How to adjust bubble’s adhesion on solid in aqueous media

Manipulation and control of gas bubbles in aqueous environments is of vital importance in many fields. Research has revealed that figuring out the interaction between bubbles and solid surfaces in water is the key factor of underwater bubble manipulation. In addition, further research has shown that the behavior of bubbles on a solid surface is mainly affected by the bubbles’ own buoyancy, external traction force and adhesion force. To date, few researchers have managed to realize the control of underwater bubbles from the first two aspects. In fact, it has been hypothesized that by making the bubble adhesion to a given solid more adjustable except for the traditional ultralow and ultrahigh adhesion, the bubbles’ manipulation will can be more flexible, which; nonetheless, is difficult to actualize due to the high requirement for the surface topography, and thus rarely reported. Fortunately, femtosecond laser ablation has emerged to be one of the most effective methods to construct the surface morphology due to the ultra-short pulse width and extremely high peak power; however, its yet to be fully explored in the context of this work.

Evidently, resolving the interrelation between underwater bubbles’ wettability and the solid surfaces topography to achieve the bubble adhesion regulation is a crucial factor of realizing the precise bubble manipulation without external stimulation, and a great challenge. To address this, Xi’an Jiaotong University researchers: Dr. Jinglan Huo, Dr. Xue Bai, Dr. Jiale Yong, Dr. Yao Fang, Professor Qing Yang, Dr. Xun Hou and Professor Feng Chen, validated their hypothesis where they postulated that underwater bubble adhesion could be adjusted from ultralow to low, high, and ultrahigh. For this, they focused on combining fish-scale-like morphology and rose-petal-like morphology into one sample and changing the proportion of each part, to achieve their goal. Their work is currently published in the research journal, Chemical Engineering Journal.

In their approach, the researchers designed a rough square-patterned array on intrinsic aerophobic and high-adhesive solid surface by femtosecond laser ablation to realize the adjusted bubble’s adhesion force on solid and figure out the relationship between the solid structure pattern and its adhesion force to bubble. The solid tested in this experiment was the thermal-response SMP film. In their set up, the samples with different adhesion could be used to losslessly transport a bubble from one surface to another in horizontal and vertical direction.

The authors reported that by taking advantages of the microscopic and macroscopic shape-memory characteristic of the SMP film, the controllable in-situ bubble release and reverse bubble adhesion transition were realized. Moreover, it was seen that the sample with specific adhesion could be used to split microbubbles from a “big” bubble and form the rewritable microbubble pattern freely. Consequently, the pattern was easy to be erased and rewritten again.

In summary, the study proposed four types of bubble adhesion states on solid surface and realized multi-manipulation of bubbles in aqueous environment using femtosecond laser-induced square-patterned array SMP surface. Remarkably, the presented multi-manipulation of underwater bubble based on the solid’s bubble adhesion variation was reported to be in good agreement with existing literature. In a statement to Advances in Engineering, the authors explained their study will inspire further research focused on developing novel strategies to achieve multi-manipulation of bubbles in practical applications.