Cell Filling in Gravure Printing for Printed Electronics

Abstract

Highly scaled direct gravure is a\npromising printing technique\nfor printed electronics due to its large throughput, high resolution,\nand simplicity. Gravure can print features in the single micron range\nat printing speeds of ∼1 m/s by using an optimized cell geometry\nand optimized printing conditions. The filling of the cells on the\ngravure cylinder is a critical process, since the amount of ink in\nthe cells strongly impacts printed feature size and quality. Therefore,\nan understanding of cell filling is crucial to make highly scaled\ngravure printed electronics viable. In this work we report a novel\nexperimental setup to investigate the filling process in real time,\ncoupled with numerical simulations to gain insight into the experimental\nobservations. By varying viscosity and filling speed, we ensure that\nthe dimensionless capillary number is a good indicator of filling\nregime in real gravure printing. In addition, we also examine the\neffect of cell size on filling as this is important for increasing\nprinting resolution. In the light of experimental and simulation results,\nwe are able to rationalize the dominant failure in the filling process,\ni.e., air entrapment, which is caused by contact line pinning and\ninterface deformation over the cell opening.