Preparation and application of additive-free MXene sediment inks for printed flexible electronics

Abstract Printable functional conductive inks have significantly advanced the scalable fabrication of smart electronic devices, such as energy storage units, antennas, and wearable electronics. Among these, additive-free inks with high electrical conductivity have garnered particular attention, as they eliminate the need for costly post-treatment processes to remove sacrificial components. However, such inks often require a high filler content, posing considerable challenges in formulation design. In this study, we developed an additive-free MXene sediment ink with suitable rheological properties for scalable screen printing. Notably, this ink is primarily composed of unetched precursors and multilayer MXene sediments, which are typically discarded after the delamination process. We successfully demonstrated the coating of this sediment-based ink on various substrates and achieved spatially uniform screen-printed structures on PET substrates, enabling applications such as electrodes for flexible alternating current electroluminescent (ACEL) devices, conductive circuits, and integrated wiring patterns. The fabricated flexible ACEL electrodes exhibited low sheet resistance (8 Ω/□), outperforming many previously reported MXene- or graphene-based devices. This "waste-to-ink" formulation strategy offers a novel approach for waste-free screen printing of MXene sediments and highlights their great potential in the scalable and sustainable manufacturing of wearable smart electronics.