London, March 22 (ANI): Scientists at the Massachusetts Institute of Technology (MIT) in Cambridge and his colleagues have come up with a nanodevice that could be used as a simple, portable water-desalination system run from a battery or on solar power, which would help to desalinate seawater in disaster zones.
According to a report in Nature News, Jongyoon Han and colleagues at the MIT developed the device.
Han and his team were investigating the physics behind a phenomenon called ion-concentration polarization.
This occurs when a voltage is applied across a membrane, setting up an ion current.
Because only positive ions can pass through the membrane, a mismatch is created across it.
A higher proportion of positive ions amass on one side of the membrane together with the negative ions that were unable to traverse it.
The researchers decided to try to exploit this effect to scrub salts out of water.
Instead of a membrane, however, they used an ion-selective material called Nafion to make a nanojunction.
This connects to a larger, micrometre-sized channel that has sea water flowing through it.
When a voltage is turned on across the nanojunction, salts are repelled from the sea water as it flows by, although the sea water doesn't actually touch the nanojunction.
The microchannel splits into two at the junction, with fresh water flowing straight on to be collected while the repelled salty water is pushed away through the second microchannel.
The sea water from Crane Beach in Ipswich, Massachusetts, repelled more than just salt, eliminating any charged particles, including many proteins and microorganisms.
The team tested this by contaminating the water with human blood that had been stained with fluorescent markers, and found that the markers flowed into the same channel as the salts.
Because the sea water doesn't touch the nanojunction, the device is unlikely to get fouled up by microbes sticking to it.
The device is just a few centimetres square, and not enough water passes through one for practical purposes - just 250 nanolitres of fresh water can be collected per minute.
But Han said that if it were possible to put many of the devices onto some kind of chip he could produce something to rival portable household water filters.
"This would lead to flow rates of about 100 millilitres per minute," he said. "If you hit that kind of flow rate, it's going to be really useful," he added.
According to Desmond Lawler, an engineer who works on water desalination at the University of Texas at Austin, said that such a device could be used in disaster zones, where small amounts of ure water are needed quickly and cheaply. (ANI)