Manufacturing USA: High-Resolution Flexography for Printed Electronics Using Nanoporous Carbon Nanotube Stamps

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For centuries, innovations in printing technologies have gone hand-in-hand with advances in communication, education, and industrialization. Even though digital media has replaced a significant fraction of print media, further breakthroughs in printing technologies are now essential for scalable manufacturing of electronic devices in new formats, for example, on windows, contact lenses, and product packaging. However, the inability to print electronic materials with micron-scale resolution at high throughput is a major roadblock to realizing printed electronics. This award supports research to advance a new printing process as a state-of-art manufacturing platform for low-cost printed devices. The recently invented printing process, which uses nanoporous stamps, can produce features with micron-scale lateral dimensions (less than 10 micrometers), fine-edge roughness (less than 1 micrometer) and highly uniform thickness in the less than 100 nanometer range, at industrial scale printing speeds (greater than 0.1 meter per second). The practical significance of advances in printed electronics and the relevance of this topic to industry partners and the NextFlex Flexible Hybrid Electronics Manufacturing Innovation Institute suggest a pathway for transition of fundamental research in printed electronics to the commercial marketplace. Therefore, this activity directly enhances the nation's prosperity and security. In addition, the project emphasizes mentorship and outreach not only to graduate and undergraduate students in research, but to broad audiences through initiatives such as promotion of nanomaterials using artistic imagery, and a new nanomanufacturing teaching module for a Massive Open Online Course (MOOC) on Fundamentals of Manufacturing Processes.The new printing process uses engineered nanoporous stamps composed of polymer coated carbon nanotube (CNT) forests, which are highly porous (90 percent), retain the ink within their volume rather than on their surfaces only, and can transfer highly uniform ink layers under mechanical contact. The project focuses on the following three main thrust areas: (1) investigation of the ink transfer mechanics and precision process control, by combination of analytical and experimental approaches; (2) roll-to-roll printing and reliability studies, wherein the nanoporous stamps are fabricated on rollers and high-speed roll-to-roll printing is studied using a desktop apparatus; and (3) demonstration of printed devices for three high-value applications that leverage the unique capabilities of nanoporous flexography process, namely quantum dot (QD) filters for imaging spectrometers, high-resolution thin-film transistors, and optical metasurfaces. Understanding from these efforts enable precision control of lateral and vertical dimensions of printed features, and scalable nanoporous stamp materials that resist both mechanical degradation and loss of print quality.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.