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Surface evolution of manganese chloride aqueous droplets resulting in self-suppressed evaporation.

Zeng X, Zhang Y, Xia Z, Wang L, Wang C, Huang Y, Shen R, Wen W - Sci Rep (2015)

Bottom Line: A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride.The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C.In contrast, a pure water droplet can only be sustained for a few minutes.

View Article: PubMed Central - PubMed

Affiliation: Nano Science and Technology Program / Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

ABSTRACT
The exchange kinetics of liquid water, which are of fundamental interest and have potential applications, remain unclear. A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride. As observed from the evolution of this type of droplet, a thin film was formed on the surface with an exothermic phase transition, resulting in self-suppressed evaporation. The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C. In contrast, a pure water droplet can only be sustained for a few minutes. The self-suppressed evaporation of doped water may be due to the special hydration of the accumulated manganese and chloride ions at the surface, decreasing the surface tension.

No MeSH data available.


Related in: MedlinePlus

(a) Schematic representation of the homemade apparatus for the observation of the surface evolution in the manganese chloride droplet evaporation process. (b) Evolution of the diffraction patterns.
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f3: (a) Schematic representation of the homemade apparatus for the observation of the surface evolution in the manganese chloride droplet evaporation process. (b) Evolution of the diffraction patterns.

Mentions: Inspired by the study of Newton’s ring and interference fringes formed with curved thin sheets2324, a creative homemade light apparatus was designed to monitor the surface evolution of the droplet with manganese chloride. As shown in Fig. 3a, a 20-μl droplet was dropped onto a modified glass slide mounted on a heating system with the temperature was maintained at 40 °C. A 633 nm laser beam with a diameter of approximately 1 mm vertically penetrated through the centre of the droplet and then was reflected on a vertical screen with a reflector. The patterns of the laser on the screen were recorded by a commercial CCD (Fig. 3a). After several minutes of evaporation, some interesting patterns began to appear, as shown in Fig. 3b. The interference patterns were easily identified at approximately 15 minutes. The irregular patterns evolved as the evaporation progressed, which may be due to some small thin film fragments being formed and fluctuating on the surface of the droplet. After approximately 20 minutes, the film fragments joined together, and the distance of the interference fringes began to decrease. Therefore, the thickness of the film continued to increase. The interference fringes became obscure and finally disappeared after approximately 35 minutes, which indicated that the thickness was too large to produce interference or there was no clean-cut difference between the film and the bulk of the droplet. A simple simulation was performed with COMSOL Multiphysics to confirm the diffraction phenomena due to the curved thin film. The model, which was based on the Wave Optics module, was scaled down by 50 times compared to the actual situation due to computational complexity. The film thickness was 1 μm, and its index of refraction was 1.4. In addition, the diffraction patterns are shown in Fig. 4.


Surface evolution of manganese chloride aqueous droplets resulting in self-suppressed evaporation.

Zeng X, Zhang Y, Xia Z, Wang L, Wang C, Huang Y, Shen R, Wen W - Sci Rep (2015)

(a) Schematic representation of the homemade apparatus for the observation of the surface evolution in the manganese chloride droplet evaporation process. (b) Evolution of the diffraction patterns.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4544006&req=5

f3: (a) Schematic representation of the homemade apparatus for the observation of the surface evolution in the manganese chloride droplet evaporation process. (b) Evolution of the diffraction patterns.
Mentions: Inspired by the study of Newton’s ring and interference fringes formed with curved thin sheets2324, a creative homemade light apparatus was designed to monitor the surface evolution of the droplet with manganese chloride. As shown in Fig. 3a, a 20-μl droplet was dropped onto a modified glass slide mounted on a heating system with the temperature was maintained at 40 °C. A 633 nm laser beam with a diameter of approximately 1 mm vertically penetrated through the centre of the droplet and then was reflected on a vertical screen with a reflector. The patterns of the laser on the screen were recorded by a commercial CCD (Fig. 3a). After several minutes of evaporation, some interesting patterns began to appear, as shown in Fig. 3b. The interference patterns were easily identified at approximately 15 minutes. The irregular patterns evolved as the evaporation progressed, which may be due to some small thin film fragments being formed and fluctuating on the surface of the droplet. After approximately 20 minutes, the film fragments joined together, and the distance of the interference fringes began to decrease. Therefore, the thickness of the film continued to increase. The interference fringes became obscure and finally disappeared after approximately 35 minutes, which indicated that the thickness was too large to produce interference or there was no clean-cut difference between the film and the bulk of the droplet. A simple simulation was performed with COMSOL Multiphysics to confirm the diffraction phenomena due to the curved thin film. The model, which was based on the Wave Optics module, was scaled down by 50 times compared to the actual situation due to computational complexity. The film thickness was 1 μm, and its index of refraction was 1.4. In addition, the diffraction patterns are shown in Fig. 4.

Bottom Line: A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride.The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C.In contrast, a pure water droplet can only be sustained for a few minutes.

View Article: PubMed Central - PubMed

Affiliation: Nano Science and Technology Program / Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

ABSTRACT
The exchange kinetics of liquid water, which are of fundamental interest and have potential applications, remain unclear. A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride. As observed from the evolution of this type of droplet, a thin film was formed on the surface with an exothermic phase transition, resulting in self-suppressed evaporation. The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C. In contrast, a pure water droplet can only be sustained for a few minutes. The self-suppressed evaporation of doped water may be due to the special hydration of the accumulated manganese and chloride ions at the surface, decreasing the surface tension.

No MeSH data available.


Related in: MedlinePlus