Ultrafast Solid-State Electrochemical Imprinting Utilizing Polymer Electrolyte Membrane Stamps for Static/Dynamic Structural Coloration and Letter Encryption.

Micro and nanopatterned surfaces hold potential for various applications, such as wettability control, antibiofouling, and optical components. However, conventional patterning processes are characterized by complexity, high costs, and environmental burdens because of the use of resists. Therefore, this paper proposes facile and ultrafast electrochemical imprinting employing a polymer electrolyte membrane (PEM) stamp for achieving micro and nanoscale patterning on Si surfaces. The solid-state electrochemical process efficiently generates oxide and hydrated oxide (Si-OH) patterns within several seconds at room temperature in a dry ambient environment. The formed oxide pattern can be employed as an etching mask to prepare diffraction gratings with diverse high-resolution (≈100 nm) patterns utilizing the dry PEM stamp. The resulting oxide pattern on the Si surface exhibits instantaneous structural coloration upon exposure to humid air, attributable to the formation of a water microdroplet array on the oxide pattern. The oxide pattern is successfully applied for dynamic diffraction grating and letter encryption. The proposed solid-state electrochemical oxidation scheme based on a PEM stamp, which eliminates the need for liquid electrolyte and resist, represents a simple and ultrafast process with a time cost of a few seconds, characterized by low processing costs and environmental impact.