Design Optimisation of Optical Planar Waveguide Sensor for Microplastics Detection in Water

Abstract Nowadays, microplastics pollution has become a global concern as it endangers the ecology and marine animals and causes health threats to human beings. This paper demonstrated a simulation of an optical planar waveguide sensor design for microplastics detection in water via Wave Optics Module-COMSOL Multiphysics®. The design optimisation of the sensor was conducted by changing the cladding thickness ranging from 0 to 5 µm. The change in analyte refractive index ranging from 1.480 to 1.500 refractive index unit (RIU) in reference to the microplastics’ refractive index has been performed to evaluate the simulated sensing performance. The simulation results showed that reducing the cladding thickness can vastly improve the sensor sensitivity. The sensor showed the highest sensitivity in the absence of cladding layer i.e.; the cladding thickness of 0 µm with 10 7 difference in the order of magnitude of sensitivity compared to that of 5-µm thickness. Thus, the optimised sensor design with 0 µm cladding thickness assures an excellent sensor for microplastics detection in water.