A planar, integrated total internal reflection sensor for biofouling detection

Abstract

A planar, integrated total internal reflection (TIR) sensor for the characterizations of biofouling has been demonstrated based on angular interrogation of Fraunhofer diffraction. This sensor is made of a two-mask process to have optical prism and built-in waveguides of 4×0.25μm2 in cross section area. The core and cladding layer of the waveguide are made of silicon nitride and silicon dioxide, respectively and a 780nm in wavelength light source is used in the experiments. Water, ethanol, acetone and glycerol, have all been tested to illustrate the basic refractive index sensing principle of the prototype sensor. Biofouling measurements show that after been immersed into milk as the testing liquid, the surface refractive index of a prototype TIR sensor shifted continuously to as much as 0.0089 for a 9-hour test. As such, this technique could be useful to various biofouling control and monitoring applications, including water desalination, medical, marine and electronic device industries.