Direct printing of functional inks is critical for applications in diverse areas including electrochemical energy storage, smart electronics and healthcare. However, the available printable ink formulations are far from ideal. Either surfactants/additives are typically involved or the ink concentration is low, which add complexity to the manufacturing and compromises the printing resolution. Here, we demonstrate two types of two-dimensional titanium carbide (Ti 3 C 2 T x ) MXene inks, aqueous and organic in the absence of any additive or binary-solvent systems, for extrusion printing and inkjet printing, respectively. We show examples of all-MXene-printed structures, such as micro-supercapacitors, conductive tracks and ohmic resistors on untreated plastic and paper substrates, with high printing resolution and spatial uniformity. The volumetric capacitance and energy density of the all-MXene-printed micro-supercapacitors are orders of magnitude greater than existing inkjet/extrusion-printed active materials. The versatile direct-ink-printing technique highlights the promise of additive-free MXene inks for scalable fabrication of easy-to-integrate components of printable electronics.

The ongoing miniaturization of devices and development of wireless and implantable technologies demand electromagnetic interference (EMI)‐shielding materials with customizability. Additive manufacturing of conductive polymer hydrogels with favorable conductivity and biocompatibility can offer new opportunities for EMI‐shielding applications. However, simultaneously achieving high conductivity, design freedom, and shape fidelity in 3D printing of conductive polymer hydrogels is still very challenging. Here, an aqueous Ti3C2‐MXene‐functionalized poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate ink is developed for extrusion printing to create 3D objects with arbitrary geometries, and a freeze–thawing protocol is proposed to transform the printed objects directly into highly conductive and robust hydrogels with high shape fidelity on both the macro‐ and microscale. The as‐obtained hydrogel exhibits a high conductivity of 1525.8 S m–1 at water content up to 96.6 wt% and also satisfactory mechanical properties with flexibility, stretchability, and fatigue resistance. Furthermore, the use of the printed hydrogel for customizable EMI‐shielding applications is demonstrated. The proposed easy‐to‐manufacture approach, along with the highlighted superior properties, expands the potential of conductive polymer hydrogels in future customizable applications and represents a real breakthrough from the current state of the art.

E -m a i l : b e a t r i x . m e n d o z a @ g m a i l . c o m"These authors contributed equally to this work Abstract Manganese oxide nanosheets were synthesized using liquid-phase exfoliation that achieved suspensions in isopropanol with concentrations of up to 0.45 mg ml -1 . A study of solubility parameters showed that the exfoliation was optimum in N,N-Dimethylformamide followed by isopropanol and diethylene glycol. Isopropanol was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. For the first time, a hybrid of graphene and manganese oxide nanosheets was synthesized using a single-step co-exfoliation process. The 2D hybrid was synthesized in isopropanol suspensions with concentrations of up to 0.5 mg ml -1 and demonstrated stability against re-aggregation for up to 6 months. The co-exfoliation was found to be a energetically favorable process in which both solutes, graphene and manganese oxide nanosheets, exfoliate with an improved yield as compared to the single-solute exfoliation procedure. This work demonstrates the remarkable versatility of liquid-phase exfoliation *To whom correspondence should be addressed 2 with respect to the synthesis of hybrids with tailored properties, and it provides proof-of-concept ground work for further future investigation and exploitation of hybrids made of two or more 2D nanomaterials that have key complementary properties for various technological applications.

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Additive manufacturing strategies are gaining more importance in the context of lithium‐ion batteries. The rapid prototyping, reduced waste and complex 3D structures achievable are powerful and attractive tools that are out of the reach of current fabrication techniques. Additionally, thanks to the potential that these manufacturing techniques hold for the fabrication of micro‐energy storage devices, they are gaining increasing attention in the literature. Here, some of the more common additive manufacturing techniques are compared to standard methodologies by systematically evaluating their electrochemical performance and correlating it with the physical changes induced by the printing process. By using LTO/CNT‐based inks, it is observed that the inner arrangement of the conductive additive is significatively altered depending on the technique used and that this has an impact on the rate performance of the device. By using a model that links the capacity‐rate data to the physical properties of the batteries, it is possible to find the limiting factor on the printed electrodes and correlate it with the material arrangement that each technique produces.

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