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.
Biological systems have evolved over billions of years to develop wetting strategies for advantageous structure–property–performance relations that are crucial for their survival. The discovery of ...these intriguing relationships has inspired tremendous efforts to investigate the micro/nanoscale features of naturally occurring structures with superwettability. Researchers have since developed new methods and techniques to construct artificial materials that mimic natural structures and functionalities. Here, a brief review of natural hierarchical architectures with liquid repellent properties is presented, and the critical underlying mechanism is summarized with an emphasis on the micro/nanoscopic architectures. The state‐of‐the‐art micro/nanofabrication techniques for creating bioinspired hierarchical superwettability structures that are categorized by random and exquisite features are also reviewed, followed by an overview of their emerging applications, with special attention to biomedical‐related fields. The development of fabrication techniques enhances capabilities relative to those of living systems, paving the way toward advanced structural materials with superior functions and unprecedented characteristics for potential applications.
Bioinspired superwettability micro/nanoarchitectures including recently developed omniphobic and lubricant‐infused surfaces are reviewed. New developments in fabrication techniques and emerging potential applications of bioinspired hierarchical structural materials are highlighted.
Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as ...a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.
Oxygen carriers are attracting extensive interest in biomedical research and clinical applications such as wound healing, alternative blood transfusion, and acute trauma treatment. Great efforts have ...been devoted to the generation of oxygen carriers with special functions and properties to meet specific demands. Here, we present black phosphorus (BP)-loaded separable responsive microneedles (MNs) with oxygen carrying and controllable oxygen delivering ability for wound healing. Such MNs are composed of a polyvinyl acetate (PVA) backing layer and gelatin methacryloyl (GelMA) tips that are loaded with BP quantum dots (BP QDs) and hemoglobin (Hb). Taking advantage of the fast dissolvability of PVA, the backing layer soon disappears after the MNs are applied to skin and the noncytotoxic, biocompatible GelMA tips are left inside the skin. Due to the excellent photothermal effect of BP QDs and the reversible oxygen binding property of Hb, the local temperature of the skin will increase after near-infrared ray irradiation, resulting in the responsive oxygen release. Notably, the practical performance of such MNs has been demonstrated by treating the full-thickness cutaneous wounds of a type I diabetes rat model, indicating their potential value in wound healing and other related biomedical fields.
Biologically inspired self-healing structural color hydrogels were developed by adding a glucose oxidase (GOX)- and catalase (CAT)-filled glutaraldehyde cross-linked BSA hydrogel into methacrylated ...gelatin (GelMA) inverse opal scaffolds. The composite hydrogel materials with the polymerized GelMA scaffold could maintain the stability of an inverse opal structure and its resultant structural colors, whereas the protein hydrogel filler could impart self-healing capability through the reversible covalent attachment of glutaraldehyde to lysine residues of BSA and enzyme additives. A series of unprecedented structural color materials could be created by assembling and healing the elements of the composite hydrogel. In addition, as both the GelMA and the protein hydrogels were derived from organisms, the composite materials presented high biocompatibility and plasticity. These features of self-healing structural color hydrogels make them excellent functional materials for different applications.
Abstract
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.
Considerable efforts have been devoted to developing artificial micro/nanomotors that can convert energy into movement. A flow lithography integrated microfluidic spinning and spiraling system is ...developed for the continuous generation of bioinspired helical micromotors. Because the generation processes could be precisely tuned by adjusting the flow rates and the illuminating frequency, the length, diameter, and pitch of the helical micromotors were highly controllable. Benefiting from the fast online gelation and polymerization, the resultant helical micromotors could be imparted with Janus, triplex, and core–shell cross‐sectional structures that have never been achieved by other methods. Owing to the spatially controlled encapsulation of functional nanoparticles in the microstructures, the helical micromotors can perform locomotion not only by magnetically actuated rotation or corkscrew motion but also through chemically powered catalytic reaction.
Bioinspired helical micromotors with Janus, triplex, and core–shell cross‐sectional structures were precisely generated from a flow lithography integrated microfluidic spinning and spiraling system. The helical micromotors can perform locomotion not only by magnetically actuated rotation or corkscrew motion but also through chemically powered catalytic reaction.
Helical objects are among the most important and landmark structures in nature, and represent an emerging group of materials with unique spiral geometry; because of their enriched physical and ...chemical properties, they can have multiple functionalities. However, the fabrication of such complex helical materials at the micro‐ or nanoscale level remains a challenge. Here, a coaxial capillary microfluidic system, with the functions of consecutive spinning and spiraling, is presented for scalable generation of helical microfibers. The generation processes can be precisely tuned by adjusting the flow rates, and thus the length, diameter, and pitch of the helical microfibers are highly controllable. Varying the injection capillary design of the microfluidics enables the generation of helical microfibers with structures such as the novel Janus, triplex, core–shell, and even double‐helix structures. The potential use of these helical microfibers is also explored for magnetically and thermodynamically triggered microsprings, as well as for a force indicator for contraction of cardiomyocytes. These indicate that such helical microfibers are highly versatile for different applications.
Helical microfibers with novel Janus, triplex, core–shell, and even double‐helix structures are precisely generated by a coaxial capillary microfluidic system. The applications of these helical microfibers for magnetically and thermodynamically triggered microsprings, as well as for a force indicator for contraction of cardiomyocytes are all explored.
As an important characteristic of many creatures, structural colors play a crucial role in the survival of organisms. Inspired by these features, an intelligent structural color material with a ...heterogeneous striped pattern and stimuli‐responsivity by fast self‐assembly of colloidal nanoparticles in capillaries with a certain diameter range are presented here. The width, spacing, color, and even combination of the structural color stripe patterns can be precisely tailored by adjusting the self‐assembly parameters. Attractively, with the integration of a near‐infrared (NIR) light responsive graphene hydrogel into the structural color stripe pattern, the materials are endowed with light‐controlled reversible bending behavior with self‐reporting color indication. It is demonstrated that the striped structural color materials can be used as NIR‐light‐triggered dynamic barcode labels for the anti‐counterfeiting of different products. These features of the bioinspired structural color stripe pattern materials indicate their potential values for mimicking structural color organisms, which will find important applications in constructing intelligent sensors, anti‐counterfeiting devices, and so on.
Bioinspired structural color stripes with tailorable width, spacing, color, and even combination of the colored patterns are generated by assembling colloidal nanoparticles in capillaries. With the integration of a graphene hydrogel, the materials are endowed with NIR‐light‐controlled reversible bending behavior with self‐reporting color indication, which also show a great potential anti‐counterfeiting application as NIR‐light‐triggered dynamic barcode labels.
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