Plastic optical fiber evanescent wave sensor for accurate measurement of microalgae biomass

A plastic optical fiber sensor with double U-shaped probes (i. e. the sensor and reference probes) was created to accurately measure microalgae biomass. Firstly, two D-shaped fibers were created by a grinding method. The D-shaped fibers were subjected to numerous rounds of heating-cooling treatment to obtain U-shaped ones. One of the prepared U-shaped fibers was employed as the sensing probe and to sense the algal cells and changes in the liquid-phase (concentration and composition), and the other prepared U-shaped fiber coated with a hydrophilic mixed cellulose ester membrane was used as the reference probe to separate the liquids from the cells and to measure the liquid concentration and composition. Furthermore, the plastic optical fiber sensor with double U-shaped probes was implemented based on the sensing probe and the reference probe. A theoretical model was established to examine the performance parameters of the probes and the response properties of the sensor for the microalgae biomass. The measuring results show that the output signal of the prepared sensor is a function of the biomass and is not affected by changes in the liquid-phase composition or concentration. The developed sensor can accurately measure the low and high level biomasses. When the biomass of the chlorella pyrenoidosa in the range of 0-598.998 mg/L (the absorbance at OD680 nm in the range of 0-2.986), the maximum relative error between the fitted curve and the experiment results is 2.46%, and the relative error mean is 1.28%. © 2015, Chinese Academy of Sciences. All right reserved.