Princeton University scientists have developed a cheap, flat, sponge-like device that absorbs water from a pond or lake, then releases purified water when placed under the sunlight.
The filter’s core consists of a polymer gel with a mesh-like microstructure. That gel is encased in a layer of a material known as polydopamine, surrounded by an algae-derived substance called alginate.
The gel’s mesh remains loose and open when the device is left to float on the water. Water subsequently flows in via the two outer layers’ pores, as it’s drawn to hydrophilic (water-attracting) molecules within the polymer gel. However, the alginate’s pores are small enough to block any pathogens and pollutants from passing through.
When the filter is removed from the water and placed in the sunlight, the polydopamine increases its solar intake, causing heat. As it heats up, hydrophobic (water-repelling) molecules in the gel are attracted toward one another. This leads to the gel contracting, wringing the purified water out of the spongey material, where the water is collected in a container below the filter.
To test the device, the scientists placed it in the 77 ºF (25 ºC) water of Lake Carnegie at the Princeton campus for 60 minutes. Then, it was taken out and set under the sunlight for another hour, heating it to 91ºF (33ºC) and releasing the water that it had absorbed. The resulting water was free of toxins, harmful microbes, and pathogens. The study was published on March 31, 2021, in the journal Advanced Materials.
Other exciting water filters include:
- Algae-based water filters developed by a team of scientists from Uppsala University, Sweden, and Dhaka University, Bangladesh;
- The GoSun Flow portable solar-powered water purification and sanitation system that’s small enough to fit in a backpack;
- An ultra-efficient, gravity-defying aluminum panel that uses solar power to purify water;
- (The Solar Desalination Skylight – stores the sun’s energy to provide free lighting at night while distilling seawater into drinking water.)
