DIFFUSION COEFFICIENT MEASUREMENT BASED ON DIFFUSION- INDUCED FOCUSING IN OPTOFLUIDIC WAVEGUIDE

This paper presents a new optofluidic method to measure the mutual diffusion coefficient in binary solutions by directly analyzing the diffusion-induced focusing pattern based on a single optical micrograph. The average diffusion coefficient of ethylene glycol (EG) and deionized water binary solution is measured under different mass fractions and flow rates to demonstrate the proposed method. Experimental results show good agreement with the reported data and indicate that the mutual diffusion coefficient is slightly decreased with the increase of the flow rate and is inversely proportional to the mass fraction of EG.