Cryo‐snap: A simple modified freeze‐fracture method for SEM imaging of membrane cross‐sections

Cross‐sections of thin film polymeric membranes, including reverse osmosis (RO), ultrafiltration (UF), and hollow fiber microfiltration (MF) membranes, are frequently used for both material analysis and for failure and fouling investigation. However, many techniques currently used to prepare cross‐sections are far from ideal and result in distortion at cut surfaces. A modified freeze fracture method (Cryo‐snap), where the specimen is embedded in ice before cleaving, was developed to minimize the stresses put on the sample during fracturing, thereby reducing the distortion to the cross‐section and increasing the resulting detailed resolution. This method was compared to two commonly used sectioning methods, razor sectioning, and direct freeze fracturing. The Cryo‐snap method rapidly yielded cross‐sections with fewer artifacts than the traditional methods and the sample distortion was extremely low. The method is superior for membrane applications.