Water-based solution processing and wafer-scale integration of all-graphene humidity sensors

One of the main advantages of 2D materials for various applications is that they can be prepared in form of water-based solutions. The high yield and cost-effectiveness of this method makes them of great interest for printed electronics, composites, bio and healthcare technologies. However, once deposited on a substrate, etching away these solution-processed materials is a difficult task, yet crucial for pattern definition and thus device fabrication. In particular, the realization of micron-size patterns requires mesh and paste optimization when screen-printed or solvent-engineering and surface functionalization when inkjet-printed, both usually involving additional post-deposition steps. These constrains are holding back the integration of these 2D materials in devices and applications. In this work, a novel method for the fabrication of micron-size welldefined patterns in water-based 2D materials, is presented, with an extensive characterization of the films and patterns obtained. The method was ultimately used to create humidity sensors with performance comparable to that of commercial ones. These sensor devices were fabricated onto a 4’ silicon and PET wafers to create allgraphene humidity sensors that are flexible, transparent, and compatible with current CMOS and roll-to-roll workflows.