The challenge is interesting for its own sake. Like nearly everything else here, I had some exposure to closely-relateds. My experience was the (natural!) surface of the Moth Chitinous Cornea... back when I was collecting insects for the Dept. of Agr. circa 1970-71, in the jungles of Panama. Electron microscopy reveals that the surface is entirely covered with tiny little protuberances on a quasi-hexagonal matrix. They stick out like little icicles orthogonal to the macroscopic surface topology. They provide two advantages: 1) prevent dew from forming, 2) profound broadband antireflection. I did a bunch of math modeling to compute the ARC properties... also measured. White paper "Reflectivity of the Chitinous Moth Cornea."
I later resurrected that experience to research and develop ARC coatings for lenses at Bausch & Lomb. My boss was a chemist, so did plenty to come up with concoctions that would mimic that sub-sub-micron surface. (Must be many wavelengths long and sub lambda wide... = icicles!) Well, we produced that and here is the inexorable problem: extremely fragile, can't be touched, can't be cleaned --- ever!
This would also be true of the carbon nanotubes black stuff. So, as a surface treatment for telescope parts... might not be practical... but still of great theoretical interest! Tom