Web Unevenness due to Thermal Deformation in Roll–to–Roll Manufacturing Process

Int. J. of Precis. Eng. and Manuf.-Green Tech.

et al. 2021

Self Cite

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.

Section: Methodsmentioning

confidence: 99%

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

Int. J. of Precis. Eng. and Manuf.-Green Tech.

et al. 2021

Self Cite

“…A roll-to-roll (R2R) additive manufacturing process is widely used in the flexible and stretchable electronic devices manufacturing because of the advantages of environmentally friendly, low cost and mass production [1][2][3]. Notably, the process is an excellent candidate to fabricate large-area flexible functional devices; many research groups have reported its superiority on the creation of large-area molecular diagnostic chip, fuel cells, organic photovoltaics, and flexible printed circuit board.…”

Section: Introductionmentioning

confidence: 99%

Residual Interfacial Deformation in Flexible Copper Clad Laminate Occurring During Roll-to-Roll Composite Film Manufacturing

Int. J. of Precis. Eng. and Manuf.-Green Tech.

et al. 2021

Self Cite

Flexible copper clad laminate has been used to fabricate flexible electronics such as bio-inspired tactile sensor, microfluidicsbased sensor, and flexible printed circuits board. Herein, the effects of thermal property difference between the component layers on the residual interfacial deformation in a flexible copper clad laminate occurring during roll-to-roll composite film manufacturing were analyzed. The thermal behaviors of polyimide film and copper meshes in the laminate were examined, and it was found that differences of the coefficient of thermal expansion and elastic modulus between the two components could cause the residual deformation in the laminate. The three factors affecting the residual strain due to the thermal characteristic difference, i.e., temperature and pressure of the lamination roll and web tension, were selected in the controllable operating conditions in a roll-to-roll lamination process. Mathematical models to estimate the elastic and thermal residual strains according to the factors were developed and experimentally verified. Finally, the effects of the three factors on the residual strain in the laminate were determined using the developed model. In this study, we demonstrate that, in the lamination process, the thermal strain of the laminate component materials after thermal cycling generates a significant residual deformation, which causes defects in the flexible copper clad laminate. The developed model can be used to accurately estimate the residual elastic and thermal residual strains occurring during the roll-to-roll manufacturing according to the process conditions.

Numerical Modeling of Ink Widening and Coating Gap in Roll-to-Roll Slot-Die Coating of Solid Oxide Fuel Cell Electrolytic Layer

et al. 2020

Polymers

Slot-die coatings are advantageous when used for coating large-area flexible devices; in particular, the coating width can be controlled and simultaneous multi-layer coatings can be processed. To date, the effects of ink widening and the coating gap on the coating thickness have only been considered in a few studies. To this end, we developed two mathematical models to accurately estimate the coating width and thickness that consider these two effects. We used root mean square deviation (RMSD) to experimentally verify the developed method. When the coating gap was increased, the coating width increased and the coating thickness decreased. Experimental results showed that the estimated performances of the coating width and thickness models were as high as 98.46% and 95.8%, respectively. We think that the developed models can be useful for determining the coating conditions according to the ink properties to coat a functional layer with user-defined widths and thicknesses in both lab- and industrial-scale roll-to-roll slot-die coating processes.