Prof S Pushpavanam, department of chemical engineering at IIT-M, said the cellulose-based paper coated with a chemical specific to the antibiotic/heavy metal changes colour when it interacts with polluted water. The colours are the products or a third chemical formed due to the reaction.
“We make a design like a club in a playing card and have a chemical specific to an antibiotic or heavy metal in each of the three lobes. We then pass the water sample from the end of the club. It passes through all the three lobes, each having a chemical reaction and changing colour depending on the presence of the antibiotic or the heavy metal. The intensity of the colour produced gives its quantity. So, we can do a whole range of antibiotics using one strip,” said Prof Pushpavanam, who led the research team along with Prof T Renganathan.
The research was funded by the Centre’s Department of Science and Technology in collaboration with UK’s Natural Environment Research Council and Engineering and Physical Sciences Research Council under the Indo-UK Water Quality Research Programme.
Studies have shown antibiotics in surface water possibly due to effluents from wastewater treatment plants, aquaculture and livestock production activities and untreated sewage.
Unlike a blotting paper where an ink spot can spread in all directions, here water passes through a specific channel. A laser jet printer with an ink cartridge having a wax-like material is used to print a pattern on the paper coated with a chemical to let the water pass only through the non-printed region in a particular direction. The paper’s porousness allows water to flow without a pump.
“We generate a calibration chart which can quantify the antibiotic/heavy metal in water with that of the intensity of the colour produced. The more the antibiotic, the more the colour intensity,” he added.
The team is working on developing a portable sensor which can also be taken to a places like lakes for onsite testing. “You could also possibly use your mobile phone camera to capture images and analyse the image to understand the concentration of the metal or antibiotic,” he said, adding that the team is working to detect pesticides and early detection of diseases like cervical cancer using the concept.