Fig 5. Relaxation rate dispersion and quantification of mean air bubble radius for ageing hydrogel foam.
(a) Several experimental R 2 values (symbols) measured at different imaging times of ageing hydrogel foam with a 0.5 T benchtop relaxometer [19] was used to fit the analytical model with R 2 from Eq (23) and respective spectral parameters as determined above (solid lines; for further details, please see main text). Fit parameters for characteristic time τ and intrinsic relaxation rate R 2,0 can be found in Table 1. (b) Mean air bubble radius as obtained through Eq (5) from the different values for τ of the fitted model. These values are compared to values obtained by triangulating μCT images of voxel size 19.4 μm of the same foam cross-sections that served to acquire the R 2 dispersion curves [19]. In addition, the time evolution of radii by random walk simulations is shown as performed in [19]. The continuous lines are fits of second order polynomials to the data. The mean relative error of the model and random walk simulation data points to the fit curve of μCT data is 5.84 ± 1.28% and 14.36 ± 2.66%, respectively.