Cross-sectional Images of Membranes by AFM

As mentioned earlier, the study of the cross-sectional structure of membranes by AFM was hampered by difficulties involved in making a smooth cross-sectional surface. Wood [14] made some earlier studies on the cross section of poly(phenylene oxide) (PPO) hollow fibers. But her attempt did not provide clear information on the nodular structure. 

Khulbe et al. [4] conducted an AFM study of the cross section of UF poly(ether-imide) hollow fibers, fabricated by the dry-wet spinning method at various air gaps. 

Khulbe et al. [4] also measured the nodule sizes (the average of at least 20 measurements) at the inner surface, at the areas near the inner surface, in the middle section and near the outer surface, and at the outer surface for hollow fibers fabricated at different air gaps. Table 6.1 summarizes the results. 

The nodule sizes are similar to those measured by Fuji et al. [13]. 

The nodule sizes at the inner surface and near the inner surface are similar. There is no signihcant effect of air gap on the nodule sizes observed in this region. 

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