Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150449

150449 - Understanding the Pinch-Off of a Bubble on Superhydrophobic Surfaces 

A superhydrophobic surface (SHS) is characterized by its liquid repellency and low droplet adhesion with a contact angle greater than 150 degrees (θ>150°). Research on SHS holds significant potential for applications in various fields, including industrial, maritime, and biomedical sectors. This is due to their unique properties, such as drag reduction (Mohammadshahi et al., 2024) and anti-corrosion (Xiang et al., 2018). The formation of an air bubble inside water has been the subject of numerous studies due to its various industrial and scientific implementations, such as mass transfer, fluid dynamics, and cavitation processes. However, the formation of this phenomenon on SHS is poorly understood. 

We performed tests to understand the pinch-off of the bubble on micro-textured SHS. During this process, the air bubble on an SHS develops a thin neck that progressively narrows until the moment of rupture dictated by the interfacial forces, viscosity, and surface tension. 

 

We fabricated the samples using a 2x2 inch aluminum base, and then a circular piece of sandpaper, varying in diameter, was affixed to the base. The SHS samples were placed at the bottom of a water-filled acrylic chamber. At the same time, air was injected from below, utilizing an air pump at a fixed rate. Thus, air bubbles are formed at a constant speed, so we can capture images of a bubble's necking process as it detaches from the SHS. A high-speed camera was used to capture images at 10,000 frames per second with a resolution of 624 x 612 pixels. 

The captured images were analyzed using MatLab scripts. The radius of each bubble's neck was measured across the images. The millimeter-to-pixel ratio of the images was 0.0315 mm/px. Subsequently, these measurements were utilized to plot the radius as a function of time, with time zero (t=0) defined as the moment when the bubble ruptures, followed by the images before the rupture. 

Previous research has conducted similar experiments to understand bubble formation on non-hydrophobic surfaces. The studies show that the relation between the neck R and time t radius follows a power-law trendline of R~t^0.5 (Burton et al., 2005). Our results indicate that the previously established relationship does not apply to surfaces with superhydrophobic properties. The function's behavior varies due to the surface's superhydrophobic nature. Likewise, minor trendline changes take place when considering different surface diameters. This work is expected to contribute to the broader research of SHS and its application in the industry.

Presenting Author: Isaac Rodriguez University of Massachussets Dartmouth

Presenting Author Biography: Motivated second-year aerospace engineering student seeking opportunities to utilize classroom learning and gain hands-on experience in analysis processes. Eager to contribute to new projects that will challenge me to improve my technical and social skills. Excited about contributing my knowledge and generating innovative ideas

Authors:

Isaac Rodriguez University of Massachussets Dartmouth
Daniel O'coin University of Massachussets Dartmouth
Hangjian Ling University of Massachussets Dartmouth