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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. Friction isolated rotary system for high-precision roll-to-roll manufacturing

   https://doi.org/10.1016/j.precisioneng.2020.12.018  

   Kang, Dongwoo; Dong, Xin; Kim, Hyunchang; Park, Pyungwon; Okwudire, Chinedum E. (March 2021, Precision Engineering)

   null (Ed.)
3. Robust high-dynamic-range optical roll sensing

   https://doi.org/10.1364/OL.40.002497  

   Gillmer, Steven R.; Yu, Xiangzhi; Wang, Chen; Ellis, Jonathan D. (January 2015, Optics Letters)
4. Development of high-performance roll-to-roll-coated gas-diffusion-electrode-based fuel cells

   https://doi.org/10.1016/j.jpowsour.2021.230039  

   Mauger, Scott A.; Wang, Min; Cetinbas, Firat C.; Dzara, Michael J.; Park, Jaehyung; Myers, Deborah J.; Ahluwalia, Rajesh K.; Pylypenko, Svitlana; Hu, Leiming; Litster, Shawn; et al (September 2021, Journal of Power Sources)

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5. Spatial-Terminal Iterative Learning Control for Registration Error Elimination in High-Precision Roll-to-Roll Printing Systems

   https://doi.org/10.1115/MSEC2023-106259  

   Wang, Zifeng; Jin, Xiaoning (June 2023, American Society of Mechanical Engineers)

   Abstract Roll-to-roll (R2R) printing techniques are promising for high-volume continuous production of substrate-based electronic products, as opposed to the sheet-to-sheet approach suited for low-volume work. However, one of the major challenges in R2R flexible electronics printing is achieving tight alignment tolerances, as specified by the device resolution (usually at micrometer level), for multi-layer printed electronics. The alignment of the printed patterns in different layers, known as registration, is critical to product quality. Registration errors are essentially accumulated positional or dimensional deviations caused by un-desired variations in web tensions and web speeds. Conventional registration control methods rely on model-based feedback controllers, such as PID control, to regulate the web tension and the web speed. However, those methods can not guarantee that the registration error always converges to zero due to lagging problems. In this paper, we propose a Spatial-Terminal Iterative Learning Control (STILC) method combined with PID control to enable the registration error to converge to zero iteratively, which achieves unprecedented control in the creation, integration and manipulation of multi-layer microstructures in R2R processes. We simulate the registration error generation and accumulation caused by axis mismatch between roller and motor that commonly exists in R2R systems. We show that the STILC-PID hybrid control method can eliminate the registration error completely after a reasonable number of iterations. We also compare the performances of STILC with a constant-value basis and a cosine-form basis. The results show that the control model with a cosine-form basis provides a faster convergence speed for R2R registration error elimination. 

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