Researchers develop self-powered floating water purification capsule

A SMALL, self-powered water purification system has been developed by a team of international researchers as an affordable and portable solution for drinking water access.

In a project led by South Korea’s Yonsei University, with the help of the Korea Institute of Science and Technology, the University of Bath and the Renmin University of China, researchers have developed a water purifier that can be dropped in wild water and activated through natural movement.

The “all-in-one” floating canister is designed for decentralised water treatment, and does not need a battery or chemical additives for treating water.

Building on previous research from Yonsei University, the study, led by Professor Sang-Woo Kim, looks at how everyday human motion can be used as a disinfection mechanism.

The system, as explained by project team members Min Jae Park and Dong-Min Lee, is intended to act as a supplementary tool alongside centralised water treatment infrastructure in scenarios where access to such infrastructure could be limited or inaccessible, including in natural disasters or in remote fieldwork.

Everyday motion

The capsule works as a detection and disinfection device. The first step uses electromagnetic induction, where the manual movement of the water current activates a magnet inside a coil to generate electricity, which powers a total dissolved solids (TDS) sensor and bluetooth module.

These components measure chemical pollutants in the water and collect data that is sent to a user interface, a phone or smart watch. If less than 250mg of TDS is detected in the water, the data kickstarts the second step of the system of disinfection. When the capsule is in motion, it generates electrostatic charges at the interface between water and the dielectric shell. The charges sit near polypyrrole nanorods on the capsule surface, producing local electric fields that can inactivate bacteria and viruses through electroporation.

Park and Lee said: “A key feature of the system is that different forms of motion are matched with different functional requirements. Fast manual shaking provides the relatively high current needed for sensing and wireless transmission, whereas gentle low-frequency motion provides continuous electrostatic charge for disinfection.

“This design allows detection and treatment to be integrated into a single self-powered platform.”

When taking in water samples of the treated water, researchers found the capsule was able to destroy E. coli, MS2 and B. subtilis. In looking at the longevity of the capsule, the team found that the capsule was able to clean 4L of river water in just under an hour.

Costs

The researchers say their main challenge was balancing function and simplicity, needing more sensors to improve capability and trying to keep costs for a single capsule down.

A single capsule would cost US$25, with the team estimating that it could cost less if the technology is scaled up.

It said: “We aimed to keep the system simple enough for point-of-use operation while still providing three essential functions: sensing, communication and disinfection.”