Innovative low-cost optical sensor platform for water quality monitoring

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Water is essential to life. Access to safe drinking water may be norm in developed countries, but two billion people in developing countries, like India have limited access to clean water and according to the WHO, mortality of water associated diseases exceeds 5 million people per year. Waste water from geological sources contains pollutants like arsenic and fluorides or discharge from industries, agricultural farms, and household wastes contain pharmaceutical, heavy metals, pesticides, fertilisers, organic waste, and faeces discharged to rivers and lakes. Waterborne diseases are caused by pathogenic microorganisms that mostly are transmitted in contaminated fresh water and results from bathing, washing, drinking and in the preparation of food. Bacterial pathogens, cause major diarrhoea, resulting in millions of avoidable deaths, with more suffering of children. Industrial wastes such as heavy metals are toxic to marine life and subsequently to humans who eat those causing birth defects and cancers. Effect of many industrial wastes can be very slow, often identified very late. Waste organic matter, fertilisers, and nutrients deplete oxygen from water and cause suffocation to fish and other aquatic organisms and ultimately human consuming these infected fish. CITY has excellent facilities for fabricating FBG and LPG, complements IISc expertise. Several concatenated gratings can be fabricated on the same optical fibres to detect several species simultaneously and each grating can be prepared for different selectivity with different Bragg wavelengths for multiplexing. Advanced micro-fibres, micro-knots and micro-spheres can also be functionalised for more compact optical sensors. On the other hand, silicon nanophotonics is an exciting emerging area of research and innovation, which exploits the well developed CMOS technology developed by highly matured semiconductor industries. Exotic slot waveguide, where light is confined in a low-index region, can easily be functionalised for much more compact optical sensors, often just several micron long. Highly sensitive silicon ring resonator less than 5 micron in radius which can detect 10E-5 refractive index change and 2 micron diameter micro-resonators supporting whispering gallery modes are capable of detecting a single molecule. Such tiny sensors can be mass manufactured at vastly reduced cost, hundreds of them in a mm-square wafer, and then multiplexed and excited by a single 500 nm nanowire optical bus for rapid multi-parameters sensing. IISc has expertise in functionalisation and bio-sensing complements CITY expertise in physical and chemical sensing.The present water quality monitoring systems over the whole India, from large metropolis to small towns and remote villages are of diverse quality. There is a lack of standardised criteria for defining the safe limits of various key pollutants. Effect of some pollutants can be very slow, such as that of heavy metals, and this can be even more difficult to identify at a low level of contaminations until prolonged suffering by people. A solution to this problem is to improve the surveillance systems, both for fast acting bio-pathogens and slow-acting chemical pollutants and one way to achieve this is to develop methods to rapidly, in-situ, accurate and continuous monitoring of water quality and identify any potential breakdown in quality control well before it can be identified from the outbreak of any major diseases with many avoidable sufferings.The objective of this research proposal is to develop frugal, compact multi-channel optical sensors for innovative and cost-effective development of multi species rapidly, reliably and selectively to detect protein, peptides, cytokine, from bacterial and viral pathogens and chemical residues for in-situ and real-time drinking, general use and waste water monitoring, which can be deployable to large metropolis to small rural community.