A capillary rise method for studying the effective surface tension of monolayer nanoparticle-covered liquid marbles

Significance 

Amongst the liquid droplets coated with particles in an air environment, one stands out. Liquid marble is used in numerous applications such as material synthesis and chemical analysis. Presently, a simple method for producing liquid marbles involving attaching the powder-derived particles on the droplet surface is available. Unfortunately, it is quite difficult to control the particle coverage due to random particle agglomerates, unknow layers and non-uniform particle distribution which hinders understanding of other vital properties such as the surface tension. As a way of promoting surface tension studies, a new method for producing liquid marbles has been developed.

This is a jamming-relief basedmethod using a xerogel film which has proved a useful tool for producing monolayer nanoparticles-covered marbles for investigating surface tension due to its simplicity and clear surface composition. Although simple sessile and pendent drop methods have proved feasible for studying the effective surface tension of the monolayer nanoparticles-covered marble, more sophisticated methods are required that would enhance understanding of the surfaces tension and its effects on the various droplet quantities.

Recently, Northwestern Polytechnical University researchers from School of Science, Department of Applied Physics and led by Dr. Xiaoguang Li cross-examined liquid marble covered with a xerogel-derived nanoparticle monolayer. Fundamentally, they investigated whether optimized capillary rise method could be effective for studying surface tension in monolayer nanoparticles-covered marbles with different densities. Their work is currently published in the journal, Soft Matter.

Briefly, the research method employed by the five researchers entailed: first, modification of the theoretical and experimental details of the previously liquid marbles studied using the same method. This involved using numerical instead of approximation to solve the principal radii of the liquid marbles. Measurement accuracy was further enhanced by changing the baseline for measuring the height from the entry position to the maximum diameter. Next, the main aim of the researchers was to obtain a surface tension of the droplet at a specific point instead of the entire marble. Eventually, the characteristics of the effective surface tension of the liquid marble were examined based on the results and compared to the initially obtained results.

The authors observed that unlike in the initial methods, using optimized capillary method enable obtaining of effective surface tension at specific points instead of considering the entire marble. This ensured that the method here could be easily distinguished from the others. Additionally, a lower capillary rise and the low effective surface tension was recorded for monolayer nanoparticles-covered water marbles as compared to the water droplets of the same volume. Furthermore, it was feasible to investigate effective surface tension at maximum diameter position with a particle coverage ranging from 100%-10% which exhibited a slowly increasing trend.

In summary, Xiaoguang Li and his colleagues successfully developed a capillary rise method for studying the effective surface tension of monolayer nanoparticle-covered liquid marbles, with their results compared with . those in the already published literature. They concluded that the effective surface tension of liquid marbles is depended on specific conditions including measurement methods and all liquid marble parameters.

About the author

Xiaoguang Li received a bachelor degree in Applied Physics in 2008 and a PhD in Condensed Matter Physics in 2013, from Tongji University, China. From 2010 to 2012, he underwent joint PhD training in CSIRO-National Center of Precise Optics, Australia. From 2013 to 2015 he did postdoctoral research in Tongji University and Peking University. Since joining Northwestern Polytechnical University, China, as an associate professor in 2015, his research has focused on particle-laden droplets and surface wettability.

Department of Applied Physics, School of Science, Northwestern Polytechnical University, Xi’an, 710129, China. [email protected]

Reference

Li, X., Wang, R., Huang, S., Wang, Y., & Shi, H. (2018). A capillary rise method for studying the effective surface tension of monolayer nanoparticle-covered liquid marblesSoft Matter, 14(48), 9877-9884.

Go To Soft Matter

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