Although several patterning methods, such as lithography, spray-masking and laser cutting, have been used for facile fabrication of those devices, the complicated processing and excessive material consumption in these protocols limit the scalable production of flexible devices. [4] So far, it remains a significant challenge to achieve multifunctional devices such as EMI shielding, [5] Joule heater, [6] sensor, [7][8][9] radio frequency identification (RFID) tags, [10] and energy storage unit [11] by using simple and low-cost methods. In addition, seeking a suitable material is vital to develop and design high-performance multifunctional devices in low cost.Recent progress in liquid-phase exfoliation of two-dimensional (2D) nanomaterials has highlighted the rational design of functional inks for additive manufacturing of high-performance devices with complex architectures based on printing strategies, such as screen printing, gravure printing and inkjet printing. [12] Screen printing among them is of critical importance to manufacture integrated multifunctional devices by formulating functional inks, without using expensive and complicate equipment. [13] Specially, screen printing provides the highest deposition rate (per unit time deposition material weight) than other printing technologies. [14] One of the main challenges lies in formulation of functional inks with appropriate rheological properties, which are prerequisite for screenprinting multifunctional devices with high resolution. [15,16] As a new family of 2D layered transition metal carbides or nitrides, MXenes have become promising candidate for formulation of printable inks because of their remarkable electronic, optical, and mechanical properties. [17] Generally, MXenes are usually synthesized by selectively etching A layer in the precursor of MAX phase. They can be represented by M n+1 X n T x , where M is the early transition metal, X stands for carbon and/ or nitrogen, and T x represents the terminal hydroxyl, oxygen, or fluorine groups. [18,19] As a result, MXenes offer solution processing capabilities owing to their superior hydrophilicity and high negative surface charge. [20] Clay-like behavior of MXene slurry and the formation of stable colloidal suspension have thus facilitated the fabrication of conducting films, nanocomposites, coatings and fibers for applications in energy MXenes have exhibited potential for application in flexible devices owing to their remarkable electronic, optical, and mechanical properties. Printing strategies have emerged as a facile route for additive manufacturing of MXene-based devices, which relies on the rational design of functional inks with appropriate rheological properties. Herein, aqueous MXene/xanthan gum hybrid inks with tunable viscosity, excellent printability, and long-term stability are designed. Screen-printed flexible MXene films using such hybrid inks exhibit a high conductivity up to 4.8 × 10 4 S m −1 , which is suitable to construct multifunctional devices mainly including electromagnetic shield...

High-efficiency electromagnetic interference (EMI) shielding and heat dissipation synergy materials with flexible, robust, and environmental stability are urgently demanded in nextgeneration integration electronic devices. In this work, we report the lamellar MXene/Aramid nanofiber (ANF) composite films, which establish a nacre-like structure for EMI shielding and heat dissipation by using the intermittent filtration strategy. The MXene/ ANF composite film filled with 50 wt % MXene demonstrates enhanced mechanical properties with a strength of 230.5 MPa, an elongation at break of 6.2%, and a toughness of 11.8 MJ•m 3 (50 wt % MXene). These remarkable properties are attributed to the hydrogen bonding and highly oriented structure. Furthermore, due to the formation of the MXene conductive network, the MXene/ANF composite film shows an outstanding conductivity of 624.6 S/cm, an EMI shielding effectiveness (EMI SE) of 44.0 dB, and a superior specific SE value (SSE/t) of 18847.6 dB•cm 2 /g, which is better than the vacuum filtration film. Moreover, the MXene/ANF composite film also shows a great thermal conductivity of 0.43 W/m•K. The multifunctional MXene/ANF composite films with high-performance EMI shielding, heat dissipation, and joule heating show great potential in the field of aerospace, military, microelectronics, microcircuit, and smart wearable electronics.

Among the increasingly popular miniature and flexible smart electronics, two-dimensional materials show great potential in the development of flexible electronics owing to their layered structures and outstanding electrical properties. MXenes have attracted much attention in flexible electronics owing to their excellent hydrophilicity and metallic conductivity. However, their limited interlayer spacing and tendency for self-stacking lead to limited changes in electron channels under external pressure, making it difficult to exploit their excellent surface metal conductivity. We propose a strategy for rapid gas foaming to construct interlayer tunable MXene aerogels. MXene aerogels with rich interlayer network structures generate maximized electron channels under pressure, facilitating the effective utilization of the surface metal properties of MXene; this forms a self-healable flexible pressure sensor with excellent sensing properties such as high sensitivity (1,799.5 kPa–1), fast response time (11 ms), and good cycling stability (>25,000 cycles). This pressure sensor has applications in human body detection, human–computer interaction, self-healing, remote monitoring, and pressure distribution identification. The maximized electron channel design provides a simple, efficient, and scalable method to effectively exploit the excellent surface metal conduction of 2D materials.

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