Fragility is a common problem in surface treatments, sometimes called "nanotechnology". There are super hydrophobic surface treatments that are very effective. They generate a surface which is a forest of tiny sharp points. The surface tension of water is too high to cling to such a surface. You can make something that just will not get wet. The problem is that the points are fragile, and wear destroys the effect.

Another example is ultra black coatings. Those are a forest of tiny black objects arranged so that light gets reflected multiple times and is absorbed. The commercial version is called "Vantablack". It doesn't wear well, but for optical applications such as the insides of camera lenses and telescopes, that's fine.

It's such a good book! Like any dad reading history, I have been annoying my family for years with fun facts I learned in that book. David McCullough's other books like The Great Bridge (about building the Brooklyn Bridge) are also great.