination of high electrical conductivity, mechanical strength, and the fast yet scalable 3D‐printing technology positions the CNT–NFC composite microfiber as a promising candidate for wearable electronic devices.