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

## TL;DR

A new 4D printing method creates smart hydrogel films that can change appearance, texture, and shape in response to stimuli, mimicking cephalopod camouflage.

## Contribution

A halftone-encoded 4D printing method enables multifunctional smart skins with reconfigurable optical and mechanical properties.

## Key findings

- Halftone binary patterns control polymer-solvent interactions and microstructural heterogeneities in hydrogels.
- The method allows simultaneous control over optical appearance, mechanical properties, and shape transformation.
- This approach enables reconfigurable smart skins with applications in soft robotics and adaptive surfaces.

## 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.

Designing materials to simultaneously control optical appearance, mechanical properties, and shape transformation is promising for camouflage or signaling though it is challenging to design materials with dynamic controls. Here the authors use a 4D-printing method to design a responsive hydrogel for programmable smart skins.