Influence of Surface Wettability on Microbubble Formation

Over the last 20 years bubbles and their properties have been of high interest in the field of engineering and have found their way into a variety of applications such as biofuel production, medical imaging, and drug delivery. Lately, there has been a surge of interest in the study of microbubbles which are found in the size range of 1-999μm. The appeal of microbubbles comes from the fact that they possess a high surface area for a given gas volume and therefore enable high levels of mass transfer which is linked with the interfacial area between two phases.

Investigation into microbubble formation is essential in order to fully utilise their properties in applications. Many features of bubble formation have previously been explored and have been found to have a large impact, these include pore size and orientation, and flow rate.  The university and Polymer centre academic Dr Jonathan Howse et al. present an investigation into how the wettability of the diffuser surface impacts upon the dynamics of bubble formation process. Effects were studied at the orifice as well as upon the resultant bubble cloud produced by the wetting variations. The study comprises a thorough investigation into bubble formation by examining bubbles formed from a single pore, multiple well-defined pores, and sintered diffusers with a random network of pores.

Various surfaces were investigated during the course of this study which displayed contact angles from 107.9° to 13.1°. It was found that when a surface displays a contact angle lower than 90° the bubbles that are emitted are significantly smaller than those emitted from a surface with a contact angle above 90°. This data indicates that a contact angle of 90° is a switching point where the bubble size vastly changes.

Original article: Influence of Surface Wettability on Microbubble Formation, D. J. Wesley, R. M. Smith, W. B. Zimmerman, J. R. Howse, Langmuir, 2016, 32, 1269-1278.

Article by Thomas Neal; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.