Bifunctional carbon nanotube yarns fabricated using biscrolling technology for pseudocapacitors and paramagnetic actuators

Recently, carbon nanotube (CNT) yarns produced by the continuous spinning method have triggered significant interest owing to their excellent strength and electrical and thermal conductivities. Hence, they can be used for energy storage in ion batteries, supercapacitors, energy harvesters, and sensors. This study aims to develop a "bifunctional yarn" to let both energy input and output function heterogeneously while it is working. A buckypaper type of CNTs took advantage of a technique called "biscrolling technology," which was used to load up to 90 wt% or more of a guest material. Furthermore, performances of iron (Fe3O4) as the guest material in the bifunctional yarn were significantly considered owing to its magnetic force, attraction/repulsion as a soft magnet, and high supercapacitor due to large potential window, specific high capacitance, and different valence states, simultaneously. This study demonstrates that the fabricated "bifunctional yarn" acts as a magentic torsional actuator and supercapacitor simultaneously. The bifunctional yarn in the magnetic torsional actuator wirelessly produced torsional actuation of a maximum of 1200° due to application of magnetic field; two symmetrically bifunctional yarns with 90 wt% of Fe3O4 loading coated by quasi-solid-state of poly (vinyl alcohol) (PVA)-LiCl gel electrolyte can be configured in parallel as a supercapacitor.