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The wettability of nanofluid is a key factor affecting oil recovery and fluid heat transfer. However, the traditional wettability measurement method consisting in determining the contact angle enables to assess the wettability at a solid–liquid contact point only and not within the continuous detection range. Therefore, in this work, a lateral friction detection system is used to continuously measure the wettability of hydroxylated multi-walled carbon nanotubes/deionized water (MWCNT-OH/DIW) nanofluids on polydimethylsiloxane surfaces. Specifically, MWCNT-OH/DIW nanofluids with various mass fractions are configured, and different surfactants are introduced to regulate the dispersion in deionized water. The results reveal that the surface tension and contact angle decrease simultaneously with the increase in MWCNT-OH/DIW mass fraction. Meanwhile, this change also causes an increase in the lateral friction at the nanofluid/PDMS interface. Furthermore, both sodium dodecyl sulfate and cetyltrimethylammonium bromide (CTAB) as surfactants can effectively reduce its surface tension. Notably, when CTAB is added, the maximum static friction (132.62 μN) exceeds that of SDS (113.13 μN). Therefore, the proposed method opens up new prospects in wettability detection of nanofluids. [ABSTRACT FROM AUTHOR]

Wettability is an important factor that influences surfactant oil displacement efficiency, where surfactant solutions wet rock surfaces better and have lower interfacial tensions with crude oil, thus enhancing the oil recovery rate. Therefore, understanding the wetting of rock surfaces and selecting suitable surfactant solutions are essential for enhanced oil recovery. In this paper, a self-built system to measure the lateral friction at solid and liquid interfaces was established, and the effects of different types and concentrations of inorganic salt additives on the dynamic wettability of the surfactant solution on the solid surface were studied. A rough silica surface was used to simulate the reservoir environment, and methylene chloride was used as the simulation oil. The experimental results show that when the concentration of sodium dodecyl sulfonate is lower than the critical micelle concentration, the inorganic salt additives (NaCl, Na2SO4, and KCl) affect the surface tension, contact angle, and lateral friction of the solution. As the concentration of the inorganic salt additives increased, the surface tension and contact angle of the solution continuously decreased, the lateral friction of the solution on the simulated silica surface increased, and the wettability of the surfactant solution on the solid surface improved. [ABSTRACT FROM AUTHOR]

Here, a high sensitivity gas sensing ink based on sulfonated rGO (S-rGO) decorated with SnS 2 is synthesized for room temperature NO 2 and NH 3 detection. This sensing ink demonstrated an excellent sensitivity to ppb-level NO 2 (17% response to 125 ppb) and sub-ppm-level NH 3 (11% response to 1 ppm). The unique absorption properties of SnS 2 improve the sensitivity of S-rGO 4.2 and 55 times to NO 2 and NH 3 , respectively. Besides, the superhydrophobicity of the SnS 2 endows the sensor with exceptional immunity to high relative humidity (RH). Furthermore, the sensors exhibit negligible degradation to NO 2 and less than 15% degradation to NH 3 in a wide range of RH from 30 (ambient humidity) to 90%. More importantly, the obtained full-written ink can be applied to common substrates, such as glass, clothes, and paper, and maintain excellent performance after being bent and twisted by 180°.