Halftone-encoded 4D printing of stimulus-reconfigurable binary domains for cephalopod-inspired synthetic smart skins

Abstract

Cephalopods exhibit versatile control over their optical appearance, texture, and shape for adaptive camouflage and signaling. Achieving such multi-feature dynamic control in synthetic materials remains a significant challenge. Here, we introduce a halftone-encoded 4D printing method that enables simultaneous and programmable control over optical appearance, mechanical properties, surface texture, and shape transformation within a single smart hydrogel film in response to various external stimuli (e.g., temperature, solvents, and mechanical stress)-a capability beyond existing synthetic materials. By encoding halftone binary patterns composed of highly crosslinked ("1") and lightly crosslinked ("0") domains, we spatially regulate localized polymer-solvent interactions and microstructural heterogeneities. The interplay, arrangement, and integration of these binary domains collectively dictate macroscale multifunctionality within a single material system. This binary encoding approach offers a simple yet powerful platform for designing multifunctional synthetic materials with complex, reconfigurable behaviors, unlocking opportunities in soft robotics, adaptive surface engineering, and secure information storage.