Nano-engineered cotton promises to wipe out water bugs
Cotton impregnated with silver nanowires and carbon nanotubes (CNTs) could provide a cheap and effective method of purifying water in remote locations.
A new filter needs only gravity and a weak electric current to produce its sterilising effect, making it suitable for a portable water-treatment device.
The fabric is easy to produce, says lead researcher Yi Cui at Stanford University in California. Cui's team simply dip a piece of cotton into a solution of CNTs and then pipette droplets containing silver nanowires onto the cotton.
Analysing the fabric with a scanning electron microscope reveals that the CNTs stick to the individual cotton fibres, while the slightly larger silver nanowires form a mesh between the fibres. The nanoparticles enable the fabric to conduct electricity, so a weak electric current can run across it. This helps kill bacteria by damaging their outer membranes, while the silver nanowires' anti-bacterial properties do the rest.
So when Cui and his colleagues poured water contaminated with the bacteriumEscherichia coli (pictured) through the silver-coated, electrically-conducting fabric, they found it killed 89 per cent of the bacteria. By conducting three successive runs through the fabric, they were able to kill over 98 per cent - enough to make the water safe to drink.
As well as testing the fabric with other micro-organisms, Cui is making sure the CNTs and silver nanowires aren't washed into the water. "So far, our evidence suggests that they don't come off," Cui told New Scientist.
"It is an interesting academic study," says nanoengineer Eric Hoek at the University of California, Los Angeles. He says proving that the potentially harmful CNTs do not leach into the water will be a key step in finding out if it is useful on a practical level.
Reflections:
This new technology could prove useful in third-world countries where proper sanitation and supply of fresh water is unavailable. However, this could also be very costly if there is not enough research is being carried out. Thus, few countries may want to utilise this method since a large sum of money would have to be invested in these. They might feel that it is not worth to spend so much money. Thus, this method might not prove feasible in various countries, especially third-world countries such as South Africa, since the high cost might bother them. However, the current challenge is to prevent the CNTs from leaking into the water, as mentioned by Eric, "proving that the potentially harmful CNTs do not leach into the water will be a key step in finding out if it is useful on a practical level." This effort to create a new technology, is definitely beneficial to people in third-world countries, and I hope others of the upper class would fund his research, which I believe will significantly enhance the living conditions of third-world countries, as well as the people's health. As technology in the world advances rapidly, more inventions can be created to help improve the lives of the people. Therefore, I feel that technology plays an important part in people's lives, as well as to help to improve the living conditions of others.
manufactured in the country. The Andhra farmers spray 45% of the pesticides on cotton, 17% on paddy, and 8.5% on crops. The use of pesticides by them has been increasing every year at an alarming rate of 2% to 5% every year. These pesticides disturb the balance of the natural nutrients in the soil and cause water pollution when they are washed by the rainwater into streams and water. As a result of this, many citizens actually drink water which they may not know are polluted, and as a result, might be poisoned and suffer from diseases such as cholera. With this new-technology, I am sure that these contaminated water can be turned into drinkable water again and may save the lives of many innocent people. Since water pollution is becoming a serious problem in various countries, this new method of converting contaminated water into drinkable water would be useful.
