Are Smart Coatings Getting Smarter

By Cynthia Challener

Interest in multifunctional coatings has grown in recent years as end users seek high­performance surface protection combined with added features. Therefore, the idea of smart coatings that can respond to stimuli has become very attractive. Research groups continue to investigate novel coating systems that can self-heal, self-clean, and provide
on-demand corrosion protection, among other functionalities. Some of these technologies have been commercialized on a small scale, while others are nearing commercialization and many more are in the early stages of dis­covery and development.

Even given the advances that have been made in this field, there still remains some debate about what defines a smart coating, and many also question the appropriateness of the “smart” label.

For purposes of this discussion, smart coat­ings are considered to be those that sense and respond to changes in the environment or within themselves, and preferably do so in a reversible manner. These changes include variations in light, temperature, pressure, air flow, surface tension, electrical current, acidity, chemical composition, bioactivity, surface contamination, etc. When a change in one of these conditions occurs, a smart coating responds by undergoing some further transformation-releasing a material, allowing a chemical reaction to take place, aligning polymer chains in a certain way-that addresses a problem. Once the stimulus is removed, the response is halted and ideally the coating returns to its original state.