Spatial‐Color Encoding for Multimodal Optical Encryption via an Electrowetting Display Platform

ABSTRACT Optical encryption and secure display technologies provide physical‐layer protection for visual information, yet most platforms face a trade‐off between rapid response and simple optical readout. Here, we report a confined electrowetting display (EWD) platform for optical encryption, featuring mask‑free programmable patterning, direct optical readout, and millisecond‐scale response. An encoding strategy combining spatial and color coding is proposed, for the first time, for multimodal information encryption. Inkjet‐printed conductive micropillars locally enhance the electric field at pixel quarter‐edges, inducing deterministic oil‐film rupture and directional retraction that define four spatial states, while a vertically stacked cyan‐magenta‐yellow structure enables subtractive color mixing. As demonstrations, the encrypted patterns are revealed only upon simultaneous application of independent voltage keys. Decryption supports dual‑level readout: direct visual recognition of the reconstructed mixed‑color pattern, and microscopic decoding of spatial pixel states mapped via a Base64 scheme to retrieve digital and textual information. In addition to a fast switching time of 25 ms, the experimentally demonstrated Base64 mapping corresponds to an estimated areal payload density of 1.77 × 10 8 bits/m 2 . This scalable EWD platform integrates programmable patterning, key‑gated access, rapid response, and two‐level optical readout, opening a new avenue toward high‑speed secure displays and advanced anti‑counterfeiting technologies.