Microstructural Tuning of Twisted Carbon Nanotube Yarns through the Wet-Compression Process: Implications for Multifunctional Textiles

Light-weight and multifunctional carbon nanotube (CNT) yarn possessing outstanding mechanical properties as individual CNTs is highly desirable in the field of smart textiles as well as multifunctional composites, yet remains exceptionally challenging to be obtained because of the loose packing of CNTs within the carbon nanotube assemblies resulting in a low density and weak interaction between the individual CNTs. Herein, we utilized a simple but effective technique to densify CNT yarn by compression using acetone (wet compression) to attain high mechanical properties along with extraordinary Joule heating presentation. Owing to having a low surface tension, acetone is easy to be penetrated into the CNT fibers and acts as a lubricant decreasing the interactions between the neighboring CNTs under load. Therefore, the CNT yarn was condensed in density from 0.211 to 0.465 gm/cm3 (120% increment) with the diameter of 175 ± 5 μm. Subsequently, the tensile strength, modulus, electrical conductivity, and gauge factor of wet-compressed CNT yarn were amplified by 185, 887.5, 105, and 305%, respectively, along with a proper reliability and stability for sensing performance. The as-produced CNT yarn reached a brilliant electrothermal stability (∼2.5 min) at the steady-state temperature of 275 °C only within 15 s, even under various deformations (bending and knotting). The outstanding strength with the controlled diameter and admirable Joule heating performance of wet-compressed CNT yarn is aimed for multifunctional uses, including but not limited to wearable electronics, smart textiles, and therapy devices, as well as for incorporation in fabric heaters.