The market for antimicrobial coatings is creating opportunities because of (1) the growing need for antimicrobials in traditional healthcare/medical markets and (2) the emergence of entirely new markets for antimicrobials. These new markets are highly diverse and include household appliances (especially in Asia), fitness equipment, showers/baths, kitchen surfaces, textiles and perhaps even consumer electronics.

Each of these new addressable markets is huge, but antimicrobials will penetrate these sectors slowly because, for now at least, antimicrobial functionality may be viewed as a high-priced luxury in some cases. For example, not everyone wants a shower door or cell phone that kills bugs.

Some emerging parts of the antimicrobial coatings business are in fact still no more than niches. Yet they are big enough it seems to attract the attention of important players. PPG, to take one example, is already interested in silver-based antimicrobial coatings for laptop computers.

Smarts Sells

In this market environment, n-tech sees the development of smarter antimicrobial coatings as an important product strategy for two primary reasons:

• Enhanced image: Smart antimicrobial coatings cater to the luxury image that we think antimicrobial coatings will engender in consumer markets initially;

• Plays into existing markets for antimicrobials:Such coatings also play into traditional healthcare/medical markets where advanced technology per se can be a selling feature. For example, smart antimicrobials can be marketed as a technology that addresses the high incidence of hospital-acquired infections and strains of microbes that are resistant to conventional antimicrobials.

On top of this, any declaration that a coating is smart is a way to make a coating stand out in the marketplace. “Smart” in this context typically refers to the most functional of functional coatings at any given time. Hence, the meaning of what constitutes a smart microbial coating changes over time as coatings firms seek new materials to make these coatings smarter.

Silver Linings

Today smart antimicrobial coatings are frequently based on the sustained release of silver ions. Silver – especially nanosilver – is highly effective as an antimicrobial. It not only kills bacteria but also molds and fungi. It is already widely used, notably as a coating on medical devices. But silver is also not without its issues, which has firms seeking better platforms for smart antimicrobials.

Currently, when a silver antimicrobial coating is said to be smart, this usually means that the silver is deposited in a way that it is slowly released from the surface. In a typical coating of this kind, silver nanoparticles are either deposited directly on the device surface or in a polymeric surface coating.

Despite its effectiveness, the performance of silver as an antimicrobial varies alot, which is obviously a very big deal in a medical environment. Two particular concerns in this context are (A) the rise of silver-resistant species of microorganisms and (B) the ability of bacteria to sustain growth at low silver concentrations.

There are also concerns about the use of nanosilver from a health perspective and the uncertainties about regulations affecting its use. Specific worries in this regard are the potential threat of nanosilver to aquatic organisms, and the environmental impact of silver nanoparticles that are washed out in sewage treatment plants.

One could use larger silver particles instead, but this approach has a tendency to impart a grey color on coatings (which may or may not be a problem). More importantly, if silver particles agglomerate, their effectiveness as an antimicrobial declines.

With all this in mind, coatings firms are seeking a better understanding of silver’s antimicrobial mechanism. They are also seeking entirely new materials platforms for smart antimicrobials.

Desperately Seeking Smart Antimicrobials

What n-tech is seeing is a slew of novel materials aimed at future antimicrobials. Broadly speaking, we see these as falling into three types: simple additives, new smart cores and smart multifunctional coatings.

• Simple Additives

These don’t have much to do with smart coatings directly – for example, some chitosan-related materials can serve as a mildly antimicrobial additive. But they might play a role in some future antimicrobial composite coating.

• Smart Cores

Another direction – the major thrust of most current industrial R&D in this space – is the introduction of new smart core materials. An important example here are stabilized silane coatings of various kinds that, when applied smartly, assemble to form an antimicrobial surface that tears apart microbes that come in contact with it.

Several firms already sell smart coatings products based on silanes. But it is just one of many based on an inorganic chemistry.

Another approach involves a polymer coating in which chlorine dioxide has been encapsulated. Here the water-in-oil encapsulation provides a slow and controlled release of chlorine dioxide as antimicrobial. In this case, the timing of the release can be controlled through an increase in temperature and moisture. Therefore, a designer coating based on this approach can provide both contact killing and time-release killing properties.

Other interesting core materials remain in the lab, including some whose “smarts” are based on biological mechanisms. For example, a research team at the University of Bern has developed a liposome-based substance. When applied – and it is apparently still an open question as to whether this could be done as a coating – these liposomes act as decoys for bacterial toxins and so are able to sequester and neutralize them.

Towards the Multi-functional Coating

As the examples above suggest, there are plenty of directions that new smart antimicrobial coatings can take in the medium-term future and, we think that new coatings of this kind that come on the market in (say) the next five years, will mostly be based on some new smart core material that has well defined advantages over silver.

In the future, however, our view at n-tech is that smart antimicrobials will be swept up in a trend that we see impacting the whole of the smart coatings space; namely the shift to multifunctional coatings. The idea here is to combine functionalities in a smart coating in a manner that makes market sense.

One obvious example here is a natural fit between smart antimicrobials and self-cleaning surfaces, and this particular combination is enabled by the fact that some smart antimicrobial coatings have hydrophobic or hydrophilic properties.

It is easy to see how a coating that is both self-cleaning and antimicrobial could find widespread use in a hospital or school. More advanced multifunctional coatings are possible – some research suggests the combination of smart antimicrobial coatings and smart drug delivery coatings. This again would be based on a confluence of matching technologies (controlled release of both antimicrobials and drugs) and matching markets – there are obviously a myriad of circumstances in which one would need both antimicrobials and drugs to be delivered.

As n-tech sees it, the revenues from smart antimicrobials could ultimately prove quite significant. We have quantified specific medical applications for smart antimicrobial surfaces and these are expected to reach about $120 million in 2020, growing to $305 million in 2022.

However, to this must be added the many other applications that are discussed at the beginning of this article, which could easily double or triple these figures.

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