Hand-powered device disinfects drinking water with nanoparticles

A simple jar with a cranked handle could revolutionise the provision of clean drinking water in disaster zones and remote communities without power.

Xu Deng at the University of Electronic Science and Technology of China in Chengdu says he and his colleagues were determined to create a simple way to rid water of parasites, as well as bacterial, viral and fungal pathogens.

“We kept running into the same roadblock with decentralised water treatment,” says Deng. “Most point-of-use options either need electricity or strong sunlight, and they’re slow.”

In off-grid communities and disaster zones, traditional systems aren’t reliable, so they wanted an invention that could completely disinfect water with a minute of easy, manual stirring.

Their solution is based on spherical silica nanoparticles coated with amine group chemicals, which are positively charged in water, and gold nanoparticles, which become negatively charged in the stirred water.

“Think of a hand-cranked jar with a small dose of engineered, sand-like powder,” says Deng. “A few turns of the handle creates gentle shear in the water and that motion ‘wakes up’ our nanoparticles.”

The flow of water on the surface of the gold and amine nanoparticles create an electric charge, in turn leading to the formation of oxidising chemicals called reactive oxygen species.

“Those reactive oxygen species punch holes in microbial membranes, so pathogens can’t survive or reproduce,” says Deng. “When you stop stirring, the powder separates from the water on its own, and you draw clean water from the outlet.”

The team tested the device on 16 highly transmissible pathogens that pose a serious public health risk. It achieved a 99.9999 percent reduction in Escherichia coli with just 15 seconds of stirring the water at 50°C, and the same reduction in Vibrio cholerae within 1 minute. Overall, it inactivated more than 95 per cent of all the tested microorganisms.

The device is still in its proof-of-concept phase, says Deng, so the researchers haven’t yet determined how many litres of water can be disinfected.

“What we can say is the same batch of particles is recovered after each cycle and reused,” he says. “And once charged, the system provides long-lasting protection against recontamination for many hours.”

Because the amount of gold nanoparticles is so small, their cost is insignificant, he says – the cost of the materials is dominated by the silica powder and the plastic housing.

Chiara Neto at the University of Sydney, Australia, says she is extremely impressed with the science and the novel application of nanoparticles to blast the pathogens’ cell membranes. “It’s very clever, fantastic work.”