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1. EFFECT OF THE PROCESSING AND TRANSPORT PARAMETERS ON MOLD FILLING IN ROLL-TO-ROLL NANOIMPRINT LITHOGRAPHY

   Gomez-Constante, J.P ; Pagilla, P.R ; Rajagopal, K.R ( June 2019 , Proceedings of the Fifteenth International Conference on Web Handling)

   Based on a model developed for the roll-to-roll imprinting process, this paper describes the relative importance of the processing, material properties, and transport parameters in Roll-to-Roll Nanoimprint Lithography (R2RNIL). In particular, the model is utilized to investigate the effect of web speed, fluid film thickness, viscosity, stress relaxation time, mold pattern geometry and size on mold filling. Based on a typical imprint roller configuration, kinematic analysis, and the conservation laws from classical mechanics, the behavior of the squeezing of a viscoelastic fluid film into a rigid mold cavity is described. Further, the effect of web speed, fluid film thickness and key rheological parameters, namely the Weissenberg and Deborah numbers, are discussed. These dimensionless numbers are typically employed to quantify viscoelastic effects in fluid flow problems. The effect of other scale-sensitive and geometric parameters, such as the capillary number and pattern width-to-height ratio, on the imprint process is also discussed. Numerical simulations are provided to corroborate the discussions and to quantify the relative importance of the parameters.
2. Mechanics of Cambered Web Belts on Aligned Rollers

   Shi, J. ; Smith, J. ; Markum, R. ; Good, J.K. ( June 2019 , Proceedings of the Fifteenth International Conference on Web Handling)

   The lateral deformations of webs in roll-to-roll (R2R) process machines can affect the quality of the manufacturing process. Webs can enter a cylindrical roller normally if the forces required to sustain normal entry and do not exceed the available friction forces. Webs with simple non-uniform length variation across their width (camber) will steer toward the long side, affecting the steady state lateral deformation and hence registration. Most previous studies have focused on tests and modeling a cambered web span in a free span between two rollers. Often these studies assume some displacement and slope boundary conditions are known and seek the remaining condition(s) that would dictate the steady state lateral deformation of the cambered web in the free span. In many spans in a process machine there may be no known boundary conditions and no steady state deformation of the cambered web. The web may travel toward the long side continually from one web span until the next until a web guide attempts to return the web to an acceptable lateral location in the process machine. The simplest case of multiple span cambered web lateral behavior is that of a cambered web belt transiting two aligned rollers which is themore »focus of the current work. Dynamic simulation (Abaqus/Standard) has been used to better understand the response of cambered webs under tension that has been witnessed in tests.« less
3. Predicting the Web Length and Layers in a Wound Roll

   Gajjalla, A. ; Markum, R. ; Good, J.K ( June 2019 , Proceedings of the Fifteenth International Conference on Web Handling)

   The length of web in a wound roll is one mark of roll quality. The available web length in a roll is a concern for many who process webs and those who convert webs. There are algorithms that estimate the length of web and layers in a wound roll based on simple geometry and inputs of inside and outside radius and web thickness. If webs were infinitely stiff in the machine and out-of-plane directions such calculations could be accurate but this is not the case. Webs deform as the result of winder operating conditions such as winding tension and the contact pressures and stresses due to winding. Length calculations based on geometry will err as a result of web deformation in the length and radial directions. Webs are generally subject to tension during transport through process machines, the apparent deformed web length will vary with transport tension. The mission of this paper is to describe means by which the available deformed web length and the number of layers in a wound roll can be accurately predicted. The accuracy of the predictions will be verified by winding trials in the laboratory. The winding trials will demonstrate the levels of accuracy thatmore »can be realized on laboratory and production machines.« less
4. Tension Control in Roll-to-Roll Mechanical Peeling for 2D Material Transfer and Transfer Printing

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

   Sreenivasan, S.V. (Ed.)

   A major challenge of the large-scale application of two-dimensional (2D) materials is the scaling up of the process for its growth and transfer. Mechanical peeling has been demonstrated to be a promising method for transferring graphene in a fast and environmentally friendly manner. However, efforts in scaling up the process have been lacking. Performing mechanical peeling using a roll-to-roll (R2R) system could significantly increase the throughput of graphene transfer. Such a R2R process does not exist in industry. In this paper a novel R2R mechanical peeling system that has both speed and tension control capabilities is presented. Controllers that control the peeling tensions on both sides of the peeling front are developed based on a tension dynamics model. Both controllers contain a feedback and a feedforward term to account for large steady-state error. The control performance is validated using both experiments and simulation, demonstrating that the R2R mechanical peeling technique can be a viable method for dry transfer of 2D materials in a high-throughput industrial setting.
5. Impact of Large Deformations of Webs Transiting Rollers

   Shi, Jinxin ; Markum, Ron E. ; Good, James K. ( June 2017 , Proceedings of Fourteenth International Conference on Web Handling)

   Webs are subjected to large out-of-plane deformations when transiting rollers in process machinery. Webs are often treated as membranes in analysis but become subject to significant bending strains when transiting rollers. Anticlastic bending of thick plates is a known phenomenon. The anticlastic effect is often ignored for webs which are thin. The objective of this paper is to demonstrate that the large bending deformations webs are subjected to on rollers influence the internal membrane stresses and deformations in the web. The results will show that the concept of normal entry of a web to a roller has complexity that has previously not been considered. It will be demonstrated that a cross direction tensile membrane stress results from the large deformations that acts to stabilize the web and inhibit wrinkle formation.