U-bent polymer optical fiber (POF) for escherichia coli detection

Abstract

This research presents a plastic optical fiber (POF) based sensor to detect Escherichia coli at concentration of 103, 104, 105 and 106cfu/ml. The ESKA POF fiber composed of PMMA core and fluorinated polymer clad with refractive index of 1.49 and 1.41 respectively. Ethyl acetate solution was used to unclad 3 cm length of POF fibers and etched until 960 μm for all fiber sensors. U-shaped fiber with bending radius of 4 mm and 6 mm was developed by heating the fiber inside glass capillary tube. The penetration depth of the sensor is calculated by considering the internal and external curves of the U-shaped geometry. When tested with E. coli, fiber with bending radius of 4 mm shows a sensitivity of 9.5842 μW/RIU with slope linearity more than 97.82 % while, 6 mm produce sensitivity of 0.0353 μW/RIU with slope linearity 91.94 %. The performance of the sensor improved as the curvature radius decreased due to the light leaking and interact with the external medium. This can be concluded that by decreasing the bending radius, the penetration will be increased and thus affect the fiber’s sensitivity.