Highly Sensitive Detection of Biological Substances using Microfluidic Enhanced Fabry-Perot Etalon-Based Optical Biosensors

A microfluidic based optical biosensor is introduced to detect concentrations of biochemical substances in solution using refractive index measurement with high sensitivity and accuracy. The sensor consists of a liquid channel forming a Fabry-Perot cavity between two semitransparent Ag/SiO_2 reflective surfaces. Light is transmitted through the cavity to construct interference peaks in the transmission spectra which depend on the refractive index of the test samples in the channel. The refractive index of glucose, potassium chloride, and sodium chloride solutions is measured in different concentrations. Continuous change in refractive index is resolved by observing the peak wavelength shift in the transmitted spectrum. The sensor is characterized using the contact angle measurer, surface profilometer, and spectrophotometer. The proposed Fabry-Perot etalon biosensor shows real time linear responses as well as high accuracy and sensitivity of 10^(-3) refractive index per percent of glucose, 1.4 × 10^(-3) and 1.8 × 10^(-3) refractive index per percent of KCl and NaCl solution, respectively