Henri-Louis Girard:

If you have icing rain, for instance, on a wing, the time that it's going to spend on the surface will determine whether it ices or it doesn't.

So we want to minimize the time that it spends on the surface. And the way we do that is that we create microscopic ridges on the surface. And if we impact a drop now on the middle of the ridge, we can see that it breaks up in two parts that will bounce off independently.

And because these two parts are smaller than the initial drop, they bounce off faster. And this is because when the drop bounces, it actually acts like a spring that gets compressed when it expands and then retracts. And smaller drops act like smaller springs that are actually stiffer than the larger drop. And stiffer springs will bounce off faster.