Configurable swellability of hydrogel microstructure for structural-color-based imaging concealment/encryption

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Dynamic structural color is crucial for optical information concealment and encryption.
• Existing responsive materials face challenges in synthesis, control, and resolution.
• Metal-hydrogel-metal (MHM) nanocavities offer potential for tunable structural color.

Purpose of the Study:

• To develop a novel humidity-driven strategy for structural color-based imaging concealment and encryption.
• To utilize MHM nanocavities with configurable swellability for dynamic structural color generation.
• To demonstrate a method for concealing and revealing images using humidity changes.

Main Methods:

• Fabrication of multi-stage MHM nanocavities with hydrogel interlayers.
• Tuning hydrogel swelling ratios (1.05–2.08) via controlled exposure doses.
• Development of a double exposure technique for image concealment and revelation.

Main Results:

• Achieved dynamic structural color across the visible spectrum by controlling hydrogel swelling.
• Demonstrated image concealment by configuring swellable and non-swellable hydrogel pixels.
• Successfully revealed hidden images using the double exposure method under moist conditions.

Conclusions:

• The proposed MHM nanocavity strategy enables effective humidity-driven optical information concealment.
• Configurable hydrogel swellability allows for dynamic structural color and image hiding.
• This approach presents a powerful method for high-density optical information encryption applications.