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[Display omitted] Heart-on-chips have emerged as a powerful tool to promote the paradigm innovation in cardiac pathological research and drug development. Attempts are focused on improving microphysiological visuals, enhancing bionic characteristics, as well as expanding their biomedical applications. Herein, inspired by the bright feathers of peacock, we present a novel optical and electrical dual-responsive heart-on-a-chip based on cardiomyocytes hybrid bright MXene structural color hydrogels for hormone toxicity evaluation. Such hydrogels with inverse opal nanostructure are generated by using pregel to replicate MXene-decorated colloidal photonic crystal (PhC) array templates. The attendant MXene in the hydrogels could not only enhance the saturation of structural color, but also ensure the composite hydrogel with excellent electroconductivity to facilitate the synergetic beating of their surface cultured cardiomyocytes. In this case, the hydrogels would undergo a synchronous deformation and generate shift in corresponding photonic band gap and structural color, which could be employed as visual signal for self-reporting of the cardiomyocyte mechanics. Based on these features, we demonstrated the practical value of the optical and electrical dual-responsive structural color MXene hydrogels constructed heart-on-a-chip in hormone toxicity testing. These results indicated that the proposed heart-on-a-chip might find broad prospects in drug screening, biological research, and so on. [ABSTRACT FROM AUTHOR]

Background: Wound healing has become a worldwide healthcare issue. Attempts in the area focus on developing patches with the capabilities of avoiding wound infection, promoting tissue remolding, and reporting treatment status that are of great value for wound treatment. Results: In this paper, we present a novel inverse opal film (IOF) patch based on a photo-crosslinking fish gelatin hydrogel with the desired features for wound healing and dynamic monitoring. The film with vibrant structure colors was constructed by using the mixture of fish gelatin methacryloyl, chitosan, and polyacrylic acid (PAA) to replicate colloidal crystal templates. As the structures of these natural biomolecules are well-retained during the fabrication, the resultant IOF was with brilliant biocompatibility, low immunogenicity, antibacterial property, as well as with the functions of promoting tissue growth and wound healing. In addition, the IOF presented interconnected nanopores and high specific surface areas for vascular endothelial growth factor loading, which could further improve its angiogenesis capability. More attractively, as the pH-responsive PAA was incorporated, the IOF patch could report the wound healing status through its real-time structural colors or reflectance spectra. Conclusions: These features implied the practical value of the multifunctional fish gelatin hydrogel IOFs in clinical wound management. [ABSTRACT FROM AUTHOR]

Structural colors have a demonstrated value in constructing various functional materials. Efforts in this area are devoted to developing stratagem for generating heterogeneous structurally colored materials with new architectures and functions. Here, inspired by icing process in nature and ice-templating technologies, we present freeze-derived heterogeneous structural color hydrogels with multiscale structural and functional features. We find that the space-occupying effect of ice crystals is helpful for tuning the distance of non-close-packed colloidal crystal nanoparticles, resulting in corresponding reflection wavelength shifts in the icing area. Thus, by effectively controlling the growth of ice crystals and photo-polymerizing them, structural color hydrogels with the desired structures and morphologies can be customized. Other than traditional monochromatic structure color hydrogels, the resultant hydrogels can be imparted with heterogeneous structured multi-compartment body and multi-color with designed patterns through varying the freezing area design. Based on these features, we have also explored the potential value of these heterotypic structural color hydrogels for information encryptions and decryptions by creating spatiotemporally controlled icing areas. We believe that these inverse ice-template structural color hydrogels will offer new routes for the construction and modulation of next generation smart materials with desired complex architectures. While most of the structural colored materials only present isotropic colors, limiting their functions and many practical applications, while realizing anisotropic structural color materials remains challenging. Here, the authors develop a freeze-derived heterogeneous structural color hydrogels for information encryption and decryption. [ABSTRACT FROM AUTHOR]

Structural color hydrogels (SCHs) have ushered in a new era for a variety of fields including sensing, display, and anti‐counterfeiting. Attempts in this area are trending to improve their functions to implement the practical values. Herein, bioinspired by chameleons, a novel multi‐responsive angle‐independent SCH is presented. The SCH consists of responsive poly(N‐isopropylacrylamide) (PNIPAM) with vivid structural colors replicated from photonic crystal particle templates, which is fixed within a non‐responsive hydrogel film. Due to the thermal‐sensitivity of PNIPAM, the distance between nanopores of inverse opal can be tuned, leading to a shift of the reflection peak. Besides, the structural colors are angle‐independent since the structural color elements are spherical. Intriguingly, as the elastic deformation of the non‐responsive hydrogel is only in local positions, the total volume of the SCH film is kept near‐constant, making its stability superior to traditional structural color films. To further broaden its function, reduced graphene oxide nanoparticles and carbon nanotubes are integrated into the SCH film to gain near‐infrared (NIR) photo‐thermal and electro‐thermal response. It is verified that the SCH can respond to temperature change, NIR irradiation, and electric signal, exhibiting chromatic shifting with constant volume and wide viewing angles, indicating unpredicted potential in diverse fields. [ABSTRACT FROM AUTHOR]

Electronic skins have received increasing attention in biomedical areas. Current efforts about electronic skins are focused on the development of multifunctional materials to improve their performance. Here, the authors propose a novel natural‐synthetic polymers composite structural color hydrogel film with high stretchability, flexibility, conductivity, and superior self‐reporting ability to construct ideal multiple‐signal bionic electronic skins. The composite hydrogel film is prepared by using the mixture of polyacrylamide (PAM), silk fibroin (SF), poly(3,4‐ethylenedioxythiophene):poly (4‐styrene sulfonate) (PEDOT:PSS, PP), and graphene oxide (GO) to replicate colloidal crystal templates and construct inverse opal scaffolds, followed by subsequent acid treatment. Due to these specific structures and components, the resultant film is imparted with vivid structural color and high conductivity while retaining the composite hydrogel's original stretchability and flexibility. The authors demonstrate that the composite hydrogel film has obvious color variation and electromechanical properties during the stretching and bending process, which could thus be utilized as a multi‐signal response electronic skin to realize real‐time color sensing and electrical response during human motions. These features indicate that the proposed composite structural color hydrogel film can widen the practical value of bionic electronic skins. [ABSTRACT FROM AUTHOR]

As a new class of two-dimensional (2D) materials, molybdenum disulfide (MoS 2) has huge potential in biomedical area; while its applications in multiplex bioassays are still a challenge. Here, we present novel MoS 2 -integrated silica colloidal crystal barcode (SCCB) for multiplex microRNA (miRNA) screening. MoS 2 was adsorbed on SCCBs by electrostatic interaction, and quantum dots (QDs) decorated hairpin probes were coupled on MoS 2 by covalent linkage. As the MoS 2 could quench the QDs of the hairpin probes, they together formed a molecular beacon (MB) structure before the detection. When used in assays, target miRNA could form a double strand with the probe and made QDs keep away from MoS 2 sheets to recovery their fluorescence. Because the released QDs were positively correlated with the concentration of the hybridized nucleic acid, the target miRNAs could be quantified by measuring the fluorescence signal of the QDs on the SCCBs. In addition, by utilizing different MoS 2 -integrated structural color encoded SCCBs, multiplexed miRNA quantification could also be realized. Based on this strategy, we have demonstrated that several pancreatic cancer-related miRNAs could be selectivity and sensitivity detected with a detection limit of 4.2 ± 0.3 nM. These features make the MoS 2 -integrated SCCB ideal for many potential applications. • A novel MoS 2 -integrated silica colloidal crystal barcodes (SCCBs) for multiplex miRNA screening. • MoS 2 sheets on SCCBs and the QD-decorated hairpin probes formed a molecular beacon (MB) structure for target detection. • MiRNAs could be quantified by measuring the fluorescent signal which positively correlated with their concentration. • The label-free strategy demonstrated good accuracy and high sensitivity multiplexed miRNA quantification. [ABSTRACT FROM AUTHOR]

• Self-assembled colloidal nanoparticles films are traditionally lack of robust. • A new self-assembly method to construct functional hierarchical superhydrophobic surface. • This method is more operability and can prepare the desired film with structural color on arbitrary intricate surfaces. • The structural color provides a visualized method to monitor the losses. Functional materials with specific wettability surfaces are valuable for many areas. Extensive applications for superwettbility have led to demand for integrating devices with flexible and multi-functional. Here, inspired by the super-adhesive of mussels and the hierarchical structures of mosquitos' compound eyes, we proposed a new method to construct functional hierarchical superhydrophobic surface by self-assembly of colloidal nanoparticles. The monolayer micron-scaled photonic crystal film is self-assembled on the surface of the liquid and deposited on the as-prepared dopamine-modified substrate. Then, a single layer of nanoscale photonic crystal film is self-assembled on the surface of the liquid and deposited on the prepared monolayer micron-scale film. In addition, the assembled structure is highly ordered and presents a certain structural color. When the surface is changed, the liquid will be injected into the ordered structure, causing the change of structure color. The hierarchical photonic crystal films with structural hydrophobic can be prepared on arbitrary intricate surfaces. Moreover, we have also explored the potential use of these hierarchical films as indicators for the surface wettability. These indicate that the hierarchical films are highly versatile for different applications. [ABSTRACT FROM AUTHOR]

Heart‐on‐a‐chip based on microfluidic platform can simulate the structure and reveal the function of heart at the micrometer level, compensating the gap between organism and experiments in vitro. In this paper, a novel heart‐on‐a‐chip system integrated with reduced graphene oxide (rGO) hybrid anisotropic structural color film is designed for cardiac sensing and evaluation. This hybrid anisotropic film is based on the opposite adhesion properties of the polyethylene glycol diacrylate (PEGDA) and gelatin methacryloyl (GelMA). The PEGDA area with low adhesion rate has inverse opal structure and specific reflection peak, while microgroove‐patterned rGO‐doped GelMA area with high adhesion rate provides the cardiomyocytes with excellent growing environment and induced orientation property. Benefiting from the design, the cultured cardiomyocytes only adhere in specific area without affecting the surface microstructure of the structural color. When cardiomyocytes recover beating, its elongation and contraction will stretch the structure of PEGDA and result in a color shift, which realizes the transformation from micromechanics to macroscopic optics. In addition, the heart‐on‐a‐chip system based on the anisotropic structural color hydrogels and microfluidics provides an outstanding visible method for cardiac sensing, which is of great significance in cardiac pathophysiological studies and drug detection in vitro. [ABSTRACT FROM AUTHOR]

• Patterned electric-tunable wettability of PIPCCFs are facilely developed. • PIPCCFs with conductive paths have quick response to electro-thermal conversion. • PIPCCFs with parallel paths can handle different droplets at the same time. • An economical and efficient approach to manipulate droplets. Slippery liquid-infused porous surfaces (SLIPs), especially capable of tunable and smart response to the external stimuli, play important roles in the field of intelligent transportation, microreactors, self-cleaning, anti-icing, and beyond. Herein, a novel electric-tunable wettability of paraffin-infused porous colloidal crystal films (PIPCCFs) is presented. Approaches to manipulate the local wettability are proposed by sputtering patterned conductive paths between the PIPCCFs and the glass slide, which can be used as the reversible electro-thermal sources. In addition, smart pathways can be facilely constructed by integrating conductive paths with different shapes to force the droplets transport in fixed orbits. More importantly, with the integration of parallel connection conductive paths, PIPCCFs can individually handle different droplets at the same time. It is demonstrated that electric-tunable wettability on the PIPCCFs could not only supply a quick response to electro-thermal conversion, but also simplify droplets handling in versatile and complex sliding pathways. These features make it a low-cost and high efficiency method for droplets manipulation. [ABSTRACT FROM AUTHOR]