Design, modeling, and control of a roll-to-roll mechanical transfer process for two-dimensional materials and printed electronics

Flexible electronics, as an emerging field, has gained tremendous attention over the past few years with the advancement in areas such as two-dimensional (2D) materials fabrication and transfer printing techniques. Mechanical peeling, where thin film materials or printed patterns are transferred from a donor substrate to a target substrate, is demonstrated to be a promising and key operation to transfer 2D material or fabricating complex flexible electronic devices, and it is shown that in many cases performing the mechanical peeling process at a desired peeling condition is needed for high quality product. However, despite the promise of mechanical peeling techniques, studies on scaling up the process and enabling the process in a high-volume manufacturing setting are lacking. In this study, a R2R mechanical peeling process that enables continuous and high-throughput transfer of 2D materials and printed electronics has been developed. The system allows for speed and tension control and is used for performing 2D materials transfer. A system model of the R2R process is derived by integrating the peeling process with the R2R system dynamics. The proposed model provides fundamental understanding of the physics involved in the process, including the interactions between peeling front and the roller dynamics. The model can be effectively used for control design and simulation. The success of the R2R peeling process is dependent on the peeling front geometry and its stability during the peeling process. A real-time supervisory control strategy is developed to enable the peeling angle control in a R2R mechanical peeling process. The supervisory control strategy utilizes a peeling front model to estimate the peeling speed and the adhesion energy between the donor substrate and the material to be transferred. The information is used to generate reference signals for the web tension controllers at the regulatory level to adjust the web tensions in order to achieve desired peeling angles. The proposed control strategy is demonstrated with both simulation and experimental results. To reject periodic disturbances originating from rotating roller shafts and adhesion energy changes in the laminate, a model-based repetitive controller is developed and demonstrated.