Keeping Surfaces Clean, Anywhere, Anytime
By Dr. Giovanni Palmisano
Imagine being able to keep a surface clean, dry, and cool, without expending any energy or taking any particular action. That would mean you could deploy many different materials – like glass on solar panels – efficiently, easily and remotely, without worrying about the cleaning, maintenance, or degradation of their surfaces.
Scientists have discovered such self-cleaning capabilities in the common chemical of titanium dioxide. The mineral, when coated over the surface of say, a solar cell, gives the surface superhydrophilicity, or an extreme affinity to water. This means that when water comes into contact with the titanium dioxide-coated surface, the water spreads out, maximizing contact between the water and the surface, which ensures that the water glides evenly across the surface, taking any dirt with it.
The water-grabbing and water-spreading nature of a superhydrophilic surface helps it resist dirt and fog build-up, and if any dirt has accumulated, then simply flowing water over the surface easily cleans it. These characteristics have already been leveraged in a number of outdoor applications, like glass, concrete materials, road paving blocks, and ceramic tiles. However, achieving superhydrophilicity with titanium dioxide requires that thin layers of the chemical be irradiated, or exposed to light. But now, we are working towards achieving the same superhydrophilic capabilities without light, which would greatly expand its potential commercial use to numerous indoor materials.
I am part of a team of scientists with PhD student Corrado Garlisi exploring a new class of thin film materials that are able to impart superhydrophilic properties to a surface without light. This would allow the desirable superhydrophilic properties to be existent indoors and outdoors, even at night.
The film we have developed is so thin that it is transparent, which opens up the possibility for use on glass and other surfaces requiring transparency. We have filed a patent on this thin film with the US Patent and Trademark Office in recognition of its novelty and potential commercial scope.
Another benefit of the titanium dioxide thin film we developed is that we have made it using inorganic material that is inexpensive and very stable over many years. Our proprietary method of applying the thin film was developed in the clean rooms of Masdar Institute and has already been experimentally tested to produce a surface film with the desired structural characteristics, morphology and wettability properties.
A further attribute of these films is their ability to clean dirty surfaces by degrading adsorbed organic molecule by simple exposure to artificial or natural light. For example, volatile organic compounds (VOCs), responsible for air pollution, were shown to be oxidized, or destroyed, on these surfaces, contributing to a better quality of indoor air. This latter feature is especially attractive for indoor surfaces that need to be transparent and are located near sources of VOCs.
Collaboration with local and international stakeholders is now being explored and the further development of such research activities will help UAE to foster opportunities for the manufacture of novel materials in the country.
Dr. Giovanni Palmisano is Assistant Professor of Chemical and Environmental Engineering at the Masdar Institute of Science and Technology.
18 October 2016