Hi Jean,

Mechanical durability under abrasion is currently the biggest issue. In fabrics, some of the coating is buried in the fabric and protected, so they are one application, clothes etc.

Self-cleaning windows is another, though soot in cities tends to be problematic, cloaking the nanostructure and destroying the self cleaning properties.

Regards,
Tommi

"In this house, we obey the laws of thermodynamics!"
-Homer J. Simpson