Mechanical Design and Analysis of a Roll to Roll Microcontact Printer

                Flexible electronics have demonstrated potential in a wide range of applications including wearable sensors, photovoltaics, medical devices and more, due to their properties of extreme adaptability while also being lightweight and highly robust. The main challenge standing in the way of progress in this field is the difficulty of large-scale manufacturing of these flexible electronics compared to their rigid counterparts. Microcontact printing is a form of soft lithography in which an elastomeric stamp is used to transfer sub-micron scale surface patterns onto a flexible substrate via ink monolayers. The integration of microcontact printing into R2R will enable continuous printing of flexible electronics and scale up it for massive manufacturing.

                The proposed work outlines a novel mechanical design for a microcontact printer which utilizes flexural motion stages with integrated position and force sensors to control the print process on a roll-to-roll (R2R) system. The printhead is designed to fit the available space on the pre-installed UMass Amherst Intelligent Sensing Laboratory test table and breadboard. The R2R system includes motorized rollers for winding/unwinding the PET (polyethylene terephthalate) web substrate, and idler rollers for guiding a web through the print system. As the central element to this design, two matching plate flexures are designed on the two ends of the printer roller to control the tilting and positioning of the print roller. Flexure mechanisms rely on bending and torsion of flexible elements: this allows them to achieve much higher precision in positioning compared to conventional mechanisms which rely on surface interaction between multiple moving parts. The print resolution target for this design is 500 nm (linewidth).

                In the initial version of the printhead design, a total of 33 components are custom fabricated for assembly and installation in the R2R system lab setup. These include everything from the components of the print roller, specially adapted air-bearing mounts, support structures, and connectors. The design and fabrication process for every component is outlined here along with the functionality, as every component was designed with the system objectives and constraints in mind. Using SolidWorks simulation, FEA analysis is performed for every part of the assembly that is subjected to stress in the real system, so that predictions can be made about the displacement of the motion stages and the frequency of vibration. These predictions are evaluated by  comparation with the experimental results from tests conducted on the real system hardware and used to assess the quality of the fabricated assembly.

                The work conducted enables advancements in the assembly of an updated, optimized R2R system and has led to an experimentally functioning lab setup that is ripe for further improvements. Completion and calibration of this augmented R2R system will, in future, enable UMass Amherst in-house production of large-area flexible electronics which may be used in a wide range of applications, including medical sensors, solar cells, displays, and more. In addition to microcontact printing, this R2R system may also be applied to nanoimprint lithography, another contact-based print method, or integrated with inkjet printing, a non-contact method.