ABSTRACT
Nanohybrid assemblies provide an effective platform for integrating the intrinsic properties of individual components into microscale fibers. In this study, a novel approach for creating mechanically and environmentally stable MXene fibers through the synergistic assembly of MXene and polyacrylonitrile (PAN), is introduced. Unlike fibers generated via a conventional stabilization process, which relies on air-based stabilization to transform the PAN molecules into ring structures fundamental to carbon fibers, the hybrid fibers are annealed in an Ar atmosphere. This unique approach suggests MXene can serve as an oxygen provider that is essential for stabilizing PAN. As a result, significantly improved interfiber compactness is achieved and the oxidation stability of MXene is enhanced under atmospheric conditions. The resulting fibers exhibit exceptional stability, even after extended exposure to high humidity and elevated temperatures. This highlights the suitability of the thermally annealed MXene-PAN (T-MX-PAN) fibers as robust electric heating elements. Notably, these fibers consistently generate heat over 1800 bending cycles. When integrated into fabrics, they demonstrate the capability to generate sufficient heat for melting ice and rapid evaporation. This study highlights the potential of T-MX-PAN fibers as next-generation wearable heaters and offers valuable insights into advancing wearable technology in demanding environments.
ABSTRACT
Achieving a simple yet sustainable printing technique with minimal instruments and energy remains challenging. Here, a facile and sustainable 3D printing technique is developed by utilizing a reversible salting-out effect. The salting-out effect induced by aqueous salt solutions lowers the phase transition temperature of poly(N-isopropylacrylamide) (PNIPAM) solutions to below 10 °C. It enables the spontaneous and instant formation of physical crosslinks within PNIPAM chains at room temperature, thus allowing the PNIPAM solution to solidify upon contact with a salt solution. The PNIPAM solutions are extrudable through needles and can immediately solidify by salt ions, preserving printed structures, without rheological modifiers, chemical crosslinkers, and additional post-processing steps/equipment. The reversible physical crosslinking and de-crosslinking of the polymer through the salting-out effect demonstrate the recyclability of the polymeric ink. This printing approach extends to various PNIPAM-based composite solutions incorporating functional materials or other polymers, which offers great potential for developing water-soluble disposable electronic circuits, carriers for delivering small materials, and smart actuators.