A manufacturer’s mission does not end even after completing a product. Its mission is also to make a product that maintains a clean and normal condition. This is the principle that drove Mitsubishi Electric to develop its own state-of-the-art self-cleaning coatings — a project that began over 15 years ago and continues to generate innovative solutions.

Coatings: The Unsung Heroes

Mitsubishi Electric is proud of its wide range of electrical products, such as home appliances to elevators, generators, satellites and so on. Although these products play a key role in people’s lives, we tend to forget that each product was made possible by numerous technologies that never get the attention. One example is the company’s self-cleaning coatings.

These technologies — which can be found in Mitsubishi Electric air conditioners, duct fans, lighting instruments, refrigerators, and other products — apply a thin, membranous coating to plastic and other materials to prevent dirt from collecting. This not only improves a product’s reliability and performance but also keeps it clean, removing the need for constant maintenance. It’s a true gift to the user.

There is a wide variety of dirt. One is hydrophilic such as dust. Another is hydrophobic such as grease and soot. Both types of dirt can be found around the home. Conventional self-cleaning coatings are inadequate for protecting against both types. They are also difficult to properly apply on plastic. For these reasons, Mitsubishi Electric has been developing its own self-cleaning coatings over many years.

Protection from All Dirt

"Conventional self-cleaning coatings can be largely divided into oil-based fluoropolymer coatings and hydrophilic coatings made from photocatalysts and silica," explains Yasuhiro Yoshida of Mitsubishi Electric’s Advanced Technology R&D Center. "The first type prevents dust from collecting on a surface but makes it easier for grease to stick. The second type prevents grease from sticking but also allows dust to collect."

To resolve this issue, Mitsubishi Electric has developed a Hybrid Nano coating that applies a hydrophilic layer of silica particles embedded with scattered hydrophobic fluoropolymer particles. The coating can prevent any kind of dirt from collecting. "Sounds too good to be true, doesn’t it?" jokes Yoshida. But of course, he has the concrete data to back up his assertions.

He explains that the coating can help, for example, an air conditioner to maintain an optimal level of performance and lower its energy consumption: "Applying the coating to an air conditioner’s heat exchanger helps prevent both hydrophilic and hydrophobic dirt from collecting on it. This means that any particle of dirt landing on the air conditioner simply falls off, reducing the need to clean it. If you don’t clean your conditioner, more and more power consumption is needed. By simply applying this hybrid nanocoating, the air conditioner can reduce energy consumption to only one-third during ten years of use."

Following the success of this hybrid nanocoating, Mitsubishi Electric has developed another self-cleaning coating: Smart Air Coating. This technology has both the ability to prevent dry dust from collecting on a surface and water-repellency. These features make it potent against mud, other wet dirts, droplets, and even snow and ice, etc. Smart Air Coating applies a super-water-repellent layer of micrometer-sized ridges and grooves. This is why Smart Air coating has the same water-repellency as a drop of water rolling off a lotus leaf like a marble.

Looking Beyond Household Dirt

In developing its self-cleaning coatings, Mitsubishi Electric has focused not just on developing a high level of dust- and water-repellency, but also on keeping costs low to make them practical for use on home appliances. It also focuses on reducing environmental load. The company is now trying to develop innovative coatings.

"We are now developing a coating that is effective against conditions that cause underwater surfaces to become slippery: biofilms and dirt related to moss, algae, and other microorganisms," says Yoshida. "We are also actively taking on new challenges by developing coating capabilities we haven’t attempted in the past, such as rustproofing and heat control."

He adds that future projects may involve more collaborations with other companies as an approach to open innovation.

"We are looking into joint projects for developing self-cleaning building materials such as window panes," he says. "Also, because it’s possible to produce antibacterial coatings, we have been approached about producing antiviral coatings. The need is becoming more urgent this year."

He says that his team has been contracted by building material makers — as well as companies in a wide range of other fields, from medical to high-tech — broaching detailed ideas that he has found to be "very forward-thinking and interesting." These unlikely collaborations could result in innovative new products and technologies that may soon benefit people’s lives in ways no one ever imagined. Mitsubishi Electric is developing innovative technology for the future.

(This article was originally published on November 17, 2020)

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