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1. High-speed in-line optical angular scatterometer for high-throughput roll-to-roll nanofabrication

   https://doi.org/10.1117/12.2593730  

   Faria-Briceno, Juan J; Sasidharan, Vineeth; Neumann, Alexander; Singhal, Shrawan; Sreenivasan, SV; Brueck, Steven_R J (February 2021, Proceedings of SPIE the International Society for Optical Engineering)

   Panning, Eric M; Liddle, J Alexander (Ed.)

   Roll-to-roll and other high-speed printing manufacturing processes are increasingly being extended to micro- and nanoelectronics and photonics due to cost and throughput advantages as compared with traditional wafer-scale manufacturing. The extra degrees of freedom associated with a moving web require high speed, in-line metrology to control the manufacturing process. Many state-of-the-art metrology approaches have sub-10 nm resolution but cannot be implemented during real-time fabrication processes because of environmental constraints or contact/cross sectional requirements. Optical angular scatterometry is a non-contact metrology approach that can be implemented at high speed. We demonstrate a system that uses 45° off-axis parabolic mirrors and an 8kHz resonant scanner to vary the incident/reflected angle from ~17° to ~67°, suitable for nanoscale metrology at web speeds of up to 350 cm/s, well-beyond the speed of current manufacturing tools. Scatterometry is sensitive not only to gross defects (missing pattern sections) but also to variations in nanoscale pattern details, offering a pathway to feedback control of the manufacturing process. 

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2. Data-Driven Model Predictive Control for Roll-to-Roll Process Register Error

   https://doi.org/10.1115/IAM2022-96840  

   Shah, Karan; He, Anqi; Wang, Zifeng; Du, Xian; Jin, Xiaoning (October 2022, Proceedings of the 2022 International Additive Manufacturing Conference. 2022 International Additive Manufacturing Conference. Lisbon, Portugal.)

   Abstract Roll-to-Roll (R2R) printing techniques are promising for high-volume continuous production of substrate-based products, as opposed to sheet-to-sheet (S2S) approach suited for low-volume work. However, meeting the tight alignment tolerance requirements of additive multi-layer printed electronics specified by device resolution that is usually at micrometer scale has become a major challenge in R2R flexible electronics printing, preventing the fabrication technology from being transferred from conventional S2S to high-speed R2R production. Print registration in a R2R process is to align successive print patterns on the flexible substrate and to ensure quality printed devices through effective control of various process variables. Conventional model-based control methods require an accurate web-handling dynamic model and real-time tension measurements to ensure control laws can be faithfully derived. For complex multistage R2R systems, physics-based state-space models are difficult to derive, and real-time tension measurements are not always acquirable. In this paper, we present a novel data-driven model predictive control (DD-MPC) method to minimize the multistage register errors effectively. We show that the DD-MPC can handle multi-input and multi-output systems and obtain the plant model from sensor data via an Eigensystem Realization Algorithm (ERA) and Observer Kalman filter identification (OKID) system identification method. In addition, the proposed control scheme works for systems with partially measurable system states. 

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3. The Line Speed Effect in Roll-to-Roll Dry Transfer of Chemical Vapor Deposition Graphene,

   Hong, N. (December 2021, 2021 International Conference on Micro- and Nano-devices Enabled by R2R Manufacturing)

   Sreenivasan, S.V. (Ed.)

   A roll-to-roll (R2R) technique is especially desirable for transfer of chemical vapor deposition (CVD) graphene towards high-speed, low-cost, renewable, and environmentally friendly manufacturing of graphene-based electronic devices, such as flexible touchscreens, field effect transistors and organic solar cells. A R2R graphene dry transfer system is recently developed. Monolayer graphene is transferred from a copper growth substrate to a polymer backing layer by mechanical peeling. In this work, we present an experimental study to examine the effects of line speed of the mechanical peeling process on the transferred graphene quality. It is shown that the effect of line speed is not monotonic, and an optimal speed exists to yield the highest and most consistent electrical conductivity of transferred graphene among the process conditions studied. This study provides understanding of process parameter effects and demonstrates the potential of the R2R dry transfer process for large-scale CVD graphene toward industrial applications. 

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4. A Review of Advanced Roll-to-Roll Manufacturing: System Modeling and Control

   https://doi.org/10.1115/1.4067053  

   Martin, Christopher; Zhao, Qishen; Patel, Anjali; Velasquez, Enrique; Chen, Dongmei; Li, Wei (April 2025, Journal of Manufacturing Science and Engineering)

   Abstract Roll-to-roll (R2R) manufacturing is a highly efficient industrial method for continuously processing flexible webs through a series of rollers. With advancements in technology, R2R manufacturing has emerged as one of the most economical production methods for advanced products, such as flexible electronics, renewable energy devices, and 2D materials. However, the development of cost-effective and efficient manufacturing processes for these products presents new challenges, including higher precision requirements, the need for improved in-line quality control, and the integration of material processing dynamics into the traditional web handling system. This paper reviews the state of the art in advanced R2R manufacturing, focusing on modeling and control, and highlights research areas that need further development. 

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5. A Dynamic System Model for Roll-to-Roll Dry Transfer of Two-Dimensional Materials and Printed Electronics

   https://doi.org/10.1115/1.4054187  

   Zhao, Qishen; Hong, Nan; Chen, Dongmei; Li, Wei (July 2022, Journal of Dynamic Systems, Measurement, and Control)

   Abstract Roll-to-roll (R2R) dry transfer is an important process for manufacturing of large-scale two-dimensional (2D) materials and printed flexible electronics. Existing research has demonstrated the feasibility of dry transfer of 2D materials in a roll-to-roll setting with mechanical peeling. However, the process presents a significant challenge to system control due to the lack of understanding of the mechanical peeling behavior and the complexity of the nonlinear system dynamics. In this study, an R2R peeling process model is developed to understand the dynamic interaction among the peeling process parameters, including adhesion energy, peeling force, angle, and speed. Both simulation and experimental studies are conducted to validate the model. It is shown that the dynamic system model can capture the transient behavior of the R2R mechanical peeling process and be used for the process analysis and control design. 

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