No abstract

Free‐standing films that display high strength and high electrical conductivity are critical for flexible electronics, such as electromagnetic interference (EMI) shielding coatings and current collectors for batteries and supercapacitors. 2D Ti3C2Tx flakes are ideal candidates for making conductive films due to their high strength and metallic conductivity. It is, however, challenging to transfer those outstanding properties of single MXene flakes to macroscale films as a result of the small flake size and relatively poor flake alignment that occurs during solution‐based processing. Here, a scalable method is shown for the fabrication of strong and highly conducting pure MXene films containing highly aligned large MXene flakes. These films demonstrate record tensile strength up to ≈570 MPa for a 940 nm thick film and electrical conductivity of ≈15 100 S cm−1 for a 214 nm thick film, which are both the highest values compared to previously reported pure Ti3C2Tx films. These films also exhibit outstanding EMI shielding performance (≈50 dB for a 940 nm thick film) that exceeds other synthetic materials with comparable thickness. MXene films with aligned flakes provide an effective route for producing large‐area, high‐strength, and high‐electrical‐conductivity MXene‐based films for future electronic applications.

The discovery of liquid crystalline (LC) phases in dispersions of two-dimensional (2D) materials has enabled the development of macroscopically aligned three-dimensional (3D) macrostructures. Here, we report the first experimental observation of self-assembled LC phases in aqueous Ti 3 C 2 T x MXene inks without using LC additives, binders, or stabilizing agents. We show that the transition concentration from the isotropic to nematic phase is influenced by the aspect ratio of MXene flakes. The formation of the nematic LC phase makes it possible to produce fibers from MXenes using a wet-spinning method. By changing the Ti 3 C 2 T x flake size in the ink formulation, coagulation bath, and spinning parameters, we control the morphology of the MXene fibers. The wet-spun Ti 3 C 2 T x fibers show a high electrical conductivity of ∼7750 S cm −1 , surpassing existing nanomaterial-based fibers. A high volumetric capacitance of ∼1265 F cm −3 makes Ti 3 C 2 T x fibers promising for fiber-shaped supercapacitor devices. We also show that Ti 3 C 2 T x fibers can be used as heaters. Notably, the nematic LC phase can be achieved in other MXenes (Mo 2 Ti 2 C 3 T x and Ti 2 CT x ) and in various organic solvents, suggesting the widespread LC behavior of MXene inks.

Magnetic liquid marbles capable of hosting both aqueous and organic fluids may serve as new miniature chemical reactors. Chemical reactions can occur either within a single liquid marble or between two magnetic liquid marbles (as illustrated). The liquid marbles can also interact with external devices simply by opening and closing the powdery shell under a magnetic field.