Multicolor photonic patterns through an intensity-controlled single photopolymerization step

A multi-responsive 3D deformable soft actuator with tunable structural color enabled by a graphene/cholesteric liquid crystal elastomer composite

Intelligent soft robots that integrate both structural color and controllable actuation ability have attracted substantial attention for constructing biomimetic systems, biomedical devices, and soft robotics. However, simultaneously endowing single-layer cholesteric liquid crystal elastomer (CLCE) soft actuators with reversible 3D deformability and vivid structural color changes is still challenging. Herein, a multi-responsive (force, heat and light) single-layer 3D deformable soft actuator with vivid structural color-changing ability is realized through the reduced graphene oxide (RGO) deposition-induced Janus structure of the CLCE using a precisely-controlled evaporation method. This single-layer structural color soft actuator can directly transform from a flat shape to a 3D shape through the photothermal effect. The introduction of RGO not only improves the mechanical properties and color saturation of the CLCE, but also endows it with near-infrared (NIR) light responsiveness via the photothermal effect. Moreover, due to the structural gradient resulting from the spontaneous deposition of RGO during the deswelling process, CLCEs show a stacked structure of the helical CLC layer and RGO-dispersed amorphous layer, which are capable of undergoing multiple reversible 3D deformations. The reversible deformations of biomimetic devices such as petal-like films imitating blooming flowers, thin strips imitating plant tendrils, and a cobweb-inspired catching net are achieved to demonstrate applications of this single-layer RGO/CLCE composite film. This work provides a simple strategy for the construction of single-layer 3D deformable soft actuators.

Sticky Multicolor Mechanochromic Labels

Sticky-colored labels are an efficient way to communicate visual information. However, most labels are static. Here, we propose a new category of dynamic sticky labels that change structural colors when stretched. The sticky mechanochromic labels can be pasted on flexible surfaces such as fabric and rubber or even on brittle materials. To enhance their applicability, we demonstrate a simple method for imprinting structural color patterns that are either always visible or reversibly revealed or concealed upon mechanical deformation. The mechanochromic patterns are imprinted with a photomask during the ultraviolet (UV) cross-linking of acrylate-terminated cholesteric liquid crystal oligomers in a single step at room temperature. The photomask locally controls the cross-linking degree and volumetric response of the cholesteric liquid crystal elastomers (CLCEs). A nonuniform thickness change induced by the Poisson's ratio contrast between the pattern and the surrounding background might lead to a color-separation effect. Our sticky multicolor mechanochromic labels may be utilized in stress-strain sensing, building environments, smart clothing, security labels, and decoration.