TOTO: Taking photocatalysis into the future

The process of self-cleaning using photocatalysis originated in Japan, where the principle was discovered. A new generation of coatings and glazes was developed on this basis. Photocatalytic finishes enable progressive functions that benefit booth people and the environment. In future, such intelligent glazes and coatings will be as indispensable to the bathroom as the toilet or shower.


In 1967, Japanese scientists Akira Fujishima and Kenichi Honda (University of Tokyo) discovered the active cleansing effect of titanium dioxide in photocatalysis. They researched this phenomenon, now known as the “Honda-Fujishima Effect”, and published a report entitled “The Effect of Photokatalysator TiO2” in Nature magazine in 1972.


Discovering the hydrophiles

However, the passive cleansing effect of photocatalysis was only discovered in the 1990s by development engineers at TOTO, the Japanese bathroom manufacturer, who were collaborating with the University of Tokyo. The passive cleansing effect is based on the hydrophilic properties of titanium dioxide. Surfaces treated with titanium dioxide dramatically reduce the surface tension of falling water. Instead of sliding off the surface as individual drops, the water flows off the edges in the form of an ultra-thin film – removing all dust and dirt particles in the process.


Unlike the so-called lotus effect (hydrophobia), water applied to the titanium dioxide-treated surface was able to eliminate even oily or greasy substances without leaving any dirty film behind.


Active cleansing effect

The first active cleansing effect of photocatalysis discovered by researchers occurs due to the light-sensitive titanium dioxide, which is embedded in the surface layer in the form of tiny particles. If these particles are exposed to UV light, oxygen from the surrounding air is chemically activated. This activated oxygen destroys organic matter along with other pollutants without attacking the surface. In other words, the dirt literally dissolves in the air. Together with superhydrophilic elements, photocatalysis from the titanium bond represents the ultimate self-cleaner – both environmentally friendly and sustainable. This type of cleansing is ideal for areas that require outstanding hygiene, such as bathrooms and other sanitary facilities.


The ultimate in hygiene

Toilet hygiene plays a major role in sanitary facilities – and TOTO has focused its efforts on this topic for decades. The company ushered in the era of the high-tech toilet 33 years ago when it produced its first WASHLET in 1980 – and has manufactured 33 million since.

The Japanese manufacturer recently started using innovative photocatalytic technologies in its WASHLETs. The latest generation of WASHLETs, the “Neorest AC”, offers familiar technologies and comfort functions such as the warm water spray, dryer and heated seat. It also has self-cleaning features that employ photocatalytics, which TOTO calls “Actilight”. According to the company, the “Neorest AC” is the first completely self-cleaning WASHLET. It makes additional cleansers practically unnecessary for the toilet bowl, and far exceeds the previous standards achieved in the areas of hygiene and convenience.


Clean and green

By using “Actilight” technology, TOTO has laid the foundation for a very special type of toilet hygiene. The oxygen activated in photocatalysis naturally breaks down all organic substances on the surface. This effect is never depleted, but continues to work effectively over the long term. The superhydrophilic properties of the zirconium coating on the toilet bowl further ensure the effortless elimination of waste and bacteria.


The new zirconium coating also makes it easy to keep the WASHLETs clean, dramatically reducing the amount of chemical cleansers and time needed for cleaning. This reduces costs and, last but not least, protects the environment.


Two components are responsible for producing the self-cleaning photocatalytic effect in the new WASHLET – UV light and a coating that contains titanium dioxide. The new “Neorest AC” is equipped with an integrated UV light in the toilet lid. This automatically turns on for an hour once the sensor-based lid shuts following each use. An especially durable and long-lasting zirconium coating was chosen for the toilet bowl.


“Actilight” also works in combination with another hygiene technology: “ewater+”. The cleaning process in the toilet works as follows: When the sensor-based toilet lid rises prior to use, the entire toilet bowl is sprayed with water. After all, less waste sticks to wet ceramic surfaces. Once the toilet is flushed, the toilet bowl is sprayed once again with electrolysed water. This “ewater” is a slightly acidic pH value and has cleansing as well as antibacterial properties.


The food industry uses electrolysed water to clean fruit and vegetables. It is completely harmless, safe and can be returned to the water cycle without issue. Once the toilet bowl is sprayed with “water”, the lid closes automatically, the UV light turns on, and the process of breaking down all organic substances begins.


The superhydrophilic surface also ensures the thorough removal of waste and bacteria. According to TOTO, “Neorest AC” is the most technologically sophisticated and hygiene toilet on the market today.