The wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces; however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) on few layers of hexagon boron nitride (h-BN) and SiO2/Si. Our study clearly shows that while this class of two-dimensional materials are not completely wetting transparent, there seems to be a significant amount of influence on their wetting properties by the underlying substrate due to dominant vdW forces. Contact angle measurements indicate that graphene and graphene-like layered transitional metal dichalcogenides invariably have intrinsically dispersive surfaces with a dominating London-vdW force-mediated wettability.

Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal-boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal-stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)-grown WSe monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD-grown WSe bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe for which the device performance becomes degraded above a strain of 0.63%.

This study presents and verifies the deep-well wet air oxidation (WAO) reaction model for treating organic sludge (among the various by-products discharged from produced water treatment facilities) for recycling, and predicts the reaction characteristics. The deep-well WAO reaction model is established theoretically and a simulation model is developed. The validity of the simulation model is examined by comparing the modeled pressure change inside the reactor with that given by a model developed in a previous study. In terms of the pressure profile inside the reactor, the developed simulation model shows a 2.3% difference from the previously proposed model. It is confirmed that the increase in reaction pressure and residence time inside the deep-well WAO reactor improves organic decomposition by increasing the oxygen mass transfer rate in water containing such organics.

The nanofiber sheets consisted of N-carboxyethyl chitosan (CECH) and poly(ethylene oxide) (PEO) were developed using an electrospinning process to prevent abdominal adhesions after surgical operations. Successful synthesis of CECH from chitosan was confirmed by FTIR. The morphology and biocompatibility of the nanofiber sheets werecharacterized using a scanning electron microscope and MTT assay. For in vivo assessments, CECH/PEO nanofiber sheets were implanted into the abdominal surgical site and the abdominal tissues were evaluated by histological examination. When the weight ratio of CECH to PEO was 3:3, the nanofiber showed the most similar thickness between them. The MTT assay showed that the nanofibers had no significant toxicity toward NIH/3T3 cells at the high elution concentrations. The macroscopic and histological observation after 7 days of surgical process demonstrated that the CECH/ PEO nanofiber sheets prevented abdominal adhesion effectively. In conclusion, the CECH/PEO nanofiber sheets can be exploited to prevent postsurgical adhesions.