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Optical platforms for monitoring the quality of liquids

by IT on 20-12-2018
Water distributers and beverage industries have the concern to guarantee the desirable quality parameters of their products during all their grid systems and production lines. The activity coordinated by Rogério Nogueira and Lúcia Bilro (both from IT in Aveiro) aims to develop low-cost, smart optical platforms for on-line and real-time measurement of liquid properties and/or chemical and biological constituents. These platforms are based in optical fiber technology and framed as a natural development after the conclusion of the IT internal project “sWAT”.

sWAT project provided the base on-line cloud platform which was developed to store, treat and display data from sensors placed in the field, such as water suppling tanks. Previously developed sensors for turbidity, color and refractive index sensing can be wireless connected to this platform. The first developed prototype was the turbidity sensor used to measure the quantity of suspended solids directly from a suppling point of water installed in Segadães, Águeda. It uses the transmission and scattering of infrared light guided through plastic optical fibers (POF) that are in contact with the water.

The evolution of this sensor led to the development of a color sensor prototype where other light wavelengths were added to give color sensing capability. With this prototype, machine learning and data fusion data treatment algorithms were developed to optimize the selectivity and detection limits of the sensor.

Finally, two low-cost refractive index (RI) sensors were also designed and developed. The first one, uses a hybrid POF to prism structure and is intended to monitor the quality of water with real-time high precision measurements. By determining the position of light that is totally reflected in a prism-liquid interface, a value for RI can be obtained. The direct measurement of RI can give us an indirect value of any variation in the quality of a liquid. A pilot case study will be conducted soon. The alternative approach to this sensor uses a POF side polished that will be in contact with the liquid to be measured. The principle of operation is based on the variation of the transmitted light through the side-polished section of the fiber due to RI variations of the liquid being monitored. Future work will use this device as a base where polymeric layers are deposited over, which are sensitive to chemical and biological constituents. This work will be further developed in the recently initiated AQUATICsens FCT project.