The unique structure of a vertically aligned carbon nanotube (VACNT) array makes it behave most similarly to a blackbody. It is reported that the optical absorptivity of an extremely black VACNT ...array is about 0.98–0.99 over a large spectral range of 200 nm–200 μm, inspiring us to explore the performance of VACNT arrays in solar energy harvesting. In this work, we report the highly efficient steam generation simply by laminating a layer of VACNT array on the surface of water to harvest solar energy. It is found that under solar illumination the temperature of upper water can significantly increase with obvious water steam generated, indicating the efficient solar energy harvesting and local temperature rise by the thin layer of VACNTs. We found that the evaporation rate of water assisted by VACNT arrays is 10 times that of bare water, which is the highest ratio for solar-thermal-steam generation ever reported. Remarkably, the solar thermal conversion efficiency reached 90%. The excellent performance could be ascribed to the strong optical absorption and local temperature rise induced by the VACNT layer, as well as the ultrafast water transport through the VACNT layer due to the frictionless wall of CNTs. Based on the above, we further demonstrated the application of VACNT arrays in solar-driven desalination.
Nanomaterials serve as promising candidates for strain sensing due to unique electromechanical properties by appropriately assembling and tailoring their configurations. Through the crisscross ...interlacing of graphene microribbons in an over-and-under fashion, the obtained graphene woven fabric (GWF) indicates a good trade-off between sensitivity and stretchability compared with those in previous studies. In this work, the function of woven fabrics for highly sensitive strain sensing is investigated, although network configuration is always a strategy to retain resistance stability. The experimental and simulation results indicate that the ultrahigh mechanosensitivity with gauge factors of 500 under 2% strain is attributed to the macro-woven-fabric geometrical conformation of graphene, which induces a large interfacial resistance between the interlaced ribbons and the formation of microscale-controllable, locally oriented zigzag cracks near the crossover location, both of which have a synergistic effect on improving sensitivity. Meanwhile, the stretchability of the GWF could be tailored to as high as over 40% strain by adjusting graphene growth parameters and adopting oblique angle direction stretching simultaneously. We also demonstrate that sensors based on GWFs are applicable to human motion detection, sound signal acquisition, and spatially resolved monitoring of external stress distribution.
The Scholander–Hammel pressure chamber has been used in thousands of papers to measure osmotic pressure, πc, turgor pressure, Pₜ, and bulk modulus of elasticity, ε, of leaf cells by pressure–volume ...(PV) curve analysis. PV analysis has been questioned in the past. In this paper we use micromechanical analysis of leaf cells to examine the impact on PV curve analysis of negative turgor in living cells (Pₜ). Models predict negative Pₜ (−0.1 to −1.8 MPa) depending on leaf cell size and shape in agreement with experimental values reported by J. J. Oertli. Modeled PV curves have linear regions even when Pₜ is quite negative, contrary to the arguments of M.T. Tyree. Negative Pₜ is totally missed by PV curve analysis and results in large errors in derived πc and Pₜ but smaller errors in ε. A survey of leaf cell sizes vs habitat (arid, temperate, and rainforest), suggests that the majority of published PV curves result in errors of 0.1–1.8 MPa in derived πc and Pₜ, whereby the error increases with decreasing cell size. We propose that small cell size in leaves is an ecological adaptation that permits plants to endure negative values of water potential with relatively little water loss.
High-performance sealants using rubber composites containing multiwalled carbon nanotubes (MWNTs) were developed in order to probe and excavate oil in deeper wells. However, the stress–strain ...behavior and the reinforcing mechanism of highly concentrated MWNT/rubber composites subjected to large deformation remain largely unexplored. Here we report on the complete stress–strain relationships of MWNT/rubber composites under uniaxial tension before rupture, with a suggestion of a novel reinforcement effect of high concentration of MWNTs. A theoretical model is developed to understand the reinforcing mechanism and estimate the mechanical properties of MWNT/rubber composites under large deformation. We have demonstrated that persistence length and reorientation of MWNTs during stretch have a significant impact on mechanical properties, such as the modulus of the rubber composite. These results provide guidelines for developing MWNT-reinforced composites to achieve desired nonlinear and extreme mechanical performance for a wide range of applications.
Water striders are a type of insect with the remarkable ability to stand effortlessly and walk quickly on water. This article reports the water repellency mechanism of water strider legs. Scanning ...electron microscope (SEM) observations reveal the uniquely hierarchical structure on the legs, consisting of numerous oriented needle-shaped microsetae with elaborate nanogrooves. The maximal supporting force of a single leg against water surprisingly reaches up to 152 dynes, about 15 times the total body weight of this insect. We theoretically demonstrate that the cooperation of nanogroove structures on the oriented microsetae, in conjunction with the wax on the leg, renders such water repellency. This finding might be helpful in the design of innovative miniature aquatic devices and nonwetting materials.
To understand why lotus leaf surfaces have a two-scale structure, we explore in this paper two stability mechanisms. One is the stability of the Cassie-Baxter wetting mode that generates the ...superhydrophobicity. A recent quantitative study (Zheng et al., Langmuir 2005, 21, 12207) showed that the larger the slenderness ratio of the surface structures was, the more stable the Cassie-Baxter wetting mode would be. On the other hand, it is well-known that more slender surface structures can only sustain lower critical water pressures for structure buckling, or Euler instability, while in the natural environments, the water pressure impacting on the lotus surface can reach a fairly high value (105 Pa in a heavy rain). Our analysis reveals that the two-scale structure of the lotus leaf surfaces is necessary for keeping both the structure and the superhydrophobicity stable. Furthermore, we find that the water−air interfacial tension makes the slender surface structure more instable and the two-scale structure a necessity.
In this paper, we design the elastic metamaterial cavities with multiple cavity modes for harvesting the flexural wave energy. The metamaterial plate is formed by drilling periodic holes in a thin ...aluminum plate, which exhibits a flexural wave mode band-gap. The metamaterial L1–L4 cavities are designed. The flexural waves are highly confined inside these metamaterial cavities due to the existence of the band-gap. The designed cavities can be utilized to confine and convert the mechanical wave energy to electricity for more than one cavity mode. To experimentally validate the multi-mode cavity design, a metamaterial L3 cavity is fabricated. The three cavity modes of the L3 cavity are observed experimentally, which agrees well with the numerical prediction. Three piezoelectric discs are attached in the metamaterial L3 cavity as the energy harvesters. The electrical outputs are measured to evaluate the performance of the metamaterial energy harvester. Compared to the reference harvester on a bare plate, the average power outputs are amplified by the metamaterial L3 cavity at three resonant frequencies. For the optimal resistance load, more than 40 times of the power amplification is achieved by the L3 cavity energy harvester. As prior energy harvesters based on a metamaterial cavity are usually efficient only for a single frequency, the multi-mode metamaterial cavity design can effectively widen the frequency bandwidth of the energy harvester.
Reported values （0.2 MPa-7.0 GPa） of the interlayer shear strength （ISS） of graphite are very dispersed. The main challenge to obtain a reliable value of the ISS using conventional measuring methods ...was the unavailability of sufficiently large single crystalline graphite. Here we present a novel experimental method to measure the ISS, and obtain the value as -0.14 GPa. Our result can serve as an important basis for understanding mechanical behavior of graphite or graphene-based materials.
Snake antivenomimmunoglobulins are considered to be the most efficient drugs in snake envenomings. Most snake antivenomimmunoglobulins all over the world are still prepared by fragmentation of ...polyclonal antibodies isolated from hyper-immunized horse serum till now. In this review, we retrospect the history of snake antivenomimmunoglobulins, analysis the present situation and pay the close attention on the key technological links in the process of research and manufacturing, such as properties of IgG and its fragments, selection and preparation of immunogen, optimization of immunization schedule and protein isolation and purification, which can be available for the reference in the research and development of snake antivenom.
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