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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