Self-sustained programmable hygro-electronic interfaces for humidity-regulated hierarchical information encryption and display.

The emerging moisture-driven energy generation (MEG) technology opens up new possibilities for humidity-responsive materials, devices and interdisciplinary opportunities in fields like information security. However, such potential remains untapped. Here, we report an original MEG structure with a hygro-ionic energy-conversion route by selective coating of ionic hygroscopic hydrogels on a carbon black surface. The hygro-ionic route features a process in which the scavenged energy is stored in the electrical double layers formed at the interfaces between the ionic hydrogel and the carbon nanoparticles. The resultant electrical field developed across the hydrogel-coated wet carbon and the rest dry carbon area is thus durably lasted. Based on this unique structure, we put forward the hygro-electronic information interfaces (HEII) for humidity-regulated information encryption and display by devising the hydrogel patterns on the carbon platform. Further by tuning the hygroscopicity of ionic hydrogels and incorporating encoding methods (e.g., Morse code), we demonstrate that the HEII platform is programmable to carry different information in certain humidity ranges. Unlike those conventional anticounterfeiting methods that optically reveal the hidden information once the required stimulus is provided, the new HEII serves as a hierarchical solution for high-security encryption and display. This article is protected by copyright. All rights reserved.