Resistance Control of an Additively Manufactured Conductive Layer in Roll-to-Roll Gravure Printing Systems

Flexible pressure sensors, which are employed in robotic arms and electronic skin, are conventionally prepared using methods such three-dimensional printing, laser scribing, and spray coating. However, they are time-consuming and unsuitable for large-scale production. Thus, to overcome these limitations, roll-to-roll (R2R)-based fabrication techniques have been employed for low-cost mass production of flexible pressure sensors. Gravure printing is a promising R2R based technique, but it faces limitations in terms of ink-flow and printing defects causing short circuit, which may affect the performance of printed electronic devices. In this study, we analyzed the effects of printing conditions, web speed, tension, and nip pressure on the drag-out tail defects and conductance in the gravel printing process. We statistically optimized the optimal conditions to obtain minimum drag-out tail defects and conductance using a Box–Behnken design. We also fabricated two flexible pressure capacitive sensors using the conductive patterns to verify optimal conditions. Our results showed that the resistance decreased with increasing web speed, tension, and nip pressure, whereas the drag-out tail increased with increasing tension and nip pressure and decreasing web speed. Additionally, under the optimal conditions, the resistance and drag-out tail severity were improved by 74% and 53%, respectively, over those of the conventionally printed pattern. Finally, using the two flexible pressure capacitive sensors, we showed that the sensor using the conductive pattern had a higher sensitivity after optimization.