Hydrogel‐Based Reconfigurable Visualization with Pixel‐Scale Programmability by Vapor Exhalation

Abstract Heading toward real‐life applications outside the laboratory, a longstanding obstacle for meta‐optics is to achieve an easy‐accessible tuning approach with practical characteristics, including a large tuning area, low complexity, low cost, and low energy consumption. Water (H 2 O) stimuli, a ubiquitous substance in nature, can potentially serve as a rescue solution and has attracted broad interest. However, despite its great simplicity, water tuning still faces an unresolved but critical challenge, that is, to enable independent‐programmable functionalities transformation. Herein, a pixel‐scale programmable visualization transformation simply tuned by exhaling water vapors through constructing a hydrogel‐based reconfigurable architectural metasurface (HRAM) with its geometric sensitivity to water molecules is originally demonstrated. Due to the moisture‐induced resonant mode switch from HRAM scaling up/down, the amplitude‐programmable meta‐pixels for obtaining multi‐channel encoding freedom are successfully created. Via simply exhaling vapors to the sample pattern, it dynamically exhibits independent‐programmable visualization (nanoprinting and meta‐holography) switch in real‐time at the prior‐/post‐humid states, beyond the conventional coloring change or simply on‐and‐off style switch utilizing humidity tuning scheme. Such a tuning strategy with good programmability, repeatability, and a large tuning area would blaze new trails for meta‐display dynamics in practical applications, including display/cosmetics, information storage/encryption, and humidity sensors.