How Droplets of Emulsions Behave When They Hit Different Surfaces: From Smooth to Microstructured

What is it about?

Have you ever noticed how a drop of water behaves differently when it lands on a waxy surface compared to a regular glass? Now imagine replacing water with a mixture of oil and water, like those found in cosmetics, food products, or industrial sprays. These mixtures, called emulsions, are used in countless applications, but we still don’t fully understand how they interact with different surfaces when they hit them at high speeds. In our research, we explored how emulsion droplets behave when they hit surfaces with varying properties. We used smooth surfaces, like glass and Teflon, as well as specially designed microstructured surfaces with tiny patterns. By creating emulsions without surfactants (which are substances that stabilize oil and water mixtures), we focused on the natural interplay between the liquids and the surfaces. Our findings revealed that: 1.- On smooth surfaces, water spreads more than emulsions, but emulsions dissipate energy more effectively, reducing their spread. 2.- Bouncing: On superhydrophobic surfaces (those that repel water strongly), we found that emulsion droplets with high viscosity could stop bouncing altogether due to a suction effect caused by the liquid infiltrating the surface. 3.- Splashing: On microstructured surfaces, denser structures triggered splashing at lower speeds, and emulsions with lower surface tension splashed more readily.

Featured Image

Photo by Jakob Owens on Unsplash

Photo by Jakob Owens on Unsplash

Why is it important?

Droplets play a critical role in industrial processes like inkjet printing, pesticide application, and even drug delivery. By understanding how emulsions interact with different surfaces, we can design more efficient processes and products.