VISUALIZATION OF AN ULTRAFILTRATION MEMBRANE BY NONCONTACT ATOMIC-FORCE MICROSCOPY AT SINGLE PORE RESOLUTION

Non-contact atomic force microscopy (AFM) has been used to investigate the surface pore structure of a polyethersulfone ultrafiltration memb rane of specified molecular weight cut off (MWCO) 25 000 (ES625, PCI M embrane Systems). Excellent images at up to single pore resolution wer e obtained. This is the first time that AFM images of a membrane at su ch high resolution have been presented. Analysis of the images gave a mean pore size of 5.1 nm with a standard deviation of 1.1 nm. The resu lts have been compared to previously published studies of membranes of comparable MWCO using contact AFM and electron microscopy. Non-contac t AFM is a powerful means of studying the surface pore characteristics of ultrafiltration membranes.