During a new coronavirus pandemic, people in developed countries have access to an ample supply of clean water and wash their hands as often as needed to protect themselves from disease.
However, nearly a third of the world's population is not even guaranteed clean drinking water.
Researchers at the University of Rochester have found a way to solve this problem by using sunlight, which is available to everyone, to evaporate and purify contaminated water with more than 100 percent efficiency.
In a paper published in the journal Nature Sustainability, researchers in the lab of Chunlei Guo, professor of optics, demonstrated how a beam of femtosecond laser pulses etched the surface of a plain aluminum plate into a material with super-absorbent and super-energy-absorbent properties.
Experiments in the lab showed that the method reduced the presence of all common contaminants such as detergents, dyes, urine, heavy metals and glycerin to safe levels for drinking.
This technology can also be used in developed countries to alleviate water scarcity in arid regions and for desalination projects.
In addition, although boiling has long been recognized as a method of eliminating microbial pathogens and reducing deaths from diarrheal infections. But boiling water does not eliminate heavy metals and other contaminants.
Solar-based water purification, however, can greatly reduce these contaminants because when evaporated water becomes gaseous and then condenses and collects, nearly all impurities remain.
The most common method of solar-based water evaporation is volumetric heating, in which a large amount of water is heated, but only the top layer can evaporate.
This is clearly inefficient, Guo says, because only a small fraction of the heating energy is used.
The solar panels developed in Guo's lab avoid the inefficiencies of traditional solar methods of evaporating water by drawing a thin layer of water from a reservoir and placing it directly onto the surface of a solar absorber for heating and evaporation.
"In addition, because we use a slotted surface, it's easy to clean with a spray," says Guo.
"The biggest advantage," he adds, "is that the angle of the panels can be constantly adjusted to face the sun directly as it rises, and then move across the sky before the sun sets" - to maximizing energy absorption.
The project was funded by the Bill and Melinda Gates Foundation, the National Science Foundation and the U.S. Army Research Office.
