Abstract
To address the global water shortage crisis, one of the promising solutions is to collect freshwater from the environmental resources such as fog. However, the efficiency of conventional fog ...collectors remains low due to the viscous drag of fog-laden wind deflected around the collecting surface. Here, we show that the three-dimensional and centimetric
kirigami
structures can control the wind flow, forming quasi-stable counter-rotating vortices. The vortices regulate the trajectories of incoming fog clusters and eject extensive droplets to the substrate. As the characteristic structural length is increased to the size of vortices, we greatly reduce the dependence of fog collection on the structural delicacy. Together with gravity-directed gathering by the folds, the
kirigami
fog collector yields a collection efficiency of 16.1% at a low wind speed of 0.8 m/s and is robust against surface characteristics. The collection efficiency is maintained even on a 1 m
2
collector in an outdoor setting.
Herein, we developed a nanocomposite membrane with synergistic photodynamic therapy and photothermal therapy antibacterial effects, triggered by a single near-infrared (NIR) light illumination. ...First, upconversion nanoparticles (UCNPs) with a hierarchical structure (UCNPs@TiO2) were synthesized, which use NaYF4:Yb,Tm nanorods as the core and TiO2 nanoparticles as the outer shell. Then, nanosized graphene oxide (GO), as a photothermal agent, was doped into UCNPs@TiO2 core–shell nanoparticles to obtain UCNPs@TiO2@GO. Afterward, the mixture of UCNPs@TiO2@GO in poly(vinylidene) fluoride (PVDF) was applied for electrospinning to generate the nanocomposite membrane (UTG-PVDF). Generation of reactive oxygen species (ROS) and changes of temperature triggered by NIR action were both investigated to evaluate the photodynamic and photothermal properties. Upon a single NIR light (980 nm) irradiation for 5 min, the nanocomposite membrane could simultaneously generate ROS and moderate temperature rise, triggering synergistic antibacterial effects against both Gram-positive and -negative bacteria, which are hard to be achieved by an individual photodynamic or photothermal nanocomposite membrane. Additionally, the as-prepared membrane can effectively restrain the inflammatory reaction and accelerate wound healing, thus exhibiting great potentials in treating infectious complications in wound healing progress.
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Natural materials have always attracted intensive attention from multidisciplinary scientists all over the world. In fact, the ingenious and reasonable synthetic strategies of the ...limited components can always make natural materials achieve a superior performance that is far beyond their own. Meanwhile, the local properties can determine the overall performance through regulating multiple characteristics, including structure, composition, and interface. Living organisms can inspire the fabrication of artificial materials, which provides a clear vision for advanced materials research. Therefore, inspired by this strategy, biomimetic structural materials are used to meet the strict and even extreme requirements of engineering materials. In this review, we mainly clarify the difference of local properties in natural materials and explain how living organisms utilize very limited elements and compounds to control the local properties and further realize some specific function to adapt to the specific requirement of the environment. In addition, the manufacturing technologies and strategies common to bio-inspired structural materials are summarized. Finally, a summary and prospects on the limitations of current techniques and the direction of future developments for the design of novel bio-inspired materials are given.
Grasping and manipulation are fundamental ways for many creatures to interact with their environments. Different morphologies and grasping methods of “grippers” are highly evolved to adapt to harsh ...survival conditions. For example, human hands and bird feet are composed of rigid frames and soft joints. Compared with human hands, some plants like Drosera do not have rigid frames, so they can bend at arbitrary points of the body to capture their prey. Furthermore, many muscular hydrostat animals and plant tendrils can implement more complex twisting motions in 3D space. Recently, inspired by the flexible grasping methods present in nature, increasingly more bio‐inspired soft grippers have been fabricated with compliant and soft materials. Based on this, the present review focuses on the recent research progress of bio‐inspired soft grippers based on impactive gripping. According to their types of movement and a classification model inspired by biological “grippers”, soft grippers are classified into three types, namely, non‐continuum bending‐type grippers, continuum bending‐type grippers, and continuum twisting‐type grippers. An exhaustive and updated analysis of each type of gripper is provided. Moreover, this review offers an overview of the different stiffness‐controllable strategies developed in recent years.
According to movement ways and the classification model inspired by biological “grippers”, the soft grippers are divided into three types: non‐continuum bending‐type grippers, continuum bending‐type grippers, and continuum twisting‐type grippers. For each type of gripper, material properties, device architectures, and manipulation strategies are systematically explored and analyzed. In addition, an overview of stiffness‐controllable strategies developed in recent years is proposed.
Cicada wings, covered with arranged nanostructures, were widely studied owing to their high transparency and low reflection. However, limited by technologies, their exquisite surface structures and ...multifunctional features were not inherited and applied by most artificial materials adequately. Here, the excellent optical properties of the cicada wing were investigated in detail experimentally and theoretically. Besides, a flexible self-cleaning broadband antireflective film inspired by the cicada wing has been successfully fabricated by a well-designed biological template method and sol–gel process. The cicada wing (Megapomponia intermedia) was selected as the original template directly, and a SiO2 negative replica was obtained by a sol–gel process. Then, chemical corrosion was used to remove the original template, retaining the pure negative replica. Subsequently, the polymethyl methacrylate (PMMA) positive replica could be rebuilt after another sol–gel process. Compared with a flat PMMA film, the average reflectivity of the structured PMMA film over the visible region was reduced from 10 to 2%. Besides, the bio-inspired film with a thickness of 0.18 mm exhibited satisfactory comprehensive performances with low reflectance (≤2%) in most of the visible region, as well as superhydrophobic property and perfect flexibility. Our results offered a quick and simple method to rebuild the nanostructured functional materials, promoting the practical applications of the bionic nanostructured materials. Meanwhile, the modified biomimetic fabrication method provides a solution for rebuilding exquisite biological materials and designing multifunctional surfaces. Moreover, the multifunctional antireflective film with wider universality will exhibit an enormous potential application value in optical communications, photoelectric devices, flexible display screens, and antidazzle glasses.
Solid particle erosion is a common phenomenon in engineering fields, such as manufacturing, energy, military and aviation. However, with the rising industrial requirements, the development of ...anti-solid particle erosion materials remains a great challenge. After billions of years of evolution, several natural materials exhibit unique and exceptional solid particle erosion resistance. These materials achieved the same excellent solid particle erosion resistance performance through diversified strategies. This resistance arises from their micro/nanoscale surface structure and interface material properties, which provide inspiration for novel multiple solutions to solid particle erosion. Here, this review first summarizes the recent significant process in the research of natural anti-solid particle erosion materials and their general design principles. According to these principles, several erosion-resistant structures are available. Combined with advanced micro/nanomanufacturing technologies, several artificial anti-solid particle erosion materials have been obtained. Then, the potential applications of anti-solid particle erosion materials are prospected. Finally, the remaining challenges and promising breakthroughs regarding anti-solid particle erosion materials are briefly discussed.
Morpho butterfly, famous for its iridescence wing scales, has gradually evolved a diversity of functions and has attracted much attention recently. On the other hand, it is known that the wing ...surface of Morpho butterfly has some complex and so- phisticated structures. In fact, they are composed of an alternating multilayer film system of chitin and air layers, which have different refractive indexes. More importantly, these structures can interact strongly with visible light because the feature size of the structures is in the same order of magnitude with light wavelength. It is noteworthy that it is these optical architectures that cause the excellent multifunction including structural color, antireflection, thermal response, selective vapour response, direc- tional adhesion, superhydrophobicity and so on. This review mainly covers the excellent multifunctional features of Morpho butterfly wings with representative functional structures of multilayer film system, photonic crystal and ridges. Then, the mechanism of the structure-based optical multifunction of Morpho butterfly is analyzed. In order to facilitate mechanism analysis, the models of bionic functional structures are reported, as well as the interaction process between the multiscale structures and the external media It is concluded that these functions of Morpho butterfly wings have inevitable and corre- sponding regularity connection with the structural parameters and the dielectric coefficient of the filled medium. At last, the future direction and prospects of this field are briefly addressed. It is hoped that this review could be beneficial to provide some innovative insoirations and new ideas to the researchers in the fields of engineering, biomedicine, and materials science.
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•Precise, and controlled deposition of responsive polymer on complex natural photonic crystal structures is achieved.•It achieves the dual responsiveness of natural photonic crystals ...to external stimuli.•The synergistic action of the polymer and the natural structure solves the limitations of colloidal photonic crystals.•The synergistic effect of the structures and materials on the optical response is revealed.
Responsive photonic crystals (PCs) with bio-inspired microstructures and tailorable functionalities are of critical importance for their potential applications in diverse fields such as biological detection, sensing, decoration, anti-counterfeiting, etc. However, limited by preparation technologies and design theories, it is still a challenge to accurately and uniformly deposit smart responsive materials on natural PC structures and achieve dual stimulus response. Herein, a simple and rapid in situ polymerization method is presented for preparing dual-responsive PCs with ultra-precise micro-/nanoscale hierarchical structures. Exposure of the reaction site by deacetylation of Morpho butterfly wings allows in situ polymerisation of poly (N-isopropylacrylamide-co-acrylic acid) (P(NIPAAM-co-AAc)) on the surface of the natural photonic structure. The obtained P(NIPAAM-co-AAc) photonic crystals (P(NIPAAM-co-AAc)-PCs) exhibited a dual response to pH and temperature reversibility. In addition, the synergistic effect of the structures and materials on the optical response of the natural PCs is revealed. This work allows the combination of natural hierarchical PC structures with smart hydrogel to achieve an optical response to pH and temperature, thus opening up the channels for responsive PC to multiple stimulus responses.
Walking on the water surface is an effective method for miniature robots to transport payloads with dramatically decreased interfacial drag. Current aquatic robots reported are generally actuated by ...a beam of focused light that can trigger asymmetrical deformation, enabling the directional movement through horizontal momentum transfer of photoinduced actuation force to the water. However, the operations are heavily dependent on manual manipulation of the focused light, making the long-term actuation and application of the aquatic robots in vast scenarios challenging. Herein, we developed a kind of water strider-inspired robot that can autonomously manage the motion on the water surface under solar irradiation, with their direction steerable by a magnetic field. The motion of this bioinspired robot on the water surface was achieved by the use of a solar cell panel as a driving module to enable propulsive motion based on the conversion of light-electric-mechanical energies. The superhydrophobic design of its leg surfaces enables the aquatic robots with weight-bearing and drag-reducing abilities. With the assistance of magnetic navigation, the bioinspired robot can continuously and controllably locomote to the oily spill floating on the water body and collect them with high efficiency. For further demonstration, the treatment of oil spills in a campus pool with high efficiency has also been achieved. This on-site oil-spill treating strategy, taking advantage of a home-made bioinspired robot actuated by natural sunlight under magnetic steering, shows great potential applications in water-body remediation.
The imitation and application of manipulability and dexterity of human arm have been investigated actively as it can improve the time efficiency and save labor cost greatly. Most of the current ...studies in this area only focus on recreating the structure of human arm without considering how to use the finger path for forming. In this paper, the authors present a flexible bio-inspired stretch-forming machine (SFM) for the fabrication of parts, which are large and possess large radius bends, with small spring back and smooth surfaces. The flexible bio-inspired SFM was composed by two pairs of finger-inspired jaws in conjunction with six couples of muscle-inspired hydraulic cylinders (the sum of numbers is 60), which only integrates six solenoid types of reversing valves. The path of finger-inspired jaws was planned by setting up the parameters of loading order, stretching direction, and cylinder pull force. The finger-inspired jaws, driven by the muscle-inspired hydraulic cylinders, moved along the given route to realize sheet metal forming. The finite element simulation and experiment results on a series of large radius bends parts formed by the flexible finger-inspired SFM have been reported. The remarkable results are that an effective solution for stretch forming of sheet metal with short free edge has been founded, and an easy control process of stretch forming with finger-inspired jaws has been developed, respectively. This work has an important value in implementation of stretch-forming technology from aircraft to vehicle and building.
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