Nature Nanotechnology, 2017, 12 (4), 343-350

Water-based and biocompatible 2D crystal inks for all-inkjet printed heterostructures

Daryl McManus , Sandra Vranic, Freddie Withers, Veronica Sanchez Romaguera, Massimo Macucci, Huafeng Yang, Roberto Sorrentino, Khaled Parvez, Seokkyun Son, Giuseppe Iannaccone, Kostas Kostarelos, Gianluca Fiori, Cinzia Casiraghi*

Exploiting the properties of 2-dimensional (2D) crystals requires a mass production method able to produce heterostructures of arbitrary complexity on any substrate. Solution processing of graphene allows simple and low-cost techniques such as inkjet printing to be used for device fabrication. However, available inkjet printable formulations are still far from ideal as they are either based on toxic solvents, have low concentration, or require time-consuming and expensive formulation processing. In addition, none of the current formulations are suitable for thin-film heterostructure fabrication due to the re-mixing of different 2D crystals, giving rise to uncontrolled interfaces and poor device performance and reproducibility. Here we show a general approach to achieve concentrated and inkjet printable water-based 2D crystal formulations, which also provide optimal film formation for multi-stack fabrication. We show examples of all-inkjet printed heterostructures, such as large area arrays of photosensors on plastic and paper and programmable logic memory devices. Finally, dose-escalation cytotoxicity assays using human lung and skin cell cultures confirm the ink biocompatibility, extending the possible use of such formulations to biomedical applications.