The rapid progress in flexible electronic devices has attracted immense interest in many applications, such as health monitoring devices, sensory skins, and implantable apparatus. Here, inspired by the adhesion features of mussels and the color shift mechanism of chameleons, a novel stretchable, adhesive, and conductive structural color film is presented for visually flexible electronics. The film is generated by adding a conductive carbon nanotubes polydopamine (PDA) filler into an elastic polyurethane (PU) inverse opal scaffold. Owing to the brilliant flexibility and inverse opal structure of the PU layer, the film shows stable stretchability and brilliant structural color. Besides, the catechol groups on PDA impart the film with high tissue adhesiveness and self‐healing capability. Notably, because of its responsiveness, the resultant film is endowed with color‐changing ability that responds to motions, which can function as dual‐signal soft human‐motion sensors for real‐time color‐sensing and electrical signal monitoring. These features make the bio‐inspired hydrogel‐based electronics highly potential in the flexible electronics field.

Bionic electronic skin (E-skin) that could convert external physical or mechanical stimuli into output signals has a wide range of applications including wearable devices, artificial prostheses, software robots, etc. Here, we present a chameleon-inspired multifunctional E-skin based on hydroxypropyl cellulose (HPC), Poly(Acrylamide-co-Acrylic acid) (PACA), and carbon nanotubes (CNTs) composited liquid-crystal hydrogel. We found that the HPC could still form cholesteric liquid-crystal photonic structures with the CNTs additive for enhancing their color saturation and PACA polymerization for locating their assembled periodic structures. As the composite hydrogel containing HPC elements and the PACA scaffold responds to different stimuli, such as temperature variations, mechanical pressure, and tension, it could correspondingly change its volume or internal nanostructure and report these as visible color switches. In addition, due to the additive of CNTs, the composite hydrogel could also output these stimuli as electrical resistance signals. Thus, the hydrogel E-skins had the ability of quantitatively feeding back external stimuli through electrical resistance as well as visually mapping the stimulating sites by color variation. This dual-signal sensing provides the ability of visible-user interaction as well as antiinterference, endowing the multifunctional E-skin with great application prospects.

Structural coloration is an intriguing phenomenon that exists widely in living creatures. A genuine bionic design of artificial structural colors requires accommodating of molecular interactions that contribute to dynamic optical responses over various external stimuli. Novel composite cellulose cholesteric liquid crystals are reported with additional molecular interactions and dynamic regulations as a bionic prototype for biological structural coloration. It is found that the incorporation of polymer monomers increases the amount of hydrogen bonds, leading to a broader range of color tunability. In addition, the crosslinking of the polymer is accompanied by a timedependent structure alternation of the cellulose cholesteric liquid crystals, which offers a duration control of irradiation over the color. Based on these phenomena, a series of structural color materials is developed with dynamic photonic responsiveness and high-resolution patterns; their utility in wearable sensors, graphic displays, and information encryption is demonstrated. It is believed that this study presents a next-generation biomimetic photonic material design and applications for different areas.

Inspired by the actuator mechanism of Venus flytrap leaves, presented is a bilayer structural color hydrogel actuator by employing a hybrid inverse opal scaffold to join the poly(acrylic acid‐co‐acrylamide) layer and the poly(N‐isopropylacrylamide) layer together. The nanostructure of the inverse opal scaffold imparts the bilayer hydrogel with brilliant structural color, which can show a reversible coloration switch during the structural change. An internal water distribution occurs in the composite bilayer hydrogel during the heating or cooling process because of the opposite thermo‐responsiveness of the two hydrogels. Thus, this intelligent soft material can work in various environments and break the limitation of aqueous media of most structural color hydrogels. In addition, the water transference of the bilayer hydrogel enables the material with bending/unbending deformations and hence a series of complex motions like screwing, catching, and releasing can be achieved. Attractively, with the integrating of graphene oxide, the hydrogel systems can even be imparted with near‐infrared remote responsiveness to both of their color change and 3D deformation. These features of the bioinspired bilayer structural color hydrogel indicate its potential values in a variety of intelligent soft material applications.

Lung‐on‐a‐chip models hold great promise for disease modeling and drug screening. Herein, inspired by the iridescence phenomenon of soap bubbles, a novel biomimetic 3D microphysiological lung‐on‐a‐chip system with breathing visualization is presented. The system, with an array of pulmonary alveoli at the physiological scale, is constructed and coated with structural color materials. Cyclic deformation is induced by regular airflow, resembling the expansion and contraction of the alveoli during rhythmic breathing. As the deformation is accompanied with corresponding synchronous shifts in the structural color, the constructed system offers self‐reporting of the cell mechanics and enables real‐time monitoring of the cultivation process. Using this system, the dynamic relationships between the color atlas and disease symptoms, showing the essential role of mechanical stretching in the phenotypes of idiopathic pulmonary fibrosis, are investigated. These features make this human lung system ideal in biological study, disease monitoring, and drug discovery.

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The in-depth development of biological materials, especially natural polymer materials, has injected strong vitality into clinical wound treatment. Here, a new type of controllable responsive microparticles composed of several natural polymer materials was presented for drug release and wound healing. These hybrid microparticles consisted of silk fibroin, gelatin, agarose, and black phosphorus quantum dots (BPQDs) and were loaded with growth factors and antibacterial peptides. Under near-infrared (NIR) irradiation, BPQDs could absorb the NIR light and increase the temperature of the microparticles to the melting point of gelatin. When the gelatin started to melt, the encapsulated drugs were gradually released because of the reversible phase transformation. Both in vitro and in vivo experiments have demonstrated that the BPQD-laden microparticles with a NIR-responsive feature could achieve the desired controllable release of growth factors to promote neovascularization formation. In addition, because antibacterial peptides were also mixed with the secondary hydrogel and encapsulated in the scaffolds, the microparticles are imparted with the antibacterial ability during storage and usage. These characteristics of BPQD-laden natural protein hybrid microparticles make them ideal for drug delivery and wound healing.

Significance We propose a printable structural color ink composed of cholesteric cellulose liquid crystals together with gelatin and a thermal-responsive hydrogel. The ink is endowed with vivid structural colors and printability due to its constituents. Based on this, we print a series of graphics and three-dimensional (3D) objects with vivid color appearances. Moreover, the printed objects possess dual thermal responsiveness, which results in visible color change around body temperature. These performances, together with the biocompatibility of the constituents, indicate that the present ink represents a leap forward to the next-generation 3D printing and would unlock a wide range of real-life applications.