Producing Uniform Foam Patterns

Ostwald ripening is a process where particles is a solution (and occasionally a solid) group together over time. This can be the literal particles themselves such as the water droplets in breath or pseudo particles such as bubbles in a liquid. The large particles that exist will always tend to consume their smaller neighbours even if we don’t want them to. To be able to prevent Ostwald ripening from occurring would give us more control over the evolution of a particle system and give us the ability to manipulate the physics metallurgy, biology, topological morphology and the important one for today: foams. As this subject has been studied for over fifty years there have been multiple advancements and some very impressive mathematical models that describe foam’s development such as Lemlich’s model and the von Neumann’s law. Using these models suggestions have been given for how Ostwald ripening could be limited using everything from nanoparticles to external temperature fields but these would only act to slow the collation of the foam and so a new idea was required.

The plan that has been developed is to use a surface that has been imprinted  with a microscopic pattern in order to control the evolution of these foams in a 2D plane. Small protrusions described as “pillars” are able to set the radius of the bubbles that are likely to form and channels help to mediate the transfer of the gas between the bubbles. When the progression is kept controlled not only can Ostwald ripening be prevented it can actually be reversed with some mechanisms acting to break apart large bubbles and halt their eternal growth. By controlling the template it is believed that precise control even over the normally random movement of bubbles can also be achieved through biasing the bubbles to prefer certain zones on the micropattern. Because of the linear distribution of the bubbles in the foam it is plausible that the material will have different characteristics. Acoustic absorption was one suggested feature as well as the foam itself being used for an even greater pattern. However the greater revelation here is that the method that worked for controlling Ostwald ripening in this system may work in similar ones and so this process may go on to create many different 2D networks.

Paper links: A general patterning approach by manipulating the evolution of two-dimensional liquid foams

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