Although their value proposition is self-evident, self-cleaning surfaces are only just taking off in the marketplace. A handful of private homes have self-cleaning windows and low-end aftermarket self-cleaning coatings are readily available, but these are niche businesses at best.
The only sizeable market for self-cleaning surfaces is represented by self-cleaning ovens, which are such a mature market that they no longer constitute much of an opportunity. On a more positive note, we note that there are already many instances of dirt resistant surfaces and the sector where such surfaces are common represent a natural market for self-cleaning surfaces of the future.
Missing: An Effective Smart-Cleaning Technology
The analysis contained in the following exhibit suggests to us that for the most part, self-cleaning is not quite ready for prime time. Specifically, n-tech sees three major challenges that are holding back the market for self-cleaning surfaces and coatings
Mediocre performance: A major challenge is that today’s self-cleaning coatings and surfaces often fail to do an adequate job. For example, in some environments “self-cleaning” windows need to be washed down regularly, which appears self-defeating. In the automotive sector there is talk about cars that do not need windshield wipers; but no self-cleaning technology to provide a level of performance in that area comes close to regulatory muster.
Given the potential outlined above, it is no surprise that there is growing development work to come up with self-cleaning products that exceed current levels of performance both in terms of being longer-lasting and in being more autonomic. If these objectives can be achieved, then n-tech believes the addressable market for smart materials will grow exponentially.
Live long and prosper: Longevity is a problem for self-cleaning coatings, notably in the construction industry where the ideal lifetimes for coatings can run into decades. However, for now many of the end-user applied self-cleaning coatings that are currently available for use on car exteriors and windows last only two or three years, which begs the question as to whether the self-cleaning functionality is really worth the trouble
Self-cleaning glass can do better than this. Pilkington offers a 10-year guarantee with its product. But again, this is still less than many windows are expected to last and it appears that self-cleaning glass loses its effectiveness, all that can be done is to replace the panes, or the windows themselves.
Three Technology Paths to Self-Cleaning
There are three types of research programs that n-tech believes worth looking at as a way to achieve these goals. For now the most important of these programs involve upgrading existing self-cleaning smart materials technology to the next stage. Also, interesting are programs that also use smart materials, but which take entirely new directions than the hydrophilic and hydrophobic technology that is currently common for self-cleaning surfaces.
The third type of program potentially offers self-cleaning, but without the use of smart materials. We are thinking here on ultrasound and technologies based on micro-vacuum technology.
Next-Generation hydrophobics and hydrophilics: Much of the R&D on self-cleaning coatings—not to mention self-cleaning products themselves—is currently based on hydrophobic and hydrophilic materials. Terms of art that appear to be emerging in this context are “superhydrophobic” and “superhydrophilic.”
These terms typically describe work being done to increase performance and expand the capabilities and longevity of today’s self-cleaning surfaces and coatings. The challenge is also to find approaches to next-generation hydrophobics and hydrophilics that can be easily and effectively manufactured in volume:
Some of these programs in this space use metal (copper or steel) substrates and nanocoatings in order to create more durable self-cleaning surfaces that are often resistant to oil as well as other easier-to-clean dirt. The long-term goal here is the omniphobic surface—a surface that can self-clean itself from almost anything.
As an example of a problems that need to be solved we note that oxide polystyrene composites for superhydrophobic coatings are more durable than the gel-based coatings, however the process of applying the coating is much more involved and costly.
Despite such issues n-tech thinks that most of the revenues that will be generated from self-cleaning surfaces in the next few years will involve advanced/improved hydrophobic or hydrophilic materials of some kind.
The future of self-cleaning: Nonetheless, we see other self-cleaning materials and coatings emerging fairly quickly from labs, so we would expect to see some of these new types of self-cleaning technologies become increasingly commercially successful over the next five years or so.
The two technologies that n-tech expect to be notable with regard to breaking out of the hydrophobic/hydrophilic mode in the medium term are electrostatics and catalysis. They will not eclipse the hydrophobic/hydrophilic program, but will rather offer different tradeoffs between cost, longevity and the kind of applications where they are best suited.
And finally, we have to take into consideration the business potential for multifunctional surfaces that combine self-cleaning with other smart material functionality. As n-tech sees it, there are significant markets for materials that combine self-cleaning with some kind of self-healing or smart antimicrobial functionality.