Droplet‐Pen Writing of Ultra‐Uniform Graphene Pattern for Multi‐Spectral Applications

Abstract Artificial optical patterns bring wide benefits in applications like structural color display, photonic camouflage, and electromagnetic cloak. Their scalable coating on large‐scale objects will greatly enrich the multimodal‐interactive society. Here, a droplet‐pen writing (DPW) method to directly write multi‐spectral patterns of thin‐film graphene is reported. By amphiphilicity regulations of 2D graphene nanosheets, ultra‐uniform and ultrathin films can spontaneously form on droplet caps and pave to the substrate, thus inducing optical interference. This allows the on‐surface patterning by pen writing of droplets. Specifically, drop‐on‐demand thin films are achieved with millimeter lateral size and uniformity up to 97% in subwavelength thickness (<100 nm), corresponding to an aspect ratio of over 30 000. The pixelated thin‐film patterns of disks and lines in an 8‐inch wafer scale are demonstrated, which enable low‐emittance structural color paintings. Furthermore, the applications of these patterns for dual‐band camouflage and infrared‐to‐visible encryption are investigated. This study highlights the potential of 2D material self‐assembly in the large‐scale preparation and multi‐spectral application of thin film‐based optical patterns.