Microfluidics Sensor to Detect Water Salinity and Bacteria Using Optical and Electrical Methods

Contaminants of various sources pollute waters worldwide and pose serious health issues to humans. Thereby, regular monitoring of the water quality is crucial. In this respect, this thesis aims to design an inexpensive microfluidic-based sensor with two microwire electrodes to narrow the gap between conventional lab-based methods and the necessary point-of-need qualities like miniaturization and lower cost. As two critical contaminators, the detection of NaCl and bacteria in water were picked to investigate the sensor’s performance. The sensor could measure water salinity in 1-120 ppm range using electrical conductivity with the limit of detection (LOD) of 0.39 ppm. The same sensor was then modified for bacteria detection in water samples with 106 and 107 CFU/mL. Afterwards, the feasibility of detecting bacteria from photothermal responses was studied to enhance the detection performance. The sensor demonstrated the bacteria detection in the 10-107 CFU/mL range with a state-of-the-art LOD of 10 CFU/ml.