Arrange yourselves! Evaporation induced self-stratification and phase separation in binary colloidal mixtures.

Summary

Everyday products like water-based paint contain mixtures of tiny particles suspended in water. These particles, called colloids, are incredibly small, roughly five million times smaller than a golf ball. When the paint dries, the particles don’t just stay where they are, they can actually move and arrange themselves in interesting ways. For example, smaller particles often rise to the top, a process known as self-stratification. In other cases, the different particles may separate sideways instead of vertically. In our research, we studied how and why this kind of separation happens during drying. We tracked how the particles moved as the water evaporated, and we built models to predict how things like the starting amount of particles or the drying speed affect the final result. Understanding this is important if we want to control exactly where the particles end up in the final dry layer. By using particles with different properties, we can create layered coatings where each part has specific functions, all without having to apply multiple layers of paint.