Membranes and Porous Films

A limitation of AFM approaches in the study of porous materials is the limited ability of the scanned probe tip to penetrate and probe into smaller pores. This is illustrated in Chap. 2 (Fig. 2.23). Clearly, ultrasharp, high aspect ratio probe tips comprise an improvement in this respect. While carbon nanotube functionalized tips are not yet of widespread availability, conventional TM probes are preferred over CM probes because of the different opening angles (compare Chap. 2). In addition, 

In addition to the assessment of pore sizes and quality control, AFM provides direct access to the dynamic changes of smart pores, for instance pores that are equipped with a stimulus-responsive coating. Iwata et al. reported on the pH control of pore opening and closing of poly (acrylic acid) (PAA) -functionalized pores, as shown in Fig. 3.83. [174] The pores of two different membranes are closed, as seen by CM-AFM, at high pH due to the deprotonation of the PAA coating and concomitant expansion of the polymeric layer into the opening of the pore. 

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