Self-Aligned, High-Yield Inkjet-Printed Capacitors and RC Circuits on Flexible Substrates via a Roll-to-Roll Compatible Printing Process

Abstract

Continuous roll-to-roll (R2R) manufacturing strategies are potentially important for the commercialization of large-area flexible electronics, but print resolution and precise intra- and interlayer registration of electronic inks remain a challenge. In this study, a self-registering, R2R compatible printing process called self-aligned capillarity-assisted lithography for electronics (SCALE) is used to fabricate capacitors and RC circuits. Capacitor production by SCALE follows a three-step process. In step one, ultraviolet (UV) microimprinting creates an impression in resist material thereby defining contact pads and interdigitated, 3.5 μm-wide electrodes. In step two, silver ink is delivered by inkjet to the contact pad reservoirs only and capillary flow spontaneously fills the interdigitated electrode pattern. In step three, the silver electrodes and pads are sintered. Importantly, the imprint resist that forms the 1.5 μm thick walls between the silver electrodes serves as the capacitor dielectric. Overall, the process has 100% yield for a batch of 32 devices and produces capacitors with areal capacitances of 2.4 nF/cm², standard deviations of 4.3%, and good mechanical resilience to repeated bending tests at 2.3% maximum surface strain. These capacitors were integrated into fully printed RC filters using the SCALE process. Overall, this work demonstrates a robust high-resolution printing process for capacitors that is promising for integration into a fully self-aligned R2R process for large-area circuits.