Sodium MRI measurement of ion convection-diffusion in swelling gels

Convection diffusion of ions plays a major role in munerous cellular processses in biology. A quadriphasic mixture model has been developed to model the coupling between diffusion, convection, swelling and deformation in gels and tissues. Sodium and hydrogen MRI is used to measure convection-diffusion of sodium ions in homogenous ionised gels subject to swelling. A sodium chloride concentration jump from 0.5 M to 0 M at the boundary of a pAA sample is applied. Subsequently, sodium and hydrogen levels are measured in the sample for 5 days. Then the boundary condition is reversed and measurement is continued for another 5 days. The quadriphasic mixture model is fitted to the experimental data to estimate the di??usion coefficient of sodium and chloride. The best fit results were obtained forDNa = 1:1510-5cm2=s and for DCl = 2:1510-5cm2=s. Different time constants were observed for the swelling and deswelling.