Direct Writing of Additive-Free MXene-in-Water Ink for Electronics and Energy Storage

Additive-free, single step formulations of MXene-in-water inks are developed from clay-like titanium carbide (Ti₃C₂) sediments. Solution-processable Ti₃C₂ inks are compatible with stamping, printing, painting, and writing on a variety of substrates. Specifically, MXene-in-water inks at higher concentrations of 30 mg mL⁻¹ are employed in commercially available pens for dispensing and patterning 2D MXene directly. These MXene pens are employed either manually or automatically using an AxiDraw, enabling direct-writing and complex patterning of functional MXene devices. Versatile MXene pens show compatible writing on a variety of substrates, including paper and polymers, where the deposited ink is used as a passive circuit, similar to silver and copper nanoparticle inks. Written MXene lines without additional post-treatment exhibit length dependent resistance, showing typical resistivity values between carbon based and metal nanoparticle inks. Current collector-free fabrication of MXene micro-supercapacitors is demonstrated on unconventional platforms including paper, textiles, and curved surfaces directly.