Flexible and stretchable electronics, e.g., graphite-nanoplatelet-based (GNP-based) nanocomposite devices, have attracted great interest due to their potential application in health care, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process, and poor repeatability notoriously limit their industrial applications. For an enhancement in the spontaneous sensitivity, flexibility, and wearability in GNP-based strain sensors, in this report, synergistic crack and elastic effect engineering is employed and in turn significantly enhances the sensitivity with a gauge factor of 20 at a strain of 30% and the stability in our developed sheath–core fiber (SCF) strain sensors. Upon reliable device integration, it is demonstrated that the developed SCF strain sensor could detect the movement of a human joint effectively with generating a resistance change rate ΔR/R 0 up to 600%. Furthermore, a controlling device system based on the SCF strain sensor has been manufactured at the circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.

Superhydrophobic surfaces (SHS) for underwater drag reduction draw more and more attention owing to its promising and wide applications such as underwater vehicles, pipeline oil transportation, and aquaculture. However, the drag reduction properties are inextricably linked to the stability of air layer on SHS. This review highlights recent advances regarding SHS for underwater drag reduction in the past three years. First, the fundamental theories are briefly described. Next, the crucial influencing factors, which include dimension and arrangement of particles, layout, and shape of the microstructures, Reynolds number, and attack angle on underwater drag reducing performance of SHS are thoroughly listed. Furthermore, the superior or inferior of these manufacturing techniques is also individually illustrated. After that, the solutions of enhancing stability of the air layer are explicitly classified. Then, the practical applications and its potential value in ships and underwater vehicles, microchannels, as well as fabrics are briefly discussed. Finally, the remaining challenges and promising breakthroughs in the field of SHS for underwater drag reduction are clarified in depth.

The self-healing superhydrophobic surfaces have attracted great interest owing to restoring superhydrophobicity without preparation crafts. However, the self-healing superhydrophobic surface still faces the dilemma of long repairing time. Especially in aqueous environments, superhydrophobic surfaces are highly susceptible to contamination and damage. In the current study, a superhydrophobic surface with ultrafast repairability was developed, which apply for drag reduction in aqueous medium. The prepared superhydrophobic surface can recover superhydrophobicity in only 30 s after severe physical and chemical damage. In addition, this research pioneered the combination of superhydrophobicity and porous structures for underwater drag reduction. The study of drag reduction confirms that the superhydrophobic surface can reduce the frictional drag by about 43% in the water. However, the drag reduction rate of the superhydrophobic surface with the porous structure can be improved to 76% due to increased stability of the air layer. More importantly, the porous structure with the average pore size of 50 μm has the most excellent stability through further experiments on the underwater air layer. This is attributed to the proper size of the pore to effectively balance the capillary force and resist wetting in the marginal region. This study will bring inspiration for the large-scale application of superhydrophobic surfaces and long-term drag reduction.

We report a new type of highly flexible hybrid supercapacitors (SCs) developed by graphite nanoplatelets (GNPs)based films with a practicable fabrication method for mass production. In this report, GNP/carbon black films are featured with excellent freestanding and conductivity characteristics, thus capable of working as both active and interconnection layers (∼20 μm) in our integrated GNP-SCs. The hybrid GNP-SCs are constructed by two distinct assembling methods, series and parallel connection, which are synergistic to enlarge the working voltage window and boost up the areal energy density of the supercapacitor. With tailored thickness, the areal capacitance ∼27.5 mF/cm 2 of three-parallel GNP-SCs is ∼2.3 times higher than that of the single GNP-SC. On the other hand, the gap-coating fabrication method is utilized to achieve low cost, easy operation, and simplified process, enabling large-scale free-standing GNP-SCs films to be the most promising candidate for wearable energy-storage devices. Our studies and complementary investigations demonstrate the feasibility of innovative GNP-SCs applications in a variety of fields with optimized performance and low cost, e.g., energy supply, smart wearable devices, and human−machine interfaces.

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