Session: 16-02-01: Poster Session: NSF Research Experience for Undergraduates (REU)

Paper Number: 77296

Start Time: Wednesday, 02:25 PM

77296 - Design and Test of an Inking System for Roll-to-Roll Microcontact Printing 

Microcontact printing is a soft lithographic technique in which self-assembled monolayers (SAMs) are transferred to an elastomeric stamp, then printed onto a molded polymer substrate [1]. Modern-day flexible electronics can be fabricated on these pliable substrates for wearable medical devices, entertainment appliances, applications in photovoltaics, and so on. Flexible electronics demonstrate large potential in commercialization for their robust adaptability, and hence call for a large scale, low cost, and highly efficient manufacturing platform, such as roll-to-roll (R2R) printing processes [2].  

This project focuses on the development of a robust inking system for a continuous R2R microcontact printing process, ultimately to achieve advancements in the field of large scale R2R printing of flexible electronics. Instead of pressing the elastomeric stamp to a substrate in the traditional batch-to-batch fashion, R2R microcontact printing continuously transfers a print pattern from a roller stamp to a moving web [3]. With decreased cost in printing results from standard practices, the proposed inking system will reflect high-precision printing and comprehensive pattern transfer capable of achieving results on a sub-micron scale, as well as anticipated printing speeds up to 5 in/s.

The inking tank and drying system is developed for a pre-existing R2R microcontact printing machine in our lab, which includes flexural motion stages and motorized rollers. These flexural stages have incorporated motion and position sensors to ensure high microcontact print precision. The vast majority of the ink tank and drying system design is situated in prototyping and testing newly developed parts through SolidWorks and low-cost 3D printing.

The central mechanical design of the 3D printed tank includes a hollow semi-circular chamber offset in diameter by 20.5 mm compared with the diameter of a cylindrical polydimethylsiloxane (PDMS) stamp. The tank is located directly underneath the PDMS stamp and displays vertical movement controlled by a voice coil actuator. The location of the tank is determined to allow the ink meniscus within the tank to greet the PDMS stamp without causing liquid leakage or other consequential disturbances.

Attachment mounts are additionally designed to accommodate for the movement of the actuator, demonstrating motion adaptability for the experimental setup of the R2R printing. Hexadecanethiol (HDT), mixed with ethanol, is selected as ink for R2R microcontact printing because HDT can be rapidly transferred to the gold substrate as the SAM resists. In addition, preliminary experimental results show that when PDMS material is placed in contact with the ink mixture, HDT and ethanol have strong attachment capabilities with the elastomeric stamp.

After wetting the PDMS stamp through direct contact with the meniscus of the ink, a drying system must occur on the wet ink before the stamp becomes printed onto the gold-coated PET substrate. To accomplish this, a nitrogen gas tank is connected by plastic tubing to a 3D printed nozzle as the first step in the drying process; each nozzle design is run through the built-in flow simulation in SolidWorks. The main goal is to maximize the magnitude of the velocity output while also displaying uniform flow under laminar and atmospheric conditions. When the nozzle is held closely to the stamp, drying of the wet ink can then occur. Experimental results show that attaching multiple tubings within the nozzle can allow nitrogen gas velocities up to 18 m/s. After the HDT ink dries, the stamp can make contact with the gold-coated substrate. We demonstrate novel designs to improve the efficiency and precision of the entire system’s performance.

[1] Otsuka, H., 2014, Colloid and Interface Science in Pharmaceutical Research and Development, Elsevier, Amsterdam, Netherlands, Chap. 11.

[2] Merian, C. A., 2016, “Development of an Inking System for Continuous Roll-to-Roll Microcontact Printing of Hexadecanethiol (HDT) on Gold-Coated PET,” M.S. Thesis, Massachusetts Institute of Technology.

[3] Riza, M. N., 2020, “Mechanical Design & Analysis: High-Precision Microcontact Printhead for Roll-to-Roll Printing of Flexible Electronics,” M.S. Thesis, University of Massachusetts Amherst.

Presenting Author: Jessica Wu University of Massachusetts Amherst

Authors:

Jessica Wu University of Massachusetts Amherst
Jingyang Yan University of Massachusetts Amherst
Xian Du University of Massachusetts Amherst