By: Mimi Martinez
Bubble nucleation is essential for the creation of many products. As air is whipped in during the creation of ice cream, dough rises in the oven, and soda and beer fizz, vapor bubbles are spontaneously forming in liquids and surfaces due to perfect thermodynamic conditions. This process is called bubble nucleation. Outside of food, this process also allows for the creation of many other products such as polymer foams, advanced porous materials, and cosmetics.
Bubble nucleation can happen in either homogeneous or heterogeneous solutions. In the vastly studied homogeneous solutions, perfectly integrated solutions allow for the bubble creation to occur spontaneously inside the liquid, without needing any specific surfaces or sites to start forming, since the solution is fairly homogeneous.
By contrast, in the less studied heterogeneous solutions, heterogeneous nucleation happens when bubbles form at existing interfaces, like on container walls, particles, or in small cavities within the liquid. This is due to the inability of the solution’s components to fully integrate.
This process is particularly relevant in emulsions, which are stable mixtures of two liquids that normally don't mix well, such as oil and water. Emulsions are evenly dispersed within each other, forming what's called a colloidal system. Their stability relies on emulsifiers, which help keep the liquids mixed together.
A new study[i] expands research for the role of heterogeneous solutions in bubble nucleation, exploring how bubbles form emulsions under controlled conditions. The study looks at how factors like gas solubility, viscosity, and mixing methods affect bubble formation, especially for industrial uses like making foams. The findings suggest that bubbles form differently depending on the thickness of the liquids, with thicker oils helping bubbles stay inside droplets but also making them grow bigger. Adding glycerol (a thickening agent) to the water phase slowed down gas movement, causing more bubbles to form inside the droplets rather than outside.
The study also showed that moderate mixing speeds created the best droplet sizes and gas transfer, while too much mixing caused bubbles to merge, making the process less efficient. Controlling the properties of the liquids can therefore help design better materials, like foams and microcapsules, by adjusting factors like liquid thickness or adding solvents that affect gas behavior. Proof-of-concept tests showed that it’s possible to trap bubbles in thick oils, opening up new possibilities for creating porous materials for different industries.
[i]https://www.nature.com/articles/s41598-025-06117-3
