title: Ultrathin high-resolution flexographic printing using nanoporous stamps.
abstract: Since its invention in ancient times, relief printing, commonly called flexography, has been used to mass-produce artifacts ranging from decorative graphics to printed media. Now, higher-resolution flexography is essential to manufacturing low-cost, large-area printed electronics. However, because of contact-mediated liquid instabilities and spreading, the resolution of flexographic printing using elastomeric stamps is limited to tens of micrometers. We introduce engineered nanoporous microstructures, comprising polymer-coated aligned carbon nanotubes (CNTs), as a next-generation stamp material. We design and engineer the highly porous microstructures to be wetted by colloidal inks and to transfer a thin layer to a target substrate upon brief contact. We demonstrate printing of diverse micrometer-scale patterns of a variety of functional nanoparticle inks, including Ag, ZnO, WO3, and CdSe/ZnS, onto both rigid and compliant substrates. The printed patterns have highly uniform nanoscale thickness (5 to 50 nm) and match the stamp features with high fidelity (edge roughness, ~0.2 μm). We derive conditions for uniform printing based on nanoscale contact mechanics, characterize printed Ag lines and transparent conductors, and achieve continuous printing at a speed of 0.2 m/s. The latter represents a combination of resolution and throughput that far surpasses industrial printing technologies.
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Sanha
authors.identifier: 0000-0002-3548-6173
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.; Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Hossein
authors.initials: H
authors.lastname: Sojoudi
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Hangbo
authors.identifier: 0000-0001-5229-4192
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Dhanushkodi
authors.initials: D
authors.lastname: Mariappan
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Gareth H
authors.identifier: 0000-0001-8323-2779
authors.initials: GH
authors.lastname: McKinley
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Karen K
authors.identifier: 0000-0001-6127-1056
authors.initials: KK
authors.lastname: Gleason
authors.affiliation: Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: A John
authors.identifier: 0000-0002-7372-3512
authors.initials: AJ
authors.lastname: Hart
keywords: Printed electronics; carbon nanotube; flexography; porous; stamp