Printed functional conductive inks have triggered scalable production of smart electronics such as energy‐storage devices, antennas, wearable electronics, etc. Of particular interest are highly conductive‐additive‐free inks devoid of costly postdeposition treatments to eliminate sacrificial components. Due to the high filler concentration required, formulation of such waste‐free inks has proven quite challenging. Here, additive‐free, 2D titanium carbide MXene aqueous inks with appropriate rheological properties for scalable screen printing are demonstrated. Importantly, the inks consist essentially of the sediments of unetched precursor and multilayered MXene, which are usually discarded after delamination. Screen‐printed structures are presented on paper with high resolution and spatial uniformity, including micro‐supercapacitors, conductive tracks, integrated circuit paths, and others. It is revealed that the delaminated nanosheets among the layered particles function as efficient conductive binders, maintaining the mechanical integrity and thus the metallic conductive network. The areal capacitance (158 mF cm−2) and energy density (1.64 µWh cm−2) of the printed micro‐supercapacitors are much superior to other devices based on MXene or graphene. The ink formulation strategy of “turning trash into treasure” for screen printing highlights the potential of waste‐free MXene sediment printing for scalable and sustainable production of next‐generation wearable smart electronics.

or solvent mixture) which can be further processed into a printable or coatable ink. The behavior of these suspensions is often described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, [3] which implies that the concentration of the nanosheets in the suspensions has an upper limit above which the suspension becomes unstable. [4] Nevertheless, highconcentration suspensions (inks) are necessary for the formation of percolated particle networks, [5] and fulfilling the rheological requirements of high-throughput printing and coating methods (e.g., high viscosity). Regardless of their concentration, suspensions are thermodynamically unstable, and particles tend to reduce their surface energy by aggregation. [6] To lower the rate of sedimentation, the surface energy difference between the solvent and the 2D material must be minimized, [3] which limits the choices of the dispersionmedia to a few solvents whose solubility envelope may not be suitable for subsequent processing. In conventional ink formulations, additives such as surfactants, binders, and rheology modifiers are used to address the aforementioned problems and process the 2D material suspensions into printable or coatable inks. [7][8][9][10] For instance, large concentrations of polymeric binders (e.g., 70 mg mL −1 cellulose acetate butyrate) are needed to increase the viscosity of graphene inks to a level that is suitable for screen printing. [11] Since typical additives adversely affect the electronic properties (e.g., Processing 2D materials into printable or coatable inks for the fabrication of functional devices has proven to be quite difficult. Additives are often used in large concentrations to address the processing challenges, but they drastically degrade the electronic properties of the materials. To remove the additives a high-temperature post-deposition treatment can be used, but this complicates the fabrication process and limits the choice of materials (i.e., no heat-sensitive materials). In this work, by exploiting the unique properties of 2D materials, a universal strategy for the formulation of additive-free inks is developed, in which the roles of the additives are taken over by van der Waals (vdW) interactions. In this new class of inks, which is termed "vdW inks", solvents are dispersed within the interconnected network of 2D materials, minimizing the dispersibility-related limitations on solvent selection. Furthermore, flow behavior of the inks and mechanical properties of the resultant films are mainly controlled by the interflake vdW attractions. The structure of the vdW inks, their rheological properties, and film-formation behavior are discussed in detail. Large-scale production and formulation of the vdW inks for major high-throughput printing and coating methods, as well as their application for room-temperature fabrication of functional films/devices are demonstrated.

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The influence of nano-or micron-sized structures on polymer films as well as the impact of fiber diameter of electrospun membranes on endothelial cell (EC) and blood response has been studied for vascular tissue engineering applications. However, the influence of surface structures on micronsized fibers on endothelial cells and blood interaction is currently not known. In this work, electrospun membranes with distinct fiber surface structures were designed to study their influence on the endothelial cell viability and thrombogenicity. The thermodynamically derived Hansen-solubilityparameters model accurately predicted the formation of solvent dependent fiber surface structured poly(caprolactone) membranes. The electrospun membranes composed of microfibers (MF) or structured MF were of similar fiber diameter, macroscopic roughness, wettability, and elastic modulus. In vitro evaluation with ECs demonstrated that cell proliferation and morphology were not affected by the fiber surface structure. Similarly, investigating the blood response to the fiber meshes showed comparable fibrin network formation and platelet activation on MF and structured MF. Even though the presented results provide evidence that surface structures on MF appear neither to affect EC viability nor blood coagulation, they shed light on the complexity and challenges when studying biology-material interactions. They thereby contribute to the understanding of EC and blood-material interaction on electrospun membranes.

Heat dissipation is an important issue in many electronic devices and therefore materials showing high thermal conductivity are required for their construction and packaging. The intrinsically low thermal conductivity of polymeric materials can be improved when employing (nano-) composites; however, the required high filler content then renders these materials opaque. This paper reports on a composite material that combines high transparency and improved thermal conductivity by using calcium fluoride (CaF 2 ) particles in a silicone elastomer. The refractive index of the silicone matrix is matched to the filler material, light scattering is prevented, and transparent composites with enhanced thermal conductivity at modest filler content (starting at 0.2 volume fraction) are obtained.