Flexible conductive materials have gained considerable research interest in recent years because of their potential applications in flexible energy storage devices, sensors, touch panels, electronic ...skins, etc. With excellent flexibility, outstanding electric properties and tunable mechanical properties, conductive hydrogels as conductive materials offer plentiful insights and opportunities for flexible electronic devices. Numerous synthetic strategies have been developed to obtain various conductive hydrogels, and high‐performance flexible electronic devices based on these conductive hydrogels have been realized. This review provides a comprehensive overview of conductive‐hydrogel‐based flexible electronics, ranging from conductive hydrogels synthesis to several important flexible devices applications, including touch panels, sensors and energy storage. Finally, we provide new future research directions and perspectives for conductive‐hydrogel‐based flexible and portable electronic devices.
Conductive hydrogels are ideal candidates for use in flexible electronic devices due to their unique properties such as good electronic properties, tunable mechanical flexibility, and easy to process. This review provides a comprehensive overview of conductive hydrogel‐based flexible electronics, ranging from conductive hydrogels synthesis to several important flexible devices applications, including touch panels, sensors and energy storage.
Construction and application of surfaces with switchable liquid–solid adhesion have generated worldwide interest during the past a few years. These surfaces are of great importance not only for ...fundamental research but for various practical applications in smart and fluid‐controllable devices. This Feature Article reviews several techniques that have been developed to switch the adhesion on liquid/solid interfaces, including tuning the surface chemical composition, tailoring the surface morphology, and applying external stimuli. Particular attention is paid to superhydrophobic surfaces with reversible switching between low‐ and high‐adhesion to water droplets in response to external stimuli. The dynamic behavior of water droplets on such surfaces can be controlled ranging from rolling to pinning state, while maintaining superhydrophobic states. In addition, smart adhesion in oil/water/solid system and platelet/water/solid system are also discussed, which is of importants for application in designing novel anti‐bioadhesion materials.
The dynamic behavior of water droplets on superhydrophobic surfaces can be controlled ranging from a low‐adhesion rolling state to a high‐adhesion pinning state.This Feature Article discusses several techniques that have been developed to switch the adhesion on liquid/solid interfaces, including tuning the surface chemical composition, tailoring the surface morphology, and applying external stimuli.
Anti‐biofouling surfaces are of high importance owing to their crucial roles in biosensors, biomedical devices, food processing, the marine industry, etc. However, traditional anti‐biofouling ...surfaces based on either the release of biocidal compounds or surface chemical/physical design cannot satisfy the practical demands when meeting real‐world complex conditions. The outstanding performances of natural anti‐biofouling surfaces motivate the development of new bioinspired anti‐biofouling surfaces. Herein, a novel strategy is proposed for rationally designing bioinspired anti‐biofouling surfaces based on superwettability. By utilizing the trapped air cushions or liquid layers, Lotus leaf inspired superhydrophobic surfaces, fish scales inspired underwater superoleophobic surfaces, and Nepenthes pitcher plants inspired omniphobic slippery surfaces have been successfully designed as anti‐biofouling surfaces to effectively resist proteins, bacteria, cells, and marine organisms. It is believed that these novel superwettability‐based anti‐biofouling surfaces will bring a new era to both biomedical technology and the marine industry, and will greatly benefit human health and daily life in the near future.
A superwettability strategy for the rational design and development of bioinspired anti‐biofouling surfaces will bring a promising way to effectively resist proteins, bacteria, cells, and marine organisms for both biomedical and industrial applications.
Object detection, as a fundamental task in computer vision, has been developed enormously, but is still challenging work, especially for Unmanned Aerial Vehicle (UAV) perspective due to small scale ...of the target. In this study, the authors develop a special detection method for small objects in UAV perspective. Based on YOLOv3, the Resblock in darknet is first optimized by concatenating two ResNet units that have the same width and height. Then, the entire darknet structure is improved by increasing convolution operation at an early layer to enrich spatial information. Both these two optimizations can enlarge the receptive filed. Furthermore, UAV-viewed dataset is collected to UAV perspective or small object detection. An optimized training method is also proposed based on collected UAV-viewed dataset. The experimental results on public dataset and our collected UAV-viewed dataset show distinct performance improvement on small object detection with keeping the same level performance on normal dataset, which means our proposed method adapts to different kinds of conditions.
The confined synthesis of two-dimensional covalent organic framework (2D COF) thin films was developed by using thin superspreading water on the hydrogel immersed under oil as reactor. Through ...loading two monomers into oil and hydrogel, respectively, COF thin films are synthesized at the oil/water/hydrogel interface. This strategy provides a new way for synthesis of freestanding 2D COF thin films. Detailed characterizations of the COF thin films reveal homogeneous topography, large area, controllable thickness from 4 to 150 nm, and crystallinity with certain orientation. Young’s modulus of COF film is measured by AFM indentation as 25.9 ± 0.6 GPa, showing good mechanical properties. On the basis of the freestanding COF films, a nanofilter membrane and photoelectrochemical sensors for Ru3+ were successfully developed. Moreover, the strategy was extended to the synthesis of crystalline zeolitic imidazolate framework-8 thin film, which exhibited high application potential.
A novel superhydrophilic and underwater superoleophobic polyacrylamide (PAM) hydrogel‐coated mesh is successfully fabricated in an oil/water/solid three‐phase system. Compared to traditional ...oleophilic materials, the as‐prepared hydrogel‐coated meshes can selectively separate water from oil/water mixtures with the advantages of high efficiency, resistance to oil fouling, and easy recyclability.
Synthetic gels with switchable interfacial properties have great potential in smart devices and controllable transport. Herein, we design an organogel by incorporating a binary liquid mixture with an ...upper critical solution temperature (UCST) into a polymer network, resulting in reversible modulation of lubrication and adhesion properties. As the temperature changes, the lubricating mechanism changes reversibly from boundary lubrication to hydrodynamic lubrication due to phase separation within the binary solution permeating the gel (friction coefficient 0.4–0.03). Droplets appear on the gel surface at low temperature and disappear with temperature higher than the critical phase separation temperature (Tps) of the organogel. The organogel possesses a relatively low ice adhesive strength (less than 1 kPa). This material has potential applications in anti‐icing and smart devices, and we believe that this design strategy can be expanded to other systems such as aqueous solutions and hydrogels.
Thermosecreting organogel: Binary‐solution‐permeated organogels undergo thermoresponsive phase separation. The reversible secretion‐absorption of droplets change the lubricating mechanism and produce anti‐icing property.
Self‐cleaning on various surfaces is obtained using the facile approach of modifying the surface with a thin organogel film. The film not only absorbs oil but also holds it in a crosslinked network, ...which endows the material with excellent self‐cleaning properties. This facile method can be applied to various common engineering metals.
Bioinspired water-repellent materials offer a wealth of opportunities to solve scientific and technological issues. Lotus-leaf and pitcher plants represent two types of antiwetting surfaces, i.e., ...superhydrophobic and lubricant-infused “slippery” surfaces. Here we investigate the functions and applications of those two types of interfacial materials. The superhydrophobic surface was fabricated on the basis of a hydrophobic fumed silica nanoparticle/poly(dimethylsiloxane) composite layer, and the lubricant-infused “slippery” surface was prepared on the basis of silicone oil infusion. The fabrication, characteristics, and functions of both substrates were studied, including the wettability, transparency, adhesive force, dynamic droplet impact, antifogging, self-cleaning ability, etc. The advantages and disadvantages of the surfaces were briefly discussed, indicating the most suitable applications of the antiwetting materials. This contribution is aimed at providing meaningful information on how to select water-repellent substrates to solve the scientific and practical issues, which can also stimulate new thinking for the development of antiwetting interfacial materials.
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