Pressure-Activated Differential Wettability Paper for Naked-Eye Detection of Encrypted Information.

Abstract

Differential wetted surfaces designed for droplet directional infiltration contributed to naked-eye recognition of cryptographic patterns by relying on controlling the reflection light difference. However, constructing stable and energy-saving differential wettability surfaces is still a critical and challenging task. In this work, we prepared an information-encrypted fibrous paper featuring hydrophobic to hydrophilic switching via a one-step patterned pressing strategy. The flexible hydrophobic segment of the fiber shell layer ensures the selective wettability and pattern resolution, while the elastic hydrophilic segment of the core minimizes the whiteness difference and induces water infiltration after pressing. By adjusting the different concentrations of decryption solutions, the revelation of encrypted information possesses a time-dependent effect, and the shortest decryption time can be controlled within 5 s. Furthermore, the encrypted information can be permanently destroyed by a household printer. This study provides new strategies for intelligent, responsive interface design and information security encryption.