Silk-Based Aqueous Microcontact Printing

Abstract

Lithography, the transfer of patterns to a film or substrate, is the basis by which many modern technological devices and components are produced. However, established lithographic approaches generally use complex techniques, expensive equipment, and advanced materials. Here, we introduce a water-based microcontact printing method using silk that is simple, inexpensive, ecofriendly, and recyclable. Whereas the traditional microcontact printing technique facilitates only negative lithography, the synergetic interaction of the silk, water, and common chemicals in our technique enables both positive and negative patterning using a single stamp. Among diverse application possibilities, we exemplify a proof of concept of the method through optimizing its metal lift-off process and demonstrate the fabrication of electromagnetic metamaterial elements on both solid and flexible substrates. The results indicate that the method demonstrated herein is universally applicable to device production and technology development.

Patterning of protein‐based materials

“…The localized conformational change from β‐sheet to random coil rendered the contact areas water‐soluble yielding pattern of the water‐insoluble crystalline regions after treatment with aqueous solutions. [ 34 ] In the process of negative lithography, crosslinking solutions (methanol or ethanol) were stamped directly on nonstructured fibroin films causing the locally increased crystallinity due to the β‐sheet formation whereas noncontacted areas could be washed out. In a combination with gold coating, the fabrication of split ring resonators was possible enabling electromechanical and optical systems in a biocompatible, recyclable way.…”

“…In a combination with gold coating, the fabrication of split ring resonators was possible enabling electromechanical and optical systems in a biocompatible, recyclable way. [ 34 ] Sun et al . [ 35 ] developed a so‐called Patterning on Topography technique by applying extracellular matrix (ECM) proteins on surfaces of a thermally‐sensitive poly(N‐isopropylacrylamide) (PIPAAm) flat substrate.…”

“…Schematic illustration of the silk microcontact printing process established by Ganesh Kumar et al . [ 34 ] A, To use fibroin as a positive resist, the silk film was physically crosslinked with methanol after coating. The microcontact printing of LiBr as ink led to a conformational change of the silk proteins and increased the water solubility.…”

“…C, With this approach, split ring resonators for electromagnetic applications could be fabricated (white light measurement with color bar indicating film thickness). Reproduced from Reference [34] with permission of American Chemical Society…”

Photolithographic Masking Method to Chemically Pattern Silk Film Surfaces

“…To date, patterning methods employing silk have primarily focused on producing topological or structural patterns in silk. Microcontact printing, nanoimprinting, and plasma etching have been used to make grooves or holes in silk films, and multiphoton lithography printing can produce 3D silk structures . Unmodified silk can serve as a resist for e-beam lithography, deep-UV lithography, and microcontact printing techniques, while several reports have employed sericin, − fibroin, , or the light-chain of silk fibroin modified with UV-active methacrylate groups as a photoresist to produce a variety of high-resolution silk patterns.…”