This water purification system is powered by static electricity
Sang-Woo Kim/Yonsei University in South Korea
A bottle can disinfect drinking water by channelling static electricity built up from just 10 minutes of walking – no limited supply of water purification tablets or external power sources required.
“Our water disinfection approach holds particular significance for populations in underdeveloped regions, isolated areas, disaster zones and conflict areas lacking adequate sanitation infrastructure,” says Sang-Woo Kim at Yonsei University in South Korea.
Kim and his colleagues took a reusable 500-millilitre water bottle and installed a polymer electrode inside that incorporates an array of nanorods made from the conducting polymer Polypyrrole. Those nanorods concentrate the electrostatic charges that accumulate on the human body during walking to create electric fields strong enough to kill or otherwise inactivate bacteria and viruses.
A small piece of aluminium foil attached to the outside of the bottle serves as a gripping point, while also collecting static electricity from the person’s hand, which then flows along a copper wire to reach the electrode inside the bottle.
Testing showed that this walking-powered method can completely disinfect river water containing both bacteria and viruses within 10 minutes – and sometimes faster if the person holding the bottle picks up the walking pace.
But the choice of footwear affects the amount of electrostatic charge harvested from the friction between the shoe materials and the ground. Shoes made from polycarbonate, rubber and polyvinyl chloride (PVC) enabled significantly higher electrical output than shoes made from leather, says Zheng-Yang Huo at Renmin University of China, a coauthor on the study. And very humid conditions can also reduce the effectiveness of this method.
Still, the self-sufficiency of this water disinfection method and the estimated cost of less than $2 per bottle could prove especially valuable in scenarios where people lack both clean water supplies and stable electricity.
The team is now focused on developing a more efficient manufacturing process for the nanorods. “We plan to develop commercially viable technology for affordable and sustainable portable containers for water purification,” says Huo.
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