Interfacial solar evaporation (ISE) is a promising technology to relieve worldwide freshwater shortages owing to its high energy conversion efficiency and environmentally sustainable potential. So far, many innovative materials and evaporators have been proposed and applied in ISE to enable highly controllable and efficient solar-to-thermal energy conversion. With rational design, solar evaporators can achieve excellent energy management for lowering energy loss, harvesting extra energy, and efficiently utilizing energy in the system to improve freshwater production. Beyond that, a strategy of reducing water vaporization enthalpy by introducing molecular engineering for water-state regulation has also been demonstrated as an effective approach to boost ISE. Based on these, this article discusses the energy nexus in two-dimensional (2D) and three-dimensional (3D) evaporators separately and reviews the strategies for design and fabrication of highly efficient ISE systems. The summarized work offers significant perspectives for guiding the future design of ISE systems with efficient energy management, which pave pathways for practical applications.

Piezoelectric nanogenerators (PENGs) are promising for harvesting renewable and abundant mechanical energy with high efficiency. Up to now, published research studies have mainly focused on increasing the sensitivity and output of PENGs. The technical challenges in relation to practicability, comfort, and antibacterial performance, which are critically important for wearable applications, have not been well addressed. To overcome the limitations, we developed an all-nanofiber PENG (ANF-PENG) with a sandwich structure, in which the middle poly(vinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP))/ZnO electrospun nanofibers serve as the piezoelectric layer, and the above and below electrostatic direct-writing P(VDF-HFP)/ZnO nanofiber membranes with a 110 nm Ag layer on one side that was plated by vacuum coating technique serve as the electrode layer. As the ANF-PENG only has 91 μm thick and does not need further encapsulating, it has a high air permeability of 24.97 mm/s. ZnO nanoparticles in ANF-PENG not only improve the piezoelectric output, but also have antibacterial function (over 98%). The multi-functional ANF-PENG demonstrates good sensitivity to human motion and can harvest mechanical energy, indicating great potential applications in flexible self-powered electronic wearables and body health monitoring.

Flexible strain sensors with high sensitivity, wide detection range, and low detection limit have continuously attracted great interest due to their tremendous application potential in areas such as health/medical-care, human–machine interface, as well as safety and security. While both of a high sensitivity and a wide working range are desired key parameters for a strain sensor, they are usually contrary to each other to be achieved on the same sensor due to the tightly structure dependence of both of them. Here, a flexible strain sensor with both high sensitivity and wide strain detection range is prepared based on the design of an integrated membrane containing both of parallel aligned and randomly aligned carbon nanofibers (CNFs). The parallel aligned CNF membrane (p-CNF) exhibits a low strain detection limit and high sensitivity, while the random aligned CNF membrane (r-CNF) exhibits a large strain detection range. Taking the advantages of both p-CNF and r-CNF, the strain sensor with stacked p-CNF and r-CNF (p/r-CNF) exhibits both high sensitivity and wide working range. Its gauge factor (GF) is 1,272 for strains under 0.5% and 2,266 for strain from 70% to 100%. At the same time, it can work in a wide strain range of 0.005% to 100%, fulfilling the requirements for accurately detecting full-range human motions. We demonstrated its applications in the recognition of facial expressions and joint movements. Furtherly, we constructed an intelligent lip-language recognition system, which can accurately track phonetic symbols and may help people with language disabilities, proving the potential of this strain sensor in health management and medical assistance. Besides, we foresee that the dual-alignment structure design of the p/r-CNF strain sensor may also be applied in the design of other high performance sensors.

Carbon nanotubes (CNTs) hold great promise in many fields because of their unique structures and properties. However, the preparation of CNTs generally involves cumbersome equipment and time-consuming processes. Here, we report an ultra-fast carbothermal shock (CTS) approach for synthesizing CNTs with a simple homemade setup by employing Joule heating of a carbon substrate. Carbonized silk fabric (CSF) loaded with transition metal salts in ethanol solution was used as the substrate, which was treated with a pulse voltage of 40 V for only 50 ms and then covered with uniform CNTs grown with bimetallic alloy catalyst nanoparticles (diameter: ~ 9 nm). The temperature ramp rate is as high as 10⁵ K/s. The as-obtained sample has a unique fluffy structure similar to the trichobothrium of spiders, endowing it versatile applications such as airflow sensors or air filters. The CTS technique presents an easy-accessible and highly efficient approach for synthesizing CNTs, which may be also applied in synthesizing other nanomaterials.

Stretchable and flexible supercapacitors are highly desired due to their many potential applications in wearable devices. However, it is challenging to fabricate supercapacitors that can withstand large tensile strain while maintaining high performance. Herein, we report an ultra-stretchable wire-shaped supercapacitor based on carbon nanotube@graphene@MnO₂ fibers wound around a superelastic core fiber. The supercapacitor can sustain tensile strain up to 850%, which is the highest value reported for this type of device to date, while maintaining stable electrochemical performance. The energy density of the supercapacitor is 3.37 mWh·cm^–3 at a power density of 54.0 mW·cm^–3. The results show that 82% of the specific capacitance is retained after 1, 000 stretch–release cycles with strains of 700%, demonstrating the superior durability of the elastic supercapacitor and showcasing its potential application in ultra-stretchable flexible electronics.

With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted structures developed through natural selection, which inspired us for the design of biomimetic materials or devices. Particularly, human fingertip skin, where many epidermal ridges amplify external stimulations, might be a good example to imitate for highly sensitive sensors. In this work, based on unique chemical vapor depositions (CVD)-grown 3D graphene films that mimic the morphology of fingertip skin, we fabricated flexible pressure sensing membranes, which simultaneously showed a high sensitivity of 110 (kPa)^-1 for 0–0.2 kPa and wide workable pressure range (up to 75 kPa). Hierarchical structured PDMS films molded from natural leaves were used as the supporting elastic films for the graphene films, which also contribute to the superior performance of the pressure sensors. The pressure sensor showed a low detection limit (0.2 Pa), fast response (< 30 ms), and excellent stability for more than 10, 000 loading/unloading cycles. Based on these features, we demonstrated its applications in detecting tiny objects, sound, and human physiological signals, showing its potential in wearable electronics for health monitoring and human/machine interfaces.

Fast and uniform growth of high-quality graphene on conventional glass is of great importance for practical applications of graphene glass. We report herein a confined-flow chemical vapor deposition (CVD) approach for the high-efficiency fabrication of graphene glass. The key feature of our approach is the fabrication of a 2–4 μm wide gap above the glass substrate, with plenty of stumbling blocks; this gap was found to significantly increase the collision probability of the carbon precursors and reactive fragments between one another and with the glass surface. As a result, the growth rate of graphene glass increased remarkably, together with an improvement in the growth quality and uniformity as compared to those in the conventional gas flow CVD technique. These high-quality graphene glasses exhibited an excellent defogging performance with much higher defogging speed and higher stability compared to those previously reported. The graphene sapphire glass was found to be an ideal substrate for growing uniform and ultra-smooth aluminum nitride thin films without the tedious pre-deposition of a buffer layer. The presented confined-flow CVD approach offers a simple and low-cost route for the mass production of graphene glass, which is believed to promote the practical applications of various graphene glasses.

Silk is a widely available, edible, biocompatible, and environmentally sustainable natural material. Particulate matter (PM) pollution has drawn considerable attention because it is a serious threat to public health. Herein, we report a human-friendly silk nanofiber air filter, which exhibits superior filtration efficiency for both PM_2.5 and submicron particles with obviously low pressure drop and low basis weight compared to typical commercial microfiber air filters. Additionally, other functions such as antibacterial activity could be easily integrated into the silk nanofiber air filters, enabling the fabrication of multifunctional air filters. All the above characteristics, combined with the natural abundance and biocompatibility of silk, suggest a great potential for the use of silk nanofibers as air filters, especially as comfortable and personal air purifiers.

Single-crystal graphene domains grown by chemical vapor deposition (CVD) intrinsically tend to have a six-fold symmetry; however, several factors can influence the growth kinetics, which can in turn lead to the formation of graphene with different shapes. Here we report the growth of oriented large-area pentagonal single-crystal graphene domains on Cu foils by CVD. We found that high-index Cu planes contributed selectively to the formation of pentagonal graphene. Our results indicated that lattice steps present on the crystalline surface of the underlying Cu promoted graphene growth in the direction perpendicular to the steps and finally led to the disappearance of one of the edges forming a pentagon. In addition, hydrogen promoted the formation of pentagonal domains. This work provides new insights into the mechanism of graphene growth.