20th- to 21st-century technological challenges in soft coatings.

Coatings are among the most ancient technologies of humankind. Relatively soft coatings comprising organic materials such as blood, eggs, and extracts from plants were in use more than 20,000 years ago, and coating activity has been continuously practiced since then with gradually improving materials and application techniques. The fundamental purposes of protecting and/or decorating substrates have remained ubiquitous across all the centuries and cultures of civilization. This article attempts to extrapolate the long tale of change in soft coating technology from its current state by identifying some key problems that attract research and development efforts as our 21st century begins.