Bubbles with great potential

It is not easy for Dr. Björn Braunschweig to relax at the end of the day: Even when he tries to enjoy an after-work beer, the researcher from the Cluster of Excellence Engineering of Advanced Materials at the Friedrich-Alexander University (FAU) in Erlangen-Nuremberg, Germany, can’t help but notice the foam at the top of his glass. Why does the local beer from Bavaria have larger bubbles that pop faster than the Guinness^® on the next table? “The head on the Irish stout is much more stable because the nitrogen gas used in the carbonation process is less soluble in liquid than the carbon dioxide used for draft German beer,” Braunschweig explains. The 30-something scientist knows a thing or two about foam: In 2014, he received a €1.5 million starting grant for up-and-coming research leaders from the European Research Council for a five-year project to conduct basic research on foams.

Fabulously functional foams

It might seem odd that funding is being channeled into research on foams, of all things, but foam is a very versatile material with a bright future. Layers of Styrodur^®, for example, are not only used for insulation, they also reduce the stresses that earthquakes put on buildings, thus giving planners the confidence they need to build in seismically active areas. And joggers need to use less energy when they wear running shoes made with foam beads from BASF because the shoe’s dynamic sole springs back into its original shape immediately after impact. Even as we sleep we can reap the benefits of polyurethane foams because they provide the same high elasticity in mattresses and pillows that was previously only possible with latex, and at the same time they are breathable and long-lasting. “Foams are a booming market,” says Braunschweig. “The air bubbles make the material very light and foams have the huge advantage of extreme plasticity.” In lightweight vehicle construction, foams ensure an optimal balance between robustness and weight. At first glance, a vehicle body made of metallic foam seems just as hard as a traditional one. But if there is a crash, the foam body doesn’t break and split. Instead, it undergoes plastic deformation and – similarly to an airbag – can absorb the impact. To create foams with particular properties, researchers will need to understand every aspect of the foam, from the smallest molecules to the bubbles themselves. The interface – the place where the gas and liquid or the gas and the solid meet in the individual bubbles – is especially important. Which molecular components stabilize this surface? What interactions take place with the molecules there?