Stable MXene Dough with Ultrahigh Solid Fraction and Excellent Redispersibility toward Efficient Solution Processing and Industrialization

Abstract

Two-dimensional (2D) transition metal carbides, and/or nitrides, so-called MXenes, have triggered intensive research interests in applications ranging from electrochemical energy storage to electronics devices. Producing these functional devices by printing necessitates to match the rheological properties of MXene dispersions to the requirements of various solution processing techniques. In particular, for additive manufacturing such as extrusion-printing, MXene inks with high solid fraction are typically required, which is commonly achieved by tediously removing excessive free water (top-down route). Here, the study reports on a bottom-up route to reach a highly concentrated binary MXene-water blend, so-called MXene dough, by controlling the water admixture to freeze-dried MXene flakes by exposure to water mist. The existence of a critical threshold of MXene solid content (≈60%), beyond which no dough is formed, or formed with compromised ductility is revealed. Such metallic MXene dough possesses high electrical conductivity, excellent oxidation stability, and can withstand a couple of months without apparent decay, providing that the MXene dough is properly stored at low-temperature with suppressed dehydration environment. Solution processing of the MXene dough into a micro-supercapacitor with gravimetric capacitance of 161.7 F g −1 is demonstrated. The impressive chemical and physical stability/redispersibility of MXene dough indicate its great promise in future commercialization.

3D bioprinting approaches for spinal cord injury repair

“…Extrusion printing provides several distinct advantages in creating scaffolds with specific properties for spinal cord repair. By squeezing out the bioink and assembling it layer-by-layer to form the desired shape [89], extrusion printing is more beneficial for constructing complex 3D structures (figure 2(F)). The micro-level control over bioink extrusion can more faithfully replicate the intended 3D structure, while the final scaffold is also mechanically stable and not prone to collapse due to structural instability [90,91] (figures 2(G) and (H)).…”

Current Trends and Promising Electrode Materials in Micro-Supercapacitor Printing

“…In particular, making the dispersion using deoxygenated water followed by storage in sealed argon-filled vessels at low temperatures (~5 °C) results in longer ink life. Furthermore, it was found [ 186 ] that suspensions and pastes with higher concentration of MXene exhibit better resistance to oxidative degradation compared to diluted ones.…”

“…Notably, for dispersions in the above solvents, it was found in a study [ 187 ] that their viscosity is generally lower than when water is used as the dispersion medium; however, it may also be due to the higher concentration of MXene that is achievable in the aqueous medium. For example, in the work of Deng and co-workers [ 186 ], to form a highly concentrated paste of MXene, Ti 3 C 2 T x , not the classical technique of concentrating a dilute dispersion, was used, but a dosed injection into lyophilized after rapid freezing Ti 3 C 2 T x powder via exposure to water mist was performed. It showed high electrical conductivity and retention of properties for two months without noticeable MXene decay (in case of storage at reduced temperature with suppressed hydration).…”

Ti3C2Tx MXene: A New Promising 2D Material for Optoelectronics

“…13 Also, the possibility of work function engineering, 14 by diversely tuning the surface functional groups, is an added advantage. Among all other MXenes, Ti 3 C 2 T x MXene is the highly preferred owing to its high metallic conductivity, 15,16 chemical stability, 17 high anisotropic carrier mobility, 18 high optical transmittance, 19 ease of aqueous solution processing, 20 tunable work functions, 21 wide range of optical absorption from Ultraviolet (UV) to Near-infrared (NIR) range, 22 and plasmonic 23,24 and nonlinear optical properties. 25,123,126 Several review articles discussed the material properties of MXenes and their applications, especially in photocatalysis 26,27 and energy storage.…”