Mechanisms and Strategies to Achieve Stability in Inkjet Printed 2D Materials Electronics

Printed electronics are electronic devices fabricated on flexible substrates using a wide range of printing techniques, which have the characteristics of lightness, thinness, softness, bendability, and transparency. Inkjet printing is a suitable printing technique for the fabrication of high-precision and low-cost flexible electronic devices because they are customizable, integrable, and reconfigurable. However, maintaining the stability during the ink preparation, printing, and evaporation process to ensure the high accuracy and quality of the fabricated devices has posed tremendous challenges until today. In this paper, the principles and methods of maintaining stability from three aspects: ink preparation, ink printing, and ink evaporation are reviewed. First, the comprehensive colloidal dispersion mechanisms involved in the ink dispersion process are summarized and reviewed the recent advancements made in the preparation of 2D material inks. Second, the fluid dynamics principles involved in inkjet printing for achieving stable straight lines are analyzed, and originally proposed the "phase diagram" for predicting the morphology of printed lines, the first to theoretically predict the necessary conditions for obtaining straight yet stable printed lines. Finally, methods are supposed to suppress/eliminate/utilize the "coffee ring effect", especially several self-assembly methods. Achieving stability during 2D materials ink formulation, printing, and solvent evaporation to ensure the quality of printed electronics has posed tremendous challenges. This study reviewed the principles and methods of maintaining the stability from three aspects: colloidal dispersion mechanisms of 2D material inks, "phase diagram" for predicting morphologies of printed lines, self-assembly methods to utilize the "coffee ring effect". image